2020
Famulari, Gabriel; Duclos, Marie; Enger, Shirin A.
A novel 169 Yb-based dynamic-shield intensity modulated brachytherapy delivery system for prostate cancer Journal Article
In: Medical Physics, vol. 47, no. 3, pp. 859–868, 2020, ISSN: 2473-4209.
Abstract | Links | BibTeX | Tags: Brachytherapy, Cohort Studies, Computer-Assisted, Humans, IMBT, Intensity-Modulated, Male, Monte Carlo, Monte Carlo Method, prostate cancer, Prostatic Neoplasms, Radioisotopes, Radiotherapy, Radiotherapy Planning, Uncertainty, Yb-169, Ytterbium
@article{famulari_novel_2020,
title = {A novel 169 Yb-based dynamic-shield intensity modulated brachytherapy delivery system for prostate cancer},
author = {Gabriel Famulari and Marie Duclos and Shirin A. Enger},
doi = {10.1002/mp.13959},
issn = {2473-4209},
year = {2020},
date = {2020-03-01},
journal = {Medical Physics},
volume = {47},
number = {3},
pages = {859--868},
abstract = {PURPOSE: Intensity modulated brachytherapy (IMBT) is a novel high dose rate brachytherapy (HDR BT) technique which incorporates static or dynamic shielding to increase tumor coverage and/or spare healthy tissues. The purpose of this study is to present a novel delivery system (AIM-Brachy) design that can enable dynamic-shield IMBT for prostate cancer.
METHODS: The AIM-Brachy system dynamically controls the rotation of platinum shields, placed within interstitial catheters, which partially collimate the radiation emitted from an 169 Yb source. Conventional HDR BT (10 Ci 192 Ir) and IMBT (18 Ci 169 Yb) plans were generated for 12 patients using an in-house column generation-based optimizer, coupled to a Geant4-based dose calculation engine, RapidBrachyMC. Treatment plans were normalized to match the same PTV D90 coverage as the clinical plan. Intershield attenuation effects were taken into account. A sensitivity analysis was performed to evaluate the dosimetric impact of systematic longitudinal source positioning errors ( ± 1 mm, ± 2 mm, and ± 3 mm) and rotational errors ( ± 5 ∘ , ± 10 ∘ , and ± 15 ∘ ) on clinically relevant parameters (PTV D90 and urethra D10 ).
RESULTS: The platinum shield reduced the dose rate on the shielded side at 1 cm to 18.1% of the dose rate on the unshielded side. For equal PTV D90 coverage, the urethral D10 was reduced by 13.3% ± 4.7%, without change to other plan quality indices (PTV V100 , V150, V200 , bladder V75 , rectum V75 , HI, COIN). Delivery times for HDR BT and IMBT were 9.2 ± 1.6 min and 18.6 ± 4.0 min, respectively. In general, the PTV D90 was more sensitive to source positioning errors than rotational errors, while the urethral D10 was more sensitive to rotational errors than source positioning errors. For a typical range of positioning errors ( ± 1 mm, ± 5 ∘ ), the overall tolerance was textless2%.
CONCLUSIONS: The AIM-Brachy system was proposed to deliver dynamic-shield IMBT for prostate cancer with the potential to create a low dose tunnel within the urethra. The urethra-sparing properties are desirable to minimize the occurrence and severity of urethral strictures or, alternatively, to provide a method for dose escalation.},
keywords = {Brachytherapy, Cohort Studies, Computer-Assisted, Humans, IMBT, Intensity-Modulated, Male, Monte Carlo, Monte Carlo Method, prostate cancer, Prostatic Neoplasms, Radioisotopes, Radiotherapy, Radiotherapy Planning, Uncertainty, Yb-169, Ytterbium},
pubstate = {published},
tppubtype = {article}
}
PURPOSE: Intensity modulated brachytherapy (IMBT) is a novel high dose rate brachytherapy (HDR BT) technique which incorporates static or dynamic shielding to increase tumor coverage and/or spare healthy tissues. The purpose of this study is to present a novel delivery system (AIM-Brachy) design that can enable dynamic-shield IMBT for prostate cancer.
METHODS: The AIM-Brachy system dynamically controls the rotation of platinum shields, placed within interstitial catheters, which partially collimate the radiation emitted from an 169 Yb source. Conventional HDR BT (10 Ci 192 Ir) and IMBT (18 Ci 169 Yb) plans were generated for 12 patients using an in-house column generation-based optimizer, coupled to a Geant4-based dose calculation engine, RapidBrachyMC. Treatment plans were normalized to match the same PTV D90 coverage as the clinical plan. Intershield attenuation effects were taken into account. A sensitivity analysis was performed to evaluate the dosimetric impact of systematic longitudinal source positioning errors ( ± 1 mm, ± 2 mm, and ± 3 mm) and rotational errors ( ± 5 ∘ , ± 10 ∘ , and ± 15 ∘ ) on clinically relevant parameters (PTV D90 and urethra D10 ).
