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Title: Agreement Between Institutional Measurements and Treatment Planning System Calculations for Basic Dosimetric Parameters as Measured by the Imaging and Radiation Oncology Core-Houston

Abstract

Purpose: To compare radiation machine measurement data collected by the Imaging and Radiation Oncology Core at Houston (IROC-H) with institutional treatment planning system (TPS) values, to identify parameters with large differences in agreement; the findings will help institutions focus their efforts to improve the accuracy of their TPS models. Methods and Materials: Between 2000 and 2014, IROC-H visited more than 250 institutions and conducted independent measurements of machine dosimetric data points, including percentage depth dose, output factors, off-axis factors, multileaf collimator small fields, and wedge data. We compared these data with the institutional TPS values for the same points by energy, class, and parameter to identify differences and similarities using criteria involving both the medians and standard deviations for Varian linear accelerators. Distributions of differences between machine measurements and institutional TPS values were generated for basic dosimetric parameters. Results: On average, intensity modulated radiation therapy–style and stereotactic body radiation therapy–style output factors and upper physical wedge output factors were the most problematic. Percentage depth dose, jaw output factors, and enhanced dynamic wedge output factors agreed best between the IROC-H measurements and the TPS values. Although small differences were shown between 2 common TPS systems, neither was superior to the other.more » Parameter agreement was constant over time from 2000 to 2014. Conclusions: Differences in basic dosimetric parameters between machine measurements and TPS values vary widely depending on the parameter, although agreement does not seem to vary by TPS and has not changed over time. Intensity modulated radiation therapy–style output factors, stereotactic body radiation therapy–style output factors, and upper physical wedge output factors had the largest disagreement and should be carefully modeled to ensure accuracy.« less

Authors:
;  [1];  [2];  [2]; ; ; ;  [1];  [2];  [1];  [2];  [2]
  1. Department of Radiation Physics, The University of Texas Health Science Center-Houston, Houston, Texas (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
22648773
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Radiation Oncology, Biology and Physics; Journal Volume: 95; Journal Issue: 5; Other Information: Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; BIOMEDICAL RADIOGRAPHY; DEPTH DOSE DISTRIBUTIONS; DOSIMETRY; LINEAR ACCELERATORS; RADIOTHERAPY

Citation Formats

Kerns, James R., Followill, David S., Imaging and Radiation Oncology Core-Houston, The University of Texas Health Science Center-Houston, Houston, Texas, Graduate School of Biomedical Sciences, The University of Texas Health Science Center-Houston, Houston, Texas, Lowenstein, Jessica, Molineu, Andrea, Alvarez, Paola, Taylor, Paige A., Imaging and Radiation Oncology Core-Houston, The University of Texas Health Science Center-Houston, Houston, Texas, Kry, Stephen F., E-mail: sfkry@mdanderson.org, Imaging and Radiation Oncology Core-Houston, The University of Texas Health Science Center-Houston, Houston, Texas, and Graduate School of Biomedical Sciences, The University of Texas Health Science Center-Houston, Houston, Texas. Agreement Between Institutional Measurements and Treatment Planning System Calculations for Basic Dosimetric Parameters as Measured by the Imaging and Radiation Oncology Core-Houston. United States: N. p., 2016. Web. doi:10.1016/J.IJROBP.2016.03.035.
Kerns, James R., Followill, David S., Imaging and Radiation Oncology Core-Houston, The University of Texas Health Science Center-Houston, Houston, Texas, Graduate School of Biomedical Sciences, The University of Texas Health Science Center-Houston, Houston, Texas, Lowenstein, Jessica, Molineu, Andrea, Alvarez, Paola, Taylor, Paige A., Imaging and Radiation Oncology Core-Houston, The University of Texas Health Science Center-Houston, Houston, Texas, Kry, Stephen F., E-mail: sfkry@mdanderson.org, Imaging and Radiation Oncology Core-Houston, The University of Texas Health Science Center-Houston, Houston, Texas, & Graduate School of Biomedical Sciences, The University of Texas Health Science Center-Houston, Houston, Texas. Agreement Between Institutional Measurements and Treatment Planning System Calculations for Basic Dosimetric Parameters as Measured by the Imaging and Radiation Oncology Core-Houston. United States. doi:10.1016/J.IJROBP.2016.03.035.
