Bio
Originally from Massachusetts, USA, Jonathan came to Montréal to study Physics at McGill University in 2017. He began working with the Enger Lab in January 2020, and graduated with a B.Sc. in Physics in August 2020. After a year as a research assistant in the lab, Jonathan returned to McGill for his M.Sc. in Medical Physics, and graduated in 2024. He is currently persuing his Ph.D in Physics with the Enger Lab. His graduate research centers on the translation of rectal intensity modulated brachytherapy to the clinic.
Current Projects
Toward the Clinical Implementation of Intensity Modulated Brachytherapy for the Treatment of Rectal Cancer (M.Sc and Ph.D project)
Intensity modulated brachytherapy (IMBT) utilizes dynamically-rotating metallic shields to shield healthy tissue and provide conformal dose coverage of tumours. Our lab has designed an intensity modulated brachytherapy shielded applicator for rectal cancer, and have shown using Monte Carlo simulations that it offers a substantial dose reduction to organs at risk. The goal of my M.Sc and Ph.D centers around developing and creating hardware and software technology to take rectal intensity modulated brachytherapy from a hypothetical to a treatment that can be delivered clinically.
Development of a delivery system for rectal intensity modulated brachytherapy
Components of the rectal intensity modulated brachytherapy will include the 180° degree tungsten shield, mould applicator, rotation system, remote afterloader, and rotation software. These separate technologies must be combined into a robust system that is capable of delivering a treatment plan.
Design of a 3D printed patient-specific deformable pelvic phantom for rectal intensity modulated brachytherapy and characterization of 3D printed materials
We are designing a 3D printed, patient-specific, deformable pelvic phantom to assess anatomical changes and perform dose quality assurance for treatment plans. We are also characterizing the non-water-equivalent materials used in the phantom using novel methods to ensure that their radiation attenuation properties can be properly simulated.
Creation of an optimization workflow for rectal intensity modulated brachytherapy
With an extra degree of freedom, a rectal intensity modulated brachytherapy dose optimization protocol must go beyond current clinical optimization techniques. We are investigating new optimization methods to achieve the most conformal doses possible with intensity modulated brachytherapy
Development of a Selenium-75 brachytherapy source
Continuing the M.Sc work of Jake Reid, I will work towards the creation and characterization of a selenium-75 brachytherapy source with a clinically-viable activity (~20 Ci).
RapidBrachyTG43: A Geant4-based TG-43 Parameter Calculation Engine for Brachytherapy Applications
The American Association of Physicists in Medicine Task Group 43 (TG-43) report specifies an analytic formalism for brachytherapy dose calculations, approximating patients as effectively infinite water phantoms and ignoring differential scattering and attenuation by brachytherapy hardware, patient tissues, and air interfaces. TG-43 is still in use as the recommended dose calculation method for clinical brachytherapy dosimetry. This project involved the development of a Geant4 usercode and accompanying module of RapidBrachyMCTPS to facilitate TG-43 parameter calculations for brachytherapy sources. The module also enables the use of these parameters in fast dose to water calculations in RapidBrachyMCTPS.
Monte Carlo-based Dosimetry for GRID Radiotherapy
Spatially-fractionated radiotherapy, also known as GRID, involves the placement of a perforated metallic block in the beam of a conventional linear accelerator, resulting in a treatment field consisting of many spatially-separated ‘pencil’ beams. GRID is used for single-fraction dose escalation for large tumours, offering better control and reduced side-effects versus equivalent doses in the open-field case. Jonathan will use Geant4-based Monte Carlo simulations to investigate the dose distributions delivered in patients treated with GRID and evaluate the accuracy of the current ‘pencil and paper’ dosimetry protocol used for this technique.
2026
Esmaelbeigi, Azin; Tomic, Nada; Kalinowski, Jonathan; Watson, Peter G. F.; Rivard, Mark J.; Devic, Slobodan; Enger, Shirin A.
In: Medical Physics, vol. 53, iss. 1, no. e70151, 2026, ISSN: 2473-4209.
@article{Esmaelbeigi2025-wwb,
title = {Investigation of inter-source and intra-source spectral variations in an electronic brachytherapy source using spectral measurements and Monte Carlo simulations},
author = {Azin Esmaelbeigi and Nada Tomic and Jonathan Kalinowski and Peter G. F. Watson and Mark J. Rivard and Slobodan Devic and Shirin A. Enger},
url = {https://aapm.onlinelibrary.wiley.com/doi/10.1002/mp.70151},
doi = {10.1002/mp.70151},
issn = {2473-4209},
year = {2026},
date = {2026-01-05},
journal = {Medical Physics},
volume = {53},
number = {e70151},
issue = {1},
abstract = {Background
The Xoft electronic brachytherapy source is commonly used to treat superficial lesions and tumors at shallow depths. However, uncertainties in material composition and geometry—mainly due to manual assembly of x-ray tube components—can cause inter-source variability in the output spectrum. In addition, aging of the x-ray tube may lead to intra-source spectral variability.
Purpose
To investigate inter- and intra-source spectral variability for the Xoft S7500 model using experimental measurements and simulations, and to evaluate the dosimetric impact of this variability.
Methods
An Amptek X123 CdTe x-ray spectrometer was used to measure spectra from the Xoft S7500 source. The spectrometer was calibrated using ¹³⁷Cs, ¹⁵²Eu, and ⁵⁷Co. Spectra were measured at both the tip and side of the source at a distance of 15.5 cm from the source tip. The source was secured to an optical table using a 3D-printed holder and aligned with a laser. Intra-source variability was assessed by measuring one source in five trials. Inter-source variability was assessed by measuring five different S7500 sources at the tip and side. Output symmetry was evaluated by comparing tip and side spectra. Measurements were compared with simulated spectra generated using the E-Brachy Monte Carlo software package, incorporating manufacturer-reported ranges in material composition. To assess clinical significance, depth-dose curves were compared for simulations using the upper and lower bounds of the material-composition uncertainty range.
Results
A linear regression calibration mapped detector channels to energy (keV). Escape-peak and background corrections were applied, and counts near the cadmium (26.7 keV) and tellurium (31.8 keV) K-edges were adjusted to better resolve silver peaks. Intra-source variability showed consistent peak resolution for tungsten, yttrium, and silver, with a coefficient of variation (CV) of 0.5%–9.8%. Inter-source variability showed larger differences between tip and side measurements, with variation up to 13.5%. Simulations demonstrated that material composition affects characteristic peak intensities; the measured peak intensities fell between simulations using higher and lower yttrium/silver concentration limits. Depth-dose simulations showed minimal differences between material compositions (<1.2%).
Conclusions
Measured and simulated spectra for the Xoft S7500 source were in good agreement. Differences in depth-dose curves remained within 2%, consistent with AAPM TG-568 recommendations, and observed spectral variations for the S7500 model were within the recommended range.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Background
The Xoft electronic brachytherapy source is commonly used to treat superficial lesions and tumors at shallow depths. However, uncertainties in material composition and geometry—mainly due to manual assembly of x-ray tube components—can cause inter-source variability in the output spectrum. In addition, aging of the x-ray tube may lead to intra-source spectral variability.
Purpose
To investigate inter- and intra-source spectral variability for the Xoft S7500 model using experimental measurements and simulations, and to evaluate the dosimetric impact of this variability.
Methods
An Amptek X123 CdTe x-ray spectrometer was used to measure spectra from the Xoft S7500 source. The spectrometer was calibrated using ¹³⁷Cs, ¹⁵²Eu, and ⁵⁷Co. Spectra were measured at both the tip and side of the source at a distance of 15.5 cm from the source tip. The source was secured to an optical table using a 3D-printed holder and aligned with a laser. Intra-source variability was assessed by measuring one source in five trials. Inter-source variability was assessed by measuring five different S7500 sources at the tip and side. Output symmetry was evaluated by comparing tip and side spectra. Measurements were compared with simulated spectra generated using the E-Brachy Monte Carlo software package, incorporating manufacturer-reported ranges in material composition. To assess clinical significance, depth-dose curves were compared for simulations using the upper and lower bounds of the material-composition uncertainty range.
Results
A linear regression calibration mapped detector channels to energy (keV). Escape-peak and background corrections were applied, and counts near the cadmium (26.7 keV) and tellurium (31.8 keV) K-edges were adjusted to better resolve silver peaks. Intra-source variability showed consistent peak resolution for tungsten, yttrium, and silver, with a coefficient of variation (CV) of 0.5%–9.8%. Inter-source variability showed larger differences between tip and side measurements, with variation up to 13.5%. Simulations demonstrated that material composition affects characteristic peak intensities; the measured peak intensities fell between simulations using higher and lower yttrium/silver concentration limits. Depth-dose simulations showed minimal differences between material compositions (<1.2%).
Conclusions
Measured and simulated spectra for the Xoft S7500 source were in good agreement. Differences in depth-dose curves remained within 2%, consistent with AAPM TG-568 recommendations, and observed spectral variations for the S7500 model were within the recommended range.
The Xoft electronic brachytherapy source is commonly used to treat superficial lesions and tumors at shallow depths. However, uncertainties in material composition and geometry—mainly due to manual assembly of x-ray tube components—can cause inter-source variability in the output spectrum. In addition, aging of the x-ray tube may lead to intra-source spectral variability.
Purpose
To investigate inter- and intra-source spectral variability for the Xoft S7500 model using experimental measurements and simulations, and to evaluate the dosimetric impact of this variability.
Methods
An Amptek X123 CdTe x-ray spectrometer was used to measure spectra from the Xoft S7500 source. The spectrometer was calibrated using ¹³⁷Cs, ¹⁵²Eu, and ⁵⁷Co. Spectra were measured at both the tip and side of the source at a distance of 15.5 cm from the source tip. The source was secured to an optical table using a 3D-printed holder and aligned with a laser. Intra-source variability was assessed by measuring one source in five trials. Inter-source variability was assessed by measuring five different S7500 sources at the tip and side. Output symmetry was evaluated by comparing tip and side spectra. Measurements were compared with simulated spectra generated using the E-Brachy Monte Carlo software package, incorporating manufacturer-reported ranges in material composition. To assess clinical significance, depth-dose curves were compared for simulations using the upper and lower bounds of the material-composition uncertainty range.
