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Treatment Delivery Fidelity for 2 Head and Neck Treatment Techniques

P Rassiah-Szegedi

P Rassiah-Szegedi*, S lloyd , F Su , L Huang , Y Huang , Y Hitchcock , H Zhao , M Szegedi , A Paxton , B Salter , University Utah, Salt Lake City, UT


SU-I-GPD-T-396 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: This study is undertaken to characterize the dosimetric impact of patient positioning for two types of treatment plans in head and neck treatments. i.e which method has better fidelity in treatment delivery.

Methods: Previously treated Head and Neck (HN) patients with 9 static IMRT fields and a matched anterior field (plan type 1) datasets were used. Corresponding full HN IMRT plans extending into the neck and clavicular region (plan type 2) were also developed. CT on rails (CToR) image datasets acquired at treatment time was fused to the reference CT using the physician approved image guided shifts. The contours (PTV1, PTV2, PTV3, esophagus, spinal cord, larynx, brachial plexus, parotid, and brainstem) from the reference CT were deformed onto the CToR. The contours were reviewed by a single physician who specializes in HN treatments. The delivered daily dose was recalculated for both plans (see figure 1) for 10 patients for 20 CT on rails datasets each.

Results: Preliminary results show that the dose delivery fidelity for PTV2 and PTV3 which extend into the neck and clavicular region is better (on average 5% higher coverage to 95% volume) with plan type 1. There is no difference in delivery fidelity in PTV1 (located above the match point). There was no difference for any of the above listed critical structures except for the brachial plexus and larynx where the doses were 5% closer to planned dose for plan type 1.

Conclusion: IMRT matched with an anterior neck field resulted in greater treatment delivery fidelity compared to a full head and neck IMRT treatment. Future work will be done to investigate if the use of a 6D freedom couch will help increase the fidelity of treatment delivery for full head and neck IMRT.

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