Trichter Frieda, Ennis Ronald D
Department of Radiation Oncology, Columbia University College of Physicians and Surgeons, New York, NY, USA.
Int J Radiat Oncol Biol Phys. 2003 Aug 1;56(5):1225-33. doi: 10.1016/s0360-3016(03)00269-4.
Adding margin around a target is done in an attempt to ensure complete coverage of the target. The B-mode acquisition and targeting (BAT) system allows ultrasound imaging of the prostate in patients with a full bladder. This provides a setup tool for patients with localized prostate cancer that takes into account real-time prostate position and may make it possible to decrease tumor margins. Prostate localization using the conventional setup verification method and daily isocenter shifts recommended by the ultrasound imaging system (BAT) were compared and analyzed.
Daily treatment isocenter shifts for patients with localized adenocarcinoma of the prostate, obtained from two different imaging modalities, electronic portal imaging (EPI) and BAT, were calculated. We studied the difference in patient setup error calculated using BAT contour alignment and measured from EPI; the reproducibility of BAT contour alignment; intrafraction prostate motion; and how the BAT imaging procedure itself affected the prostate position. Prostate motion relative to its position during simulation was calculated by subtracting the EPI-measured isocenter shifts from the corresponding BAT-defined isocenter shifts. BAT reproducibility was measured by taking a verification BAT image after the patient was moved according to the initial BAT-defined isocenter shifts. Intrafraction prostate motion was measured by repeating BAT imaging at the end of a treatment fraction. The BAT imaging effect on prostate position was studied by examining the effect of suprapubic pressure on seed position in patients after a seed implant.
The mean BAT isocenter shifts for prostate motion were 0.32 +/- 0.46 cm in the lateral, 0.31 +/- 0.73 cm in the superoinferior, and 0.32 +/- 0.56 cm in the AP directions. Isocenter shifts obtained from EPI measurements were significantly smaller, with a mean of 0.05 +/- 0.24 cm in the lateral, 0.01 +/- 0.11 cm in the superoinferior and -0.11 +/- 0.29 cm in the AP directions. This larger shift seen by BAT was due to prostate motion. For BAT reproducibility, the results showed that for BAT verification images, 90% of the lateral shifts were <0.2 cm, 93% of the superoinferior shifts were <0.3 cm, and 83% of the AP shifts were <0.2 cm. The mean isocenter shift (intrafraction localization error) during patient treatment fraction was 0.02 +/- 0.28 cm in the lateral, 0.04 +/- 0.48 cm in the superoinferior, and 0.0 +/- 0.32 cm in the AP direction. The BAT procedure itself induced an average motion of 1 mm in the AP and superoinferior directions.
Prostate patient setup verification on the basis of bony anatomy position does not reflect the actual prostate position. BAT ultrasound target alignment provides a real-time prostate localization system that may make it possible to measure prostate position variations and reduce margins.
在靶区周围添加边缘是为了确保靶区得到完全覆盖。B 模式采集与靶向（BAT）系统可对膀胱充盈的患者进行前列腺超声成像。这为局限性前列腺癌患者提供了一种设置工具，该工具考虑了前列腺的实时位置，并有可能减小肿瘤边缘。对使用传统设置验证方法和超声成像系统（BAT）推荐的每日等中心位移进行前列腺定位的情况进行了比较和分析。
计算了从两种不同成像方式，即电子门静脉成像（EPI）和 BAT 获得的局限性前列腺腺癌患者的每日治疗等中心位移。我们研究了使用 BAT 轮廓对齐计算并从 EPI 测量得到的患者设置误差的差异；BAT 轮廓对齐的可重复性；分次治疗期间前列腺的运动；以及 BAT 成像程序本身如何影响前列腺位置。通过从相应的 BAT 定义的等中心位移中减去 EPI 测量的等中心位移来计算前列腺相对于其在模拟期间位置的运动。通过在患者根据初始 BAT 定义的等中心位移移动后获取验证 BAT 图像来测量 BAT 的可重复性。通过在治疗分次结束时重复 BAT 成像来测量分次治疗期间前列腺的运动。通过检查耻骨上压力对种子植入后患者种子位置的影响来研究 BAT 成像对前列腺位置的影响。
前列腺运动的平均 BAT 等中心位移在横向为 0.32±0.46 厘米，在上下方向为 0.31±0.73 厘米，在前后方向为 0.32±0.56 厘米。从 EPI 测量获得的等中心位移明显较小，横向平均为 0.05±0.24 厘米，上下方向为 0.01±0.11 厘米，前后方向为 -0.11±0.29 厘米。BAT 观察到的这种较大位移是由于前列腺运动。对于 BAT 的可重复性，结果表明，对于 BAT 验证图像，90%的横向位移<0.2 厘米，93%的上下位移<0.3 厘米，83%的前后位移<0.2 厘米。患者治疗分次期间的平均等中心位移（分次治疗期间的定位误差）在横向为 0.02±0.28 厘米，在上下方向为 0.04±0.48 厘米，在前后方向为 0.0±0.32 厘米。BAT 程序本身在前后和上下方向上引起了平均 1 毫米的运动。
基于骨骼解剖位置进行前列腺患者设置验证并不能反映前列腺的实际位置。BAT 超声靶区对齐提供了一种实时前列腺定位系统，该系统有可能测量前列腺位置变化并减小边缘。
