Impact of respiratory gating using 4-dimensional computed tomography on the dosimetry of tumor and normal tissues in patients with thoracic malignancies.

OBJECTIVE: The purpose of this study is to assess the dosimetric impact of gated CT plans on tumor and surrounding normal tissues in patients with primary thoracic malignancies. MATERIALS AND METHODS: Ten patients underwent treatment planning with gated and nongated CT at Wayne State University. Gated CT images were obtained at full inspiration, expiration, and at the 25th, 50th, and 75th percentile of respiratory effort. Planning treatment volume (PTV) margin for nongated and gated plans was 1.5 cm and 0.5 cm, respectively. The tumor prescription dose was 60 to 70 Gy at 2 Gy per fraction. RESULTS: Average PTV was 292.68 mL for gated and 575.17 mL for nongated plans. Gated plans resulted in higher minimum PTV doses and comparable mean and maximum doses when compared with nongated plans (53.52, 65.17, and 70.92 Gy vs. 48.06, 65.08, and 71.40 Gy, respectively). Volumes of lung receiving doses of 20 and 10 Gy or above were 26.26% and 30.96% for gated plans and 34.82% and 40.16% for nongated plans (P < 0.0001). Gated plans resulted in lower mean lung, esophageal, and heart doses compared with nongated plans (14.27, 17.28, and 10.86 Gy vs. 19.5, 21.85, and 16.45 Gy, respectively; P