Results
A linear regression calibration mapped detector channels to energy (keV). Escape-peak and background corrections were applied, and counts near the cadmium (26.7 keV) and tellurium (31.8 keV) K-edges were adjusted to better resolve silver peaks. Intra-source variability showed consistent peak resolution for tungsten, yttrium, and silver, with a coefficient of variation (CV) of 0.5%–9.8%. Inter-source variability showed larger differences between tip and side measurements, with variation up to 13.5%. Simulations demonstrated that material composition affects characteristic peak intensities; the measured peak intensities fell between simulations using higher and lower yttrium/silver concentration limits. Depth-dose simulations showed minimal differences between material compositions (<1.2%).
Conclusions
Measured and simulated spectra for the Xoft S7500 source were in good agreement. Differences in depth-dose curves remained within 2%, consistent with AAPM TG-568 recommendations, and observed spectral variations for the S7500 model were within the recommended range.
2025
Quetin, Sébastien; Jafarzadeh, Hossein; Kalinowski, Jonathan; Bekerat, Hamed; Bahoric, Boris; Maleki, Farhad; Enger, Shirin A.
Automatic catheter digitization in breast brachytherapy Journal Article
In: Medical Physics, vol. 52, iss. 9, no. e18107, 2025, ISSN: 2473-4209.
@article{nokey,
title = {Automatic catheter digitization in breast brachytherapy},
author = {Sébastien Quetin and Hossein Jafarzadeh and Jonathan Kalinowski and Hamed Bekerat and Boris Bahoric and Farhad Maleki and Shirin A. Enger},
url = {https://aapm.onlinelibrary.wiley.com/doi/10.1002/mp.18107},
doi = {https://doi.org/10.1002/mp.18107},
issn = {2473-4209},
year = {2025},
date = {2025-09-12},
urldate = {2025-09-12},
journal = {Medical Physics},
volume = {52},
number = {e18107},
issue = {9},
abstract = {Background:
High dose rate (HDR) brachytherapy requires clinicians to digitize catheters manually. This process is time-consuming, complex, and depends heavily on clinical experience-especially in breast cancer cases, where catheters may be inserted at varying angles and orientations due to an irregular anatomy.
Purpose:
This study is the first to automate catheter digitization specifically for breast HDR brachytherapy, emphasizing the unique challenges associated with this treatment site. It also introduces a pipeline that automatically digitizes catheters, generates dwell positions, and calculates the delivered dose for new breast cancer patients.
Methods:
Treatment data from 117 breast cancer patients treated with HDR brachytherapy were used. Pseudo-contours for the catheters were created from the treatment digitization points and divided into three classes: catheter body, catheter head, and catheter tip. An nnU-Net pipeline was trained to segment the pseudo-contours on treatment planning computed tomography images of 88 patients (training and validation). Then, pseudo-contours were digitized by separating the catheters into connected components. Predicted catheters with an unusual volume were flagged for manual review. A custom algorithm was designed to report and separate connected components containing colliding catheters. Finally, a spline was fitted to every separated catheter, and the tip was identified on the spline using the tip contour prediction. Dwell positions were placed from the created tip at a regular step size extracted from the DICOM plan file. Distance from each dwell position used during the clinical treatment to the fitted spline (shaft distance) was computed, as well as the distance from the treatment tip to the one identified by our pipeline. Dwell times from the clinical plan were assigned to the nearest generated dwell positions. TG-43 dose in water was computed analytically, and the absorbed dose in the medium was predicted using a published AI-based dose prediction model. Dosimetric comparison between the clinically delivered plan dose and the created automated plan dose was evaluated regarding dosimetric indices percent error.
Results:
Our pipeline was used to digitize 408 catheters on a test set of 29 patients. Shaft distance was on average 0.70 ± 3.91 mm and distance to the tip was on average 1.37 ± 5.25 mm. The dosimetric error between the manual and automated treatment plans was, on average, below 3% for planning target volume V100, V150, V200 and for the lung, heart, skin, and chest wall D2cc and D1cc, in both water and heterogeneous media. For D0.1cc values in all the organs at risk, the average error remained below 5%. The pipeline execution time, including auto-contouring, digitization, and dose to medium prediction, averages 118 s, ranging from 63 to 294 s. The pipeline successfully flagged all cases where digitization was not performed correctly.
Conclusions:
Our pipeline is the first to automate the digitization of catheters for breast brachytherapy, as well as the first to generate dwell positions and predict corresponding AI-based absorbed dose to medium based on automatically digitized catheters. The automatically digitized catheters are in excellent agreement with the manually digitized ones while more accurately reflecting their true anatomical shape.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Background:
High dose rate (HDR) brachytherapy requires clinicians to digitize catheters manually. This process is time-consuming, complex, and depends heavily on clinical experience-especially in breast cancer cases, where catheters may be inserted at varying angles and orientations due to an irregular anatomy.
Purpose:
This study is the first to automate catheter digitization specifically for breast HDR brachytherapy, emphasizing the unique challenges associated with this treatment site. It also introduces a pipeline that automatically digitizes catheters, generates dwell positions, and calculates the delivered dose for new breast cancer patients.
Methods:
Treatment data from 117 breast cancer patients treated with HDR brachytherapy were used. Pseudo-contours for the catheters were created from the treatment digitization points and divided into three classes: catheter body, catheter head, and catheter tip. An nnU-Net pipeline was trained to segment the pseudo-contours on treatment planning computed tomography images of 88 patients (training and validation). Then, pseudo-contours were digitized by separating the catheters into connected components. Predicted catheters with an unusual volume were flagged for manual review. A custom algorithm was designed to report and separate connected components containing colliding catheters. Finally, a spline was fitted to every separated catheter, and the tip was identified on the spline using the tip contour prediction. Dwell positions were placed from the created tip at a regular step size extracted from the DICOM plan file. Distance from each dwell position used during the clinical treatment to the fitted spline (shaft distance) was computed, as well as the distance from the treatment tip to the one identified by our pipeline. Dwell times from the clinical plan were assigned to the nearest generated dwell positions. TG-43 dose in water was computed analytically, and the absorbed dose in the medium was predicted using a published AI-based dose prediction model. Dosimetric comparison between the clinically delivered plan dose and the created automated plan dose was evaluated regarding dosimetric indices percent error.
Results:
Our pipeline was used to digitize 408 catheters on a test set of 29 patients. Shaft distance was on average 0.70 ± 3.91 mm and distance to the tip was on average 1.37 ± 5.25 mm. The dosimetric error between the manual and automated treatment plans was, on average, below 3% for planning target volume V100, V150, V200 and for the lung, heart, skin, and chest wall D2cc and D1cc, in both water and heterogeneous media. For D0.1cc values in all the organs at risk, the average error remained below 5%. The pipeline execution time, including auto-contouring, digitization, and dose to medium prediction, averages 118 s, ranging from 63 to 294 s. The pipeline successfully flagged all cases where digitization was not performed correctly.
Conclusions:
Our pipeline is the first to automate the digitization of catheters for breast brachytherapy, as well as the first to generate dwell positions and predict corresponding AI-based absorbed dose to medium based on automatically digitized catheters. The automatically digitized catheters are in excellent agreement with the manually digitized ones while more accurately reflecting their true anatomical shape.
High dose rate (HDR) brachytherapy requires clinicians to digitize catheters manually. This process is time-consuming, complex, and depends heavily on clinical experience-especially in breast cancer cases, where catheters may be inserted at varying angles and orientations due to an irregular anatomy.
Purpose:
This study is the first to automate catheter digitization specifically for breast HDR brachytherapy, emphasizing the unique challenges associated with this treatment site. It also introduces a pipeline that automatically digitizes catheters, generates dwell positions, and calculates the delivered dose for new breast cancer patients.
Methods:
Treatment data from 117 breast cancer patients treated with HDR brachytherapy were used. Pseudo-contours for the catheters were created from the treatment digitization points and divided into three classes: catheter body, catheter head, and catheter tip. An nnU-Net pipeline was trained to segment the pseudo-contours on treatment planning computed tomography images of 88 patients (training and validation). Then, pseudo-contours were digitized by separating the catheters into connected components. Predicted catheters with an unusual volume were flagged for manual review. A custom algorithm was designed to report and separate connected components containing colliding catheters. Finally, a spline was fitted to every separated catheter, and the tip was identified on the spline using the tip contour prediction. Dwell positions were placed from the created tip at a regular step size extracted from the DICOM plan file. Distance from each dwell position used during the clinical treatment to the fitted spline (shaft distance) was computed, as well as the distance from the treatment tip to the one identified by our pipeline. Dwell times from the clinical plan were assigned to the nearest generated dwell positions. TG-43 dose in water was computed analytically, and the absorbed dose in the medium was predicted using a published AI-based dose prediction model. Dosimetric comparison between the clinically delivered plan dose and the created automated plan dose was evaluated regarding dosimetric indices percent error.
Results:
Our pipeline was used to digitize 408 catheters on a test set of 29 patients. Shaft distance was on average 0.70 ± 3.91 mm and distance to the tip was on average 1.37 ± 5.25 mm. The dosimetric error between the manual and automated treatment plans was, on average, below 3% for planning target volume V100, V150, V200 and for the lung, heart, skin, and chest wall D2cc and D1cc, in both water and heterogeneous media. For D0.1cc values in all the organs at risk, the average error remained below 5%. The pipeline execution time, including auto-contouring, digitization, and dose to medium prediction, averages 118 s, ranging from 63 to 294 s. The pipeline successfully flagged all cases where digitization was not performed correctly.
Conclusions:
Our pipeline is the first to automate the digitization of catheters for breast brachytherapy, as well as the first to generate dwell positions and predict corresponding AI-based absorbed dose to medium based on automatically digitized catheters. The automatically digitized catheters are in excellent agreement with the manually digitized ones while more accurately reflecting their true anatomical shape.
Kalinowski, Jonathan; Tal, Oren; Reid, Jake; 3rd, John Munro; Moran, Matthew; Armstrong, Andrea; Enger, Shirin A.
Development and characterization of a prototype selenium-75 high dose rate brachytherapy source Journal Article
In: Medical Physics, vol. 52, iss. 9, no. e18088, 2025, ISSN: 2473-4209.
