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Title: Treatment Planning to Improve Delivery Accuracy and Patient Throughput in Helical Tomotherapy

Abstract

Purpose: To investigate delivery quality assurance (DQA) discrepancies observed for a subset of helical tomotherapy patients. Methods and Materials: Six tomotherapy patient plans were selected for analysis. Three had passing DQA ion chamber (IC) measurements, whereas 3 had measurements deviating from the expected dose by more than 3.0%. All plans used similar parameters, including: 2.5 cm field-width, 15-s gantry period, and pitch values ranging from 0.143 to 0.215. Preliminary analysis suggested discrepancies were associated with plans having predominantly small leaf open times (LOTs). To test this, patients with failing DQA measurements were replanned using an increased pitch of 0.287. New DQA plans were generated and IC measurements performed. Exit fluence data were also collected during DQA delivery for dose reconstruction purposes. Results: Sinogram analysis showed increases in mean LOTs ranging from 29.8% to 83.1% for the increased pitch replans. IC measurements for these plans showed a reduction in dose discrepancies, bringing all measurements within {+-}3.0%. The replans were also more efficient to deliver, resulting in reduced treatment times. Dose reconstruction results were in excellent agreement with IC measurements, illustrating the impact of leaf-timing inaccuracies on plans having predominantly small LOTs. Conclusions: The impact of leaf-timing inaccuracies on plans with smallmore » mean LOTs can be considerable. These inaccuracies result from deviations in multileaf collimator latency from the linear approximation used by the treatment planning system and can be important for plans having a 15-s gantry period. The ability to reduce this effect while improving delivery efficiency by increasing the pitch is demonstrated.« less

Authors:
 [1];  [2];  [1];  [3];  [3];  [3]
  1. Department of Human Oncology, University of Wisconsin, School of Medicine and Public Health, Madison, WI (United States)
  2. Department of TomoTherapy, Inc., Madison, WI (United States)
  3. Department of Medical Physics, University of Wisconsin, School of Medicine and Public Health, Madison, WI (United States)
Publication Date:
OSTI Identifier:
21276924
Resource Type:
Journal Article
Journal Name:
International Journal of Radiation Oncology, Biology and Physics
Additional Journal Information:
Journal Volume: 74; Journal Issue: 4; Other Information: DOI: 10.1016/j.ijrobp.2009.02.004; PII: S0360-3016(09)00226-0; Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0360-3016
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; COMPUTERIZED TOMOGRAPHY; CT-GUIDED RADIOTHERAPY; IONIZATION CHAMBERS; PATIENTS; PLANNING; QUALITY ASSURANCE; RADIATION DOSES

Citation Formats

Westerly, David C., Soisson, Emilie, Quan, Chen, Woch, Katherine, Schubert, Leah, Olivera, Gustavo, Department of TomoTherapy, Inc., Madison, WI, Mackie, Thomas R, Department of Human Oncology, University of Wisconsin, School of Medicine and Public Health, Madison, WI, and Department of TomoTherapy, Inc., Madison, WI. Treatment Planning to Improve Delivery Accuracy and Patient Throughput in Helical Tomotherapy. United States: N. p., 2009. Web. doi:10.1016/j.ijrobp.2009.02.004.
Westerly, David C., Soisson, Emilie, Quan, Chen, Woch, Katherine, Schubert, Leah, Olivera, Gustavo, Department of TomoTherapy, Inc., Madison, WI, Mackie, Thomas R, Department of Human Oncology, University of Wisconsin, School of Medicine and Public Health, Madison, WI, & Department of TomoTherapy, Inc., Madison, WI. Treatment Planning to Improve Delivery Accuracy and Patient Throughput in Helical Tomotherapy. United States. https://doi.org/10.1016/j.ijrobp.2009.02.004
Westerly, David C., Soisson, Emilie, Quan, Chen, Woch, Katherine, Schubert, Leah, Olivera, Gustavo, Department of TomoTherapy, Inc., Madison, WI, Mackie, Thomas R, Department of Human Oncology, University of Wisconsin, School of Medicine and Public Health, Madison, WI, and Department of TomoTherapy, Inc., Madison, WI. 2009. "Treatment Planning to Improve Delivery Accuracy and Patient Throughput in Helical Tomotherapy". United States. https://doi.org/10.1016/j.ijrobp.2009.02.004.
@article{osti_21276924,
title = {Treatment Planning to Improve Delivery Accuracy and Patient Throughput in Helical Tomotherapy},
author = {Westerly, David C. and Soisson, Emilie and Quan, Chen and Woch, Katherine and Schubert, Leah and Olivera, Gustavo and Department of TomoTherapy, Inc., Madison, WI and Mackie, Thomas R and Department of Human Oncology, University of Wisconsin, School of Medicine and Public Health, Madison, WI and Department of TomoTherapy, Inc., Madison, WI},
abstractNote = {Purpose: To investigate delivery quality assurance (DQA) discrepancies observed for a subset of helical tomotherapy patients. Methods and Materials: Six tomotherapy patient plans were selected for analysis. Three had passing DQA ion chamber (IC) measurements, whereas 3 had measurements deviating from the expected dose by more than 3.0%. All plans used similar parameters, including: 2.5 cm field-width, 15-s gantry period, and pitch values ranging from 0.143 to 0.215. Preliminary analysis suggested discrepancies were associated with plans having predominantly small leaf open times (LOTs). To test this, patients with failing DQA measurements were replanned using an increased pitch of 0.287. New DQA plans were generated and IC measurements performed. Exit fluence data were also collected during DQA delivery for dose reconstruction purposes. Results: Sinogram analysis showed increases in mean LOTs ranging from 29.8% to 83.1% for the increased pitch replans. IC measurements for these plans showed a reduction in dose discrepancies, bringing all measurements within {+-}3.0%. The replans were also more efficient to deliver, resulting in reduced treatment times. Dose reconstruction results were in excellent agreement with IC measurements, illustrating the impact of leaf-timing inaccuracies on plans having predominantly small LOTs. Conclusions: The impact of leaf-timing inaccuracies on plans with small mean LOTs can be considerable. These inaccuracies result from deviations in multileaf collimator latency from the linear approximation used by the treatment planning system and can be important for plans having a 15-s gantry period. The ability to reduce this effect while improving delivery efficiency by increasing the pitch is demonstrated.},
doi = {10.1016/j.ijrobp.2009.02.004},
url = {https://www.osti.gov/biblio/21276924}, journal = {International Journal of Radiation Oncology, Biology and Physics},
issn = {0360-3016},
number = 4,
volume = 74,
place = {United States},
year = {Wed Jul 15 00:00:00 EDT 2009},
month = {Wed Jul 15 00:00:00 EDT 2009}
}