Model-based dose calculations for 125I lung brachytherapy

J. G H Sutherland, K. M. Furutani, Yolanda Isabel Garces, R. M. Thomson

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

Purpose: Model-baseddose calculations (MBDCs) are performed using patient computed tomography (CT) data for patients treated with intraoperative 125I lung brachytherapy at the Mayo Clinic Rochester. Various metallic artifact correction and tissue assignment schemes are considered and their effects on dose distributions are studied. Dose distributions are compared to those calculated under TG-43 assumptions. Methods: Dose distributions for six patients are calculated using phantoms derived from patient CT data and the EGSnrc user-code BrachyDose. 125I (GE Healthcare/Oncura model 6711) seeds are fully modeled. Four metallic artifact correction schemes are applied to the CT data phantoms: (1) no correction, (2) a filtered back-projection on a modified virtual sinogram, (3) the reassignment of CT numbers above a threshold in the vicinity of the seeds, and (4) a combination of (2) and (3). Tissue assignment is based on voxel CT number and mass density is assigned using a CT number to mass density calibration. Three tissue assignment schemes with varying levels of detail (20, 11, and 5 tissues) are applied to metallic artifact corrected phantoms. Simulations are also performed under TG-43 assumptions, i.e., seeds in homogeneous water with no interseed attenuation. Results: Significant dose differences (up to 40 for D90) are observed between uncorrected and metallic artifact corrected phantoms. For phantoms created with metallic artifact correction schemes (3) and (4), dose volume metrics are generally in good agreement (less than 2 differences for all patients) although there are significant local dose differences. The application of the three tissue assignment schemes results in differences of up to 8 for D90; these differences vary between patients. Significant dose differences are seen between fully modeled and TG-43 calculations with TG-43 underestimating the dose (up to 36 in D90) for larger volumes containing higher proportions of healthy lung tissue. Conclusions: Metallic artifact correction is necessary for accurate application of MBDCs for lung brachytherapy; simpler threshold replacement methods may be sufficient for early adopters concerned with clinical dose metrics. Rigorous determination of voxel tissue parameters and tissue assignment is required for accurate dose calculations as different tissue assignment schemes can result in significantly different dose distributions. Significant differences are seen between MBDCs and TG-43 dose distributions with TG-43 underestimating dose in volumes containing healthy lung tissue.

Original languageEnglish (US)
Pages (from-to)4365-4377
Number of pages13
JournalMedical Physics
Volume39
Issue number7
DOIs
StatePublished - Jul 2012

Fingerprint

Brachytherapy
Lung
Artifacts
Tomography
Seeds
Calibration
Delivery of Health Care
Water

Keywords

  • brachytherapy
  • dosimetry
  • I-125
  • lung
  • model-based dose calculations
  • Monte Carlo
  • permanent implants

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging

Cite this

Sutherland, J. G. H., Furutani, K. M., Garces, Y. I., & Thomson, R. M. (2012). Model-based dose calculations for 125I lung brachytherapy. Medical Physics, 39(7), 4365-4377. https://doi.org/10.1118/1.4729737

Model-based dose calculations for 125I lung brachytherapy. / Sutherland, J. G H; Furutani, K. M.; Garces, Yolanda Isabel; Thomson, R. M.

In: Medical Physics, Vol. 39, No. 7, 07.2012, p. 4365-4377.

