Publications

@article{decunha_development_2021,

title = {Development of patient-specific 3D models from histopathological samples for applications in radiation therapy},

author = {Joseph M. DeCunha and Christopher M. Poole and Martin Vallières and Jose Torres and Sophie Camilleri-Broët and Roni F. Rayes and Jonathan D. Spicer and Shirin A. Enger},

doi = {10.1016/j.ejmp.2020.12.009},

issn = {1724-191X},

year  = {2021},

date = {2021-01-01},

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 = {81},

pages = {162--169},

abstract = {The biological effects of ionizing radiation depend on the tissue, tumor type, radiation quality, and patient-specific factors. Inter-patient variation in cell/nucleus size may influence patient-specific dose response. However, this variability in dose response is not well investigated due to lack of available cell/nucleus size data. The aim of this study was to develop methods to derive cell/nucleus size distributions from digital images of 2D histopathological samples and use them to build digital 3D models for use in cellular dosimetry. Nineteen of sixty hematoxylin and eosin stained lung adenocarcinoma samples investigated passed exclusion criterion to be analyzed in the study. A difference of gaussians blob detection algorithm was used to identify nucleus centers and quantify cell spacing. Hematoxylin content was measured to determine nucleus radius. Pouring simulations were conducted to generate one-hundred 3D models containing volumes of equivalent cell spacing and nuclei radius to those in histopathological samples. The nuclei radius distributions of non-tumoral and cancerous regions appearing in the same slide were significantly different (p textless 0.01) in all samples analyzed. The median nuclear-cytoplasmic ratio was 0.36 for non-tumoral cells and 0.50 for cancerous cells. The average cellular and nucleus packing densities in the 3D models generated were 65.9% (SD: 1.5%) and 13.3% (SD: 0.3%) respectively. Software to determine cell spacing and nuclei radius from histopathological samples was developed. 3D digital tissue models containing volumes with equivalent cell spacing, nucleus radius, and packing density to cancerous tissues were generated.},

keywords = {Algorithms, Cell Nucleus, Cellular dosimetry, Histopathology, Humans, Microdosimetry, Patient-specific, Radiometry},

pubstate = {published},

tppubtype = {article}

}

@article{famulari_monte_2020,

title = {Monte Carlo dosimetric characterization of a new high dose rate 169 Yb brachytherapy source and independent verification using a multipoint plastic scintillator detector},

author = {Gabriel Famulari and Haydee M. Linares Rosales and Justine Dupere and David C. Medich and Luc Beaulieu and Shirin A. Enger},

doi = {10.1002/mp.14336},

issn = {2473-4209},

year  = {2020},

date = {2020-09-01},

journal = {Medical Physics},

volume = {47},

number = {9},

pages = {4563--4573},

abstract = {PURPOSE: A prototype 169 Yb source was developed in combination with a dynamic rotating platinum shield system (AIM-Brachy) to deliver intensity modulated brachytherapy (IMBT). The purpose of this study was to evaluate the dosimetric characteristics of the bare/shielded 169 Yb source using Monte Carlo (MC) simulations and perform an independent dose verification using a dosimetry platform based on a multipoint plastic scintillator detector (mPSD). 

METHODS: The TG-43U1 dosimetric parameters were calculated for the source model using RapidBrachyMCTPS. Real-time dose rate measurements were performed in a water tank for both the bare/shielded source using a custom remote afterloader. For each dwell position, the dose rate was independently measured by the three scintillators (BCF-10, BCF-12, and BCF-60). For the bare source, dose rate was measured at distances up to 3 cm away from the source over a range of 7 cm along the catheter. For the shielded source, measurements were performed with the mPSD placed at 1 cm from the source at four different azimuthal angles ( 0 ∘ , 9 0 ∘ , 18 0 ∘ , and 27 0 ∘ ). 

RESULTS: The dosimetric parameters were tabulated for the source model. For the bare source, differences between measured and calculated along-away dose rates were generally below 5-10%. Along the transverse axis, deviations were, on average (range), 3.3% (0.6-6.2%) for BCF-10, 1.7% (0.9-2.9%) for BCF-12, and 2.2% (0.3-4.4%) for BCF-60. The maximum dose rate reduction due to shielding at a radial distance of 1 cm was 88.8 ± 1.2%, compared to 83.5 ± 0.5% as calculated by MC. 