@article{nokey,
title = {Development and characterization of a prototype selenium-75 high dose rate brachytherapy source},
author = {Jonathan Kalinowski and Oren Tal and Jake Reid and John Munro 3rd and Matthew Moran and Andrea Armstrong and Shirin A. Enger},
url = {https://aapm.onlinelibrary.wiley.com/doi/10.1002/mp.18088},
doi = { https://doi.org/10.1002/mp.18088},
issn = {2473-4209},
year = {2025},
date = {2025-09-09},
urldate = {2025-09-09},
journal = {Medical Physics},
volume = {52},
number = {e18088},
issue = {9},
abstract = {Background:
75Se (t1/2 ≈ 120 days, Eγ,avg ≈ 215 keV) offers advantages over 192Ir (t1/2 ≈ 74 days, Eγ,avg ≈ 360 keV) as a high dose rate brachytherapy source due to its lower gamma energy and longer half-life. Despite its widespread use in industrial gamma radiography, a 75Se brachytherapy source has yet to be manufactured.
Purpose:
A novel 75Se-based source design with a vanadium diselenide core, titled the SeCure source, was proposed. This study aimed to evaluate the feasibility of this source design for dosimetry and manufacturability purposes and to develop an activated prototype source.
Methods:
The source was modeled and integrated into the Monte Carlo-based treatment planning system RapidBrachyMCTPS, where its TG-43U1 parameters, photon spectrum, and broad beam first half-value layers (HVL1) and tenth-value layers (TVL1) in lead, tungsten, and concrete were calculated. A prototype source was manufactured, and the vanadium diselenide content of the capsule was verified with neutron radiography. The source was then activated to a nominal activity of 8.5 ± 0.9 mCi at the McMaster Nuclear Reactor. The activity was measured with two separate dose calibrators. Gamma spectroscopy was used to characterize any activated radioactive contaminants in the source, and wipe testing was performed to check for any leakage of 75Se from the encapsulation.
Results:
The SeCure source's TG-43U1 parameters were computed, showing that 2.056 ± 0.003 times the activity of 75Se is required relative to 192Ir to achieve the same dose rate in water at (1 cm, 90°). The mean spectral energy of the source is 214.695 ± 0.005 keV, resulting in reduced first half-value and tenth-value layers relative to 192Ir in attenuating materials. For example, the HVL1 was reduced from 2.795 ± 0.002 mm to 1.020 ± 0.001 mm in lead, from 2.049 ± 0.002 mm to 0.752 ± 0.001 mm in tungsten, and from 70.63 ± 0.04 mm to 61.37 ± 0.03 mm in concrete. The activated source achieved the desired activity, indicated as 9.2 ± 0.2 mCi and 8.5 ± 0.9 mCi at the end of irradiation on the two dose calibrators. All identified radionuclide contaminants decaying below 0.1% of the 75Se activity after 5 days post-irradiation. Wipe testing only identified radioactive contaminants present in activated titanium, with only 1.24 ± 0.01 × 10−7 mCi of 24Na detected 72 h post-irradiation, indicating that the integrity of the encapsulation was maintained.
Conclusions:
The SeCure design possesses the dosimetric, spectral, and physical properties necessary for a feasible high dose rate brachytherapy source. Next, manufacturing of a high-activity SeCure source will be pursued.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Background:
75Se (t1/2 ≈ 120 days, Eγ,avg ≈ 215 keV) offers advantages over 192Ir (t1/2 ≈ 74 days, Eγ,avg ≈ 360 keV) as a high dose rate brachytherapy source due to its lower gamma energy and longer half-life. Despite its widespread use in industrial gamma radiography, a 75Se brachytherapy source has yet to be manufactured.
Purpose:
A novel 75Se-based source design with a vanadium diselenide core, titled the SeCure source, was proposed. This study aimed to evaluate the feasibility of this source design for dosimetry and manufacturability purposes and to develop an activated prototype source.
Methods:
The source was modeled and integrated into the Monte Carlo-based treatment planning system RapidBrachyMCTPS, where its TG-43U1 parameters, photon spectrum, and broad beam first half-value layers (HVL1) and tenth-value layers (TVL1) in lead, tungsten, and concrete were calculated. A prototype source was manufactured, and the vanadium diselenide content of the capsule was verified with neutron radiography. The source was then activated to a nominal activity of 8.5 ± 0.9 mCi at the McMaster Nuclear Reactor. The activity was measured with two separate dose calibrators. Gamma spectroscopy was used to characterize any activated radioactive contaminants in the source, and wipe testing was performed to check for any leakage of 75Se from the encapsulation.
Results:
The SeCure source's TG-43U1 parameters were computed, showing that 2.056 ± 0.003 times the activity of 75Se is required relative to 192Ir to achieve the same dose rate in water at (1 cm, 90°). The mean spectral energy of the source is 214.695 ± 0.005 keV, resulting in reduced first half-value and tenth-value layers relative to 192Ir in attenuating materials. For example, the HVL1 was reduced from 2.795 ± 0.002 mm to 1.020 ± 0.001 mm in lead, from 2.049 ± 0.002 mm to 0.752 ± 0.001 mm in tungsten, and from 70.63 ± 0.04 mm to 61.37 ± 0.03 mm in concrete. The activated source achieved the desired activity, indicated as 9.2 ± 0.2 mCi and 8.5 ± 0.9 mCi at the end of irradiation on the two dose calibrators. All identified radionuclide contaminants decaying below 0.1% of the 75Se activity after 5 days post-irradiation. Wipe testing only identified radioactive contaminants present in activated titanium, with only 1.24 ± 0.01 × 10−7 mCi of 24Na detected 72 h post-irradiation, indicating that the integrity of the encapsulation was maintained.
Conclusions:
The SeCure design possesses the dosimetric, spectral, and physical properties necessary for a feasible high dose rate brachytherapy source. Next, manufacturing of a high-activity SeCure source will be pursued.
75Se (t1/2 ≈ 120 days, Eγ,avg ≈ 215 keV) offers advantages over 192Ir (t1/2 ≈ 74 days, Eγ,avg ≈ 360 keV) as a high dose rate brachytherapy source due to its lower gamma energy and longer half-life. Despite its widespread use in industrial gamma radiography, a 75Se brachytherapy source has yet to be manufactured.
Purpose:
A novel 75Se-based source design with a vanadium diselenide core, titled the SeCure source, was proposed. This study aimed to evaluate the feasibility of this source design for dosimetry and manufacturability purposes and to develop an activated prototype source.
Methods:
The source was modeled and integrated into the Monte Carlo-based treatment planning system RapidBrachyMCTPS, where its TG-43U1 parameters, photon spectrum, and broad beam first half-value layers (HVL1) and tenth-value layers (TVL1) in lead, tungsten, and concrete were calculated. A prototype source was manufactured, and the vanadium diselenide content of the capsule was verified with neutron radiography. The source was then activated to a nominal activity of 8.5 ± 0.9 mCi at the McMaster Nuclear Reactor. The activity was measured with two separate dose calibrators. Gamma spectroscopy was used to characterize any activated radioactive contaminants in the source, and wipe testing was performed to check for any leakage of 75Se from the encapsulation.
Results:
The SeCure source's TG-43U1 parameters were computed, showing that 2.056 ± 0.003 times the activity of 75Se is required relative to 192Ir to achieve the same dose rate in water at (1 cm, 90°). The mean spectral energy of the source is 214.695 ± 0.005 keV, resulting in reduced first half-value and tenth-value layers relative to 192Ir in attenuating materials. For example, the HVL1 was reduced from 2.795 ± 0.002 mm to 1.020 ± 0.001 mm in lead, from 2.049 ± 0.002 mm to 0.752 ± 0.001 mm in tungsten, and from 70.63 ± 0.04 mm to 61.37 ± 0.03 mm in concrete. The activated source achieved the desired activity, indicated as 9.2 ± 0.2 mCi and 8.5 ± 0.9 mCi at the end of irradiation on the two dose calibrators. All identified radionuclide contaminants decaying below 0.1% of the 75Se activity after 5 days post-irradiation. Wipe testing only identified radioactive contaminants present in activated titanium, with only 1.24 ± 0.01 × 10−7 mCi of 24Na detected 72 h post-irradiation, indicating that the integrity of the encapsulation was maintained.
Conclusions:
The SeCure design possesses the dosimetric, spectral, and physical properties necessary for a feasible high dose rate brachytherapy source. Next, manufacturing of a high-activity SeCure source will be pursued.
Dumančić, Mirta; Kalinowski, Jonathan; Diaz-Martinez, Victor D; Li, Joanna; Behmand, Behnaz; DeCunha, Joseph M; Enger, Shirin A
Microdosimetry calculations in situ for clinically relevant photon sources and their correlation with the early DNA damage response Journal Article
In: Medical Physics, vol. 52, iss. 7, no. e17979, 2025, ISSN: 2473-4209.
@article{nokey,
title = {Microdosimetry calculations in situ for clinically relevant photon sources and their correlation with the early DNA damage response},
author = {Mirta Dumančić and Jonathan Kalinowski and Victor D Diaz-Martinez and Joanna Li and Behnaz Behmand and Joseph M DeCunha and Shirin A Enger},
url = {https://aapm.onlinelibrary.wiley.com/doi/10.1002/mp.17979},
doi = {10.1002/mp.17979},
issn = {2473-4209},
year = {2025},
date = {2025-07-15},
urldate = {2025-07-15},
journal = {Medical Physics},
volume = {52},
number = {e17979},
issue = {7},
abstract = {Background:
Radiobiological data suggests variations in relative biological effectiveness (RBE) between clinically used photon-based sources. A microdosimetric formalism using Monte Carlo (MC) methods can mechanistically describe the photon RBE. Experimentally derived RBE based on DNA double-strand breaks (RBEDSB) has been shown to scale with the microdosimetry quantity dose-mean lineal energy (yD).
Purpose:
To calculate microdosimetric spectra for clinically relevant photon sources, spanning from soft x-rays produced by a 50 kVp x-ray source through various brachytherapy sources up to a 6 MV medical linac. Furthermore, we investigated the correlation between RBEDSB and yD of different photon sources.
Methods:
Photon sources simulated include low-energy x-rays (50 kVp), orthovoltage x-rays (225 kVp), high-dose-rate brachytherapy sources (75Se, 192Ir and 60Co), and a 6 MV medical linac. Secondary electron spectra at the cellular level were calculated for in vitro cell irradiation setups using Geant4 MC-based packages, RapidBrachyMCTPS and RapidExternalBeam. The obtained spectra were used in MicroDose, a microdosimetry simulation software, to obtain microdosimetric quantities, including single-event lineal energy (y) and specific energy (z) spectra, and dose-mean and frequency-mean quantities (yF, yD, zsF, zsD). Uniform spherical targets (1–14 μm radius) and realistic HeLa and PC3 cell nucleus models were simulated using cell size data obtained from literature and nuclei size data from confocal microscopy imaging. Radiobiological experiments using γH2AX foci quantified DNA double-strand breaks for HeLa and PC3 cells after irradiations with 50 and 225 kVp, 192Ir, and 6 MV linac, and RBEDSB was determined using 225 kVp as the reference.
