Toward correcting drift in target position during radiotherapy via computer‐controlled couch adjustments on a programmable Linac. Issue 5 (30th April 2013)

• Record Type: Journal Article
• Authors: McNamara, Joseph E.; Regmi, Rajesh; Michael Lovelock, D.; Yorke, Ellen D.; Goodman, Karyn A.; Rimner, Andreas; Mostafavi, Hassan; Mageras, Gig S.
• Is Part Of: Medical physics. Volume 40:Issue 5(2013)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2013-04-30
• Subjects: Treatment strategy -- Image analysis -- Computed tomography -- Biomedical instrumentation and transducers, including micro‐electro‐mechanical systems (MEMS) -- Radiation therapy equipment -- Pneumodyamics, respiration; biomedical equipment -- computerised tomography -- image motion analysis -- Kalman filters -- linear accelerators -- medical control systems -- medical image processing -- phantoms -- pneumodynamics -- position control -- radiation therapy -- target tracking; respiratory motion -- tracking -- mean‐position estimation -- adaptive radiotherapy; Computerised tomographs -- Radiation therapy -- Digital computing or data processing equipment or methods, specially adapted for specific applications -- Image data processing or generation, in general -- Analysis of motion -- Linear accelerators; Cancer -- Linear accelerators -- Cameras -- Motion compensation -- Real time information delivery -- Pneumodynamics -- Tracking devices -- Sequence analysis -- Robotics -- Radiation therapy; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1118/1.4802736
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: : Real‐time tracking of respiratory target motion during radiation therapy is technically challenging, owing to rapid and possibly irregular breathing variations. The authors report on a method to predict and correct respiration‐averaged drift in target position by means of couch adjustments on an accelerator equipped with such capability. Methods: : Dose delivery is broken up into a sequence of 10 s field segments, each followed by a couch adjustment based on analysis of breathing motion from an external monitor as a surrogate of internal target motion. Signal averaging over three respiratory cycles yields a baseline representing target drift. A Kalman filter predicts the baseline position 5 s in advance, for determination of the couch correction. The method's feasibility is tested with a motion phantom programmed according to previously recorded patient signals. Computed couch corrections are preprogrammed into a research mode of an accelerator capable of computer‐controlled couch translations synchronized with the motion phantom. The method's performance is evaluated with five cases recorded during hypofractionated treatment and five from respiration‐correlated CT simulation, using a root‐mean‐squared deviation (RMSD) of the baseline from the treatment planned position. Results: : RMSD is reduced in all 10 cases, from a mean of 4.9 mm (range 2.7–9.4 mm) before correction to 1.7 mm (range 0.7–2.3 mm) after correction. Treatment time is increased ∼5% relative to that for no corrections. Conclusions: : This work illustrates the potential for reduction in baseline respiratory drift with periodic adjustments in couch position during treatment. Future treatment machine capabilities will enable the use of "on‐the‐fly" couch adjustments during treatment.