PO-0902: Improving frameless intracranial stereotactic setup with 6DOF couch using two pre-treatment CBCTs
Radiotherapy and Oncology
Purpose or Objective: Acceleration in breast cancer treatment might become the new standard. As fraction dose rises, the importance of correct positioning increases. CBCT is time consuming and uses (low dose) radiation. Increasing interval between positioning and actual treatment reduces precision. We therefore investigated a CBCT technique with lower dose and faster acquisition. Material and Methods: Both standard and fast pre-treatment CBCT imaging (STAND and FAST) were performed on XVI
... formed on XVI Elekta ® in a 5-fractions supine and whole breast irradiation scheme (5 x 5.7 Gy). The main difference between protocols was gantry speed (Table 1) . Central dose was measured with PTW equipment in a CTDI32 phantom. High resolution (HR) and contrast were measured on a Catphan Phantom. Breast contour appearance was assessed on a polystyrene breast phantom. Fifteen clinical CBCT-images for three patients to which FAST or STAND was randomly assigned, were blindly scored by a skilled oncologist. A three-level answer had to be formulated regarding visibility of 1) all clips, 2) entire breast contour, 3) lung/thorax wall edge and 4) excision cavity. Answers were decoded: 0: Not at all; 1: Yes, but only with guidance of reference CT; 2; Yes clearly, without reference CT.