Results:
The calculated yD (yF) is within the 3.5–1.2 keV/μm range (1.8–0.2 keV/μm) for 1 μm simulated target size between the lowest energy 50 kVp x-ray source and the highest energy 6 MV linac source, respectively. For the HeLa and PC3 cell nuclei models based on microscopy data, yD (yF) spans from 1.6 to 0.6 keV/μm (0.7 to 0.2 keV/μm). When compared between different target sizes, yD (yF) ranges from 3.5 to 1.0 (1.8–0.4) keV/μm between 1 and 10 μm radius targets for the 50 kVp x-ray source. A smaller change is observed for 6 MV linac, ranging from 1.2 to 0.5 keV/μm and 0.23 to 0.22 keV/μm for yD and yF, respectively. For the simulated 75Se source currently under investigation, the calculated yD values are 11%–24% higher relative to those of 192Ir in the range of target sizes between 1 and 14 μm in radius. RBEDSB for HeLa cells was 1.4 ± 0.7 for 50 kVp x-rays, 0.5 ± 0.2 for 192Ir, and 0.7 ± 0.4 for 6 MV linac irradiations. For PC3 cells, RBEDSB was 1.3 ± 0.6, 0.8 ± 0.4 and 0.5 ± 0.3 for 50 kVp, 192Ir and 6 MV linac, respectively. Measured RBEDSB values are consistent with yD ratios of the corresponding photon sources for HeLa and PC3 nucleus models.
Conclusions:
Microdosimetric spectra strongly depend on the simulated energy of photon sources and target size, with yD and zsD decreasing by a factor of ≈2–3 between diagnostic 50 kVp and 6 MV therapeutic x-rays for target sizes from 1–14 μm in radius. The early damage RBEDSB indicates this stochastic change in energy density between various photon sources as the yields of γH2AX foci per nucleus scale with yD of the source.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Background:
Radiobiological data suggests variations in relative biological effectiveness (RBE) between clinically used photon-based sources. A microdosimetric formalism using Monte Carlo (MC) methods can mechanistically describe the photon RBE. Experimentally derived RBE based on DNA double-strand breaks (RBEDSB) has been shown to scale with the microdosimetry quantity dose-mean lineal energy (yD).
Purpose:
To calculate microdosimetric spectra for clinically relevant photon sources, spanning from soft x-rays produced by a 50 kVp x-ray source through various brachytherapy sources up to a 6 MV medical linac. Furthermore, we investigated the correlation between RBEDSB and yD of different photon sources.
Methods:
Photon sources simulated include low-energy x-rays (50 kVp), orthovoltage x-rays (225 kVp), high-dose-rate brachytherapy sources (75Se, 192Ir and 60Co), and a 6 MV medical linac. Secondary electron spectra at the cellular level were calculated for in vitro cell irradiation setups using Geant4 MC-based packages, RapidBrachyMCTPS and RapidExternalBeam. The obtained spectra were used in MicroDose, a microdosimetry simulation software, to obtain microdosimetric quantities, including single-event lineal energy (y) and specific energy (z) spectra, and dose-mean and frequency-mean quantities (yF, yD, zsF, zsD). Uniform spherical targets (1–14 μm radius) and realistic HeLa and PC3 cell nucleus models were simulated using cell size data obtained from literature and nuclei size data from confocal microscopy imaging. Radiobiological experiments using γH2AX foci quantified DNA double-strand breaks for HeLa and PC3 cells after irradiations with 50 and 225 kVp, 192Ir, and 6 MV linac, and RBEDSB was determined using 225 kVp as the reference.
Results:
The calculated yD (yF) is within the 3.5–1.2 keV/μm range (1.8–0.2 keV/μm) for 1 μm simulated target size between the lowest energy 50 kVp x-ray source and the highest energy 6 MV linac source, respectively. For the HeLa and PC3 cell nuclei models based on microscopy data, yD (yF) spans from 1.6 to 0.6 keV/μm (0.7 to 0.2 keV/μm). When compared between different target sizes, yD (yF) ranges from 3.5 to 1.0 (1.8–0.4) keV/μm between 1 and 10 μm radius targets for the 50 kVp x-ray source. A smaller change is observed for 6 MV linac, ranging from 1.2 to 0.5 keV/μm and 0.23 to 0.22 keV/μm for yD and yF, respectively. For the simulated 75Se source currently under investigation, the calculated yD values are 11%–24% higher relative to those of 192Ir in the range of target sizes between 1 and 14 μm in radius. RBEDSB for HeLa cells was 1.4 ± 0.7 for 50 kVp x-rays, 0.5 ± 0.2 for 192Ir, and 0.7 ± 0.4 for 6 MV linac irradiations. For PC3 cells, RBEDSB was 1.3 ± 0.6, 0.8 ± 0.4 and 0.5 ± 0.3 for 50 kVp, 192Ir and 6 MV linac, respectively. Measured RBEDSB values are consistent with yD ratios of the corresponding photon sources for HeLa and PC3 nucleus models.
Conclusions:
Microdosimetric spectra strongly depend on the simulated energy of photon sources and target size, with yD and zsD decreasing by a factor of ≈2–3 between diagnostic 50 kVp and 6 MV therapeutic x-rays for target sizes from 1–14 μm in radius. The early damage RBEDSB indicates this stochastic change in energy density between various photon sources as the yields of γH2AX foci per nucleus scale with yD of the source.
Radiobiological data suggests variations in relative biological effectiveness (RBE) between clinically used photon-based sources. A microdosimetric formalism using Monte Carlo (MC) methods can mechanistically describe the photon RBE. Experimentally derived RBE based on DNA double-strand breaks (RBEDSB) has been shown to scale with the microdosimetry quantity dose-mean lineal energy (yD).
Purpose:
To calculate microdosimetric spectra for clinically relevant photon sources, spanning from soft x-rays produced by a 50 kVp x-ray source through various brachytherapy sources up to a 6 MV medical linac. Furthermore, we investigated the correlation between RBEDSB and yD of different photon sources.
Methods:
Photon sources simulated include low-energy x-rays (50 kVp), orthovoltage x-rays (225 kVp), high-dose-rate brachytherapy sources (75Se, 192Ir and 60Co), and a 6 MV medical linac. Secondary electron spectra at the cellular level were calculated for in vitro cell irradiation setups using Geant4 MC-based packages, RapidBrachyMCTPS and RapidExternalBeam. The obtained spectra were used in MicroDose, a microdosimetry simulation software, to obtain microdosimetric quantities, including single-event lineal energy (y) and specific energy (z) spectra, and dose-mean and frequency-mean quantities (yF, yD, zsF, zsD). Uniform spherical targets (1–14 μm radius) and realistic HeLa and PC3 cell nucleus models were simulated using cell size data obtained from literature and nuclei size data from confocal microscopy imaging. Radiobiological experiments using γH2AX foci quantified DNA double-strand breaks for HeLa and PC3 cells after irradiations with 50 and 225 kVp, 192Ir, and 6 MV linac, and RBEDSB was determined using 225 kVp as the reference.
Results:
The calculated yD (yF) is within the 3.5–1.2 keV/μm range (1.8–0.2 keV/μm) for 1 μm simulated target size between the lowest energy 50 kVp x-ray source and the highest energy 6 MV linac source, respectively. For the HeLa and PC3 cell nuclei models based on microscopy data, yD (yF) spans from 1.6 to 0.6 keV/μm (0.7 to 0.2 keV/μm). When compared between different target sizes, yD (yF) ranges from 3.5 to 1.0 (1.8–0.4) keV/μm between 1 and 10 μm radius targets for the 50 kVp x-ray source. A smaller change is observed for 6 MV linac, ranging from 1.2 to 0.5 keV/μm and 0.23 to 0.22 keV/μm for yD and yF, respectively. For the simulated 75Se source currently under investigation, the calculated yD values are 11%–24% higher relative to those of 192Ir in the range of target sizes between 1 and 14 μm in radius. RBEDSB for HeLa cells was 1.4 ± 0.7 for 50 kVp x-rays, 0.5 ± 0.2 for 192Ir, and 0.7 ± 0.4 for 6 MV linac irradiations. For PC3 cells, RBEDSB was 1.3 ± 0.6, 0.8 ± 0.4 and 0.5 ± 0.3 for 50 kVp, 192Ir and 6 MV linac, respectively. Measured RBEDSB values are consistent with yD ratios of the corresponding photon sources for HeLa and PC3 nucleus models.
Conclusions:
Microdosimetric spectra strongly depend on the simulated energy of photon sources and target size, with yD and zsD decreasing by a factor of ≈2–3 between diagnostic 50 kVp and 6 MV therapeutic x-rays for target sizes from 1–14 μm in radius. The early damage RBEDSB indicates this stochastic change in energy density between various photon sources as the yields of γH2AX foci per nucleus scale with yD of the source.
Morén, Björn; Thibodeau-Antonacci, Alana; Kalinowski, Jonathan; Enger, Shirin A.
Dosimetric impact of positional uncertainties and a robust optimization approach for rectal intensity-modulated brachytherapy Journal Article
In: Medical Physics, vol. 52, iss. 6, pp. 3528–3540, 2025, ISSN: 0094-2405.
@article{nokey,
title = {Dosimetric impact of positional uncertainties and a robust optimization approach for rectal intensity-modulated brachytherapy},
author = {Björn Morén and Alana Thibodeau-Antonacci and Jonathan Kalinowski and Shirin A. Enger},
url = {https://aapm.onlinelibrary.wiley.com/doi/10.1002/mp.17800},
doi = {10.1002/mp.17800},
issn = {0094-2405},
year = {2025},
date = {2025-03-31},
journal = {Medical Physics},
volume = {52},
issue = {6},
pages = {3528–3540},
abstract = {Background: Intensity-modulated brachytherapy (IMBT) employs rotating high-Z shields during treatment to decrease radiation in certain directions and conform the dose distribution to the target volume. Prototypes for dynamic IMBT have been proposed for prostate, cervical, and rectal cancer.
