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Title: SU-D-201-01: A Multi-Institutional Study Quantifying the Impact of Simulated Linear Accelerator VMAT Errors for Nasopharynx

Abstract

Purpose: To quantify the impact of differing magnitudes of simulated linear accelerator errors on the dose to the target volume and organs at risk for nasopharynx VMAT. Methods: Ten nasopharynx cancer patients were retrospectively replanned twice with one full arc VMAT by two institutions. Treatment uncertainties (gantry angle and collimator in degrees, MLC field size and MLC shifts in mm) were introduced into these plans at increments of 5,2,1,−1,−2 and −5. This was completed using an in-house Python script within Pinnacle3 and analysed using 3DVH and MatLab. The mean and maximum dose were calculated for the Planning Target Volume (PTV1), parotids, brainstem, and spinal cord and then compared to the original baseline plan. The D1cc was also calculated for the spinal cord and brainstem. Patient average results were compared across institutions. Results: Introduced gantry angle errors had the smallest effect of dose, no tolerances were exceeded for one institution, and the second institutions VMAT plans were only exceeded for gantry angle of ±5° affecting different sided parotids by 14–18%. PTV1, brainstem and spinal cord tolerances were exceeded for collimator angles of ±5 degrees, MLC shifts and MLC field sizes of ±1 and beyond, at the first institution. At the secondmore » institution, sensitivity to errors was marginally higher for some errors including the collimator error producing doses exceeding tolerances above ±2 degrees, and marginally lower with tolerances exceeded above MLC shifts of ±2. The largest differences occur with MLC field sizes, with both institutions reporting exceeded tolerances, for all introduced errors (±1 and beyond). Conclusion: The plan robustness for VMAT nasopharynx plans has been demonstrated. Gantry errors have the least impact on patient doses, however MLC field sizes exceed tolerances even with relatively low introduced errors and also produce the largest errors. This was consistent across both departments. The authors acknowledge funding support from the NSW Cancer Council.« less

Authors:
 [1];  [2];  [2];  [3];  [4]; ;  [1]; ; ; ; ; ;  [5];  [1];  [2];  [2];  [2];  [2]
  1. Institute of Medical Physics, The University of Sydney, Sydney, NSW (Australia)
  2. (Australia)
  3. Laboratory of Radiation Physics, Odense University Hospital, Odense (Denmark)
  4. (Denmark)
  5. Liverpool and Macarthur Cancer Therapy Centres, Liverpool, NSW (Australia)
Publication Date:
OSTI Identifier:
22624366
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 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; 61 RADIATION PROTECTION AND DOSIMETRY; COLLIMATORS; COMPARATIVE EVALUATIONS; ERRORS; HAZARDS; LINEAR ACCELERATORS; NEOPLASMS; PATIENTS; PHARYNX; PLANNING; RADIATION DOSES; RADIOTHERAPY; SENSITIVITY; SIMULATION; SPINAL CORD; TOLERANCE

