(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose:
Real-time respiratory motion monitoring with implanted fiducials (image trigger) usually lengthens delivery. This study evaluates delivery times using voluntary deep-expiration-breath-hold (DEBH) for liver SBRT patients.
Methods:
106 liver SBRT patients were treated in 26 months. Patients received 15 Gy in 3 fractions or 10 Gy in 5 fractions by 2 VMAT arcs, 10X-FFF. Patients were eligible for voluntary DEBH if they could hold =20 sec, repeated in 3 consecutive sessions. Phase-gated RPM was used if patient couldn't hold 20 sec; and if he/she was reproducible breather. Patients with small target movement or non-reproducible breathers were treated with ITV (0-90 phases) without RPM system. Prior to DEBH treatment, orthogonal kV and CBCT images were acquired for setup. During DEBH treatment, real-time kV images were triggered by gantry motion. Beams were put “on-hold” when fiducial excursions exceeded 5 mm or RPM gating box exceeded 5 mm gating amplitude.
Results:
33 out of 106 (31.1%) patients were eligible for DEBH and 63 (59.4%) were eligible for phase-gated treatment. 10 patients (9.4%) were treated with ITV (0-90 phases) without RPM system. 2 DEBH patients were excluded this analysis because they had no fiducials for trigger imaging. Among 98 treatment sessions for 31 DEBH/image-triggered patients, median beam “on-hold” was 1 (range 0-14; mean=2 SD=3). 1 out of 99 (1%) had re-CBCT, 9 (9%) had re-positioning patient using orthogonal kV. Median time from starting setup-imaging to beam-on was 11.2 (range 5.0-47.0; mean=12.4 SD=5.6) min. Median time for beam start-to-end was 4.6 (range 1.8-27.8; mean=6.2 SD=4.6) min. Median time from starting setup-imaging to beam-end was 11.2 (range 5.0-47.0; mean=18.6 SD=8.0) min. Most patients shorten delivery in late session.
Conclusion:
Real-time monitored liver SBRT improves confidence in target dose delivery. Integrated with deep-expiration-hold, it was efficient than respiratory phase gated treatment.
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