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Pass Rates of IROC Houston's Head and Neck Phantom Based On Technique, Manufacturer, and Treatment Planning System

B Lewis*, N Pajot, H Mehrens, T Nguyen, N Hernandez, S Cheng, S Edward, A Molineu, D Followill, The University of Texas MD Anderson Cancer Center, Houston, TX


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: To describe and report the passing rates of previous IROC head and neck phantom irradiations based on treatment technique, machine manufacturer, and treatment planning system.

Methods: IROC Houston’s anthropomorphic head and neck phantom is used for multi-institutional clinical trial credentialing and quality assurance purposes. It has two PTVS that house TLD and radiochromoic film. Pass rates were analyzed and compared. The Pearson Chi-Square Test was used to calculate the significance of pass rates using treatment technique, machine manufacturer and treatment planning system.

Results: 2614 irradiations have a total pass rate of 87%. Rapid Arc (n = 482), VMAT (n = 422), Dynamic MLC (n = 591), and Segmental MLC (n = 908) were the top 4 treatment techniques. Their success rates were 95%, 93%, 91%, and 77%, respectively. Of current popular machine types, CyberKnife (n = 22), Elekta (n = 420), TomoTherapy (n = 173), and Varian (n = 1765) had pass rates of 100%, 80%, 95%, and 90%, respectively. The most popular treatment planning systems used were Multiplan (n = 22), TomoTherapy (n = 173), Eclipse (n = 1237), RayStation (n = 77), and Pinnacle (n = 722). Their respective pass rates were 100%, 95%, 92%, 84%, and 81%. No treatment technique or machine type individual pass rates were statistically significantly different than the group. However, there was a statistically significant difference (p = 0.028) for the treatment technique which means that the pass rate is directly linked to each technique.

Conclusion: Based on the collective data, we can say that the type of treatment techniques used for irradiation can significantly affect the pass rate of each head and neck phantom irradiation. This may be due to the historically lower HN phantom pass rates when IMRT was first introduced and the segmental MLC technique was common.

Funding Support, Disclosures, and Conflict of Interest: This work was supported by IROC-Houston NCI grant #CA180803.


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