Kerns, James R., Followill, David S., Imaging and Radiation Oncology Core-Houston, The University of Texas Health Science Center-Houston, Houston, Texas, Graduate School of Biomedical Sciences, The University of Texas Health Science Center-Houston, Houston, Texas, Lowenstein, Jessica, Molineu, Andrea, Alvarez, Paola, Taylor, Paige A., Imaging and Radiation Oncology Core-Houston, The University of Texas Health Science Center-Houston, Houston, Texas, Kry, Stephen F., E-mail: sfkry@mdanderson.org, Imaging and Radiation Oncology Core-Houston, The University of Texas Health Science Center-Houston, Houston, Texas, and Graduate School of Biomedical Sciences, The University of Texas Health Science Center-Houston, Houston, Texas. 2016. "Agreement Between Institutional Measurements and Treatment Planning System Calculations for Basic Dosimetric Parameters as Measured by the Imaging and Radiation Oncology Core-Houston". United States. doi:10.1016/J.IJROBP.2016.03.035.
@article{osti_22648773,
title = {Agreement Between Institutional Measurements and Treatment Planning System Calculations for Basic Dosimetric Parameters as Measured by the Imaging and Radiation Oncology Core-Houston},
author = {Kerns, James R. and Followill, David S. and Imaging and Radiation Oncology Core-Houston, The University of Texas Health Science Center-Houston, Houston, Texas and Graduate School of Biomedical Sciences, The University of Texas Health Science Center-Houston, Houston, Texas and Lowenstein, Jessica and Molineu, Andrea and Alvarez, Paola and Taylor, Paige A. and Imaging and Radiation Oncology Core-Houston, The University of Texas Health Science Center-Houston, Houston, Texas and Kry, Stephen F., E-mail: sfkry@mdanderson.org and Imaging and Radiation Oncology Core-Houston, The University of Texas Health Science Center-Houston, Houston, Texas and Graduate School of Biomedical Sciences, The University of Texas Health Science Center-Houston, Houston, Texas},
abstractNote = {Purpose: To compare radiation machine measurement data collected by the Imaging and Radiation Oncology Core at Houston (IROC-H) with institutional treatment planning system (TPS) values, to identify parameters with large differences in agreement; the findings will help institutions focus their efforts to improve the accuracy of their TPS models. Methods and Materials: Between 2000 and 2014, IROC-H visited more than 250 institutions and conducted independent measurements of machine dosimetric data points, including percentage depth dose, output factors, off-axis factors, multileaf collimator small fields, and wedge data. We compared these data with the institutional TPS values for the same points by energy, class, and parameter to identify differences and similarities using criteria involving both the medians and standard deviations for Varian linear accelerators. Distributions of differences between machine measurements and institutional TPS values were generated for basic dosimetric parameters. Results: On average, intensity modulated radiation therapy–style and stereotactic body radiation therapy–style output factors and upper physical wedge output factors were the most problematic. Percentage depth dose, jaw output factors, and enhanced dynamic wedge output factors agreed best between the IROC-H measurements and the TPS values. Although small differences were shown between 2 common TPS systems, neither was superior to the other. Parameter agreement was constant over time from 2000 to 2014. Conclusions: Differences in basic dosimetric parameters between machine measurements and TPS values vary widely depending on the parameter, although agreement does not seem to vary by TPS and has not changed over time. Intensity modulated radiation therapy–style output factors, stereotactic body radiation therapy–style output factors, and upper physical wedge output factors had the largest disagreement and should be carefully modeled to ensure accuracy.},
doi = {10.1016/J.IJROBP.2016.03.035},
journal = {International Journal of Radiation Oncology, Biology and Physics},
number = 5,
volume = 95,
place = {United States},
year = 2016,
month = 8
}