RESULTS: The platinum shield reduced the dose rate on the shielded side at 1 cm to 18.1% of the dose rate on the unshielded side. For equal PTV D90 coverage, the urethral D10 was reduced by 13.3% ± 4.7%, without change to other plan quality indices (PTV V100 , V150, V200 , bladder V75 , rectum V75 , HI, COIN). Delivery times for HDR BT and IMBT were 9.2 ± 1.6 min and 18.6 ± 4.0 min, respectively. In general, the PTV D90 was more sensitive to source positioning errors than rotational errors, while the urethral D10 was more sensitive to rotational errors than source positioning errors. For a typical range of positioning errors ( ± 1 mm, ± 5 ∘ ), the overall tolerance was textless2%.
CONCLUSIONS: The AIM-Brachy system was proposed to deliver dynamic-shield IMBT for prostate cancer with the potential to create a low dose tunnel within the urethra. The urethra-sparing properties are desirable to minimize the occurrence and severity of urethral strictures or, alternatively, to provide a method for dose escalation.
METHODS: The AIM-Brachy system dynamically controls the rotation of platinum shields, placed within interstitial catheters, which partially collimate the radiation emitted from an 169 Yb source. Conventional HDR BT (10 Ci 192 Ir) and IMBT (18 Ci 169 Yb) plans were generated for 12 patients using an in-house column generation-based optimizer, coupled to a Geant4-based dose calculation engine, RapidBrachyMC. Treatment plans were normalized to match the same PTV D90 coverage as the clinical plan. Intershield attenuation effects were taken into account. A sensitivity analysis was performed to evaluate the dosimetric impact of systematic longitudinal source positioning errors ( ± 1 mm, ± 2 mm, and ± 3 mm) and rotational errors ( ± 5 ∘ , ± 10 ∘ , and ± 15 ∘ ) on clinically relevant parameters (PTV D90 and urethra D10 ).
RESULTS: The platinum shield reduced the dose rate on the shielded side at 1 cm to 18.1% of the dose rate on the unshielded side. For equal PTV D90 coverage, the urethral D10 was reduced by 13.3% ± 4.7%, without change to other plan quality indices (PTV V100 , V150, V200 , bladder V75 , rectum V75 , HI, COIN). Delivery times for HDR BT and IMBT were 9.2 ± 1.6 min and 18.6 ± 4.0 min, respectively. In general, the PTV D90 was more sensitive to source positioning errors than rotational errors, while the urethral D10 was more sensitive to rotational errors than source positioning errors. For a typical range of positioning errors ( ± 1 mm, ± 5 ∘ ), the overall tolerance was textless2%.
CONCLUSIONS: The AIM-Brachy system was proposed to deliver dynamic-shield IMBT for prostate cancer with the potential to create a low dose tunnel within the urethra. The urethra-sparing properties are desirable to minimize the occurrence and severity of urethral strictures or, alternatively, to provide a method for dose escalation.
2018
Mann-Krzisnik, Dylan; Verhaegen, Frank; Enger, Shirin A.
The influence of tissue composition uncertainty on dose distributions in brachytherapy Journal Article
In: Radiotherapy and Oncology: Journal of the European Society for Therapeutic Radiology and Oncology, vol. 126, no. 3, pp. 394–410, 2018, ISSN: 1879-0887.
Abstract | Links | BibTeX | Tags: Algorithms, Body Composition, Brachytherapy, Elemental composition, Humans, Mass energy-absorption coefficient, MBDCA, Organs at Risk, Radiotherapy Dosage, Review, Tissue heterogeneity, Uncertainty
@article{mann-krzisnik_influence_2018,
title = {The influence of tissue composition uncertainty on dose distributions in brachytherapy},
author = {Dylan Mann-Krzisnik and Frank Verhaegen and Shirin A. Enger},
doi = {10.1016/j.radonc.2018.01.007},
issn = {1879-0887},
year = {2018},
date = {2018-03-01},
journal = {Radiotherapy and Oncology: Journal of the European Society for Therapeutic Radiology and Oncology},
volume = {126},
number = {3},
pages = {394--410},
abstract = {BACKGROUND AND PURPOSE: Model-based dose calculation algorithms (MBDCAs) have evolved from serving as a research tool into clinical practice in brachytherapy. This study investigates primary sources of tissue elemental compositions used as input to MBDCAs and the impact of their variability on MBDCA-based dosimetry.
