Surface guided frameless positioning for lung stereotactic body radiation therapy

Background and purpose When treating lung tumors with stereotactic body radiation therapy (SBRT), patient immobilization is of outmost importance. In this study, the intra-fractional shifts (based on bony anatomy) tumor visible target volume) are quantified, associated impact delivered dose estimated for a frameless approach in combination surface guided (SGRT) monitoring. Methods Cone beam computed tomographies (CBCT) were collected free breathing prior after each treatment 25 patients tumors, total 137 fractions. The CBCT was registered to before focus anatomy determine shift patient, volume tumor. Rigid registrations 6 degrees freedom used. positioned immobilizations their position respiration continuously monitored by commercial SGRT system. freely within preset gating window during delivery. automatically interrupted if isocenter >4 mm or amplitudes outside detected time between acquisition CBCTs fraction examine correlations shift. observed organs at risk (OAR) gross (GTV) assessed. Results ?2 132/137 fractions vertical (vrt) lateral (lat) directions, 134/137 longitudinal (lng) direction ?4 137/137 (lat, lng) 116/137 (vrt), 123/137 115/137 136/137 (lat), 135/137 maximal evaluated data 4.6 7.2 Rotations ?3.3? all mean/standard deviation 0.2/1.0? (roll), 0.1/0.8? (yaw), 0.3/1.0? (pitch). system due 21% fractions, but always returned tolerance without need repositioning. holds 8 mm. For monitoring, least one 54% visual planned internal (ITV) end fraction. where ITV, D98% GTV decreased 0.4 Gy. OARs, difference from (D2% Dmean) ?2.6% prescribed PTV dose. No correlation found magnitude Conclusions Using motion management monitoring feasible SBRT.