CONCLUSIONS: The dose distribution for the bare/shielded 169 Yb source was independently verified using mPSD with good agreement in regions close to the source. The 169 Yb source coupled with the partial-shielding system is an effective technique to deliver IMBT.},

keywords = {Brachytherapy, Geant4, IMBT, Monte Carlo Method, mPSD, Plastics, Radiometry, Radiotherapy Dosage, shielded applicator, TG-186, TG-43, Yb-169},

pubstate = {published},

tppubtype = {article}

}

@article{morcos_monte_2020,

title = {Monte Carlo dosimetry study of novel rotating MRI-compatible shielded tandems for intensity modulated cervix brachytherapy},

author = {Marc Morcos and Shirin A. Enger},

doi = {10.1016/j.ejmp.2020.02.014},

issn = {1724-191X},

year  = {2020},

date = {2020-03-01},

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 = {71},

pages = {178--184},

abstract = {PURPOSE: Intensity modulated brachytherapy (IMBT) with rotating metal shields enables dose modulation that can better conform to the tumor while reducing OAR doses. In this work, we investigate novel rotating shields, compatible with MRI-compatible tandems used for cervix brachytherapy. Three unique shields were evaluated using the traditional 192Ir source. Additionally, 75Se and 169Yb isotopes were investigated as alternative sources. 

METHODS: Three different IMBT shields were modeled and simulated in RapidBrachyMCTPS. Each tungsten shield was designed to fit inside a 6 mm-wide MRI-compatible tandem. The active core of the source was replaced with 192Ir, 75Se and 169Yb. Transmission factors (TFs) were calculated and defined as the dose ratio at 1 cm on opposite sides of the shielded tandem on the transverse plane. Polar and azimuthal anisotropy plots were extracted from simulations. Dose homogeneities V200%V100% were calculated for all radionuclide-shield combinations. 

RESULTS: TFs are favorable for IMBT and ranged between 12.9% and 32.2% for 192Ir, 4.0%-16.1% for 75Se and 1.2-6.4% for 169Yb for all shield designs. Average beam-widths in the polar and azimuthal directions were reduced to the range of 42°-112° and 27°-107°, respectively, for all shield-radionuclide combinations. Dose homogeneities for all the radionuclide-shield combinations were within 12% of the non-IMBT tandem. 

CONCLUSIONS: This study has quantitatively assessed the influence of various rotating cervical cancer-specific IMBT tandem shields on dosimetry. The dynamic single-channel shields and narrow beam-widths in the polar and azimuthal direction give rise to highly anisotropic distributions. Intermediate-to-high energy radionuclides, 75Se and 169Yb substantially improve the modulation capacity of IMBT and pave the way for treating large and complex cervical cancer without interstitial needle implantation.},

keywords = {Anisotropy, Brachytherapy, Female, Humans, Image-guided cervix brachytherapy, Intensity modulated brachytherapy, Intensity-Modulated, Iridium Radioisotopes, Magnetic Resonance Imaging, Monte Carlo based dosimetry, Monte Carlo Method, MRI-guided GYN brachytherapy, Radiometry, Radiotherapy, Selenium Radioisotopes, Uterine Cervical Neoplasms, Ytterbium},

pubstate = {published},

tppubtype = {article}

}

@article{enger_model-based_2020,

title = {Model-Based Dose Calculation Algorithms for Brachytherapy Dosimetry},

author = {Shirin A. Enger and Javier Vijande and Mark J. Rivard},

doi = {10.1016/j.semradonc.2019.08.006},

issn = {1532-9461},

year  = {2020},

date = {2020-01-01},

journal = {Seminars in Radiation Oncology},

volume = {30},

number = {1},

pages = {77--86},

abstract = {The purpose of this study was to review the limitations of dose calculation formalisms for photon-emitting brachytherapy sources based on the American Association of Physicists in Medicine (AAPM) Task Group No. 43 (TG-43) report and to provide recommendations to transition to model-based dose calculation algorithms. Additionally, an overview of these algorithms and approaches is presented. The influence of tissue and seed/applicator heterogeneities on brachytherapy dose distributions for breast, gynecologic, head and neck, rectum, and prostate cancers as well as eye plaques and electronic brachytherapy treatments were investigated by comparing dose calculations based on the TG-43 formalism and model-based dose calculation algorithms.},

