Impact of tissue heterogeneity on intracranial Cesium-131 brachytherapy dosimetry: A patient-specific Monte Carlo Study.
5 affiliations
- 1University of Minnesota, Minneapolis, Minnesota, USA.
- 2East Carolina University, Greenville, North Carolina, USA.
- 3University of Texas MD Anderson Cancer Center, Houston, Texas, USA.
- 4Kathmandu University, Nepal.
- 5Loyola University Medical Center, Maywood, Illinois, USA.
Abstract
Background
AAPM TG-43-based dose calculations for intracranial cesium-131 (¹³¹Cs) brachytherapy ignore patient-specific heterogeneities, which can affect dose accuracy. This study investigates the dosimetric impact of these heterogeneity effects using Monte Carlo (MC) simulations and patient-specific imaging data.Purpose
To quantify the impact of tissue heterogeneity on dose distributions in intracranial brachytherapy using ¹³¹Cs sources and to evaluate the accuracy of AAPM TG-43-based treatment planning system (TPS) calculations.Methods
TG-43 dosimetric parameters for the ¹³¹Cs source were independently characterized and benchmarked against published consensus data. MC simulations using MCNP were performed in both homogeneous water phantoms and heterogeneous voxelized lattice phantoms derived from CT DICOM RT data. Single and multiple-seed configurations were investigated. TPS and MC dose distributions were compared using dose-volume histogram (DVH) metrics such as (V₆₀, V₁₀₀, D2cc, and mean dose), isodose distributions, dose difference maps, and local and global dose difference analyzes. Spatial agreement was quantified using gamma analysis.Results
Strong agreement was observed between TPS and MC calculations in homogeneous media. However, heterogeneous patient-specific MC simulations revealed systematic differences in DVH metrics for the target volume and organs at risk, including the skull and skin. Local dose differences revealed pronounced deviations near high-density bony regions, where dose enhancement effects were observed, while global dose difference analyzes demonstrated an overall dosimetric bias. Gamma pass rates decreased in heterogeneous regions, consistent with these spatial dose discrepancies. Compared with the MC simulations, the TG-43-based TPS overestimated the mean dose to the target by approximately 23.63±4.97% , V₆₀ and V₁₀₀ by approximately 24.42±4.97% , and 23.75±4.97% , respectively, and the mean dose to the skin by approximately 73.60±4.97% , while underestimating the mean dose to the skull by 220.90±4.97% .Conclusion
Although the TG-43 formalism provides accurate dose estimates in homogeneous media, it introduces clinically meaningful local and global dosimetric deviations in heterogeneous intracranial environments. Careful consideration is required when reporting doses to the target and OARs, particularly given the potential for substantially higher doses to the irradiated skull in certain cases (up to 3.2-fold in this study), as well as the possibility of target underdosage within the high-risk clinical target volume (HR-CTV). Patient-specific MC modeling highlights the importance of incorporating tissue heterogeneity into intracranial brachytherapy dose calculations to improve dosimetric accuracy and optimize treatment planning.
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BibTeX
@article{adhikari2026impact,
title = {{Impact of tissue heterogeneity on intracranial Cesium-131 brachytherapy dosimetry: A patient-specific Monte Carlo Study.}},
author = {Tirthraj Adhikari and Jae W Jung and Sherif M Gadoue and Puja Sharma and Tomas Montegegro and Farhad Jafari and Clara Ferreira},
journal = {Journal of applied clinical medical physics},
year = {2026},
month = oct,
doi = {10.1002/acm2.70872},
url = {https://europepmc.org/article/MED/42958620},
note = {CC BY},
}
RIS
TY - JOUR
TI - Impact of tissue heterogeneity on intracranial Cesium-131 brachytherapy dosimetry: A patient-specific Monte Carlo Study.
AU - Tirthraj Adhikari
AU - Jae W Jung
AU - Sherif M Gadoue
AU - Puja Sharma
AU - Tomas Montegegro
AU - Farhad Jafari
AU - Clara Ferreira
PY - 2026
DA - 2026/10/29
JO - Journal of applied clinical medical physics
DO - 10.1002/acm2.70872
UR - https://europepmc.org/article/MED/42958620
AB - Background AAPM TG-43-based dose calculations for intracranial cesium-131 (¹³¹Cs) brachytherapy ignore patient-specific heterogeneities, which can affect dose accuracy. This study investigates the dosimetric impact of these heterogeneity effects using Monte Carlo (MC) simulations and patient-specific imaging data.Purpose To quantify the impact of tissue heterogeneity on dose distributions in intracranial brachytherapy using ¹³¹Cs sources and to evaluate the accuracy of AAPM TG-43-based treatment planning system (TPS) calculations.Methods TG-43 dosimetric parameters for the ¹³¹Cs source were independently characterized and benchmarked against published consensus data. MC simulations using MCNP were performed in both homogeneous water phantoms and heterogeneous voxelized lattice phantoms derived from CT DICOM RT data. Single and multiple-seed configurations were investigated. TPS and MC dose distributions were compared using dose-volume histogram (DVH) metrics such as (V₆₀, V₁₀₀, D2cc, and mean dose), isodose distributions, dose difference maps, and local and global dose difference analyzes. Spatial agreement was quantified using gamma analysis.Results Strong agreement was observed between TPS and MC calculations in homogeneous media. However, heterogeneous patient-specific MC simulations revealed systematic differences in DVH metrics for the target volume and organs at risk, including the skull and skin. Local dose differences revealed pronounced deviations near high-density bony regions, where dose enhancement effects were observed, while global dose difference analyzes demonstrated an overall dosimetric bias. Gamma pass rates decreased in heterogeneous regions, consistent with these spatial dose discrepancies. Compared with the MC simulations, the TG-43-based TPS overestimated the mean dose to the target by approximately 23.63±4.97% , V₆₀ and V₁₀₀ by approximately 24.42±4.97% , and 23.75±4.97% , respectively, and the mean dose to the skin by approximately 73.60±4.97% , while underestimating the mean dose to the skull by 220.90±4.97% .Conclusion Although the TG-43 formalism provides accurate dose estimates in homogeneous media, it introduces clinically meaningful local and global dosimetric deviations in heterogeneous intracranial environments. Careful consideration is required when reporting doses to the target and OARs, particularly given the potential for substantially higher doses to the irradiated skull in certain cases (up to 3.2-fold in this study), as well as the possibility of target underdosage within the high-risk clinical target volume (HR-CTV). Patient-specific MC modeling highlights the importance of incorporating tissue heterogeneity into intracranial brachytherapy dose calculations to improve dosimetric accuracy and optimize treatment planning.
SN - 1526-9914
ER -