SU‐E‐T‐358: Double‐Ends Quasi‐Breath‐Hold (DE‐QBH) Technique for Respiratory Motion Management

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 audiovisual biofeedback system (AVBFS) and a respiratory motion management program (RMMP). The in‐house developed AVBFS, consisting of two infrared 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 9v5 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.