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Title: SU-E-T-86: A Systematic Method for GammaKnife SRS Fetal Dose Estimation

Abstract

Purpose: Estimating fetal dose is critical to the decision-making process when radiation treatment is indicated during pregnancy. Fetal doses less than 5cGy confer no measurable non-cancer developmental risks but can produce a threefold increase in developing childhood cancer. In this study, we estimate fetal dose for a patient receiving Gamma Knife stereotactic radiosurgery (GKSRS) treatment and develop a method to estimate dose directly from plan details. Methods: A patient underwent GKSRS on a Perfexion unit for eight brain metastases (two infratentorial and one brainstem). Dose measurements were performed using a CC13, head phantom, and solid water. Superficial doses to the thyroid, sternum, and pelvis were measured using MOSFETs during treatment. Because the fetal dose was too low to accurately measure, we obtained measurements proximally to the isocenter, fitted to an exponential function, and extrapolated dose to the fundus of the uterus, uterine midpoint, and pubic synthesis for both the preliminary and delivered plans. Results: The R-squared fit for the delivered doses was 0.995. The estimated fetal doses for the 72 minute preliminary and 138 minute delivered plans range from 0.0014 to 0.028cGy and 0.07 to 0.38cGy, respectively. MOSFET readings during treatment were just above background for the thyroid and negligiblemore » for all inferior positions. The method for estimating fetal dose from plan shot information was within 0.2cGy of the measured values at 14cm cranial to the fetal location. Conclusion: Estimated fetal doses for both the preliminary and delivered plan were well below the 5cGy recommended limit. Due to Pefexion shielding, internal dose is primarily governed by attenuation and drops off exponentially. This is the first work that reports fetal dose for a GK Perfexion unit. Although multiple lesions were treated and the duration of treatment was long, the estimated fetal dose remained very low.« less

Authors:
; ; ; ;  [1]
  1. UCSF Comprehensive Cancer Center, San Francisco, CA (United States)
Publication Date:
OSTI Identifier:
22545214
Resource Type:
Journal Article
Journal Name:
Medical Physics
Additional Journal Information:
Journal Volume: 42; Journal Issue: 6; Other Information: (c) 2015 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-2405
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 62 RADIOLOGY AND NUCLEAR MEDICINE; ATTENUATION; BRAIN; DECISION MAKING; HEAD; METASTASES; MOSFET; NEOPLASMS; PATIENTS; PELVIS; PHANTOMS; PREGNANCY; RADIATION DOSES; RADIOTHERAPY; SHIELDING; SURGERY; THYROID; UTERUS

Citation Formats

Geneser, S, Paulsson, A, Sneed, P, Braunstein, S, and Ma, L. SU-E-T-86: A Systematic Method for GammaKnife SRS Fetal Dose Estimation. United States: N. p., 2015. Web. doi:10.1118/1.4924447.
Geneser, S, Paulsson, A, Sneed, P, Braunstein, S, & Ma, L. SU-E-T-86: A Systematic Method for GammaKnife SRS Fetal Dose Estimation. United States. doi:10.1118/1.4924447.
Geneser, S, Paulsson, A, Sneed, P, Braunstein, S, and Ma, L. Mon . "SU-E-T-86: A Systematic Method for GammaKnife SRS Fetal Dose Estimation". United States. doi:10.1118/1.4924447.
@article{osti_22545214,
title = {SU-E-T-86: A Systematic Method for GammaKnife SRS Fetal Dose Estimation},
author = {Geneser, S and Paulsson, A and Sneed, P and Braunstein, S and Ma, L},
abstractNote = {Purpose: Estimating fetal dose is critical to the decision-making process when radiation treatment is indicated during pregnancy. Fetal doses less than 5cGy confer no measurable non-cancer developmental risks but can produce a threefold increase in developing childhood cancer. In this study, we estimate fetal dose for a patient receiving Gamma Knife stereotactic radiosurgery (GKSRS) treatment and develop a method to estimate dose directly from plan details. Methods: A patient underwent GKSRS on a Perfexion unit for eight brain metastases (two infratentorial and one brainstem). Dose measurements were performed using a CC13, head phantom, and solid water. Superficial doses to the thyroid, sternum, and pelvis were measured using MOSFETs during treatment. Because the fetal dose was too low to accurately measure, we obtained measurements proximally to the isocenter, fitted to an exponential function, and extrapolated dose to the fundus of the uterus, uterine midpoint, and pubic synthesis for both the preliminary and delivered plans. Results: The R-squared fit for the delivered doses was 0.995. The estimated fetal doses for the 72 minute preliminary and 138 minute delivered plans range from 0.0014 to 0.028cGy and 0.07 to 0.38cGy, respectively. MOSFET readings during treatment were just above background for the thyroid and negligible for all inferior positions. The method for estimating fetal dose from plan shot information was within 0.2cGy of the measured values at 14cm cranial to the fetal location. Conclusion: Estimated fetal doses for both the preliminary and delivered plan were well below the 5cGy recommended limit. Due to Pefexion shielding, internal dose is primarily governed by attenuation and drops off exponentially. This is the first work that reports fetal dose for a GK Perfexion unit. Although multiple lesions were treated and the duration of treatment was long, the estimated fetal dose remained very low.},
doi = {10.1118/1.4924447},
journal = {Medical Physics},
issn = {0094-2405},
number = 6,
volume = 42,
place = {United States},
year = {2015},
month = {6}
}