(Sunday, 7/29/2018) 2:05 PM - 3:00 PM
Room: Room 209
Purpose: Real-time motion monitoring usually lengthens delivery. This study compares delivery times of voluntary deep-expiration-hold vs abdomen-compression using pneumatic compression belts. Either method used real-time monitored kV images during treatment delivery.
Methods: 20 liver SBRT patients were eligible for motion management because cranio-caudal (CC) fiducial motion exceeded 5 mm as evaluated fluoroscopically prior to simulation. 10 patients were eligible for deep-expiration-hold (can hold >15 sec), 10 patients were eligible for abdomen-compression. Patients were excluded if CC fiducial motion could not be reduced to ≤5 mm with either technique. Prior to treatment, with deep-expiration-hold or abdomen-compression, orthogonal kV and CBCT images were acquired for setup. All 20 patients received 15 Gy in 3 fractions by 2 VMAT arcs, 10X-FFF. During treatment, real-time kV images were triggered by gantry motion. Beams were put “on-hold� when fiducial excursions exceeded 5 mm.
Results: 15 out of 30 (50%) deep-expiration-hold sessions and 11 out of 30 (37%) abdomen-compression sessions recorded fiducial excursion >5 mm, which required beams “on-hold� and adding 1.2 (mean) (range 0.1-11.8) min, and 0.5 (0.1-4.8) min, respectively. Treatment was continued after fiducials returned to their original positions. Re-imaging and re-adjusting patient position were required for 3 out of 30 (10%) deep-expiration-hold sessions and 6 out of 30 (20%) abdomen-compression sessions, added extra 5.6 (2.5-9.4) min and 6.2 (1.3-23) min, respectively. Starting from 1st arc beam-on to completion of 2nd arc beam, the mean delivery time was 6.1 (1.8-26.2) min for deep-expiration-hold session, and 5.1 (2.0-31.4) min for abdomen-compression session, compared to previously reported 12.1 (6.5-27.1) min for real-time monitored, respiratory gated delivery.
Conclusion: Real-time monitored Liver SBRT improves confidence in tumor treatment. Both deep-expiration-hold and abdomen-compression techniques were more efficient than that of respiratory gated treatment.
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