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Patient-Specific Fetal Dose Determination for Multi-Target Gamma Knife Radiosurgery: Computational Model and Case Report

A 42-year-old woman at 29 weeks gestation via in vitro fertilization who presented with eight metastatic brain lesions received Gamma Knife stereotactic radiosurgery (GKSRS) at our institution. In this study, we report our clinical experience and a general procedure of determining the fetal dose fro...

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Autores principales: Paulsson, Anna K, Braunstein, Steve, Phillips, Justin, Theodosopoulos, Philip V, McDermott, Michael, Sneed, Patricia K, Ma, Lijun
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Cureus 2017
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5621780/
https://www.ncbi.nlm.nih.gov/pubmed/28975062
http://dx.doi.org/10.7759/cureus.1527
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author Paulsson, Anna K
Braunstein, Steve
Phillips, Justin
Theodosopoulos, Philip V
McDermott, Michael
Sneed, Patricia K
Ma, Lijun
author_facet Paulsson, Anna K
Braunstein, Steve
Phillips, Justin
Theodosopoulos, Philip V
McDermott, Michael
Sneed, Patricia K
Ma, Lijun
author_sort Paulsson, Anna K
collection PubMed
description A 42-year-old woman at 29 weeks gestation via in vitro fertilization who presented with eight metastatic brain lesions received Gamma Knife stereotactic radiosurgery (GKSRS) at our institution. In this study, we report our clinical experience and a general procedure of determining the fetal dose from patient-specific treatment plans and we describe quality assurance measurements to guide the safe practice of multi-target GKSRS of pregnant patients. To estimate fetal dose pre-treatment, peripheral dose-to-focal dose ratios (PFRs) were measured in a phantom at the distance approximating the fundus of uterus. Post-treatment, fetal dose was calculated from the actual patient treatment plan. Quality assurance measurements were carried out via the extrapolation dosimetry method in a head phantom at increasing distances along the longitudinal axis. The measurements were then empirically fitted and the fetal dose was extracted from the curve. The computed and measured fetal dose values were compared with each other and associated radiation risk was estimated. Based on low estimated fetal dose from preliminary phantom measurements, the patient was accepted for GKSRS. Eight brain metastases were treated with prescription doses of 15-19 Gy over 143 min involving all collimator sizes as well as composite sector mixed shots. Direct fetal dose computation based on the actual patient’s treatment plan estimated a maximum fetal dose of 0.253 cGy, which was in agreement with surface dose measurements at the level of the patient’s uterine fundus during the actual treatment. Later phantom measurements also estimated fetal dose to be in the range of 0.21-0.28 cGy (dose extrapolation curve R(2 )= 0.998). Using the National Council on Radiation Protection and Measurements (NCRP) population-based model, we estimate the fetal risk of secondary malignancy, which is the primary toxicity after 25 weeks gestation, to be less than 0.01%. Of note, the patient delivered the baby via scheduled cesarean section at 36 weeks without complications attributable to the GKSRS procedure. GKSRS of multiple brain metastases was demonstrated to be safe and feasible during pregnancy. The applicability of a general patient-specific fetal dose determination method was also demonstrated for the first time for such a treatment.
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spelling pubmed-56217802017-10-03 Patient-Specific Fetal Dose Determination for Multi-Target Gamma Knife Radiosurgery: Computational Model and Case Report Paulsson, Anna K Braunstein, Steve Phillips, Justin Theodosopoulos, Philip V McDermott, Michael Sneed, Patricia K Ma, Lijun Cureus Radiation Oncology A 42-year-old woman at 29 weeks gestation via in vitro fertilization who presented with eight metastatic brain lesions received Gamma Knife stereotactic radiosurgery (GKSRS) at our institution. In this study, we report our clinical experience and a general procedure of determining the fetal dose from patient-specific treatment plans and we describe quality assurance measurements to guide the safe practice of multi-target GKSRS of pregnant patients. To estimate fetal dose pre-treatment, peripheral dose-to-focal dose ratios (PFRs) were measured in a phantom at the distance approximating the fundus of uterus. Post-treatment, fetal dose was calculated from the actual patient treatment plan. Quality assurance measurements were carried out via the extrapolation dosimetry method in a head phantom at increasing distances along the longitudinal axis. The measurements were then empirically fitted and the fetal dose was extracted from the curve. The computed and measured fetal dose values were compared with each other and associated radiation risk was estimated. Based on low estimated fetal dose from preliminary phantom measurements, the patient was accepted for GKSRS. Eight brain metastases were treated with prescription doses of 15-19 Gy over 143 min involving all collimator sizes as well as composite sector mixed shots. Direct fetal dose computation based on the actual patient’s treatment plan estimated a maximum fetal dose of 0.253 cGy, which was in agreement with surface dose measurements at the level of the patient’s uterine fundus during the actual treatment. Later phantom measurements also estimated fetal dose to be in the range of 0.21-0.28 cGy (dose extrapolation curve R(2 )= 0.998). Using the National Council on Radiation Protection and Measurements (NCRP) population-based model, we estimate the fetal risk of secondary malignancy, which is the primary toxicity after 25 weeks gestation, to be less than 0.01%. Of note, the patient delivered the baby via scheduled cesarean section at 36 weeks without complications attributable to the GKSRS procedure. GKSRS of multiple brain metastases was demonstrated to be safe and feasible during pregnancy. The applicability of a general patient-specific fetal dose determination method was also demonstrated for the first time for such a treatment. Cureus 2017-07-31 /pmc/articles/PMC5621780/ /pubmed/28975062 http://dx.doi.org/10.7759/cureus.1527 Text en Copyright © 2017, Paulsson et al. http://creativecommons.org/licenses/by/3.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
spellingShingle Radiation Oncology
Paulsson, Anna K
Braunstein, Steve
Phillips, Justin
Theodosopoulos, Philip V
McDermott, Michael
Sneed, Patricia K
Ma, Lijun
Patient-Specific Fetal Dose Determination for Multi-Target Gamma Knife Radiosurgery: Computational Model and Case Report
title Patient-Specific Fetal Dose Determination for Multi-Target Gamma Knife Radiosurgery: Computational Model and Case Report
title_full Patient-Specific Fetal Dose Determination for Multi-Target Gamma Knife Radiosurgery: Computational Model and Case Report
title_fullStr Patient-Specific Fetal Dose Determination for Multi-Target Gamma Knife Radiosurgery: Computational Model and Case Report
title_full_unstemmed Patient-Specific Fetal Dose Determination for Multi-Target Gamma Knife Radiosurgery: Computational Model and Case Report
title_short Patient-Specific Fetal Dose Determination for Multi-Target Gamma Knife Radiosurgery: Computational Model and Case Report
title_sort patient-specific fetal dose determination for multi-target gamma knife radiosurgery: computational model and case report
topic Radiation Oncology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5621780/
https://www.ncbi.nlm.nih.gov/pubmed/28975062
http://dx.doi.org/10.7759/cureus.1527
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