Research output: Contribution to journalArticle

Sutherland, JGH, Furutani, KM, Garces, YI & Thomson, RM 2012, 'Model-based dose calculations for 125I lung brachytherapy', Medical Physics, vol. 39, no. 7, pp. 4365-4377. https://doi.org/10.1118/1.4729737
Sutherland, J. G H ; Furutani, K. M. ; Garces, Yolanda Isabel ; Thomson, R. M. / Model-based dose calculations for 125I lung brachytherapy. In: Medical Physics. 2012 ; Vol. 39, No. 7. pp. 4365-4377.
@article{47cd7577e6134f7d9f7490bb8d1e2b34,
title = "Model-based dose calculations for 125I lung brachytherapy",
abstract = "Purpose: Model-baseddose calculations (MBDCs) are performed using patient computed tomography (CT) data for patients treated with intraoperative 125I lung brachytherapy at the Mayo Clinic Rochester. Various metallic artifact correction and tissue assignment schemes are considered and their effects on dose distributions are studied. Dose distributions are compared to those calculated under TG-43 assumptions. Methods: Dose distributions for six patients are calculated using phantoms derived from patient CT data and the EGSnrc user-code BrachyDose. 125I (GE Healthcare/Oncura model 6711) seeds are fully modeled. Four metallic artifact correction schemes are applied to the CT data phantoms: (1) no correction, (2) a filtered back-projection on a modified virtual sinogram, (3) the reassignment of CT numbers above a threshold in the vicinity of the seeds, and (4) a combination of (2) and (3). Tissue assignment is based on voxel CT number and mass density is assigned using a CT number to mass density calibration. Three tissue assignment schemes with varying levels of detail (20, 11, and 5 tissues) are applied to metallic artifact corrected phantoms. Simulations are also performed under TG-43 assumptions, i.e., seeds in homogeneous water with no interseed attenuation. Results: Significant dose differences (up to 40 for D90) are observed between uncorrected and metallic artifact corrected phantoms. For phantoms created with metallic artifact correction schemes (3) and (4), dose volume metrics are generally in good agreement (less than 2 differences for all patients) although there are significant local dose differences. The application of the three tissue assignment schemes results in differences of up to 8 for D90; these differences vary between patients. Significant dose differences are seen between fully modeled and TG-43 calculations with TG-43 underestimating the dose (up to 36 in D90) for larger volumes containing higher proportions of healthy lung tissue. Conclusions: Metallic artifact correction is necessary for accurate application of MBDCs for lung brachytherapy; simpler threshold replacement methods may be sufficient for early adopters concerned with clinical dose metrics. Rigorous determination of voxel tissue parameters and tissue assignment is required for accurate dose calculations as different tissue assignment schemes can result in significantly different dose distributions. Significant differences are seen between MBDCs and TG-43 dose distributions with TG-43 underestimating dose in volumes containing healthy lung tissue.",
keywords = "brachytherapy, dosimetry, I-125, lung, model-based dose calculations, Monte Carlo, permanent implants",
author = "Sutherland, {J. G H} and Furutani, {K. M.} and Garces, {Yolanda Isabel} and Thomson, {R. M.}",
year = "2012",
month = "7",
doi = "10.1118/1.4729737",
language = "English (US)",
volume = "39",
pages = "4365--4377",
journal = "Medical Physics",
issn = "0094-2405",
publisher = "AAPM - American Association of Physicists in Medicine",
number = "7",

}

TY - JOUR

T1 - Model-based dose calculations for 125I lung brachytherapy

AU - Sutherland, J. G H

AU - Furutani, K. M.

AU - Garces, Yolanda Isabel

AU - Thomson, R. M.