keywords = {Algorithms, Brachytherapy, Computer-Assisted, Female, Humans, Male, Medical, Models, Neoplasms, Photons, Practice Guidelines as Topic, Radiometry, Radiotherapy Dosage, Radiotherapy Planning, Societies, Theoretical},

pubstate = {published},

tppubtype = {article}

}

@article{kim_guide_2019,

title = {A guide to 90Y radioembolization and its dosimetry},

author = {S. Peter Kim and Claire Cohalan and Neil Kopek and Shirin A. Enger},

doi = {10.1016/j.ejmp.2019.09.236},

issn = {1724-191X},

year  = {2019},

date = {2019-12-01},

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 = {68},

pages = {132--145},

abstract = {Radioembolization gains continuous traction as a primarily palliative radiation treatment for hepatic tumours. A form of nuclear medicine therapy, Yttrium-90 containing microspheres are catheter guided and injected into the right, left, or a specifically selected hepatic artery. A multitude of comprehensive planning steps exist to ensure a thorough and successful treatment. Clear clinical and physiological guidelines have been established and nuclear imaging is used to plan and verify dose distributions. Radioembolization's treatment rationale is based on tumour and blood vessel dynamics that allow a targeted treatment approach. However, radioembolization's dosimetry is grossly oversimplified. In fact, the currently utilized clinical dosimetric standards (e.g. partition method) have persisted since the 1990s. Moreover, the multitude of radioembolization's intertwining components lies disjointed within the literature. Particularly relevant to new readers, this review provides a methodical guide that presents the treatment rationale behind every clinical step. The emerging dosimetry methods and its factors are further discussed to provide a comprehensive review on an essential research direction.},

keywords = {(90)Y, Clinical Background, Computer-Assisted, Dosimetry, Embolization, Humans, Radioembolization, Radiometry, Radiotherapy Planning, Therapeutic, Yttrium Radioisotopes},

pubstate = {published},

tppubtype = {article}

}

@article{decunha_new_2018,

title = {A new delivery system to resolve dosimetric issues in intravascular brachytherapy},

author = {Joseph M. DeCunha and Shirin A. Enger},

doi = {10.1016/j.brachy.2018.01.012},

issn = {1873-1449},

year  = {2018},

date = {2018-06-01},

journal = {Brachytherapy},

volume = {17},

number = {3},

pages = {634--643},

abstract = {PURPOSE: Renewed interest is being expressed in intravascular brachytherapy (IVBT). A number of unresolved issues exist in the discipline. Providing a homogeneous and adequate dose to the target remains difficult in IVBT. The guidewire that delivers the device to the target, arterial plaques, and stent struts are all known to reduce the dose delivered to target. The viability and efficacy of a proposed IVBT delivery system designed to resolve the issue of guidewire attenuation is evaluated and compared to that of a popular and commercially available IVBT device. 

METHODS AND MATERIALS: Monte Carlo simulations are conducted to determine distributions of absorbed dose around an existing and proposed IVBT delivery system. 

RESULTS: For the Novoste Beta-Cath 3.5F (TeamBest®), dose in water varies by 10% as a function of angle in the plane perpendicular to the delivery catheter due to off-centering of seeds in the catheter. Dose is reduced by 52% behind a stainless steel guidewire and 64% behind a guidewire, arterial plaque, and stent strut for the Novoste Beta-Cath 3.5F. Dose is not perturbed by the presence of a guidewire for the proposed device and is reduced by 46% by an arterial plaque and stent strut. 