Purpose: We considered two shielded applicators for IMBT rectal cancer treatment and investigated how rotational uncertainties in the shield angle and translational uncertainties in the source position affect plan evaluation criteria.
Methods: The effect of rotational errors of 3∘ , 5∘ and 10∘ , and translational errors of 1, 2 and 3 mm on evaluation criteria were investigated for shields with
180
∘
and
90
∘
emission windows. Further, a robust optimization approach based on quadratic penalties that includes scenarios with errors was proposed. The extent to which dosimetric effects of positional errors can be mitigated with this model was evaluated compared to a quadratic penalty model without scenarios with errors. A retrospective rectal cancer data set of ten patients was included in this study. Treatment planning was performed using the Monte Carlo-based treatment planning system, RapidBrachyMCTPS.
Results: For the largest investigated rotational error of
±
10
∘
, the clinical target volume
D
90
remained, on average, within
5
%
of the result without error, while the contralateral healthy rectal wall experienced an increase in the mean
D
0.1
c
c
,
D
2
c
c
, and
D
50
of
26
%
,
9
%
, and
1
%
for the
180
∘
shield and of 32%, 9%, and 2% for the
90
∘
shield. For translational errors of
±
2
mm, there were increases in dosimetric indices for both the superior (sup) and inferior (inf) dose spill regions. Specifically, for the
180
∘
shield, the
D
0.1
c
c
,
D
2
c
c
, and
D
50
increased by
13
%
,
11
%
, and
10
%
, respectively, for the sup region, and by
26
%
,
15
%
, and
11
%
, respectively, for the inf region. Similar results were obtained with the
90
∘
shield. Overall, the robust and traditional models had similar results. However, the number of active dwell positions obtained with the robust model was larger, and the longest dwell time was shorter.
Conclusions: We have quantified the effect of rotational shield and translational source errors of various magnitudes on evaluation criteria for rectal IMBT. The robust optimization approach was generally not able to mitigate positional errors. However, it resulted in more homogeneous dwell times, which can be beneficial in conventional high-dose-rate brachytherapy to avoid hot spots around specific dwell positions.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Background: Intensity-modulated brachytherapy (IMBT) employs rotating high-Z shields during treatment to decrease radiation in certain directions and conform the dose distribution to the target volume. Prototypes for dynamic IMBT have been proposed for prostate, cervical, and rectal cancer.
Purpose: We considered two shielded applicators for IMBT rectal cancer treatment and investigated how rotational uncertainties in the shield angle and translational uncertainties in the source position affect plan evaluation criteria.
Methods: The effect of rotational errors of 3∘ , 5∘ and 10∘ , and translational errors of 1, 2 and 3 mm on evaluation criteria were investigated for shields with
180
∘
and
90
∘
emission windows. Further, a robust optimization approach based on quadratic penalties that includes scenarios with errors was proposed. The extent to which dosimetric effects of positional errors can be mitigated with this model was evaluated compared to a quadratic penalty model without scenarios with errors. A retrospective rectal cancer data set of ten patients was included in this study. Treatment planning was performed using the Monte Carlo-based treatment planning system, RapidBrachyMCTPS.
Results: For the largest investigated rotational error of
±
10
∘
, the clinical target volume
D
90
remained, on average, within
5
%
of the result without error, while the contralateral healthy rectal wall experienced an increase in the mean
D
0.1
c
c
,
D
2
c
c
, and
D
50
of
26
%
,
9
%
, and
1
%
for the
180
∘
shield and of 32%, 9%, and 2% for the
90
∘
shield. For translational errors of
±
2
mm, there were increases in dosimetric indices for both the superior (sup) and inferior (inf) dose spill regions. Specifically, for the
180
∘
shield, the
D
0.1
c
c
,
D
2
c
c
, and
D
50
increased by
13
%
,
11
%
, and
10
%
, respectively, for the sup region, and by
26
%
,
15
%
, and
11
%
, respectively, for the inf region. Similar results were obtained with the
90
∘
shield. Overall, the robust and traditional models had similar results. However, the number of active dwell positions obtained with the robust model was larger, and the longest dwell time was shorter.
Conclusions: We have quantified the effect of rotational shield and translational source errors of various magnitudes on evaluation criteria for rectal IMBT. The robust optimization approach was generally not able to mitigate positional errors. However, it resulted in more homogeneous dwell times, which can be beneficial in conventional high-dose-rate brachytherapy to avoid hot spots around specific dwell positions.
Purpose: We considered two shielded applicators for IMBT rectal cancer treatment and investigated how rotational uncertainties in the shield angle and translational uncertainties in the source position affect plan evaluation criteria.
Methods: The effect of rotational errors of 3∘ , 5∘ and 10∘ , and translational errors of 1, 2 and 3 mm on evaluation criteria were investigated for shields with
180
∘
and
90
∘
emission windows. Further, a robust optimization approach based on quadratic penalties that includes scenarios with errors was proposed. The extent to which dosimetric effects of positional errors can be mitigated with this model was evaluated compared to a quadratic penalty model without scenarios with errors. A retrospective rectal cancer data set of ten patients was included in this study. Treatment planning was performed using the Monte Carlo-based treatment planning system, RapidBrachyMCTPS.
Results: For the largest investigated rotational error of
±
10
∘
, the clinical target volume
D
90
remained, on average, within
5
%
of the result without error, while the contralateral healthy rectal wall experienced an increase in the mean
D
0.1
c
c
,
D
2
c
c
, and
D
50
of
26
%
,
9
%
, and
1
%
for the
180
∘
shield and of 32%, 9%, and 2% for the
90
∘
shield. For translational errors of
±
2
mm, there were increases in dosimetric indices for both the superior (sup) and inferior (inf) dose spill regions. Specifically, for the
180
∘
shield, the
D
0.1
c
c
,
D
2
c
c
, and
D
50
increased by
13
%
,
11
%
, and
10
%
, respectively, for the sup region, and by
26
%
,
15
%
, and
11
%
, respectively, for the inf region. Similar results were obtained with the
90
∘
shield. Overall, the robust and traditional models had similar results. However, the number of active dwell positions obtained with the robust model was larger, and the longest dwell time was shorter.
Conclusions: We have quantified the effect of rotational shield and translational source errors of various magnitudes on evaluation criteria for rectal IMBT. The robust optimization approach was generally not able to mitigate positional errors. However, it resulted in more homogeneous dwell times, which can be beneficial in conventional high-dose-rate brachytherapy to avoid hot spots around specific dwell positions.
2024
Rahbaran, Maryam; Kalinowski, Jonathan; DeCunha, Joseph M.; Croce, Kevin J.; Bergmark, Brian A.; Tsui, James M. G.; Devlin, Phillip M.; Enger, Shirin A.
RapidBrachyIVBT: A dosimetry software for patient-specific intravascular brachytherapy dose calculations on optical coherence tomography images Journal Article
In: Medical Physics, vol. 52, iss. 2, pp. 1256-1267, 2024, ISSN: 2473-4209.
@article{Rahbaran2025-gg,
title = {RapidBrachyIVBT: A dosimetry software for patient-specific intravascular brachytherapy dose calculations on optical coherence tomography images},
author = {Maryam Rahbaran and Jonathan Kalinowski and Joseph M. DeCunha and Kevin J. Croce and Brian A. Bergmark and James M. G. Tsui and Phillip M. Devlin and Shirin A. Enger},
doi = {https://doi.org/10.1002/mp.17462},
issn = {2473-4209},
year = {2024},
date = {2024-11-19},
journal = {Medical Physics},
volume = {52},
issue = {2},
pages = {1256-1267},
abstract = {Background
Large reported variability in the material composition and geometrical components of the Xoft electronic high dose rate brachytherapy causes inter-source discrepancy in the source output. This variability is due to the manual manufacturing and assembly of the sources.
Purpose
This study aimed to develop a dosimetry software tool called E-Brachy to characterize the Xoft source and quantify the discrepancies in its photon spectrum and dosimetric properties.
Methods
E-Brachy is based on the Geant4 Monte Carlo toolkit and consists of two parts. In part one, the geometry and material composition for the source received in the computer-aided design format from the vendor were converted to the geometry description markup language format using the GUIMesh Python tool and integrated into the E-Brachy software. There was a large variation in material composition and thickness for some of the tube components. The simulation started from electrons and resulted in x-ray generations in the anode region. Multithreading, a track length estimation, and the uniform bremsstrahlung splitting variance reduction techniques were used to decrease the simulation time and increase the x-ray production. The photon energy, position, and momentum were saved into a phase space file as the photon exited the source, but before interacting with the external environment. The obtained x-ray energy spectrum was compared with measurements from the National Institute of Standards and Technology (NIST). In part two, by sampling from the generated photons, the dose rates and dosimetric parameters according to the TG-43 protocol were calculated for model S7500 and compared to the ones previously calculated for model S700 source, which were deemed identical by the manufacturer.
Results
The material composition that resulted in the most similar spectrum as the measured NIST spectrum with Pearson's correlation coefficient of 0.99 and a calculated Euclidean difference of
keV was chosen for further dosimetric analysis of the model S7500 source. Characteristic peaks showed the presence of tungsten, yttrium, and silver in the source components. Differences in dose rates between the two source models surpassed 20% for polar angles
, reaching a peak at
cm and
. The differences in the radial dose function values were within 5%. The relative difference in percentage between the anisotropy function values of the two models was closer to 0 for smaller
values, but at higher polar angles, they increased to 300%.
Conclusions
A software package called E-Brachy was successfully developed for the characterization and dosimetry of Xoft electronic brachytherapy sources. E-Brachy can be combined with spectral measurements to investigate the inter- and intra-source variability. The software package was tested by comparing the simulated spectra from the S7500 Xoft source model with NIST measurements and its TG-43 parameters with the S700 model. The TG-43 parameters between the two sources significantly exceed the recommendations of TG-56.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Background
Large reported variability in the material composition and geometrical components of the Xoft electronic high dose rate brachytherapy causes inter-source discrepancy in the source output. This variability is due to the manual manufacturing and assembly of the sources.
Purpose
This study aimed to develop a dosimetry software tool called E-Brachy to characterize the Xoft source and quantify the discrepancies in its photon spectrum and dosimetric properties.
