Analysis of movement of intrathoracic neoplasms using ultrafast computerized tomography

Twenty patients with intrathoracic neoplasms were evaluated with ultrafast (cine) computerized tomography to determine the contribution of tumor motion to geographic errors. The treatment portals were setup with conventional simulation techniques and then scanned with cine computerized tomography. Eight tomographic levels were studied, 10 images per level over 7 seconds time. Major geographic misses were detected in three patients (15%), and minor geographic misses in an additional three (15%). The greatest tumor movement was noted in lesions located adjacent to the heart or aorta or near the diaphragm. Five of six hilar lesions showed significant lateral motion (average = 9.2 mm) with cardiac contraction, and three of four lower lobe lesions showed significant craniocaudal movement with respiration. Mediastinal lesions moved an average of 8.7 mm laterally. Lesions in the upper lobes showed minimal movement (average = 2.2 mm), and tumors attached to the chest wall showed no measurable movement.