CONCLUSIONS: Dose attenuation by guidewire is likely the single greatest source of dose attenuation in IVBT in terms of absolute dose reduction and is greater than previously reported for the Novoste Beta-Cath 3.5F. The Novoste Beta-Cath 3.5F delivers an inhomogeneous dose to target. A delivery system is proposed, which resolves the issue of guidewire attenuation in IVBT and should reduce treatment times.},

keywords = {Brachytherapy, Catheterization, Catheters, Computer Simulation, Coronary Vessels, Humans, Intravascular, Monte Carlo Method, Physics, Radiation Dosage, Radiometry, Restenosis, Stents, Strontium Radioisotopes},

pubstate = {published},

tppubtype = {article}

}

@article{famulari_microdosimetric_2018,

title = {Microdosimetric Evaluation of Current and Alternative Brachytherapy Sources-A Geant4-DNA Simulation Study},

author = {Gabriel Famulari and Piotr Pater and Shirin A. Enger},

doi = {10.1016/j.ijrobp.2017.09.040},

issn = {1879-355X},

year  = {2018},

date = {2018-01-01},

journal = {International Journal of Radiation Oncology, Biology, Physics},

volume = {100},

number = {1},

pages = {270--277},

abstract = {PURPOSE: Radioisotopes such as 75Se, 169Yb, and 153Gd have photon energy spectra and half-lives that make them excellent candidates as alternatives to 192Ir for high-dose-rate brachytherapy. The aim of the present study was to evaluate the relative biological effectiveness (RBE) of current (192Ir, 125I, 103Pd) and alternative (75Se, 169Yb, 153Gd) brachytherapy radionuclides using Monte Carlo simulations of lineal energy distributions. 

METHODS AND MATERIALS: Brachytherapy sources (microSelectron v2 [192Ir, 75Se, 169Yb, 153Gd], SelectSeed [125I], and TheraSeed [103Pd]) were placed in the center of a spherical water phantom with a radius of 40 cm using the Geant4 Monte Carlo simulation toolkit. The kinetic energy of all primary, scattered, and fluorescence photons interacting in a scoring volume were tallied at various depths from the source. Electron tracks were generated by sampling the photon interaction spectrum and tracking all the interactions down to 10 eV using the event-by-event capabilities of the Geant4-DNA models. The dose mean lineal energy (y¯D) values were obtained through random sampling of transfer points and overlaying spherical scoring volumes within the associated volume of the tracks. The scoring volume diameter was determined by fitting the y¯D ratio for 125I to its observed RBE. 

RESULTS: y¯D increased with the increasing distance from the source for 192Ir, 75Se, and 169Yb, remained constant for 153Gd and 125I, and decreased for 103Pd. The diameter at which the y¯D ratio coincided with the RBE of 1.15 to 1.20 for 125I was ∼25 to 40 nm. The RBE (reference 1 MeV photons) at high doses and dose rates for 192Ir, 75Se, 169Yb, 153Gd, 125I, and 103Pd was 1.028 to 1.034, 1.05 to 1.07, 1.12 to 1.15, 1.16 to 1.21, 1.15 to 1.20, and 1.17 to 1.22, respectively. 

CONCLUSIONS: The radiation quality of the radionuclides under investigation was greater than that of high-energy photons. The present study has provided a set of values to modify the prescription doses for brachytherapy to account for the variation in radiation quality among radionuclides.},

keywords = {Brachytherapy, Gadolinium, Imaging, Iodine Radioisotopes, Iridium Radioisotopes, Linear Energy Transfer, Monte Carlo Method, Phantoms, Radioisotopes, Radiometry, Radiotherapy Dosage, Relative Biological Effectiveness, Selenium Radioisotopes, Ytterbium},

pubstate = {published},

tppubtype = {article}

}

@article{famulari_microdosimetry_2017,

title = {Microdosimetry calculations for monoenergetic electrons using Geant4-DNA combined with a weighted track sampling algorithm},

