Keen Medical Physics Co. Ltd., 901-4-4-4 Yushima, Bunkyo-ku, Tokyo 113-0034, Japan.
Med Phys. 2013 Sep;40(9):091709. doi: 10.1118/1.4818057.
Recently, much research on imaging the clinical proton-irradiated volume using positron emitter nuclei based on target nuclear fragment reaction has been carried out. The purpose of this study is to develop an activity pencil beam (APB) algorithm for a simulation system for proton-activated positron-emitting imaging in clinical proton therapy using spread-out Bragg peak (SOBP) beams.
The target nuclei of activity distribution calculations are (12)C nuclei, (16)O nuclei, and (40)Ca nuclei, which are the main elements in a human body. Depth activity distributions with SOBP beam irradiations were obtained from the material information of ridge filter (RF) and depth activity distributions of compounds of the three target nuclei measured by BOLPs-RGp (beam ON-LINE PET system mounted on a rotating gantry port) with mono-energetic Bragg peak (MONO) beam irradiations. The calculated data of depth activity distributions with SOBP beam irradiations were sorted in terms of kind of nucleus, energy of proton beam, SOBP width, and thickness of fine degrader (FD), which were verified. The calculated depth activity distributions with SOBP beam irradiations were compared with the measured ones. APB kernels were made from the calculated depth activity distributions with SOBP beam irradiations to construct a simulation system using the APB algorithm for SOBP beams.
The depth activity distributions were prepared using the material information of RF and the measured depth activity distributions with MONO beam irradiations for clinical therapy using SOBP beams. With the SOBP width widening, the distal fall-offs of depth activity distributions and the difference from the depth dose distributions were large. The shapes of the calculated depth activity distributions nearly agreed with those of the measured ones upon comparison between the two. The APB kernels of SOBP beams were prepared by making use of the data on depth activity distributions with SOBP beam irradiations that were made from the depth activity distributions with MONO beam irradiations and sorted in terms of energy, SOBP width, and thickness of FD. The data on APB kernels of SOBP beams were determined as installment data for the simulation system using the APB algorithm for SOBP beam irradiations.
A method of obtaining the depth activity distributions and the APB algorithm for clinical use of SOBP beams have been developed. It is suggested that the simulation system for imaging the clinical irradiated volume with the APB algorithm can be used in clinical proton therapy using SOBP beams by preparing and investigating the data on APB kernels of SOBP beams.
最近，已经有很多使用基于目标核碎片反应的正电子发射核素对临床质子辐照体积进行成像的研究。本研究的目的是为使用扩展布拉格峰（SOBP）束的临床质子治疗中质子激活正电子发射成像开发一种用于模拟系统的活性铅笔束（APB）算法。
活性分布计算的靶核是（12）C 核、（16）O 核和（40）Ca 核，它们是人体的主要元素。通过脊滤波器（RF）的材料信息获得 SOBP 束照射下的深度活性分布，并通过 BOLPs-RGp（安装在旋转龙门端口上的在线 PET 系统）用单能布拉格峰（MONO）束照射下测量的三种靶核的化合物的深度活性分布。对 SOBP 束照射下的深度活性分布的计算数据进行了分类，分类依据为核种类、质子束能量、SOBP 宽度和精细衰减器（FD）的厚度，并对其进行了验证。比较了 SOBP 束照射下的计算深度活性分布和测量值。从 SOBP 束照射下的计算深度活性分布中制作了 APB 核，以构建使用 SOBP 束的 APB 算法的模拟系统。
使用 RF 的材料信息和用于 SOBP 束临床治疗的 MONO 束照射下测量的深度活性分布来制备深度活性分布。随着 SOBP 宽度的变宽，深度活性分布的远端下降和与深度剂量分布的差异变大。通过比较，计算出的深度活性分布的形状与测量的深度活性分布的形状几乎一致。通过对 SOBP 束照射下的深度活性分布进行分类，获得了 SOBP 束的 APB 核，分类依据为能量、SOBP 宽度和 FD 的厚度，然后从 MONO 束照射下的深度活性分布中获得。SOBP 束的 APB 核的数据被确定为使用 SOBP 束的 APB 算法的模拟系统的安装数据。
已经开发出一种用于 SOBP 束临床应用的获取深度活性分布和 APB 算法的方法。建议通过准备和研究 SOBP 束的 APB 核的数据，可以在使用 SOBP 束的临床质子治疗中使用基于 APB 算法的临床照射体积成像模拟系统。
