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Impact of Inhomogeneous Tissue On IMRT QA for MatriXX

Y Yin

Y Yin*, J Chen, Shandong Cancer Hospital, Jinan, Shandong

SU-E-T-400 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: By applying self-made inhomogeneous phantom to MatriXX, a group of IMRT plans were delivered, to observe the impact on test results on different measuring condition.

Methods: two foam planks were made to simulate the low density tissue, e.g lung tissue, in the size of (40x40x3)cm, identical to virtual water. Three measurement condition using MatriXX were arranged: A. virtual water only (8cm top and 5cm bottom); B. one foam plank was used plus 5cm virtual water on its top, and 5cm virtual water on MatriXX bottom; C. two planks were used on the top and at the bottom of MatriXX, with 5cm and 2cm virtual water planks wrapped. The sizes in B and C condition were same to A. CT scanning images for three conditions were obtained and transmitted to TPS. QA plans were generated to the scanning images respectively. The original plans were 10 esophageal cancer IMRT plans. The QA plans were calculated in CMS xio-release 4.62, using superposition algorithm, and then delivered to Elekta Synergy. Each plan was measured in different condition, and the gamma passing rate was obtained.

Results: there was no significant difference (P<0.05) among the three measuring condition. The results, i.e gamma passing rate, in B (98.78±1.34)% and C (98.71±1.16)% were as good as in A (98.49±1.10)%.

Conclusion: the results showed that there is no difference in MatriXX measurement, no matter what phantom is used. However, more measurements should be needed to make it confirmed.

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