Poster - Thurs Eve-40: The potential of using SPECT ventilation information with IMRT for functional lung avoidance in radiotherapy of non small cell lung cancer

We have investigated the feasibility of using ventilation scans obtained from single photon emission computed tomography (SPECT) in intensity-modulated radiation therapy (IMRT) planning in lung cancer radiotherapy to avoid well functioning lung. We fused SPECT ventilation scans acquired at GE Hawkeye SPECT-CT of ten stage-III lung radiotherapy patients with planning CT in treatment planning system (Pinnacle v8.0, Philips Medical Systems). We automatically segment out 50% and 70% ventilated volumes. For each patient, we generated IMRT plans using nine equally spaced beams with and without avoiding well ventilated volume. They were compared with three beam IMRT plans with beam directions chosen to minimize the mean dose to the ventilated lung volumes, while keeping cord dose below tolerance and dose uniformity in the target. The plans generated using functional lung avoidance information reduces the doses to the functioning lung. With both IMRT avoidance plans, we could not obtain better functional avoidance or lower V-20Gy (volume receiving 20Gy or more) for total lung when the planning target volume (PTV) was surrounded by functional lung volumes. We were able to achieve better ventilated lung avoidance and lower total lung V-20Gy when the PTV is close to, but not surrounded by functioning lung volumes. For patients with the PTV that is far from 50% and 70% functional lung volumes, three-field IMRT spare the ventilated lung as well as nine-field IMRT ventilation avoidance plan, with a lower total lung V20-Gy.