MATERIALS AND METHODS: Relevant studies were retrieved through PubMed. Minimum dose delivered to 90% of the target (D90), minimum dose delivered to the hottest specified volume for organs at risk (OAR) and mass energy-absorption coefficients (μen/ρ) generated by using EGSnrc "g" user-code were compared to assess the impact of compositional variability.
RESULTS: Elemental composition for hydrogen, carbon, oxygen and nitrogen are derived from the gross contents of fats, proteins and carbohydrates for any given tissue, the compositions of which are taken from literature dating back to 1940-1950. Heavier elements are derived from studies performed in the 1950-1960. Variability in elemental composition impacts greatly D90 for target tissues and doses to OAR for brachytherapy with low energy sources and less for 192Ir-based brachytherapy. Discrepancies in μen/ρ are also indicative of dose differences.
CONCLUSIONS: Updated elemental compositions are needed to optimize MBDCA-based dosimetry. Until then, tissue compositions based on gross simplifications in early studies will dominate the uncertainties in tissue heterogeneity.},
keywords = {Algorithms, Body Composition, Brachytherapy, Elemental composition, Humans, Mass energy-absorption coefficient, MBDCA, Organs at Risk, Radiotherapy Dosage, Review, Tissue heterogeneity, Uncertainty},
pubstate = {published},
tppubtype = {article}
}
BACKGROUND AND PURPOSE: Model-based dose calculation algorithms (MBDCAs) have evolved from serving as a research tool into clinical practice in brachytherapy. This study investigates primary sources of tissue elemental compositions used as input to MBDCAs and the impact of their variability on MBDCA-based dosimetry.
MATERIALS AND METHODS: Relevant studies were retrieved through PubMed. Minimum dose delivered to 90% of the target (D90), minimum dose delivered to the hottest specified volume for organs at risk (OAR) and mass energy-absorption coefficients (μen/ρ) generated by using EGSnrc "g" user-code were compared to assess the impact of compositional variability.
RESULTS: Elemental composition for hydrogen, carbon, oxygen and nitrogen are derived from the gross contents of fats, proteins and carbohydrates for any given tissue, the compositions of which are taken from literature dating back to 1940-1950. Heavier elements are derived from studies performed in the 1950-1960. Variability in elemental composition impacts greatly D90 for target tissues and doses to OAR for brachytherapy with low energy sources and less for 192Ir-based brachytherapy. Discrepancies in μen/ρ are also indicative of dose differences.
CONCLUSIONS: Updated elemental compositions are needed to optimize MBDCA-based dosimetry. Until then, tissue compositions based on gross simplifications in early studies will dominate the uncertainties in tissue heterogeneity.
MATERIALS AND METHODS: Relevant studies were retrieved through PubMed. Minimum dose delivered to 90% of the target (D90), minimum dose delivered to the hottest specified volume for organs at risk (OAR) and mass energy-absorption coefficients (μen/ρ) generated by using EGSnrc "g" user-code were compared to assess the impact of compositional variability.
RESULTS: Elemental composition for hydrogen, carbon, oxygen and nitrogen are derived from the gross contents of fats, proteins and carbohydrates for any given tissue, the compositions of which are taken from literature dating back to 1940-1950. Heavier elements are derived from studies performed in the 1950-1960. Variability in elemental composition impacts greatly D90 for target tissues and doses to OAR for brachytherapy with low energy sources and less for 192Ir-based brachytherapy. Discrepancies in μen/ρ are also indicative of dose differences.
CONCLUSIONS: Updated elemental compositions are needed to optimize MBDCA-based dosimetry. Until then, tissue compositions based on gross simplifications in early studies will dominate the uncertainties in tissue heterogeneity.
2016
Quast, Ulrich; Kaulich, Theodor W.; Álvarez-Romero, José T.; Tedgren, Sa Carlsson; Enger, Shirin A.; Medich, David C.; Mourtada, Firas; Perez-Calatayud, Jose; Rivard, Mark J.; Zakaria, G. Abu
A brachytherapy photon radiation quality index Q(BT) for probe-type dosimetry Journal Article
In: Physica medica: PM: an international journal devoted to the applications of physics to medicine and biology: official journal of the Italian Association of Biomedical Physics (AIFB), vol. 32, no. 6, pp. 741–748, 2016, ISSN: 1724-191X.
