Abstract
Purpose: Between July 2013 and August 2019, 22% of the imaging and radiation oncology core (IROC) spine, and 15% of the moving lung phantom irradiations have failed to meet established acceptability criteria. The spine phantom simulates a highly modulated stereotactic body radiation therapy (SBRT) case, whereas the lung phantom represents a low-to-none modulation moving target case. In this study, we assessed the contribution of dose calculation errors to these phantom results and evaluated their effects on failure rates. Methods: We evaluated dose calculation errors by comparing the calculation accuracy of various institutions’ treatment planning systems (TPSs) vs IROC-Houston’s previously established independent dose recalculation system (DRS). Each calculation was compared with the measured dose actually delivered to the phantom; cases in which the recalculation was more accurate were interpreted as a deficiency in the institution's TPS. A total of 258 phantom irradiation plans (172 lung and 86 spine) were recomputed. Results: Overall, the DRS performed better than the TPSs in 47% of the spine phantom cases. However, the DRS was more accurate in 93% of failing spine phantom cases (with an average improvement of 2.35%), indicating a deficiency in the institution's treatment planning system. Deficiencies in dose calculation accounted for 60% of the overall discrepancy between measured and planned doses among spine phantoms. In contrast, lung phantom DRS calculations were more accurate in only 35% and 42% of all and failing lung phantom cases respectively, indicating that dose calculation errors were not substantially present. These errors accounted for only 30% of the overall discrepancy between measured and planned doses. Conclusions: Dose calculation errors are common and substantial in IROC spine phantom irradiations, highlighting a major failure mode in this phantom and in clinical treatment management of these cases. In contrast, dose calculation accuracy had only a minimal contribution to failing lung phantom results, indicating that other failure modes drive problems with this phantom and similar clinical treatments.
Original language | English (US) |
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Pages (from-to) | 4502-4508 |
Number of pages | 7 |
Journal | Medical physics |
Volume | 47 |
Issue number | 9 |
DOIs | |
State | Published - Sep 1 2020 |
Keywords
- IROC
- TPS dose calculation
- lung phantom
- phantom irradiation
- spine phantom
ASJC Scopus subject areas
- Biophysics
- Radiology Nuclear Medicine and imaging
MD Anderson CCSG core facilities
- Biostatistics Resource Group