WE-D-BRA-06: IMRT QA with ArcCHECK: The MD Anderson Experience

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Abstract

Purpose:

The objective of this project was to report our initial IMRT QA results and experience with the SunNuclear ArcCHECK.

Methods:

Three thousand one-hundred and sixteen cases were treated with IMRT or VMAT at our institution between October 2013 and September 2014. All IMRT/VMAT treatment plans underwent Quality Assurance (QA) using ArcCHECK prior to therapy. For clinical evaluation, a Gamma analysis is performed following QA delivery using the SNC Patient software (Sun Nuclear Corp) at the 3%/3mm level. QA Gamma pass rates were analyzed based on categories of treatment site, technique, and type of MLCs. Our current clinical threshold for passing a QA (Tclin) is set at a Gamma pass rate greater than 90%. We recorded the percent of failures for each category, as well as the Gamma pass rate threshold that would Result in 95% of QAs to pass (T95).

Results:

Using Tclin a failure rate of 5.9% over all QAs was observed. The highest failure rate was observed for gynecological (22%) and the lowest for CNS (0.9%) treatments. T95 was 91% over all QAs and ranged from 73% (gynecological) to 96.5% (CNS) for individual treatments sites. T95 was lower for IMRT and non-HD (high definition) MLCs at 88.5% and 94.5%, respectively, compared to 92.4% and 97.1% for VMAT and HD MLC treatments, respectively. There was a statistically significant difference between the passing rates for IMRT vs. VMAT and for HD MLCs vs. non-HD MLCs (p-values << 0.01). Gynecological, IMRT, and HD MLC treatments typically include more plans with larger field sizes.

Conclusion:

On average, Tclin with ArcCHECK was consistent with T95, as well as the 90% action level reported in TG-119. However, significant variations between the examined categories suggest a link between field size and QA passing rates and may warrant field size-specific passing rate thresholds.

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