Stereotactic IMRT for prostate cancer: Setup accuracy of a new stereotactic body localization system

• DOI: 10.1120/jacmp.v5i2.1947
• Publication Date: 2007-02-22T22:08:41Z
• Authors: Lu Wang; Rojymon Jacob; Lili Chen; Steve Feigenberg; Andre Konski; Charlie Ma; Benjamin Movsas
• Keywords: Isocenter; Fiducial marker; Cyberknife

The purpose of this work is to prospectively assess the setup accuracy that can be achieved with a stereotactic body localizer (SBL) in immobilizing patients for intensity-modulated radiotherapy (IMRT) prostate cancer. By quantifying important factor and target mobility SBL, we expect provide guideline selecting planning volume margins treatment planning. We analyzed data from 40 computed tomography (CT) studies (with slice thickness 3 mm) involving 10 Each patient had four sets CT scans during course radiotherapy. For study, all were obtained immobilized customized pillow formed by vacuum suction. Unlike other immobilization devices, system consists not only pillow, but also fixation sheet used suppress respiratory motion, frame stereotaxy, carbon fiber base board which both cushion are affixed. identified bony landmarks measured their coordinates on each set scans. displacements corresponding positions simulation scan (first scan) three dimensions terms overall, systematic, random categories. initial planned isocenter was marked patients' skin fiducials study. distance landmark fiducial-based compared among deviations distances those center, order determine effectiveness rigid positioning Target inter-fraction motion studied five measuring geometric center landmarks. Our results showed overall standard (SDs) 2.58 mm, 2.41 3.51 mm lateral (LAT), anterior-posterior (AP), superior-inferior (SI) directions, respectively. component SDs 1.72 2.06 2.79 systematic 0.92 –0.27 0.90 these directions. In three-dimensional vector, mean displacement over 116 measurements 3.0 an SD 1.29 mm. Compared reference, skin-mark-based reference less reliable repositioning reproducing known positions. relative , AP, LAT, SI conclusion, has ability immobilize cancer satisfactory fractionated extracranial A serves as alignment into position, while skin-based larger patients. PACS number: 87.53Ly