Beam direction arrangement using a superconducting rotating gantry in carbon ion treatment for pancreatic cancer

Abstract

OBJECTIVES: Carbon ion radiotherapy provides a concentrated dose distribution to the target and has several advantages over photon radiotherapy. This study aimed to evaluate the optimal beam direction in carbon ion pencil beam scanning and compare dose distributions between the rotating gantry system (RGS) and fixed-beam port system (FBPS).

METHODS: Patients with locally advanced pancreatic cancer were randomly selected. First, dose-volume parameters of 7-beam directions in the prone position were evaluated. Second, a composite plan developed using 4-beam directions in RGS was compared with that developed using FBPS, with a total prescribed dose of 55.2 Gy (relative biological effectiveness, RBE) in 12 fractions.

RESULTS: Target coverages in the composite plan did not widely differ. For the first and second segments of the duodenum, the mean dose of D2cc was not significantly changed (23.80 ± 11.90 Gy [RBE] and 25.63 ± 10.41 Gy [RBE] for RGS and FBPS, respectively). However, the dose-volume histogram curve in RGS showed a prominent dose reduction in the low-dose region. No significant differences were observed in the stomach, third and fourth segments of the duodenum, and spinal cord. The mean dose of the total kidney was similar between RGS and FBPS.

CONCLUSIONS: Compared with that of FBPS, the 4-beam arrangement in the prone position using RGS provides comparable or superior dose distribution in the surrounding normal organ while achieving the same target coverage. In addition, RGS allows for single-patient positioning.

ADVANCES IN KNOWLEDGE: RGS is beneficial in delivering radiotherapy doses to the duodenum and allows for single-patient positioning and a simple planning process.