title: Development and application of a real-time monitoring and feedback system for deep inspiration breath hold based on external marker tracking.
abstract: Respiration can cause tumor movements in thoracic regions of up to 3 cm. To minimize motion effects several approaches, such as gating and deep inspiration breath hold (DIBH), are still under development. The goal of our study was to develop and evaluate a noninvasive system for gated DIBH (GDIBH) based on external markers. DIBH monitoring was based on an infrared tracking system and an in-house-developed software. The in-house software provided the breathing curve in real time and was used as on-line information for a prototype of a feedback device. Reproducibility and stability of the breath holds were evaluated without and with feedback. Thirty-five patients undergoing stereotactic body radiotherapy (SBRT) performed DIBH maneuvers after each treatment. For 16 patients dynamic imaging sequences on a multislice CT were used to determine the correlation between tumor and external markers. The relative reproducibility of DIBH maneuvers was improved with the feedback device (74.5% +/- 17.1% without versus 93.0% +/- 4.4% with feedback). The correlation between tumor and marker was good (Pearson correlation coefficient 0.83 +/- 0.17). The regression slopes showed great intersubject variability but on average the internal margin in a DIBH treatment situation could be theoretically reduced by 3 mm with the feedback device. DIBH monitoring could be realized in a noninvasive manner through external marker tracking. We conclude that reduction of internal margins can be achieved with a feedback system but should be performed with great care due to the individual behavior of target motion.
authors.affiliation: Department of Radiotherapy and Radiobiology, AKH Vienna, Medical University Vienna, Vienna, Austria. markus.stock@akhwien.at
authors.forename: Markus
authors.initials: M
authors.lastname: Stock
authors.forename: Kristina
authors.initials: K
authors.lastname: Kontrisova
authors.forename: Karin
authors.initials: K
authors.lastname: Dieckmann
authors.forename: Joachim
authors.initials: J
authors.lastname: Bogner
authors.forename: Richard
authors.initials: R
authors.lastname: Poetter
authors.forename: Dietmar
authors.initials: D
authors.lastname: Georg
mesh_terms: D016477:Artifacts; D001676:Biofeedback, Psychology / Q000295:instrumentation*; D003199:Computer Systems; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D001239:Inhalation; D008175:Lung Neoplasms / Q000532:radiotherapy*; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D009068:Movement; D011835:Radiation Protection / Q000379:methods; D020266:Radiotherapy, Conformal / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012149:Restraint, Physical / Q000295:instrumentation*; D012680:Sensitivity and Specificity