The effectiveness of breath-holding to stabilize lung and pancreas tumors during radiosurgery.
OBJECTIVE
To evaluate the effect of breath-holding on the short-term reproducibility and long-term variability of tumor position during image-guided radiosurgery.


METHODS
Thirteen patients have undergone single-fraction radiosurgery treatments during which the tumor was repeatedly imaged radiographically to observe its position. The imaging data were used to monitor the efficacy of breath-holding and to periodically readjust the alignment of the treatment beam with the tumor. These measurements have allowed the effects of breathing, heartbeat, patient movement, and instrumental uncertainties to be separately identified in the record of tumor position.


RESULTS
During inspiration breath-holding, the lung tumor position was reproducible to within 1 mm, on average, in the direction of maximum displacement during regular breathing, and to within 1.8 mm in three dimensions overall. The pancreas tumor position in three dimensions was reproducible to within 2.5 mm on average. Some patients showed a slow, steady drift of tumor position during the extended sequence of breath-holds, which was compensated by periodic retargeting of the treatment beam.


CONCLUSIONS
Breath-holding can allow the reduction of tumor motion dosimetry margins to 2 mm or less for lung cancer treatments, provided that the treatment system can detect and adapt to long-term variations in the mean tumor position during a lengthy treatment fraction.
Murphy
Martin J
MJ
Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305, USA. martin@reyes.stanford.edu
Martin
David
D
Whyte
Richard
R
Hai
Jenny
J
Ozhasoglu
Cihat
C
Le
Quynh-Thu
QT
D006801:Humans; D008175:Lung Neoplasms / Q000601:surgery*; D009068:Movement; D010190:Pancreatic Neoplasms / Q000601:surgery*; D055585:Physical Phenomena; D010825:Physics; D016634:Radiosurgery / Q000379:methods*; D012119:Respiration