Lattanzi J, McNeeley S, Donnelly S, Palacio E, Hanlon A, Schultheiss T E, Hanks G E
Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, Pennsylvania, USA.
Comput Aided Surg. 2000;5(4):289-95. doi: 10.1002/1097-0150(2000)5:4<289::AID-IGS7>3.0.CO;2-D.
A mobile transabdominal ultrasound-based targeting system (BAT(R)) has been developed which can stereotactically localize the position of the prostate each treatment day and directly integrate this information into the treatment planning system. Daily target verification facilitates a marked reduction in planning treatment margins by correcting potential organ-motion and set-up errors. Previous studies have been performed to establish the precision of ultrasound localization. This report quantifies the magnitude of the patient isocenter shift parameters encountered during clinical implementation of this system.
After five weeks of conformal external beam radiation therapy, 54 patients underwent a second CT simulation. Prostate-only fields based on this scan were created with no PTV margin beyond the CTV. For each of the final conedown treatments (2-4 fractions), patients underwent ultrasound-based stereotactic prostate localization at the treatment machine. The portable system, which electronically imports the CT simulation target-contour and isocenter information, is situated adjacent to the treatment couch. Transverse and sagittal suprapubic ultrasound images are captured, and the system electronically couples this data to the baseline isocenter. The CT contours are maneuvered in three dimensions by a touch-screen menu to visually overlay the ultrasound images. The system then displays the three-dimensional (3D) couch shifts required to produce field alignment.
One hundred and eighty-nine daily ultrasound prostate position shifts were recorded for 54 patients. The isocenter field misalignment between the baseline CT and ultrasound ranged from -26.8 to 33.8 mm in the anterior/posterior (A/P) dimension, -10.2 to 30.9 mm in the lateral dimension, and -24.6 to 9.0 mm in the superior/inferior (S/I) dimension. The corresponding directed average disagreements were -3.0 mm (SD 8.3 mm) A/P, 1.86 mm (SD 5.7 mm) lateral, and -2.6 mm (SD 6.5 mm) S/I. The magnitudes of undirected misalignments were frequently larger than 5 mm (51% of A/P, 31% of lateral, and 35% of superior measurements) and oftentimes larger than 10 mm (21% of A/P, 7% of lateral, and 12% of superior measurements).
Organ motion and set-up uncertainties limit optimization of 3D treatment planning by expanding the width of PTV margins required to ensure target coverage. Transabdominal ultrasound-based stereotactic guidance is a safe and direct method for correcting patient positioning. Our experience with the BAT system in a large cohort of prostate cancer patients revealed that substantial daily isocenter corrections were encountered in a large percentage of cases. This data would suggest that daily clinical isocenter misalignments are greater than would be expected from published data on organ motion and set-up variations encountered in the study setting.
已开发出一种基于经腹超声的移动靶向系统（BAT(R)），该系统可在每个治疗日立体定位前列腺的位置，并将此信息直接整合到治疗计划系统中。每日的靶区验证通过纠正潜在的器官运动和摆位误差，有助于显著缩小计划治疗边界。此前已开展研究以确定超声定位的精度。本报告对该系统临床应用过程中患者等中心偏移参数的大小进行了量化。
在进行五周的适形外照射放疗后，54例患者接受了第二次CT模拟。基于此次扫描创建了仅针对前列腺的射野，在临床靶区（CTV）之外没有计划靶区（PTV）边界。对于每一次最终缩野治疗（2 - 4次分割），患者在治疗机上接受基于超声的前列腺立体定位。该便携式系统通过电子方式导入CT模拟的靶区轮廓和等中心信息，位于治疗床旁。采集耻骨上横向和矢状面超声图像，系统将此数据与基线等中心进行电子耦合。通过触摸屏菜单在三维空间中操作CT轮廓，以在视觉上叠加超声图像。然后系统显示实现射野对准所需的三维（3D）治疗床移位。
记录了54例患者的189次每日超声前列腺位置移位。基线CT与超声之间的等中心射野偏差在前/后（A/P）维度为 - 26.8至33.8毫米，在侧方维度为 - 10.2至30.9毫米，在上/下（S/I）维度为 - 24.6至9.0毫米。相应的定向平均差异分别为A/P方向 - 3.0毫米（标准差8.3毫米），侧方1.86毫米（标准差5.7毫米），S/I方向 - 2.6毫米（标准差6.5毫米）。无定向偏差的大小经常大于5毫米（A/P测量值的51%、侧方测量值的31%、上方测量值 的35%），且时常大于10毫米（A/P测量值的21%、侧方测量值的7%、上方测量值 的12%）。
器官运动和摆位不确定性通过扩大确保靶区覆盖所需的PTV边界宽度，限制了三维治疗计划的优化。基于经腹超声的立体定向引导是纠正患者摆位的一种安全且直接的方法。我们在一大群前列腺癌患者中使用BAT系统的经验表明，在很大比例的病例中都遇到了大量的每日等中心校正。这些数据表明，每日临床等中心偏差大于研究环境中已发表的关于器官运动和摆位变化的数据所预期的值。
