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Title: SU-E-T-197: Helical Cranial-Spinal Treatments with a Linear Accelerator

Abstract

Purpose: Craniospinal irradiation (CSI) of systemic disease requires a high level of beam intensity modulation to reduce dose to bone marrow and other critical structures. Current helical delivery machines can take 30 minutes or more of beam-on time to complete these treatments. This pilot study aims to test the feasibility of performing helical treatments with a conventional linear accelerator using longitudinal couch travel during multiple gantry revolutions. Methods: The VMAT optimization package of the Eclipse 10.0 treatment planning system was used to optimize pseudo-helical CSI plans of 5 clinical patient scans. Each gantry revolution was divided into three 120° arcs with each isocenter shifted longitudinally. Treatments requiring more than the maximum 10 arcs used multiple plans with each plan after the first being optimized including the dose of the others (Figure 1). The beam pitch was varied between 0.2 and 0.9 (couch speed 5- 20cm/revolution and field width of 22cm) and dose-volume histograms of critical organs were compared to tomotherapy plans. Results: Viable pseudo-helical plans were achieved using Eclipse. Decreasing the pitch from 0.9 to 0.2 lowered the maximum lens dose by 40%, the mean bone marrow dose by 2.1% and the maximum esophagus dose by 17.5%. (Figure 2). Linac-basedmore » helical plans showed dose results comparable to tomotherapy delivery for both target coverage and critical organ sparing, with the D50 of bone marrow and esophagus respectively 12% and 31% lower in the helical linear accelerator plan (Figure 3). Total mean beam-on time for the linear accelerator plan was 8.3 minutes, 54% faster than the tomotherapy average for the same plans. Conclusions: This pilot study has demonstrated the feasibility of planning pseudo-helical treatments for CSI targets using a conventional linac and dynamic couch movement, and supports the ongoing development of true helical optimization and delivery.« less

Authors:
; ; ; ; ;  [1]
  1. Rush University Medical Center, Chicago, IL (United States)
Publication Date:
OSTI Identifier:
22351035
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 41; Journal Issue: 6; Other Information: (c) 2014 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; BONE MARROW; COMPUTERIZED TOMOGRAPHY; CRITICAL ORGANS; CT-GUIDED RADIOTHERAPY; ESOPHAGUS; IRRADIATION; LINEAR ACCELERATORS; OPTIMIZATION; PATIENTS; RADIATION DOSES

Citation Formats

Anderson, J, Bernard, D, Liao, Y, Templeton, A, Turian, J, and Chu, J. SU-E-T-197: Helical Cranial-Spinal Treatments with a Linear Accelerator. United States: N. p., 2014. Web. doi:10.1118/1.4888527.
Anderson, J, Bernard, D, Liao, Y, Templeton, A, Turian, J, & Chu, J. SU-E-T-197: Helical Cranial-Spinal Treatments with a Linear Accelerator. United States. doi:10.1118/1.4888527.
Anderson, J, Bernard, D, Liao, Y, Templeton, A, Turian, J, and Chu, J. 2014. "SU-E-T-197: Helical Cranial-Spinal Treatments with a Linear Accelerator". United States. doi:10.1118/1.4888527.
@article{osti_22351035,
title = {SU-E-T-197: Helical Cranial-Spinal Treatments with a Linear Accelerator},
author = {Anderson, J and Bernard, D and Liao, Y and Templeton, A and Turian, J and Chu, J},
abstractNote = {Purpose: Craniospinal irradiation (CSI) of systemic disease requires a high level of beam intensity modulation to reduce dose to bone marrow and other critical structures. Current helical delivery machines can take 30 minutes or more of beam-on time to complete these treatments. This pilot study aims to test the feasibility of performing helical treatments with a conventional linear accelerator using longitudinal couch travel during multiple gantry revolutions. Methods: The VMAT optimization package of the Eclipse 10.0 treatment planning system was used to optimize pseudo-helical CSI plans of 5 clinical patient scans. Each gantry revolution was divided into three 120° arcs with each isocenter shifted longitudinally. Treatments requiring more than the maximum 10 arcs used multiple plans with each plan after the first being optimized including the dose of the others (Figure 1). The beam pitch was varied between 0.2 and 0.9 (couch speed 5- 20cm/revolution and field width of 22cm) and dose-volume histograms of critical organs were compared to tomotherapy plans. Results: Viable pseudo-helical plans were achieved using Eclipse. Decreasing the pitch from 0.9 to 0.2 lowered the maximum lens dose by 40%, the mean bone marrow dose by 2.1% and the maximum esophagus dose by 17.5%. (Figure 2). Linac-based helical plans showed dose results comparable to tomotherapy delivery for both target coverage and critical organ sparing, with the D50 of bone marrow and esophagus respectively 12% and 31% lower in the helical linear accelerator plan (Figure 3). Total mean beam-on time for the linear accelerator plan was 8.3 minutes, 54% faster than the tomotherapy average for the same plans. Conclusions: This pilot study has demonstrated the feasibility of planning pseudo-helical treatments for CSI targets using a conventional linac and dynamic couch movement, and supports the ongoing development of true helical optimization and delivery.},
doi = {10.1118/1.4888527},
journal = {Medical Physics},
number = 6,
volume = 41,
place = {United States},
year = 2014,
month = 6
}
  • Intracranial stereotactic radiosurgery has been practiced since 1951. The technique has expanded from a single dedicated unit in Stockholm in 1968 to hundreds of centers performing an estimated 100,000 Gamma Knife and linear accelerator cases in 2005. The radiation dosimetry of small photon fields used in this technique has been well explored in the past 15 years. Quality assurance recommendations have been promulgated in refereed reports and by several national and international professional societies since 1991. The field has survived several reported treatment errors and incidents, generally reacting by strengthening standards and precautions. An increasing number of computer-controlled and robotic-dedicatedmore » treatment units are expanding the field and putting patients at risk of unforeseen errors. Revisions and updates to previously published quality assurance documents, and especially to radiation dosimetry protocols, are now needed to ensure continued successful procedures that minimize the risk of serious errors.« less
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