On the sensitivity of TG‐119 and IROC credentialing to TPS commissioning errors

McVicker, Drew; Yin, Fang‐Fang; Adamson, Justus

doi:10.1120/jacmp.v17i1.5452

Cited by 17 publications

(31 citation statements)

References 19 publications

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“…Of these, dosimetric errors (i.e., outside the 3% calibration or 2% relative dosimetry tolerances) are often the most concerning because of their direct impact on patient care, i.e., dose delivery. While a given clinical treatment plan may or may not be substantially impacted by a specific error in an individual basic dosimetry parameter, basic dosimetric errors such as those evaluated in the current study have been shown to routinely manifest as problems in clinical plans [14,15]. Moreover, good dosimetric agreement should be achievable overall for this test suite because the test suite includes only relatively simple conditions: only square fields, no extremely large or small fields, and no superficial or extremely deep locations.…”

Section: Discussionmentioning

confidence: 99%

Radiation Therapy Deficiencies Identified During On-Site Dosimetry Visits by the Imaging and Radiation Oncology Core Houston Quality Assurance Center

Kry

Dromgoole

Alvarez

et al. 2017

International Journal of Radiation Oncology*Biology*Physics

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Purpose To review the dosimetric, mechanical, and programmatic deficiencies most frequently observed during on-site visits of radiotherapy facilities by the Imaging and Radiation Oncology Core Houston office (IROC Houston). Methods IROC Houston’s findings between 2000 and 2014, including 409 institutions and 1020 linacs, were compiled. IROC Houston’s on-site evaluation includes verification of absolute calibration (tolerance of ±3%), relative dosimetric review (tolerances of ±2% between TPS calculation and measurement), mechanical evaluation (including MLC and kV-MV evaluation against TG-142 tolerances), and general programmatic review (including institutional QA program versus TG-40 and TG-142). Results An average of 3.1 deficiencies was identified at each institution visited, a number that has decreased slightly with time. The most common errors are tabulated, and include TG-40/TG-142 compliance (82% of institutions were deficient), small field size output factors (59% of institutions had errors ≥3%), and wedge factors (33% of institutions had errors ≥3%). Dosimetric errors of ≥10%, including in beam calibration, were seen at many institutions. Conclusions There is substantial room for improvement of both dosimetric and programmatic issues in radiotherapy, which should be a high priority for the medical physics community. Particularly relevant was suboptimal beam modeling in the treatment planning system and a corresponding failure to detect these errors by not including TPS data in the linac QA process.

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Section: Discussionmentioning

confidence: 99%

Radiation Therapy Deficiencies Identified During On-Site Dosimetry Visits by the Imaging and Radiation Oncology Core Houston Quality Assurance Center

Kry

Dromgoole

Alvarez

et al. 2017

International Journal of Radiation Oncology*Biology*Physics

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“…[12][13][14][15] This result was also simulated in work by McVicker et al, where gamma analyses comparing plans calculated with and without commissioning errors could not reveal clinically severe effects, even with stringent 2%/2 mm criteria. 3 These data suggest that film dosimetry may have limited applicability in error detection for IMRT.…”

Section: Discussionmentioning

confidence: 99%

“…2 However, a substantial number of institutions still fail to meet the minimum criteria, thus warranting further investigation to determine the root cause. Previous works like that of McVicker et al 3 have used the H&N phantom to determine the detectability of potential commissioning errors. While this work exposes some of the limitations of the phantom, it does not address the prevalence and detection of errors in multi-institutional performance.…”

Section: Introductionmentioning

confidence: 99%

Examining credentialing criteria and poor performance indicators for IROC Houston's anthropomorphic head and neck phantom