Methods
E-Brachy is based on the Geant4 Monte Carlo toolkit and consists of two parts. In part one, the geometry and material composition for the source received in the computer-aided design format from the vendor were converted to the geometry description markup language format using the GUIMesh Python tool and integrated into the E-Brachy software. There was a large variation in material composition and thickness for some of the tube components. The simulation started from electrons and resulted in x-ray generations in the anode region. Multithreading, a track length estimation, and the uniform bremsstrahlung splitting variance reduction techniques were used to decrease the simulation time and increase the x-ray production. The photon energy, position, and momentum were saved into a phase space file as the photon exited the source, but before interacting with the external environment. The obtained x-ray energy spectrum was compared with measurements from the National Institute of Standards and Technology (NIST). In part two, by sampling from the generated photons, the dose rates and dosimetric parameters according to the TG-43 protocol were calculated for model S7500 and compared to the ones previously calculated for model S700 source, which were deemed identical by the manufacturer.
Results
The material composition that resulted in the most similar spectrum as the measured NIST spectrum with Pearson's correlation coefficient of 0.99 and a calculated Euclidean difference of
keV was chosen for further dosimetric analysis of the model S7500 source. Characteristic peaks showed the presence of tungsten, yttrium, and silver in the source components. Differences in dose rates between the two source models surpassed 20% for polar angles
, reaching a peak at
cm and
. The differences in the radial dose function values were within 5%. The relative difference in percentage between the anisotropy function values of the two models was closer to 0 for smaller
values, but at higher polar angles, they increased to 300%.
Conclusions
A software package called E-Brachy was successfully developed for the characterization and dosimetry of Xoft electronic brachytherapy sources. E-Brachy can be combined with spectral measurements to investigate the inter- and intra-source variability. The software package was tested by comparing the simulated spectra from the S7500 Xoft source model with NIST measurements and its TG-43 parameters with the S700 model. The TG-43 parameters between the two sources significantly exceed the recommendations of TG-56.
Large reported variability in the material composition and geometrical components of the Xoft electronic high dose rate brachytherapy causes inter-source discrepancy in the source output. This variability is due to the manual manufacturing and assembly of the sources.
Purpose
This study aimed to develop a dosimetry software tool called E-Brachy to characterize the Xoft source and quantify the discrepancies in its photon spectrum and dosimetric properties.
Methods
E-Brachy is based on the Geant4 Monte Carlo toolkit and consists of two parts. In part one, the geometry and material composition for the source received in the computer-aided design format from the vendor were converted to the geometry description markup language format using the GUIMesh Python tool and integrated into the E-Brachy software. There was a large variation in material composition and thickness for some of the tube components. The simulation started from electrons and resulted in x-ray generations in the anode region. Multithreading, a track length estimation, and the uniform bremsstrahlung splitting variance reduction techniques were used to decrease the simulation time and increase the x-ray production. The photon energy, position, and momentum were saved into a phase space file as the photon exited the source, but before interacting with the external environment. The obtained x-ray energy spectrum was compared with measurements from the National Institute of Standards and Technology (NIST). In part two, by sampling from the generated photons, the dose rates and dosimetric parameters according to the TG-43 protocol were calculated for model S7500 and compared to the ones previously calculated for model S700 source, which were deemed identical by the manufacturer.
Results
The material composition that resulted in the most similar spectrum as the measured NIST spectrum with Pearson's correlation coefficient of 0.99 and a calculated Euclidean difference of
keV was chosen for further dosimetric analysis of the model S7500 source. Characteristic peaks showed the presence of tungsten, yttrium, and silver in the source components. Differences in dose rates between the two source models surpassed 20% for polar angles
, reaching a peak at
cm and
. The differences in the radial dose function values were within 5%. The relative difference in percentage between the anisotropy function values of the two models was closer to 0 for smaller
values, but at higher polar angles, they increased to 300%.
Conclusions
A software package called E-Brachy was successfully developed for the characterization and dosimetry of Xoft electronic brachytherapy sources. E-Brachy can be combined with spectral measurements to investigate the inter- and intra-source variability. The software package was tested by comparing the simulated spectra from the S7500 Xoft source model with NIST measurements and its TG-43 parameters with the S700 model. The TG-43 parameters between the two sources significantly exceed the recommendations of TG-56.
Esmaelbeigi, Azin; Kalinowski, Jonathan; Tomic, Nada; Rivard, Mark J.; Vuong, Te; Devic, Slobodan; Enger, Shirin A.
E-Brachy: New dosimetry package for electronic brachytherapy sources Journal Article
In: Medical Physics, vol. 52, iss. 1, pp. 662–672, 2024, ISSN: 2473-4209.
@article{Esmaelbeigi2025-ww,
title = {E-Brachy: New dosimetry package for electronic brachytherapy sources},
author = {Azin Esmaelbeigi and Jonathan Kalinowski and Nada Tomic and Mark J. Rivard and Te Vuong and Slobodan Devic and Shirin A. Enger},
url = {https://aapm.onlinelibrary.wiley.com/doi/10.1002/mp.17462},
doi = {10.1002/mp.17462},
issn = {2473-4209},
year = {2024},
date = {2024-10-26},
urldate = {2024-10-26},
journal = {Medical Physics},
volume = {52},
issue = {1},
pages = {662–672},
abstract = {Background: Large reported variability in the material composition and geometrical components of the Xoft electronic high dose rate brachytherapy causes inter-source discrepancy in the source output. This variability is due to the manual manufacturing and assembly of the sources.
Purpose: This study aimed to develop a dosimetry software tool called E-Brachy to characterize the Xoft source and quantify the discrepancies in its photon spectrum and dosimetric properties.
Methods: E-Brachy is based on the Geant4 Monte Carlo toolkit and consists of two parts. In part one, the geometry and material composition for the source received in the computer-aided design format from the vendor were converted to the geometry description markup language format using the GUIMesh Python tool and integrated into the E-Brachy software. There was a large variation in material composition and thickness for some of the tube components. The simulation started from electrons and resulted in x-ray generations in the anode region. Multithreading, a track length estimation, and the uniform bremsstrahlung splitting variance reduction techniques were used to decrease the simulation time and increase the x-ray production. The photon energy, position, and momentum were saved into a phase space file as the photon exited the source, but before interacting with the external environment. The obtained x-ray energy spectrum was compared with measurements from the National Institute of Standards and Technology (NIST). In part two, by sampling from the generated photons, the dose rates and dosimetric parameters according to the TG-43 protocol were calculated for model S7500 and compared to the ones previously calculated for model S700 source, which were deemed identical by the manufacturer.
Results: The material composition that resulted in the most similar spectrum as the measured NIST spectrum with Pearson's correlation coefficient of 0.99 and a calculated Euclidean difference of
0.061
±
0.001
keV was chosen for further dosimetric analysis of the model S7500 source. Characteristic peaks showed the presence of tungsten, yttrium, and silver in the source components. Differences in dose rates between the two source models surpassed 20% for polar angles
θ
≥
150
∘
, reaching a peak at
r
=
3
cm and
θ
=
175
∘
. The differences in the radial dose function values were within 5%. The relative difference in percentage between the anisotropy function values of the two models was closer to 0 for smaller
θ
values, but at higher polar angles, they increased to 300%.
Conclusions: A software package called E-Brachy was successfully developed for the characterization and dosimetry of Xoft electronic brachytherapy sources. E-Brachy can be combined with spectral measurements to investigate the inter- and intra-source variability. The software package was tested by comparing the simulated spectra from the S7500 Xoft source model with NIST measurements and its TG-43 parameters with the S700 model. The TG-43 parameters between the two sources significantly exceed the recommendations of TG-56.
Keywords: dosimetry; electronic brachytherapy; monte carlo simulations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Background: Large reported variability in the material composition and geometrical components of the Xoft electronic high dose rate brachytherapy causes inter-source discrepancy in the source output. This variability is due to the manual manufacturing and assembly of the sources.
Purpose: This study aimed to develop a dosimetry software tool called E-Brachy to characterize the Xoft source and quantify the discrepancies in its photon spectrum and dosimetric properties.
Methods: E-Brachy is based on the Geant4 Monte Carlo toolkit and consists of two parts. In part one, the geometry and material composition for the source received in the computer-aided design format from the vendor were converted to the geometry description markup language format using the GUIMesh Python tool and integrated into the E-Brachy software. There was a large variation in material composition and thickness for some of the tube components. The simulation started from electrons and resulted in x-ray generations in the anode region. Multithreading, a track length estimation, and the uniform bremsstrahlung splitting variance reduction techniques were used to decrease the simulation time and increase the x-ray production. The photon energy, position, and momentum were saved into a phase space file as the photon exited the source, but before interacting with the external environment. The obtained x-ray energy spectrum was compared with measurements from the National Institute of Standards and Technology (NIST). In part two, by sampling from the generated photons, the dose rates and dosimetric parameters according to the TG-43 protocol were calculated for model S7500 and compared to the ones previously calculated for model S700 source, which were deemed identical by the manufacturer.
Results: The material composition that resulted in the most similar spectrum as the measured NIST spectrum with Pearson's correlation coefficient of 0.99 and a calculated Euclidean difference of
0.061
±
0.001
keV was chosen for further dosimetric analysis of the model S7500 source. Characteristic peaks showed the presence of tungsten, yttrium, and silver in the source components. Differences in dose rates between the two source models surpassed 20% for polar angles
θ
≥
150
∘
, reaching a peak at
r
=
3
cm and
θ
=
175
∘
. The differences in the radial dose function values were within 5%. The relative difference in percentage between the anisotropy function values of the two models was closer to 0 for smaller
θ
values, but at higher polar angles, they increased to 300%.
Conclusions: A software package called E-Brachy was successfully developed for the characterization and dosimetry of Xoft electronic brachytherapy sources. E-Brachy can be combined with spectral measurements to investigate the inter- and intra-source variability. The software package was tested by comparing the simulated spectra from the S7500 Xoft source model with NIST measurements and its TG-43 parameters with the S700 model. The TG-43 parameters between the two sources significantly exceed the recommendations of TG-56.
Keywords: dosimetry; electronic brachytherapy; monte carlo simulations.
Purpose: This study aimed to develop a dosimetry software tool called E-Brachy to characterize the Xoft source and quantify the discrepancies in its photon spectrum and dosimetric properties.
