Beam Characteristics of the First Clinical 360°-rotational Compact Scanning Pencil Beam Proton Treatment System and Comparisons against a Multi-Room System

Abstract

Two of the five patients had central tumors (within 2cm from critical midline structure). The following table shows the relevant structures and parameters. Coverage was kept consistent between plans with an average of 4750 cGy (95%) to the PTV volume. Conclusion: This study demonstrates the feasibility and advantages of SBRT treatment planning with DIBH. PTV volumes in FB were significantly larger due to the physiologic lung changes at peak inspiration and expiration. A reduction in PTV volume subsequently reduced mean OAR dose. Limitations in our study include few patients analyzed with various lung tumor locations of variable sizes. The patients with centrally located tumors appear to derive a greater dosimetric benefit with DIBH due to improved physiologic separation of tumor volume from nearby OARs. Though further investigation is warranted, and some patients are limited by their underlying pulmonary function, DIBH appears to be an effective technique for reducing PTV volumes and mean doses to OARs. Benefits should be assessed on an individualized basis. Abstract 2812; Table Structure and Parameter FB-4DCT DIBH p-value PTV Volume (cm 3) 33 30 0.02 Ipsilateral Lung Volume (cm 3) 1875 2486 0.03 Mean Ipsilateral Lung Dose (cGy) 411 321 0.06 Max Heart Dose (cGy) 628 449 0.34 Mean Heart Dose (cGy) 45 38 0.20 Mean Left Anterior Descending a. Dose (cGy) 51 44 0.04 Mean Right Coronary a. Dose (cGy) 69 120 0.38 Mean Left Circumflex a. Dose (cGy) 54 45 0.32