et al. 2016

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Purpose: To analyze the most recent results of the Imaging and Radiation Oncology Core Houston Quality Assurance Center's (IROC-H) anthropomorphic head and neck (H&N) phantom to determine the nature of failing irradiations and the feasibility of altering credentialing criteria. Methods: IROC-H's H&N phantom, used for intensity-modulated radiation therapy credentialing for National Cancer Institute-sponsored clinical trials, requires that an institution's treatment plan agrees within ±7% of measured thermoluminescent dosimeter (TLD) doses; it also requires that ≥85% of pixels pass ±4 mm distance to agreement (7%/4 mm gamma analysis for film). The authors re-evaluated 156 phantom irradiations (November 1, 2014-October 31, 2015 according to the following tighter criteria: (1) 5% TLD and 5%/4 mm, (2) 5% TLD and 5%/3 mm, (3) 4% TLD and 4%/4 mm, and (4) 3% TLD and 3%/3 mm. Failure rates were evaluated with respect to individual film and TLD performance by location in the phantom. Overall poor phantom results were characterized qualitatively as systematic errors (correct shape and position but wrong magnitude of dose), setup errors/positional shifts, global but nonsystematic errors, and errors affecting only a local region. Results: The pass rate for these phantoms using current criteria was 90%. Substituting criteria 1-4 reduced the overall pass rate to 77%, 70%, 63%, and 37%, respectively. Statistical analyses indicated that the probability of noise-induced TLD failure, even at the 5% criterion, was <0.5%. Phantom failures were generally identified by TLD (≥66% failed TLD, whereas ≥55% failed film), with most failures occurring in the primary planning target volume (≥77% of cases). Results failing current criteria or criteria 1 were primarily diagnosed as systematic >58% of the time (11/16 and 21/36 cases, respectively), with a greater extent due to underdosing. Setup/positioning errors were seen in 11%-13% of all failing cases (2/16 and 4/36 cases, respectively). Local errors (8/36 cases) could only be demonstrated at criteria 1. Only three cases of global errors were identified in these analyses. For current criteria and criteria 1, irradiations that failed from film only were overwhelmingly associated with phantom shifts/setup errors (≥80% of cases). Conclusions: This study highlighted that the majority of phantom failures are the result of systematic dosimetric discrepancies between the treatment planning system and the delivered dose. Further work is necessary to diagnose and resolve such dosimetric inaccuracy. In addition, the authors found that 5% TLD and 5%/4 mm gamma criteria may be both practically and theoretically achievable as an alternative to current criteria. C

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“…[1417] In this work, small ionization chamber (Pinpoint) was used instead of larger ionization chamber (Farmer) which was used by other researchers. [141516] The main advantage of this small chamber is its use for increasing the accuracy, in particular, in high-dose gradient and edge of the fields. [18]…”

Section: Discussionmentioning

confidence: 99%

“…[567] Recently, researchers have done TG-119 protocol on different planning systems, different detectors, and LINAC machines with different photon energies and obtained different gamma criteria. [8910111213141516]…”

Section: Introductionmentioning

confidence: 99%

Evaluation of targeted image-guided radiation therapy treatment planning system by use of american association of physicists in medicine task group-119 test cases

2018

J Med Signals Sens

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Background:This study aimed to evaluate the overall accuracy of the beam commissioning criteria of targeted image-guided radiation therapy (TiGRT) treatment planning system (TPS) based on the American Association of Physicists in Medicine (AAPM) Task Group Report 119 (TG-119).Methods:The work was performed using 6 MV energy LINAC with a variable dose rate of 200 MU/min which equipped with the high-quality external TiGRT dynamic multileaf collimator model H. The AAPM TG-119 intensity-modulated radiation therapy (IMRT) commissioning tests are composed of two preliminary tests and four clinical test cases. The clinical tests consisted of mock prostate, mock head and neck, C-shaped target, and multitarget. EDR2 film was used for evaluating the IMRT plans and point dose measured by a Pinpoint chamber positioned in slab phantom. The film analysis was done with the Sun Nuclear Corporation patient software. The dose prescription for each fraction was 200 cGy in mock prostate, mock head and neck, C-shaped target, and multitarget. Dose distributions were analyzed using gamma criteria of 3% and 2% dose difference (DD) and 3 and 2 mm distance to agreement.Results:In all test cases, the gamma criteria for 2%/2 and 3%/3 were found to be 94% and 98%, respectively. Results showed that the average gamma criteria result was in the range of 99.1% to 93% (3%/3, 2%/2) overall test cases.Conclusions:Findings were favorable and in some tests were comparable with the other studies. The dose point values were within the mean values of the range reported by TG-119. Overall, the TiGRT TPS is needed to apply IMRT technique in radiation therapy centers.

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On the sensitivity of TG‐119 and IROC credentialing to TPS commissioning errors

Cited by 17 publications

References 19 publications

Radiation Therapy Deficiencies Identified During On-Site Dosimetry Visits by the Imaging and Radiation Oncology Core Houston Quality Assurance Center

Radiation Therapy Deficiencies Identified During On-Site Dosimetry Visits by the Imaging and Radiation Oncology Core Houston Quality Assurance Center

Examining credentialing criteria and poor performance indicators for IROC Houston's anthropomorphic head and neck phantom

Evaluation of targeted image-guided radiation therapy treatment planning system by use of american association of physicists in medicine task group-119 test cases

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