author = {Gabriel Famulari and Piotr Pater and Shirin A. Enger},

doi = {10.1088/1361-6560/aa71f6},

issn = {1361-6560},

year  = {2017},

date = {2017-07-01},

journal = {Physics in Medicine and Biology},

volume = {62},

number = {13},

pages = {5495--5508},

abstract = {The aim of this study was to calculate microdosimetric distributions for low energy electrons simulated using the Monte Carlo track structure code Geant4-DNA. Tracks for monoenergetic electrons with kinetic energies ranging from 100 eV to 1 MeV were simulated in an infinite spherical water phantom using the Geant4-DNA extension included in Geant4 toolkit version 10.2 (patch 02). The microdosimetric distributions were obtained through random sampling of transfer points and overlaying scoring volumes within the associated volume of the tracks. Relative frequency distributions of energy deposition f(textgreaterE)/f(textgreater0) and dose mean lineal energy ([Formula: see text]) values were calculated in nanometer-sized spherical and cylindrical targets. The effects of scoring volume and scoring techniques were examined. The results were compared with published data generated using MOCA8B and KURBUC. Geant4-DNA produces a lower frequency of higher energy deposits than MOCA8B. The [Formula: see text] values calculated with Geant4-DNA are smaller than those calculated using MOCA8B and KURBUC. The differences are mainly due to the lower ionization and excitation cross sections of Geant4-DNA for low energy electrons. To a lesser extent, discrepancies can also be attributed to the implementation in this study of a new and fast scoring technique that differs from that used in previous studies. For the same mean chord length ([Formula: see text]), the [Formula: see text] calculated in cylindrical volumes are larger than those calculated in spherical volumes. The discrepancies due to cross sections and scoring geometries increase with decreasing scoring site dimensions. A new set of [Formula: see text] values has been presented for monoenergetic electrons using a fast track sampling algorithm and the most recent physics models implemented in Geant4-DNA. This dataset can be combined with primary electron spectra to predict the radiation quality of photon and electron beams.},

keywords = {Algorithms, DNA, DNA Damage, Electrons, Imaging, Monte Carlo Method, Phantoms, Photons, Radiometry},

pubstate = {published},

tppubtype = {article}

}

@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}

}

@article{enger_exploring_2012,

title = {Exploring (57)Co as a new isotope for brachytherapy applications},

author = {Shirin A. Enger and Hans Lundqvist and Michel D'Amours and Luc Beaulieu},

doi = {10.1118/1.3700171},

issn = {0094-2405},

year  = {2012},

date = {2012-05-01},

journal = {Medical Physics},

volume = {39},

number = {5},

pages = {2342--2345},

abstract = {PURPOSE: The characteristics of the radionuclide (57)Co make it interesting for use as a brachytherapy source. (57)Co combines a possible high specific activity with the emission of relatively low-energy photons and a half-life (272 days) suitable for regular source exchanges in an afterloader. (57)Co decays by electron capture to the stable (57)Fe with emission of 136 and 122 keV photons. 

METHODS: A hypothetical (57)Co source based on the Flexisource brachytherapy encapsulation with the active core set as a pure cobalt cylinder (length 3.5 mm and diameter 0.6 mm) covered with a cylindrical stainless-steel capsule (length 5 mm and thickness 0.125 mm) was simulated using Geant4 Monte Carlo (MC) code version 9.4. The radial dose function, g(r), and anisotropy function F(r,θ), for the line source approximation were calculated following the TG-43U1 formalism. The results were compared to well-known (192)Ir and (125)I radionuclides, representing the higher and the lower energy end of brachytherapy, respectively. 

RESULTS: The mean energy of photons in water, after passing through the core and the encapsulation material was 123 keV. This hypothetical (57)Co source has an increasing g(r) due to multiple scatter of low-energy photons, which results in a more uniform dose distribution than (192)Ir. 

CONCLUSIONS: (57)Co has many advantages compared to (192)Ir due to its low-energy gamma emissions without any electron contamination. (57)Co has an increasing g(r) that results in a more uniform dose distribution than (192)Ir due to its multiple scattered photons. The anisotropy of the (57)Co source is comparable to that of (192)Ir. Furthermore, (57)Co has lower shielding requirements than (192)Ir.},

keywords = {Anisotropy, Brachytherapy, Cobalt Radioisotopes, Monte Carlo Method, Radiation, Radiometry, Scattering},

pubstate = {published},

tppubtype = {article}

}

@article{enger_monte_2006,

title = {Monte Carlo calculations of thermal neutron capture in gadolinium: a comparison of GEANT4 and MCNP with measurements},

author = {Shirin A. Enger and Per Munck af Rosenschöld and Arash Rezaei and Hans Lundqvist},

