基于一种插值算法的金球位置追踪方法

Gold markers location tracking method based on interpolation algorithm

目的:建立一种算法,从低空间分辨力二维电离室矩阵测得的预埋有金球的穿过模体的剂量分布中读取金球投影位置坐标。方法:(1)利用Octavius 729二维电离室矩阵测得穿过埋有金球的模体的剂量分布;(2)采用一种插值算法将得到的低空间分辨力的剂量分布转换成高空间分辨力的剂量分布;(3)在得到的高空间分辨力的剂量分布上自编算法读取模体内金球投影位置坐标;(4)将得到的金球投影位置坐标与用高空间分辨力EPID图像得到的金球投影位置坐标进行比较。结果:在模体中共有3个金球,在机架角为0°条件下进行测量,计算得到3个金球的投影位置坐标,与金球实际投影位置坐标的最大偏差为2.5 mm,最小偏差为0.1 mm。结论:该插值算法及所编软件可以用于低空间分辨力二维电离室矩阵读取预埋于体内金球的投影位置识别,且软件操作方便快捷,结果可靠。

Objective To develop an algorithm for obtaining the projection positions＇ coordinates from the dose distribution of the phantom with pre-implanted gold marker. The dose distribution was measured by using two-dimensional （2D） ionization chamber array of low spatial resolution. Methods The dose distribution of the phantom wi pre-implanted gold makers was measured by using 2D ionization chamber array of Octavius 729. The measured dose distribution of low spatial resolution was converted into a dose distribution of high spatial resolution by using an interpolation algorithm. Based on the dose distribution of high spatial resolution, self-compiled algorithm was applied to read the projected positions＇ coordinates of gold markers. The read coordinates were compared with the coordinates obtained by using the electronic portal imaging device image of high spatial resolution. Results With the gantry angle at 0°, the measurement was performed for the phantom with 3 pro-implanted gold markers. The projected positions＇ coordinates of gold markers were calculated. The maximum deviation between the calculated coordinates and practical coordinates was 2.5 mm, and the minimum deviation was 0.1mm. Conclusion The interpolation algorithm and self-compiled software can be used in 2D ionization chamber array of low spatial resolution to locate the projected positions ofpre-implanted gold markers, with convenient and fast operation, and reliable results.