Methods: E-Brachy is based on the Geant4 Monte Carlo toolkit and consists of two parts. In part one, the geometry and material composition for the source received in the computer-aided design format from the vendor were converted to the geometry description markup language format using the GUIMesh Python tool and integrated into the E-Brachy software. There was a large variation in material composition and thickness for some of the tube components. The simulation started from electrons and resulted in x-ray generations in the anode region. Multithreading, a track length estimation, and the uniform bremsstrahlung splitting variance reduction techniques were used to decrease the simulation time and increase the x-ray production. The photon energy, position, and momentum were saved into a phase space file as the photon exited the source, but before interacting with the external environment. The obtained x-ray energy spectrum was compared with measurements from the National Institute of Standards and Technology (NIST). In part two, by sampling from the generated photons, the dose rates and dosimetric parameters according to the TG-43 protocol were calculated for model S7500 and compared to the ones previously calculated for model S700 source, which were deemed identical by the manufacturer.
Results: The material composition that resulted in the most similar spectrum as the measured NIST spectrum with Pearson's correlation coefficient of 0.99 and a calculated Euclidean difference of
0.061
±
0.001
keV was chosen for further dosimetric analysis of the model S7500 source. Characteristic peaks showed the presence of tungsten, yttrium, and silver in the source components. Differences in dose rates between the two source models surpassed 20% for polar angles
θ
≥
150
∘
, reaching a peak at
r
=
3
cm and
θ
=
175
∘
. The differences in the radial dose function values were within 5%. The relative difference in percentage between the anisotropy function values of the two models was closer to 0 for smaller
θ
values, but at higher polar angles, they increased to 300%.
Conclusions: A software package called E-Brachy was successfully developed for the characterization and dosimetry of Xoft electronic brachytherapy sources. E-Brachy can be combined with spectral measurements to investigate the inter- and intra-source variability. The software package was tested by comparing the simulated spectra from the S7500 Xoft source model with NIST measurements and its TG-43 parameters with the S700 model. The TG-43 parameters between the two sources significantly exceed the recommendations of TG-56.
Keywords: dosimetry; electronic brachytherapy; monte carlo simulations.
Kalinowski, Jonathan; Enger, Shirin A
RapidBrachyTG43: A Geant4-based TG-43 parameter and dose calculation module for brachytherapy dosimetry Journal Article
In: Medical Physics, vol. 51, no. 5, pp. 3746–757, 2024.
@article{kalinowski2024rapidbrachytg43,
title = {RapidBrachyTG43: A Geant4-based TG-43 parameter and dose calculation module for brachytherapy dosimetry},
author = {Jonathan Kalinowski and Shirin A Enger},
doi = {10.1002/mp.16948},
year = {2024},
date = {2024-01-01},
urldate = {2024-01-01},
journal = {Medical Physics},
volume = {51},
number = {5},
pages = {3746–757},
publisher = {Wiley Online Library},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
2023
Rahbaran, Maryam; Kalinowski, Jonathan; DeCunha, Joseph; Croce, Kevin; Bergmark, Brian; Devlin, Philip; Tsui, James; Enger, Shirin A.
Development Of a Novel Dosimetry Software for Patient-specific Intravascular Brachytherapy Treatment Planning on Optical Coherence Tomography Images Presentation
23.09.2023, (COMP-CARO 2023 Joint Scientific Meeting).
@misc{nokey,
title = {Development Of a Novel Dosimetry Software for Patient-specific Intravascular Brachytherapy Treatment Planning on Optical Coherence Tomography Images},
author = {Maryam Rahbaran and Jonathan Kalinowski and Joseph DeCunha and Kevin Croce and Brian Bergmark and Philip Devlin and James Tsui and Shirin A. Enger},
year = {2023},
date = {2023-09-23},
note = {COMP-CARO 2023 Joint Scientific Meeting},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
Rahbaran, Maryam; Kalinowski, Jonathan; Tsui, James; DeCunha, Joseph; Croce, Kevin; Bergmark, Brian; Devlin, Philip; Enger, Shirin A.
Development Of a Novel Dosimetry Software for Patient-specific Intravascular Brachytherapy Treatment Planning on Optical Coherence Tomography Images Presentation
22.06.2023, (2023 American Brachytherapy Society (ABS) Annual Meeting, Vancouver, Canada).
@misc{nokey,
title = {Development Of a Novel Dosimetry Software for Patient-specific Intravascular Brachytherapy Treatment Planning on Optical Coherence Tomography Images},
author = {Maryam Rahbaran and Jonathan Kalinowski and James Tsui and Joseph DeCunha and Kevin Croce and Brian Bergmark and Philip Devlin and Shirin A. Enger},
year = {2023},
date = {2023-06-22},
urldate = {2023-06-22},
note = {2023 American Brachytherapy Society (ABS) Annual Meeting, Vancouver, Canada},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
2022
Kalinowski, Jonathan
McGill Faculty of Medicine and Health Sciences Internal Studentship award
2022.
@award{nokey,
title = {McGill Faculty of Medicine and Health Sciences Internal Studentship},
author = {Jonathan Kalinowski},
url = {https://www.mcgill.ca/medhealthsci-gradstudies/funding-opportunities/graduate-students/internal-studentships},
year = {2022},
date = {2022-08-15},
urldate = {2022-08-15},
organization = {McGill University Faculty of Medicine and Health Sciences},
abstract = {Internal Studentships are open to highly qualified Faculty of Medicine graduate students who are registered full-time in a research training program (Thesis) leading to an M.Sc or PhD degree.
},
keywords = {},
pubstate = {published},
tppubtype = {award}
}
Internal Studentships are open to highly qualified Faculty of Medicine graduate students who are registered full-time in a research training program (Thesis) leading to an M.Sc or PhD degree.
Rahbaran, Maryam; Kalinowski, Jonathan; Tsui, James; DeCunha, Joseph; Enger, Shirin A.
Monte-Carlo Based Simulations of the Uncertainties in Clinical Water-Based Intravascular Brachytherapy Dosimetry Presentation
11.04.2022.
@misc{nokey,
title = {Monte-Carlo Based Simulations of the Uncertainties in Clinical Water-Based Intravascular Brachytherapy Dosimetry},
author = {Maryam Rahbaran and Jonathan Kalinowski and James Tsui and Joseph DeCunha and Shirin A. Enger},
year = {2022},
date = {2022-04-11},
urldate = {2022-04-11},
journal = {MCMA},
abstract = {"Introduction
Coronary artery disease (CAD) is the most common form of cardiovascular disease and is caused by excess plaque along the arterial wall, blocking blood flow to the heart (stenosis). Percutaneous transluminal coronary angioplasty widens a narrowed artery, leaving behind metal stents (1). However, in-stent restenosis (ISR) may occur due to damage to the arterial wall tissue, triggering neointimal hyperplasia which produces fibrotic and calcified plaques, narrowing the artery again. Drug-eluting stents (DES) slowly release medication to inhibit neointimal hyperplasia to prevent ISR but they fail in 3% to 20% of cases (2). Intravascular brachytherapy (IVBT), which uses b-emitting radionuclides to prevent ISR, is used in these failed cases. However, current dosimetry for IVBT is water based and does not consider attenuation of the radiation by heterogeneities such as the IVBT device guidewire, non-uniform distribution of calcified plaques, and stent material, or the angular dependence of dose distribution (3, 4, 5). The aim of this study was to investigate the uncertainties in clinical water based IVBT dosimetry, considering the effect of heterogeneities on dose distribution.
Materials & Methods
An inhouse Monte-Carlo based dosimetry package for IVBT applications based on Geant4 10.04 (patch 2) was developed. Patient’s artery was modelled as a 32 mm long, 8.4 mm diameter cylinder comprised of three layers: tunica media, represented with muscle, tunica intima, represented with fibrotic plaque, and tunica adventitia, represented with collagen. These layers had mass densities 1.06 g/cm3, 1.22 g/cm3 and 1.07 g/cm3 respectively. The innermost layer consisted of calcified plaque of density 1.45 g/cm3 with varying thicknesses between 0.9 and 1.9 mm with an eccentric shape and a rough surface. The stents had similar composition to Boston Scientific Synergy stents and were modelled to not overlap. The Novoste Beta-Cath 3.5F IVBT device model was used, which has a 90Sr90Y source. The geometry is shown in Figure 1a. A cylindrical scoring geometry was implemented. Two set of simulations were performed. In the first simulation called water phantom, the entire system consisted of water with unit density, and dose to water was calculated similar to the clinical water based dosimetry. In the second simulation called the artery model proper material and mass densities were assigned to each component. To ensure uncertainties below 0.8% within a 1 mm radial distance to the source and 2% within 4.2 mm from the source, 100 million decay events were simulated. The Penelope physics list was used to simulate the electromagnetic interactions between particles. Average, minimum, and maximum dose was calculated at 2.0 mm from the source center and directly and 1 mm behind the outermost stents and guidewire. Absorbed dose was normalized to 23 Gy at 2.0 mm from the source center.
Results
International Conference on Monte Carlo Techniques for Medical Applications, 2022
Compared to the water phantom (Figure 1b), average dose in the artery model (Figure 1c) was attenuated by 50.9% at 2 mm from the source centre and directly behind the guidewire and outermost stent by 66.2%, and by 69.5% 1 mm behind this region. There was significant variation in dose around the source due to the guidewire attenuating dose the most, and heterogeneous distribution of calcification.
Discussion & Conclusions
Dosimetry for IVBT based on dose rate in water is not accurate. Heterogeneities need to be considered to deliver adequate dose to the lesion area. Stent material, heterogenous distribution of calcification and the off cantered placement of the guidewire affects the uniformity of dose distribution around the source. Patients may benefit from personalized treatment planning taking dose-attenuating by different tissue/material heterogeneities into account.
References
[1] Virani, Salim, S., et al. ""Heart Disease and Stroke Statistics—2020 Update"". Circulation, vol. 141, no. 9, March 03, 2020, pp. e336. doi: 10.1161/CIR.0000000000000757.
[2] Lee M, Banka G. In-stent restenosis. Interv Cardiol Clin 2016;5: 211e220.
[3] Chiu-Tsao ST, Schaart DR, Soares CG, et al. Dose calculation formalisms and consensus dosimetry parameters for intravascular brachytherapy dosimetry: Recommendations of the AAPM Therapy Physics Committee Task Group No. 149. Med Phys 2007;34: 4126e4157.
[4] Rivard MJ, Coursey BM, DeWerd LA, et al. Update of AAPM Task Group No. 43 Report: A revised AAPM protocol for brachytherapy dose calculations. Med Phys 2004;31:633e674.
[5] Nath R, Amols H, Coffey C, et al. Intravascular brachytherapy physics: Report of the AAPM Radiation Therapy Committee Task group No. 60. Med Phys 1999;26:119e152.’
