A Proton Beam Therapy System Dedicated to Spot-Scanning Increases Accuracy with Moving Tumors by Real-Time Imaging and Gating and Reduces Equipment SizeReportar como inadecuado




A Proton Beam Therapy System Dedicated to Spot-Scanning Increases Accuracy with Moving Tumors by Real-Time Imaging and Gating and Reduces Equipment Size - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Purpose

A proton beam therapy PBT system has been designed which dedicates to spot-scanning and has a gating function employing the fluoroscopy-based real-time-imaging of internal fiducial markers near tumors. The dose distribution and treatment time of the newly designed real-time-image gated, spot-scanning proton beam therapy RGPT were compared with free-breathing spot-scanning proton beam therapy FBPT in a simulation.

Materials and Methods

In-house simulation tools and treatment planning system VQA Hitachi, Ltd., Japan were used for estimating the dose distribution and treatment time. Simulations were performed for 48 motion parameters including 8 respiratory patterns and 6 initial breathing timings on CT data from two patients, A and B, with hepatocellular carcinoma and with clinical target volumes 14.6 cc and 63.1 cc. The respiratory patterns were derived from the actual trajectory of internal fiducial markers taken in X-ray real-time tumor-tracking radiotherapy RTRT.

Results

With FBPT, 9-48 motion parameters achieved the criteria of successful delivery for patient A and 0-48 for B. With RGPT 48-48 and 42-48 achieved the criteria. Compared with FBPT, the mean liver dose was smaller with RGPT with statistical significance p<0.001; it decreased from 27% to 13% and 28% to 23% of the prescribed doses for patients A and B, respectively. The relative lengthening of treatment time to administer 3 Gy RBE was estimated to be 1.22 RGPT-FBPT: 138 s-113 s and 1.72 207 s-120 s for patients A and B, respectively.

Conclusions

This simulation study demonstrated that the RGPT was able to improve the dose distribution markedly for moving tumors without very large treatment time extension. The proton beam therapy system dedicated to spot-scanning with a gating function for real-time imaging increases accuracy with moving tumors and reduces the physical size, and subsequently the cost of the equipment as well as of the building housing the equipment.



Autor: Shinichi Shimizu, Naoki Miyamoto, Taeko Matsuura , Yusuke Fujii, Masumi Umezawa, Kikuo Umegaki, Kazuo Hiramoto, Hiroki Shirato

Fuente: http://plos.srce.hr/



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