  • Purpose: To describe the extent of IROC Houston’s (formerly the RPC) QA activities and audit results for radiotherapy institutions outside of North America (NA). Methods: The IROC Houston’s QA program components were designed to audit the radiation dose calculation chain from the NIST traceable reference beam calibration, to inclusion of dosimetry parameters used to calculate tumor doses, to the delivery of the radiation dose. The QA program provided to international institutions includes: 1) remote TLD/OSLD audit of machine output, 2) credentialing for advanced technologies, and 3) review of patient treatment records. IROC Houston uses the same standards and acceptance criteriamore » for all of its audits whether for North American or international sites. Results: IROC Houston’s QA program has reached out to radiotherapy sites in 43 different countries since 2013 through their participation in clinical trials. In the past two years, 2,778 international megavoltage beam outputs were audited with OSLD/TLD. While the average IROC/Inst ratio is near unity for all sites monitored, there are international regions whose results are significantly different from the NA region. In the past 2 years, 477 and 87 IMRT H&N phantoms were irradiated at NA and international sites, respectively. Regardless of the OSLD beam audit results, the overall pass rate (87 percent) for all international sites (no region separation) is equal to the NA sites. Of the 182 international patient charts reviewed, 10.7 percent of the dose calculation points did not meet our acceptance criterion as compared to 13.6 percent for NA sites. The lower pass rate for NA sites results from a much larger brachytherapy component which has been shown to be more error prone. Conclusion: IROC Houston has expanded its QA services worldwide and continues a long history of improving radiotherapy dose delivery in many countries. Funding received for QA audit services from the Korean GOG, DAHANCA, EORTC, ICON and CMIC Group.« less
  • Purpose: To provide information pertaining to IROC Houston QA Center's (RPC) credentialing process for institutions participating in NCI-sponsored clinical trials. Methods: IROC Houston issues credentials for NCI sponsored study groups. Requirements for credentialing might include any combination of questionnaires, knowledge assessment forms, benchmarks, or phantom irradiations. Credentialing requirements for specific protocols can be found on IROC Houston's website (irochouston.mdanderson.org). The website also houses the credentialing status inquiry (CSI) form. Once an institution has reviewed the protocol's credentialing requirements, a CSI form should be completed and submitted to IROC Houston. This form is used both to request whether requirements have beenmore » met as well as to notify IROC Houston that the institution requests credentialing for a specific protocol. IROC Houston will contact the institution to discuss any delinquent requirements. Once the institution has met all requirements IROC Houston issues a credentialing letter to the institution and will inform study groups and other IROC offices of the credentials. Institutions can all phone the IROC Houston office to initiate credentialing or ask any credentialing related questions. Results: Since 2010 IROC has received 1313 credentialing status inquiry forms. We received 317 in 2010, 266 in 2011, 324 in 2012, and 406 in 2013. On average we receive 35 phone calls per week with multiple types of credentialing questions. Decisions regarding credentialing status are based on the protocol specifications and previous completed credentialing by the institution. In some cases, such as for general IMRT credentialing, up to 5 sites may be credentialed based on the credentialing of one main center. Each of these situations is handled individually. Conclusion: IROC Houston will issue radiation therapy credentials for the NCI trials in the National Clinical Trials Network. Credentialing requirements and the CSI form can be found online at the IROC Houston's website. Work supported by PHS grant CA10953 and CA081647 (NCI, DHHS)« less