PY - 2012/7

Y1 - 2012/7

N2 - Purpose: Model-baseddose calculations (MBDCs) are performed using patient computed tomography (CT) data for patients treated with intraoperative 125I lung brachytherapy at the Mayo Clinic Rochester. Various metallic artifact correction and tissue assignment schemes are considered and their effects on dose distributions are studied. Dose distributions are compared to those calculated under TG-43 assumptions. Methods: Dose distributions for six patients are calculated using phantoms derived from patient CT data and the EGSnrc user-code BrachyDose. 125I (GE Healthcare/Oncura model 6711) seeds are fully modeled. Four metallic artifact correction schemes are applied to the CT data phantoms: (1) no correction, (2) a filtered back-projection on a modified virtual sinogram, (3) the reassignment of CT numbers above a threshold in the vicinity of the seeds, and (4) a combination of (2) and (3). Tissue assignment is based on voxel CT number and mass density is assigned using a CT number to mass density calibration. Three tissue assignment schemes with varying levels of detail (20, 11, and 5 tissues) are applied to metallic artifact corrected phantoms. Simulations are also performed under TG-43 assumptions, i.e., seeds in homogeneous water with no interseed attenuation. Results: Significant dose differences (up to 40 for D90) are observed between uncorrected and metallic artifact corrected phantoms. For phantoms created with metallic artifact correction schemes (3) and (4), dose volume metrics are generally in good agreement (less than 2 differences for all patients) although there are significant local dose differences. The application of the three tissue assignment schemes results in differences of up to 8 for D90; these differences vary between patients. Significant dose differences are seen between fully modeled and TG-43 calculations with TG-43 underestimating the dose (up to 36 in D90) for larger volumes containing higher proportions of healthy lung tissue. Conclusions: Metallic artifact correction is necessary for accurate application of MBDCs for lung brachytherapy; simpler threshold replacement methods may be sufficient for early adopters concerned with clinical dose metrics. Rigorous determination of voxel tissue parameters and tissue assignment is required for accurate dose calculations as different tissue assignment schemes can result in significantly different dose distributions. Significant differences are seen between MBDCs and TG-43 dose distributions with TG-43 underestimating dose in volumes containing healthy lung tissue.

AB - Purpose: Model-baseddose calculations (MBDCs) are performed using patient computed tomography (CT) data for patients treated with intraoperative 125I lung brachytherapy at the Mayo Clinic Rochester. Various metallic artifact correction and tissue assignment schemes are considered and their effects on dose distributions are studied. Dose distributions are compared to those calculated under TG-43 assumptions. Methods: Dose distributions for six patients are calculated using phantoms derived from patient CT data and the EGSnrc user-code BrachyDose. 125I (GE Healthcare/Oncura model 6711) seeds are fully modeled. Four metallic artifact correction schemes are applied to the CT data phantoms: (1) no correction, (2) a filtered back-projection on a modified virtual sinogram, (3) the reassignment of CT numbers above a threshold in the vicinity of the seeds, and (4) a combination of (2) and (3). Tissue assignment is based on voxel CT number and mass density is assigned using a CT number to mass density calibration. Three tissue assignment schemes with varying levels of detail (20, 11, and 5 tissues) are applied to metallic artifact corrected phantoms. Simulations are also performed under TG-43 assumptions, i.e., seeds in homogeneous water with no interseed attenuation. Results: Significant dose differences (up to 40 for D90) are observed between uncorrected and metallic artifact corrected phantoms. For phantoms created with metallic artifact correction schemes (3) and (4), dose volume metrics are generally in good agreement (less than 2 differences for all patients) although there are significant local dose differences. The application of the three tissue assignment schemes results in differences of up to 8 for D90; these differences vary between patients. Significant dose differences are seen between fully modeled and TG-43 calculations with TG-43 underestimating the dose (up to 36 in D90) for larger volumes containing higher proportions of healthy lung tissue. Conclusions: Metallic artifact correction is necessary for accurate application of MBDCs for lung brachytherapy; simpler threshold replacement methods may be sufficient for early adopters concerned with clinical dose metrics. Rigorous determination of voxel tissue parameters and tissue assignment is required for accurate dose calculations as different tissue assignment schemes can result in significantly different dose distributions. Significant differences are seen between MBDCs and TG-43 dose distributions with TG-43 underestimating dose in volumes containing healthy lung tissue.

KW - brachytherapy

KW - dosimetry

KW - I-125

KW - lung

KW - model-based dose calculations

KW - Monte Carlo

KW - permanent implants

UR - http://www.scopus.com/inward/record.url?scp=84864194175&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84864194175&partnerID=8YFLogxK

U2 - 10.1118/1.4729737

DO - 10.1118/1.4729737

M3 - Article

C2 - 22830769

AN - SCOPUS:84864194175

VL - 39

SP - 4365

EP - 4377

JO - Medical Physics

JF - Medical Physics

SN - 0094-2405

IS - 7

ER -