[6] Agostinelli S, Allison J, Amako K, et al. Geant4da simulation toolkit. Nucl Instrum Methods Phys Res 2003;506:230e303."},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
"Introduction
Coronary artery disease (CAD) is the most common form of cardiovascular disease and is caused by excess plaque along the arterial wall, blocking blood flow to the heart (stenosis). Percutaneous transluminal coronary angioplasty widens a narrowed artery, leaving behind metal stents (1). However, in-stent restenosis (ISR) may occur due to damage to the arterial wall tissue, triggering neointimal hyperplasia which produces fibrotic and calcified plaques, narrowing the artery again. Drug-eluting stents (DES) slowly release medication to inhibit neointimal hyperplasia to prevent ISR but they fail in 3% to 20% of cases (2). Intravascular brachytherapy (IVBT), which uses b-emitting radionuclides to prevent ISR, is used in these failed cases. However, current dosimetry for IVBT is water based and does not consider attenuation of the radiation by heterogeneities such as the IVBT device guidewire, non-uniform distribution of calcified plaques, and stent material, or the angular dependence of dose distribution (3, 4, 5). The aim of this study was to investigate the uncertainties in clinical water based IVBT dosimetry, considering the effect of heterogeneities on dose distribution.
Materials & Methods
An inhouse Monte-Carlo based dosimetry package for IVBT applications based on Geant4 10.04 (patch 2) was developed. Patient’s artery was modelled as a 32 mm long, 8.4 mm diameter cylinder comprised of three layers: tunica media, represented with muscle, tunica intima, represented with fibrotic plaque, and tunica adventitia, represented with collagen. These layers had mass densities 1.06 g/cm3, 1.22 g/cm3 and 1.07 g/cm3 respectively. The innermost layer consisted of calcified plaque of density 1.45 g/cm3 with varying thicknesses between 0.9 and 1.9 mm with an eccentric shape and a rough surface. The stents had similar composition to Boston Scientific Synergy stents and were modelled to not overlap. The Novoste Beta-Cath 3.5F IVBT device model was used, which has a 90Sr90Y source. The geometry is shown in Figure 1a. A cylindrical scoring geometry was implemented. Two set of simulations were performed. In the first simulation called water phantom, the entire system consisted of water with unit density, and dose to water was calculated similar to the clinical water based dosimetry. In the second simulation called the artery model proper material and mass densities were assigned to each component. To ensure uncertainties below 0.8% within a 1 mm radial distance to the source and 2% within 4.2 mm from the source, 100 million decay events were simulated. The Penelope physics list was used to simulate the electromagnetic interactions between particles. Average, minimum, and maximum dose was calculated at 2.0 mm from the source center and directly and 1 mm behind the outermost stents and guidewire. Absorbed dose was normalized to 23 Gy at 2.0 mm from the source center.
Results
International Conference on Monte Carlo Techniques for Medical Applications, 2022
Compared to the water phantom (Figure 1b), average dose in the artery model (Figure 1c) was attenuated by 50.9% at 2 mm from the source centre and directly behind the guidewire and outermost stent by 66.2%, and by 69.5% 1 mm behind this region. There was significant variation in dose around the source due to the guidewire attenuating dose the most, and heterogeneous distribution of calcification.
Discussion & Conclusions
Dosimetry for IVBT based on dose rate in water is not accurate. Heterogeneities need to be considered to deliver adequate dose to the lesion area. Stent material, heterogenous distribution of calcification and the off cantered placement of the guidewire affects the uniformity of dose distribution around the source. Patients may benefit from personalized treatment planning taking dose-attenuating by different tissue/material heterogeneities into account.
References
[1] Virani, Salim, S., et al. ""Heart Disease and Stroke Statistics—2020 Update"". Circulation, vol. 141, no. 9, March 03, 2020, pp. e336. doi: 10.1161/CIR.0000000000000757.
[2] Lee M, Banka G. In-stent restenosis. Interv Cardiol Clin 2016;5: 211e220.
[3] Chiu-Tsao ST, Schaart DR, Soares CG, et al. Dose calculation formalisms and consensus dosimetry parameters for intravascular brachytherapy dosimetry: Recommendations of the AAPM Therapy Physics Committee Task Group No. 149. Med Phys 2007;34: 4126e4157.
[4] Rivard MJ, Coursey BM, DeWerd LA, et al. Update of AAPM Task Group No. 43 Report: A revised AAPM protocol for brachytherapy dose calculations. Med Phys 2004;31:633e674.
[5] Nath R, Amols H, Coffey C, et al. Intravascular brachytherapy physics: Report of the AAPM Radiation Therapy Committee Task group No. 60. Med Phys 1999;26:119e152.’
[6] Agostinelli S, Allison J, Amako K, et al. Geant4da simulation toolkit. Nucl Instrum Methods Phys Res 2003;506:230e303."
Coronary artery disease (CAD) is the most common form of cardiovascular disease and is caused by excess plaque along the arterial wall, blocking blood flow to the heart (stenosis). Percutaneous transluminal coronary angioplasty widens a narrowed artery, leaving behind metal stents (1). However, in-stent restenosis (ISR) may occur due to damage to the arterial wall tissue, triggering neointimal hyperplasia which produces fibrotic and calcified plaques, narrowing the artery again. Drug-eluting stents (DES) slowly release medication to inhibit neointimal hyperplasia to prevent ISR but they fail in 3% to 20% of cases (2). Intravascular brachytherapy (IVBT), which uses b-emitting radionuclides to prevent ISR, is used in these failed cases. However, current dosimetry for IVBT is water based and does not consider attenuation of the radiation by heterogeneities such as the IVBT device guidewire, non-uniform distribution of calcified plaques, and stent material, or the angular dependence of dose distribution (3, 4, 5). The aim of this study was to investigate the uncertainties in clinical water based IVBT dosimetry, considering the effect of heterogeneities on dose distribution.
Materials & Methods
An inhouse Monte-Carlo based dosimetry package for IVBT applications based on Geant4 10.04 (patch 2) was developed. Patient’s artery was modelled as a 32 mm long, 8.4 mm diameter cylinder comprised of three layers: tunica media, represented with muscle, tunica intima, represented with fibrotic plaque, and tunica adventitia, represented with collagen. These layers had mass densities 1.06 g/cm3, 1.22 g/cm3 and 1.07 g/cm3 respectively. The innermost layer consisted of calcified plaque of density 1.45 g/cm3 with varying thicknesses between 0.9 and 1.9 mm with an eccentric shape and a rough surface. The stents had similar composition to Boston Scientific Synergy stents and were modelled to not overlap. The Novoste Beta-Cath 3.5F IVBT device model was used, which has a 90Sr90Y source. The geometry is shown in Figure 1a. A cylindrical scoring geometry was implemented. Two set of simulations were performed. In the first simulation called water phantom, the entire system consisted of water with unit density, and dose to water was calculated similar to the clinical water based dosimetry. In the second simulation called the artery model proper material and mass densities were assigned to each component. To ensure uncertainties below 0.8% within a 1 mm radial distance to the source and 2% within 4.2 mm from the source, 100 million decay events were simulated. The Penelope physics list was used to simulate the electromagnetic interactions between particles. Average, minimum, and maximum dose was calculated at 2.0 mm from the source center and directly and 1 mm behind the outermost stents and guidewire. Absorbed dose was normalized to 23 Gy at 2.0 mm from the source center.
Results
International Conference on Monte Carlo Techniques for Medical Applications, 2022
Compared to the water phantom (Figure 1b), average dose in the artery model (Figure 1c) was attenuated by 50.9% at 2 mm from the source centre and directly behind the guidewire and outermost stent by 66.2%, and by 69.5% 1 mm behind this region. There was significant variation in dose around the source due to the guidewire attenuating dose the most, and heterogeneous distribution of calcification.
Discussion & Conclusions
Dosimetry for IVBT based on dose rate in water is not accurate. Heterogeneities need to be considered to deliver adequate dose to the lesion area. Stent material, heterogenous distribution of calcification and the off cantered placement of the guidewire affects the uniformity of dose distribution around the source. Patients may benefit from personalized treatment planning taking dose-attenuating by different tissue/material heterogeneities into account.
References
[1] Virani, Salim, S., et al. ""Heart Disease and Stroke Statistics—2020 Update"". Circulation, vol. 141, no. 9, March 03, 2020, pp. e336. doi: 10.1161/CIR.0000000000000757.
[2] Lee M, Banka G. In-stent restenosis. Interv Cardiol Clin 2016;5: 211e220.
[3] Chiu-Tsao ST, Schaart DR, Soares CG, et al. Dose calculation formalisms and consensus dosimetry parameters for intravascular brachytherapy dosimetry: Recommendations of the AAPM Therapy Physics Committee Task Group No. 149. Med Phys 2007;34: 4126e4157.
[4] Rivard MJ, Coursey BM, DeWerd LA, et al. Update of AAPM Task Group No. 43 Report: A revised AAPM protocol for brachytherapy dose calculations. Med Phys 2004;31:633e674.
[5] Nath R, Amols H, Coffey C, et al. Intravascular brachytherapy physics: Report of the AAPM Radiation Therapy Committee Task group No. 60. Med Phys 1999;26:119e152.’
[6] Agostinelli S, Allison J, Amako K, et al. Geant4da simulation toolkit. Nucl Instrum Methods Phys Res 2003;506:230e303."
2021
Kalinowski, Jonathan
Merit-based recruitment award for first year MSc students. award
2021.
@award{nokey,
title = {Merit-based recruitment award for first year MSc students.},
author = {Jonathan Kalinowski},
year = {2021},
date = {2021-09-01},
urldate = {2021-09-01},
organization = {McGill Medical Physics Unit},
keywords = {},
pubstate = {published},
tppubtype = {award}
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Morcos, Marc; Antaki, Majd; Thibodeau-Antonacci, Alana; Kalinowski, Jonathan; Glickman, Harry; Enger, Shirin A.
RapidBrachyMCTPS: An open-source dose calculation and optimization tool for brachytherapy research Presentation
COMP, 01.06.2021.
@misc{Morcos2021c,
title = {RapidBrachyMCTPS: An open-source dose calculation and optimization tool for brachytherapy research},
author = {Marc Morcos and Majd Antaki and Alana Thibodeau-Antonacci and Jonathan Kalinowski and Harry Glickman and Shirin A. Enger},
year = {2021},
date = {2021-06-01},
howpublished = {COMP},
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