  • Purpose: To describe the results of IROC Houston’s international and domestic end-to-end QA phantom irradiations. Methods: IROC Houston has anthropomorphic lung, liver, head and neck, prostate, SRS and spine phantoms that are used for credentialing and quality assurance purposes. The phantoms include structures that closely mimic targets and organs at risk and are made from tissue equivalent materials: high impact polystyrene, solid water, cork and acrylic. Motion tables are used to mimic breathing motion for some lung and liver phantoms. Dose is measured with TLD and radiochromic film in various planes within the target of the phantoms. Results: The mostmore » common phantom requested is the head and neck followed by the lung phantom. The head and neck phantom was sent to 800 domestic and 148 international sites between 2011 and 2015, with average pass rates of 89% and 92%, respectively. During the past five years, a general upward trend exists regarding demand for the lung phantom for both international and domestic sites with international sites more than tripling from 5 (2011) to 16 (2015) and domestic sites doubling from 66 (2011) to 152 (2015). The pass rate for lung phantoms has been consistent from year to year despite this large increase in the number of phantoms irradiated with an average pass rate of 85% (domestic) and 95% (international) sites. The percentage of lung phantoms used in combination with motions tables increased from 38% to 79% over the 5 year time span. Conclusion: The number of domestic and international sites irradiating the head and neck and lung phantoms continues to increase and the pass rates remained constant. These end-to-end QA tests continue to be a crucial part of clinical trial credentialing and institution quality assurance. This investigation was supported by IROC grant CA180803 awarded by the NCI.« less
  • The explosion of new imaging technologies such as X ray computed tomography (CT), ultrasound (US), positron emission tomography (PET), and nuclear magnetic resonance imaging (NMR) has forced a major change in radiation therapy treatment planning philosophy and procedures. Modern computer technology has been wedded to these new imaging modalities, making possible sophisticated radiation therapy treatment planning using both the detailed anatomical and density information that is made available by CT and the other imaging modalities. This had forced a revolution in the way treatments are planned, with the result that actual beam configurations are typically both more complex and moremore » carefully tailored to the desired target volume. This increase in precision and accuracy will presumably improve the results of radiation therapy.« less
  • Purpose: The purpose of this study was to prospectively investigate clinical correlations between dosimetric parameters associated with radiation pneumonitis (RP) and functional lung imaging. Methods and Materials: Functional lung imaging was performed using four-dimensional computed tomography (4D-CT) for ventilation imaging, single-photon emission computed tomography (SPECT) for perfusion imaging, or both (V/Q-matched region). Using 4D-CT, ventilation imaging was derived from a low attenuation area according to CT numbers below different thresholds (vent-860 and -910). Perfusion imaging at the 10th, 30th, 50th, and 70th percentile perfusion levels (F10-F70) were defined as the top 10%, 30%, 50%, and 70% hyperperfused normal lung, respectively.more » All imaging data were incorporated into a 3D planning system to evaluate correlations between RP dosimetric parameters (where fV20 is the percentage of functional lung volume irradiated with >20 Gy, or fMLD, the mean dose administered to functional lung) and the percentage of functional lung volume. Radiation pneumonitis was evaluated using Common Terminology Criteria for Adverse Events version 4.0. Statistical significance was defined as a P value of <.05. Results: Sixty patients who underwent curative radiation therapy were enrolled (48 patients for non-small cell lung cancer, and 12 patients for small cell lung cancer). Grades 1, 2, and ≥3 RP were observed in 16, 44, and 6 patients, respectively. Significant correlations were observed between the percentage of functional lung volume and fV20 (r=0.4475 in vent-860 and 0.3508 in F30) or fMLD (r=0.4701 in vent-860 and 0.3128 in F30) in patients with grade ≥2 RP. F30∩vent-860 results exhibited stronger correlations with fV20 and fMLD in patients with grade ≥2 (r=0.5509 in fV20 and 0.5320 in fMLD) and grade ≥3 RP (r=0.8770 in fV20 and 0.8518 in fMLD). Conclusions: RP dosimetric parameters correlated significantly with functional lung imaging.« less