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Double-Ends Quasi-Breath-Hold (DE-QBH) Technique for Respiratory Motion Management

S Kim

S Kim1*, Y Park2, J Lee3, K Choi3, S Ye3, (1) Mayo Clinic, Jacksonville, FL, (2) Massachusetts General Hospital, Boston, MA, (3) Seoul National University, Seoul, Korea

SU-E-T-358 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: To introduce double-ends quasi-breath-hold (DE-QBH) technique and evaluate its feasibility.

Methods: It was previously demonstrated QBH, a hybrid technique combining free-breathing-gating (FBG) and breath-hold, could provide less motion uncertainty and shorter treatment time than conventional FBG. While QBH uses only one phase, either end-of-exhalation (EOE) or end-of-inhalation (EOI), DE-QBH utilizes both phases to further improve delivery efficiency. DE-QBH is realized using an audio-visual biofeedback system (AVBFS) and a respiratory motion management program (RMMP). The in-house developed AVBFS, consisting of two infra-red stereo cameras and a head mounted display, provides dynamic feedback to patients. The RMMP establishes a personalized DE-QBH model by adding a short quasi-breath-hold period to both EOI and EOE phase. Then the patient is guided to follow the model. A simulation study for 6 different maneuvers (2-2, 3-3, 4-4, 5-5, 7-5, and 9-5 sec for EOI-EOE combination) was performed with 3 volunteers. External motion signals were analyzed to obtain mean absolute error (MAE) between the measured and guided. Duty cycle was also estimated.

Results: MAEs were smaller than 1 mm for all maneuvers except 9-5 combination [0.9(+/-)1.3, 0.7(+/-)1.2, 0.6(+/-)1.1, 0.7(+/-)1.1, 0.6(+/-)1.0, and 1.1(+/-)0.8 mm for 2-2, 3-3, 4-4, 5-5, 7-5, and 9-5 combination, respectively]. Estimated duty cycles were 43, 52, 57, 62, 64, and 71% for 2-2, 3-3, 4-4, 5-5, 7-5, and 9-5 combination, respectively.

Conclusion: The proposed DE-QBH technique was feasible for respiratory motion management. It showed excellent feasibility with minimal motion uncertainty and significantly improved delivery efficiency, reaching up to 70% duty cycle.

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