SU-E-J-26：利用前列腺癌放射治疗模拟门静脉图像的患者摆位误差自动估计方法

SU-E-J-26: Automated Estimation Method of Patient Setup Errors Using Simulated Portal Images for Prostate Cancer Radiotherapy.

作者信息

Matsushita N, Arimura H, Shioyama Y, Magome T, Nakamura K, Umezu Y, Yoshitake T, Anai S, Yoshidome S, Honda H, Ohki M, Toyofuku F, Hirata H

机构信息

Kyushu University, Fukuoka, Japan.

Kyushu University Hospital, Fukuoka, Japan.

出版信息

Med Phys. 2012 Jun;39(6Part6):3658. doi: 10.1118/1.4734859.

DOI:10.1118/1.4734859

PMID:28517569

Abstract

PURPOSE

We developed a novel automated estimation method for patient setup errors based on simulated and real portal images for prostate cancer radiotherapy.

METHODS

The estimation of patient setup errors in this study was based on a template matching technique with a cross-correlation coefficient and Sobel filter between the real portal image and localized pelvic template of reference image, which were DRR (digitally reconstructed radiography) images and simulated portal images. The simulated portal image was derived by projecting a CT image according to an inverse exponential power law of x-ray attenuation for a water-equivalent path length of each voxel of the CT image on each ray from a source to each pixel on the EPID (electric portal imaging device). A localized pelvic template of each patient in AP (anterior-posterior) or lateral view was automatically extracted from the DRR or simulated portal images by cropping a rectangular region, which was determined by using the mean pelvic template and four anatomical feature points. We applied the proposed method to three prostate cancer cases, and evaluated it using the residual error between the patient setup error obtained by proposed method and the gold standard setup error determined by two radiation oncologists.

RESULTS

The average residual errors of the patient setup error for the DRR and simulated portal images were 0.79 and 1.26 mm in the left-right (LR) direction, 3.17 and 2.05 mm in the superior-inferior (SI) direction, 1.69 and 5.82 mm in the anterior-posterior (AP) direction, 3.84 and 6.94 mm in Euclidean distance (ED), respectively. If we used the simulated portal image for LR and SI directions and the DRR image for AP direction, the Euclidean distance was 3.22 mm.

CONCLUSIONS

The proposed method has a potential to correctly estimate patient setup errors for prostate cancer radiotherapy.

摘要

目的

我们基于前列腺癌放射治疗的模拟和真实射野图像，开发了一种新型的患者摆位误差自动估计方法。

方法

本研究中患者摆位误差的估计基于一种模板匹配技术，该技术利用真实射野图像与参考图像的局部盆腔模板之间的互相关系数和Sobel滤波器，参考图像为数字重建射线照相（DRR）图像和模拟射野图像。模拟射野图像是通过根据X射线衰减的反指数幂定律，将CT图像投影得到的，该定律适用于CT图像每个体素在从源到电子射野成像设备（EPID）上每个像素的每条射线上的水等效路径长度。通过裁剪一个矩形区域，从DRR或模拟射野图像中自动提取每个患者在前后（AP）或侧视图中的局部盆腔模板，该矩形区域由平均盆腔模板和四个解剖特征点确定。我们将所提出的方法应用于三个前列腺癌病例，并使用所提出方法获得的患者摆位误差与由两名放射肿瘤学家确定的金标准摆位误差之间的残余误差对其进行评估。

结果

DRR和模拟射野图像的患者摆位误差在左右（LR）方向的平均残余误差分别为0.79和1.26毫米，在上下（SI）方向分别为3.17和2.05毫米，在前后（AP）方向分别为1.69和5.82毫米，在欧几里得距离（ED）方面分别为3.84和6.94毫米。如果我们在LR和SI方向使用模拟射野图像，在AP方向使用DRR图像，欧几里得距离为3.22毫米。