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Title: VMAT QA: Measurement-guided 4D dose reconstruction on a patient

Abstract

Purpose: To develop and validate a volume-modulated arc therapy (VMAT) quality assurance (QA) tool that takes as input a time-resolved, low-density ({approx}10 mm) cylindrical surface dose map from a commercial helical diode array, and outputs a high density, volumetric, time-resolved dose matrix on an arbitrary patient dataset. This first validation study is limited to a homogeneous 'patient.'Methods: A VMAT treatment is delivered to a diode array phantom (ARCCHECK, Sun Nuclear Corp., Melbourne, FL). 3DVH software (Sun Nuclear) derives the high-density volumetric dose using measurement-guided dose reconstruction (MGDR). MGDR cylindrical phantom results are then used to perturb the three-dimensional (3D) treatment planning dose on the patient dataset, producing a semiempirical volumetric dose grid. Four-dimensional (4D) dose reconstruction on the patient is also possible by morphing individual sub-beam doses instead of the composite. For conventional (3D) dose comparison two methods were developed, using the four plans (Multi-Target, C-shape, Mock Prostate, and Head and Neck), including their structures and objectives, from the AAPM TG-119 report. First, 3DVH and treatment planning system (TPS) cumulative point doses were compared to ion chamber in a cube water-equivalent phantom ('patient'). The shape of the phantom is different from the ARCCHECK and furthermore the targets were placed asymmetrically.more » Second, coronal and sagittal absolute film dose distributions in the cube were compared with 3DVH and TPS. For time-resolved (4D) comparisons, three tests were performed. First, volumetric dose differences were calculated between the 3D MGDR and cumulative time-resolved patient (4D MGDR) dose at the end of delivery, where they ideally should be identical. Second, time-resolved (10 Hz sampling rate) ion chamber doses were compared to cumulative point dose vs time curves from 4D MGDR. Finally, accelerator output was varied to assess the linearity of the 4D MGDR with global fluence change. Results: Across four TG-119 plans, the average PTV point dose difference in the cube between 3DVH and ion chamber is 0.1 {+-} 1.0%. Average film vs TPS {gamma}-analysis passing rates are 83.0%, 91.1%, and 98.4% for 1%/2 mm, 2%/2 mm, and 3%/3 mm threshold combinations, respectively, while average film vs 3DVH {gamma}-analysis passing rates are 88.6%, 96.1%, and 99.5% for the same respective criteria. 4D MGDR was also sufficiently accurate. First, for 99.5% voxels in each case, the doses from 3D and 4D MGDR at the end of delivery agree within 0.5%local dose-error/1 mm distance. Moreover, all failing voxels are confined to the edge of the cylindrical reconstruction volume. Second, dose vs time curves track between the ion chamber and 4D MGDR within 1%. Finally, 4D MGDR dose changes linearly with the accelerator output: the difference between cumulative ion chamber and MGDR dose changed by no more than 1% (randomly) with the output variation range of 10%. Conclusions: Even for a well-commissioned TPS, comparison metrics show better agreement on average to MGDR than to TPS on the arbitrary-shaped measurable 'patient.' The method requires no more accelerator time than standard QA, while producing more clinically relevant information. Validation in a heterogeneous thoracic phantom is under way, as is the ultimate application of 4D MGDR to virtual motion studies.« less

Authors:
; ; ; ; ; ;  [1]
  1. Canis Lupus LLC, Merrimac, Wisconsin 53561 (United States)
Publication Date:
OSTI Identifier:
22100645
Resource Type:
Journal Article
Journal Name:
Medical Physics
Additional Journal Information:
Journal Volume: 39; Journal Issue: 7; Other Information: (c) 2012 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:
61 RADIATION PROTECTION AND DOSIMETRY; 60 APPLIED LIFE SCIENCES; COMPARATIVE EVALUATIONS; COMPUTER CODES; DOSIMETRY; FILMS; HEAD; IONIZATION CHAMBERS; NECK; PATIENTS; PHANTOMS; PLANNING; PROSTATE; QUALITY ASSURANCE; RADIATION DOSE DISTRIBUTIONS; RADIATION DOSES; RADIATION MONITORING; RADIOTHERAPY; SEMICONDUCTOR DETECTORS; STANDARDS; SURFACES; TIME RESOLUTION

