Treatment Planning System Calculation Errors Are Present in Most Imaging and Radiation Oncology Core-Houston Phantom Failures

Kerns, J; Stingo, Francesco C.; Followill, David S; Howell, Rebecca M.; Melancon, Adam David; Kry, Stephen F

doi:10.1016/j.ijrobp.2017.03.049

Cited by 58 publications

(77 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…IROC recently implemented an independent dose recalculation system to evaluate the contribution of dose calculation errors to failing phantom results. With this system, planning system dose calculation errors were found in 68% of failing phantom results . These results indicate that an independent calculation system may, in fact, be well‐suited for detecting plan errors, and therefore appropriate for conducting IMRT QA.…”

Section: Introductionmentioning

confidence: 83%

Independent recalculation outperforms traditional measurement‐based IMRT QA methods in detecting unacceptable plans

et al. 2019

Self Cite

View full text Add to dashboard Cite

Purpose To evaluate the performance of an independent recalculation and compare it against current measurement‐based patient specific intensity‐modulated radiation therapy (IMRT) quality assurance (QA) in predicting unacceptable phantom results as measured by the Imaging and Radiation Oncology Core (IROC). Methods When institutions irradiate the IROC head and neck IMRT phantom, they are also asked to submit their internal IMRT QA results. Separately from this, IROC has previously created reference beam models on the Mobius3D platform to independently recalculate phantom results based on the institution's DICOM plan data. The ability of the institutions’ IMRT QA to predict the IROC phantom result was compared against the independent recalculation for 339 phantom results collected since 2012. This was done to determine the ability of these systems to detect failing phantom results (i.e., large errors) as well as poor phantom results (i.e., modest errors). Sensitivity and specificity were evaluated using common clinical thresholds, and receiver operator characteristic (ROC) curves were used to compare across different thresholds. Results Overall, based on common clinical criteria, the independent recalculation was 12 times more sensitive at detecting unacceptable (failing) IROC phantom results than clinical measurement‐based IMRT QA. The recalculation was superior, in head‐to‐head comparison, to the EPID, ArcCheck, and MapCheck devices. The superiority of the recalculation vs these array‐based measurements persisted under ROC analysis as the recalculation curve had a greater area under it and was always above that for these measurement devices. For detecting modest errors (poor phantom results rather than failing phantom results), neither the recalculation nor measurement‐based IMRT QA performed well. Conclusions A simple recalculation outperformed current measurement‐based IMRT QA methods at detecting unacceptable plans. These findings highlight the value of an independent recalculation, and raise further questions about the current standard of measurement‐based IMRT QA.

show abstract

Section: Introductionmentioning

confidence: 83%

Independent recalculation outperforms traditional measurement‐based IMRT QA methods in detecting unacceptable plans

et al. 2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…These issues are particularly concerning because the measurements performed evaluate basic dosimetry that is the foundation of more advanced radiotherapy programs such as IMRT. Given the prevalence of issues identified during site-visits, it is perhaps not surprising that there are so many problems with anthropomorphic phantom irradiations[17], and that these problems with phantom irradiations appear to originate with errors in dose calculations[18,19]. Regardless of the treatment modality, it is concerning that such frequent problems were identified.…”

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

Self Cite

View full text Add to dashboard Cite

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.

show abstract

“…5 Intensity-modulated radiation therapy (IMRT) credentialing is offered by the Imaging and Radiation Oncology Core Houston branch (IROC-H) in the form of anthropomorphic phantoms for several anatomical sites. 6 Recent results from IROC-H show that 17% of institutions using the service had considerable dose calculation errors in their TPS 7 and that patient-specific IMRT quality assurance (QA) at many of these institutions failed to predict these errors. 8 Despite significant evidence that patient-specific IMRT QA fails to detect TPS errors, [9][10][11][12] many institutions continue to rely on it for TPS commissioning and validation.…”

Section: Introductionmentioning

confidence: 99%

Impact of the MLC leaf‐tip model in a commercial TPS: Dose calculation limitations and IROC‐H phantom failures

Koger

Price

Wang

et al. 2020

J Applied Clin Med Phys

View full text Add to dashboard Cite

Purpose Treatment planning system (TPS) dose calculation is sensitive to multileaf collimator (MLC) modeling, especially when treating with intensity‐modulated radiation therapy (IMRT) or VMAT. This study investigates the dosimetric impact of the MLC leaf‐tip model in a commercial TPS (RayStation v.6.1). The detectability of modeling errors was assessed through both measurements with an anthropomorphic head‐and‐neck phantom and patient‐specific IMRT QA using a 3D diode array. Methods and Materials An Agility MLC (Elekta Inc.) was commissioned in RayStation. Nine IMRT and VMAT plans were optimized to treat the head‐and‐neck phantom from the Imaging and Radiation Oncology Core Houston branch (IROC‐H). Dose distributions for each plan were re‐calculated on 27 beam models, varying leaf‐tip width (2.0, 4.5, and 6.5 mm) and leaf‐tip offset (−2.0 to +2.0 mm) values. Doses were compared to phantom TLD measurements. Patient‐specific IMRT QA was performed, and receiver‐operating characteristic (ROC) analysis was performed to determine the detectability of modeling errors. Results Dose calculations were very sensitive to leaf‐tip offset values. Offsets of ±1.0 mm resulted in dose differences up to 10% and 15% in the PTV and spinal cord TLDs respectively. Offsets of ±2.0 mm caused dose deviations up to 50% in the spinal cord TLD. Patient‐specific IMRT QA could not reliably detect these deviations, with an ROC area under the curve (AUC) value of 0.537 for a ±1.0 mm change in leaf‐tip offset, corresponding to >7% dose deviation. Leaf‐tip width had a modest dosimetric impact with <2% and 5.6% differences in the PTV and spinal cord TLDs respectively. Conclusions Small changes in the MLC leaf‐tip offset in this TPS model can cause large changes in the calculated dose for IMRT and VMAT plans that are difficult to identify through either dose curves or standard patient‐specific IMRT QA. These results may, in part, explain the reported high failure rate of IROC‐H phantom tests.

show abstract

Treatment Planning System Calculation Errors Are Present in Most Imaging and Radiation Oncology Core-Houston Phantom Failures

Cited by 58 publications

References 15 publications

Independent recalculation outperforms traditional measurement‐based IMRT QA methods in detecting unacceptable plans

Independent recalculation outperforms traditional measurement‐based IMRT QA methods in detecting unacceptable plans

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

Impact of the MLC leaf‐tip model in a commercial TPS: Dose calculation limitations and IROC‐H phantom failures

Contact Info

Product

Resources

About