doi = {10.1118/1.2150787},

issn = {0094-2405},

year  = {2006},

date = {2006-02-01},

journal = {Medical Physics},

volume = {33},

number = {2},

pages = {337--341},

abstract = {GEANT4 is a Monte Carlo code originally implemented for high-energy physics applications and is well known for particle transport at high energies. The capacity of GEANT4 to simulate neutron transport in the thermal energy region is not equally well known. The aim of this article is to compare MCNP, a code commonly used in low energy neutron transport calculations and GEANT4 with experimental results and select the suitable code for gadolinium neutron capture applications. To account for the thermal neutron scattering from chemically bound atoms [S(alpha,beta)] in biological materials a comparison of thermal neutron fluence in tissue-like poly(methylmethacrylate) phantom is made with MCNP4B, GEANT4 6.0 patch1, and measurements from the neutron capture therapy (NCT) facility at the Studsvik, Sweden. The fluence measurements agreed with MCNP calculated results considering S(alpha,beta). The location of the thermal neutron peak calculated with MCNP without S(alpha,beta) and GEANT4 is shifted by about 0.5 cm towards a shallower depth and is 25%-30% lower in amplitude. Dose distribution from the gadolinium neutron capture reaction is then simulated by MCNP and compared with measured data. The simulations made by MCNP agree well with experimental results. As long as thermal neutron scattering from chemically bound atoms are not included in GEANT4 it is not suitable for NCT applications.},

keywords = {Computer-Assisted, Fast Neutrons, Gadolinium, Humans, Imaging, Monte Carlo Method, Neutron Capture Therapy, Phantoms, Radiologic, Radiometry, Radiotherapy Planning, Reproducibility of Results, Technology},

pubstate = {published},

tppubtype = {article}

}

@article{enger_gadolinium_2006,

title = {Gadolinium neutron capture brachytherapy (GdNCB), a new treatment method for intravascular brachytherapy},

author = {Shirin A. Enger and Arash Rezaei and Per Munck af Rosenschöld and Hans Lundqvist},

doi = {10.1118/1.2146050},

issn = {0094-2405},

year  = {2006},

date = {2006-01-01},

journal = {Medical Physics},

volume = {33},

number = {1},

pages = {46--51},

abstract = {Restenosis is a major problem after balloon angioplasty and stent implantation. The aim of this study is to introduce gadolinium neutron capture brachytherapy (GdNCB) as a suitable modality for treatment of stenosis. The utility of GdNCB in intravascular brachytherapy (IVBT) of stent stenosis is investigated by using the GEANT4 and MCNP4B Monte Carlo radiation transport codes. To study capture rate, Kerma, absorbed dose and absorbed dose rate around a Gd-containing stent activated with neutrons, a 30 mm long, 5 mm diameter gadolinium foil is chosen. The input data is a neutron spectrum used for clinical neutron capture therapy in Studsvik, Sweden. Thermal neutron capture in gadolinium yields a spectrum of high-energy gamma photons, which due to the build-up effect gives an almost flat dose delivery pattern to the first 4 mm around the stent. The absorbed dose rate is 1.33 Gy/min, 0.25 mm from the stent surface while the dose to normal tissue is in order of 0.22 Gy/min, i.e., a factor of 6 lower. To spare normal tissue further fractionation of the dose is also possible. The capture rate is relatively high at both ends of the foil. The dose distribution from gamma and charge particle radiation at the edges and inside the stent contributes to a nonuniform dose distribution. This will lead to higher doses to the surrounding tissue and may prevent stent edge and in-stent restenosis. The position of the stent can be verified and corrected by the treatment plan prior to activation. Activation of the stent by an external neutron field can be performed days after catherization when the target cells start to proliferate and can be expected to be more radiation sensitive. Another advantage of the nonradioactive gadolinium stent is the possibility to avoid radiation hazard to personnel.},

keywords = {Biological, Blood Vessel Prosthesis, Brachytherapy, Computer Simulation, Computer-Assisted, Gadolinium, Graft Occlusion, Humans, Models, Monte Carlo Method, Neutron Capture Therapy, Radiometry, Radiotherapy Dosage, Radiotherapy Planning, Relative Biological Effectiveness, Statistical, Stents, Vascular},

pubstate = {published},

tppubtype = {article}

}