Citation Formats

Nelms, Benjamin E., Opp, Daniel, Robinson, Joshua, Wolf, Theresa K., Zhang, Geoffrey, Moros, Eduardo, Feygelman, Vladimir, Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612, Department of Physics, University of South Florida, Tampa, Florida 33612, Live Oak Technologies LLC, Kirkwood, Missouri 63122, and Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612. VMAT QA: Measurement-guided 4D dose reconstruction on a patient. United States: N. p., 2012. Web. doi:10.1118/1.4729709.
Nelms, Benjamin E., Opp, Daniel, Robinson, Joshua, Wolf, Theresa K., Zhang, Geoffrey, Moros, Eduardo, Feygelman, Vladimir, Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612, Department of Physics, University of South Florida, Tampa, Florida 33612, Live Oak Technologies LLC, Kirkwood, Missouri 63122, & Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612. VMAT QA: Measurement-guided 4D dose reconstruction on a patient. United States. https://doi.org/10.1118/1.4729709
Nelms, Benjamin E., Opp, Daniel, Robinson, Joshua, Wolf, Theresa K., Zhang, Geoffrey, Moros, Eduardo, Feygelman, Vladimir, Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612, Department of Physics, University of South Florida, Tampa, Florida 33612, Live Oak Technologies LLC, Kirkwood, Missouri 63122, and Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612. 2012. "VMAT QA: Measurement-guided 4D dose reconstruction on a patient". United States. https://doi.org/10.1118/1.4729709.
@article{osti_22100645,
title = {VMAT QA: Measurement-guided 4D dose reconstruction on a patient},
author = {Nelms, Benjamin E. and Opp, Daniel and Robinson, Joshua and Wolf, Theresa K. and Zhang, Geoffrey and Moros, Eduardo and Feygelman, Vladimir and Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612 and Department of Physics, University of South Florida, Tampa, Florida 33612 and Live Oak Technologies LLC, Kirkwood, Missouri 63122 and Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612},
abstractNote = {Purpose: To develop and validate a volume-modulated arc therapy (VMAT) quality assurance (QA) tool that takes as input a time-resolved, low-density ({approx}10 mm) cylindrical surface dose map from a commercial helical diode array, and outputs a high density, volumetric, time-resolved dose matrix on an arbitrary patient dataset. This first validation study is limited to a homogeneous 'patient.'Methods: A VMAT treatment is delivered to a diode array phantom (ARCCHECK, Sun Nuclear Corp., Melbourne, FL). 3DVH software (Sun Nuclear) derives the high-density volumetric dose using measurement-guided dose reconstruction (MGDR). MGDR cylindrical phantom results are then used to perturb the three-dimensional (3D) treatment planning dose on the patient dataset, producing a semiempirical volumetric dose grid. Four-dimensional (4D) dose reconstruction on the patient is also possible by morphing individual sub-beam doses instead of the composite. For conventional (3D) dose comparison two methods were developed, using the four plans (Multi-Target, C-shape, Mock Prostate, and Head and Neck), including their structures and objectives, from the AAPM TG-119 report. First, 3DVH and treatment planning system (TPS) cumulative point doses were compared to ion chamber in a cube water-equivalent phantom ('patient'). The shape of the phantom is different from the ARCCHECK and furthermore the targets were placed asymmetrically. Second, coronal and sagittal absolute film dose distributions in the cube were compared with 3DVH and TPS. For time-resolved (4D) comparisons, three tests were performed. First, volumetric dose differences were calculated between the 3D MGDR and cumulative time-resolved patient (4D MGDR) dose at the end of delivery, where they ideally should be identical. Second, time-resolved (10 Hz sampling rate) ion chamber doses were compared to cumulative point dose vs time curves from 4D MGDR. Finally, accelerator output was varied to assess the linearity of the 4D MGDR with global fluence change. Results: Across four TG-119 plans, the average PTV point dose difference in the cube between 3DVH and ion chamber is 0.1 {+-} 1.0%. Average film vs TPS {gamma}-analysis passing rates are 83.0%, 91.1%, and 98.4% for 1%/2 mm, 2%/2 mm, and 3%/3 mm threshold combinations, respectively, while average film vs 3DVH {gamma}-analysis passing rates are 88.6%, 96.1%, and 99.5% for the same respective criteria. 4D MGDR was also sufficiently accurate. First, for 99.5% voxels in each case, the doses from 3D and 4D MGDR at the end of delivery agree within 0.5%local dose-error/1 mm distance. Moreover, all failing voxels are confined to the edge of the cylindrical reconstruction volume. Second, dose vs time curves track between the ion chamber and 4D MGDR within 1%. Finally, 4D MGDR dose changes linearly with the accelerator output: the difference between cumulative ion chamber and MGDR dose changed by no more than 1% (randomly) with the output variation range of 10%. Conclusions: Even for a well-commissioned TPS, comparison metrics show better agreement on average to MGDR than to TPS on the arbitrary-shaped measurable 'patient.' The method requires no more accelerator time than standard QA, while producing more clinically relevant information. Validation in a heterogeneous thoracic phantom is under way, as is the ultimate application of 4D MGDR to virtual motion studies.},
doi = {10.1118/1.4729709},
url = {https://www.osti.gov/biblio/22100645}, journal = {Medical Physics},
issn = {0094-2405},
number = 7,
volume = 39,
place = {United States},
year = {2012},
month = {7}
}