Effects of Intrafractional Motion on Water Equivalent Pathlength in Respiratory-Gated Heavy Charged Particle Beam Radiotherapy

Cine CT with a 256-multislice CT scanner captures both volumetric cardiac and respiratory motion with a temporal resolution sufficient to estimate range fluctuations by these motions. This information can be used to assess the range perturbations that charged particle beams may experience in irradiation of lung or esophageal tumors adjacent to the heart.