Citation Formats

Pogson, E, Liverpool and Macarthur Cancer Therapy Centres, Liverpool, NSW, Ingham Institute for Applied Medical Research, Sydney, NSW, Hansen, C, Institute of Clinical Research, University of Southern Denmark, Odense, Blake, S, Thwaites, D, Arumugam, S, Juresic, J, Ochoa, C, Yakobi, J, Haman, A, Trtovac, A, Holloway, L, Liverpool and Macarthur Cancer Therapy Centres, Liverpool, NSW, Ingham Institute for Applied Medical Research, Sydney, NSW, South Western Sydney Clinical School, University of New South Wales, Sydney, NSW, and University of Wollongong, Wollongong, NSW. SU-D-201-01: A Multi-Institutional Study Quantifying the Impact of Simulated Linear Accelerator VMAT Errors for Nasopharynx. United States: N. p., 2016. Web. doi:10.1118/1.4955613.
Pogson, E, Liverpool and Macarthur Cancer Therapy Centres, Liverpool, NSW, Ingham Institute for Applied Medical Research, Sydney, NSW, Hansen, C, Institute of Clinical Research, University of Southern Denmark, Odense, Blake, S, Thwaites, D, Arumugam, S, Juresic, J, Ochoa, C, Yakobi, J, Haman, A, Trtovac, A, Holloway, L, Liverpool and Macarthur Cancer Therapy Centres, Liverpool, NSW, Ingham Institute for Applied Medical Research, Sydney, NSW, South Western Sydney Clinical School, University of New South Wales, Sydney, NSW, & University of Wollongong, Wollongong, NSW. SU-D-201-01: A Multi-Institutional Study Quantifying the Impact of Simulated Linear Accelerator VMAT Errors for Nasopharynx. United States. doi:10.1118/1.4955613.
Pogson, E, Liverpool and Macarthur Cancer Therapy Centres, Liverpool, NSW, Ingham Institute for Applied Medical Research, Sydney, NSW, Hansen, C, Institute of Clinical Research, University of Southern Denmark, Odense, Blake, S, Thwaites, D, Arumugam, S, Juresic, J, Ochoa, C, Yakobi, J, Haman, A, Trtovac, A, Holloway, L, Liverpool and Macarthur Cancer Therapy Centres, Liverpool, NSW, Ingham Institute for Applied Medical Research, Sydney, NSW, South Western Sydney Clinical School, University of New South Wales, Sydney, NSW, and University of Wollongong, Wollongong, NSW. Wed . "SU-D-201-01: A Multi-Institutional Study Quantifying the Impact of Simulated Linear Accelerator VMAT Errors for Nasopharynx". United States. doi:10.1118/1.4955613.
@article{osti_22624366,
title = {SU-D-201-01: A Multi-Institutional Study Quantifying the Impact of Simulated Linear Accelerator VMAT Errors for Nasopharynx},
author = {Pogson, E and Liverpool and Macarthur Cancer Therapy Centres, Liverpool, NSW and Ingham Institute for Applied Medical Research, Sydney, NSW and Hansen, C and Institute of Clinical Research, University of Southern Denmark, Odense and Blake, S and Thwaites, D and Arumugam, S and Juresic, J and Ochoa, C and Yakobi, J and Haman, A and Trtovac, A and Holloway, L and Liverpool and Macarthur Cancer Therapy Centres, Liverpool, NSW and Ingham Institute for Applied Medical Research, Sydney, NSW and South Western Sydney Clinical School, University of New South Wales, Sydney, NSW and University of Wollongong, Wollongong, NSW},
abstractNote = {Purpose: To quantify the impact of differing magnitudes of simulated linear accelerator errors on the dose to the target volume and organs at risk for nasopharynx VMAT. Methods: Ten nasopharynx cancer patients were retrospectively replanned twice with one full arc VMAT by two institutions. Treatment uncertainties (gantry angle and collimator in degrees, MLC field size and MLC shifts in mm) were introduced into these plans at increments of 5,2,1,−1,−2 and −5. This was completed using an in-house Python script within Pinnacle3 and analysed using 3DVH and MatLab. The mean and maximum dose were calculated for the Planning Target Volume (PTV1), parotids, brainstem, and spinal cord and then compared to the original baseline plan. The D1cc was also calculated for the spinal cord and brainstem. Patient average results were compared across institutions. Results: Introduced gantry angle errors had the smallest effect of dose, no tolerances were exceeded for one institution, and the second institutions VMAT plans were only exceeded for gantry angle of ±5° affecting different sided parotids by 14–18%. PTV1, brainstem and spinal cord tolerances were exceeded for collimator angles of ±5 degrees, MLC shifts and MLC field sizes of ±1 and beyond, at the first institution. At the second institution, sensitivity to errors was marginally higher for some errors including the collimator error producing doses exceeding tolerances above ±2 degrees, and marginally lower with tolerances exceeded above MLC shifts of ±2. The largest differences occur with MLC field sizes, with both institutions reporting exceeded tolerances, for all introduced errors (±1 and beyond). Conclusion: The plan robustness for VMAT nasopharynx plans has been demonstrated. Gantry errors have the least impact on patient doses, however MLC field sizes exceed tolerances even with relatively low introduced errors and also produce the largest errors. This was consistent across both departments. The authors acknowledge funding support from the NSW Cancer Council.},
doi = {10.1118/1.4955613},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = {Wed Jun 15 00:00:00 EDT 2016},
month = {Wed Jun 15 00:00:00 EDT 2016}
}