Obtaining information on intra-fraction prostate displacement in radiotherapy determined from pre- and post-treatment kV imaging

Abstract

Since 2007 all patients treated with radical intent for prostate cancer at Peter MacCallum Cancer Centre have three implanted fiducial markers to facilitate reproducible daily set-up using kV on-board imaging on a linear accelerator. We collected all set-up information prospectively through a record and verify system. In order to assess the appropriateness of patient movements and determine prostate displacement during treatment a second set of two orthogonal kV images was acquired after the radiotherapy delivery. In 5778 image pairs of 184 patients the initial displacement between planning and patient set-up was found to be 4.9 +/-3.0mm as a 3D vector (mean +/- 1SD). All identified set-up d..