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Int J Radiat Oncol Biol Phys. 2017 Aug 1;98(5):1197-1203. doi: 10.1016/j.ijrobp.2017.03.049. Epub 2017 Apr 4.

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

Author information

1
Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas; Imaging and Radiation Oncology Core-Houston, The University of Texas MD Anderson Cancer Center, Houston, Texas; Graduate School of Biomedical Sciences, The University of Texas Health Science Center-Houston, Houston, Texas.
2
Department of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, Texas.
3
Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas; Graduate School of Biomedical Sciences, The University of Texas Health Science Center-Houston, Houston, Texas.
4
Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas.
5
Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas; Imaging and Radiation Oncology Core-Houston, The University of Texas MD Anderson Cancer Center, Houston, Texas; Graduate School of Biomedical Sciences, The University of Texas Health Science Center-Houston, Houston, Texas. Electronic address: sfkry@mdanderson.org.

Abstract

PURPOSE:

The anthropomorphic phantom program at the Houston branch of the Imaging and Radiation Oncology Core (IROC-Houston) is an end-to-end test that can be used to determine whether an institution can accurately model, calculate, and deliver an intensity modulated radiation therapy dose distribution. Currently, institutions that do not meet IROC-Houston's criteria have no specific information with which to identify and correct problems. In the present study, an independent recalculation system was developed to identify treatment planning system (TPS) calculation errors.

METHODS AND MATERIALS:

A recalculation system was commissioned and customized using IROC-Houston measurement reference dosimetry data for common linear accelerator classes. Using this system, 259 head and neck phantom irradiations were recalculated. Both the recalculation and the institution's TPS calculation were compared with the delivered dose that was measured. In cases in which the recalculation was statistically more accurate by 2% on average or 3% at a single measurement location than was the institution's TPS, the irradiation was flagged as having a "considerable" institutional calculation error. The error rates were also examined according to the linear accelerator vendor and delivery technique.

RESULTS:

Surprisingly, on average, the reference recalculation system had better accuracy than the institution's TPS. Considerable TPS errors were found in 17% (n=45) of the head and neck irradiations. Also, 68% (n=13) of the irradiations that failed to meet the IROC-Houston criteria were found to have calculation errors.

CONCLUSIONS:

Nearly 1 in 5 institutions were found to have TPS errors in their intensity modulated radiation therapy calculations, highlighting the need for careful beam modeling and calculation in the TPS. An independent recalculation system can help identify the presence of TPS errors and pass on the knowledge to the institution.

PMID:
28721904
PMCID:
PMC5567850
DOI:
10.1016/j.ijrobp.2017.03.049
[Indexed for MEDLINE]
Free PMC Article

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