Abstract | Links | BibTeX | Tags: Absorbed dose to water, Brachytherapy, Detector response, Effective energy, Photon brachytherapy radiation quality index, Photons, Radiation, Radiometry, Scattering, Uncertainty
@article{quast_brachytherapy_2016,
title = {A brachytherapy photon radiation quality index Q(BT) for probe-type dosimetry},
author = {Ulrich Quast and Theodor W. Kaulich and José T. Álvarez-Romero and Sa Carlsson Tedgren and Shirin A. Enger and David C. Medich and Firas Mourtada and Jose Perez-Calatayud and Mark J. Rivard and G. Abu Zakaria},
doi = {10.1016/j.ejmp.2016.03.008},
issn = {1724-191X},
year = {2016},
date = {2016-06-01},
journal = {Physica medica: PM: an international journal devoted to the applications of physics to medicine and biology: official journal of the Italian Association of Biomedical Physics (AIFB)},
volume = {32},
number = {6},
pages = {741--748},
abstract = {INTRODUCTION: In photon brachytherapy (BT), experimental dosimetry is needed to verify treatment plans if planning algorithms neglect varying attenuation, absorption or scattering conditions. The detector's response is energy dependent, including the detector material to water dose ratio and the intrinsic mechanisms. The local mean photon energy E¯(r) must be known or another equivalent energy quality parameter used. We propose the brachytherapy photon radiation quality indexQ(BT)(E¯), to characterize the photon radiation quality in view of measurements of distributions of the absorbed dose to water, Dw, around BT sources. MATERIALS AND METHODS: While the external photon beam radiotherapy (EBRT) radiation quality index Q(EBRT)(E¯)=TPR10(20)(E¯) is not applicable to BT, the authors have applied a novel energy dependent parameter, called brachytherapy photon radiation quality index, defined as Q(BT)(E¯)=Dprim(r=2cm,θ0=90°)/Dprim(r0=1cm,θ0=90°), utilizing precise primary absorbed dose data, Dprim, from source reference databases, without additional MC-calculations. RESULTS AND DISCUSSION: For BT photon sources used clinically, Q(BT)(E¯) enables to determine the effective mean linear attenuation coefficient μ¯(E) and thus the effective energy of the primary photons Eprim(eff)(r0,θ0) at the TG-43 reference position Pref(r0=1cm,θ0=90°), being close to the mean total photon energy E¯tot(r0,θ0). If one has calibrated detectors, published E¯tot(r) and the BT radiation quality correction factor [Formula: see text] for different BT radiation qualities Q and Q0, the detector's response can be determined and Dw(r,θ) measured in the vicinity of BT photon sources.
CONCLUSIONS: This novel brachytherapy photon radiation quality indexQ(BT) characterizes sufficiently accurate and precise the primary photon's penetration probability and scattering potential.},
keywords = {Absorbed dose to water, Brachytherapy, Detector response, Effective energy, Photon brachytherapy radiation quality index, Photons, Radiation, Radiometry, Scattering, Uncertainty},
pubstate = {published},
tppubtype = {article}
}
INTRODUCTION: In photon brachytherapy (BT), experimental dosimetry is needed to verify treatment plans if planning algorithms neglect varying attenuation, absorption or scattering conditions. The detector's response is energy dependent, including the detector material to water dose ratio and the intrinsic mechanisms. The local mean photon energy E¯(r) must be known or another equivalent energy quality parameter used. We propose the brachytherapy photon radiation quality indexQ(BT)(E¯), to characterize the photon radiation quality in view of measurements of distributions of the absorbed dose to water, Dw, around BT sources. MATERIALS AND METHODS: While the external photon beam radiotherapy (EBRT) radiation quality index Q(EBRT)(E¯)=TPR10(20)(E¯) is not applicable to BT, the authors have applied a novel energy dependent parameter, called brachytherapy photon radiation quality index, defined as Q(BT)(E¯)=Dprim(r=2cm,θ0=90°)/Dprim(r0=1cm,θ0=90°), utilizing precise primary absorbed dose data, Dprim, from source reference databases, without additional MC-calculations. RESULTS AND DISCUSSION: For BT photon sources used clinically, Q(BT)(E¯) enables to determine the effective mean linear attenuation coefficient μ¯(E) and thus the effective energy of the primary photons Eprim(eff)(r0,θ0) at the TG-43 reference position Pref(r0=1cm,θ0=90°), being close to the mean total photon energy E¯tot(r0,θ0). If one has calibrated detectors, published E¯tot(r) and the BT radiation quality correction factor [Formula: see text] for different BT radiation qualities Q and Q0, the detector's response can be determined and Dw(r,θ) measured in the vicinity of BT photon sources.
CONCLUSIONS: This novel brachytherapy photon radiation quality indexQ(BT) characterizes sufficiently accurate and precise the primary photon's penetration probability and scattering potential.
CONCLUSIONS: This novel brachytherapy photon radiation quality indexQ(BT) characterizes sufficiently accurate and precise the primary photon's penetration probability and scattering potential.