Narayana V, Roberson P L, Winfield R J, McLaughlin P W
Providence Hospital, Southfield, MI, USA.
Int J Radiat Oncol Biol Phys. 1997 Sep 1;39(2):341-6. doi: 10.1016/s0360-3016(97)00072-2.
Ultrasound (US)-guided permanent prostate implants typically use US prostate volumes to plan the implant procedure and CT prostate volumes for 3D dosimetric evaluation of the implant. Such a protocol requires that CT and US prostate volumes be registered. We have studied the impact of prostate volume registration on postimplant dosimetry for patients with low-grade prostate cancer treated with combined US and fluoroscopic-guided permanent implants.
A US image set was obtained with the patient in the lithotomy position to delineate the prostate volume that was subsequently used for treatment planning. Each plan was customized and optimized to ensure complete coverage of the US prostate volume. After implant, a CT scan was obtained for postimplant dosimetry with the patient lying supine. Sources were localized on CT by interactively creating orthogonal images of small cubes, whose dimensions were slightly larger than the source, to assure unique identification of each seed. Ultrasound and CT 3D surfaces were registered using either (a) the rectal surface and base of the prostate, or (b) the Foley balloon and urethra as the alignment reference. A dose distribution was assigned to the US prostate volume based on the CT source distribution, and the dose-volume histogram (DVH) was calculated.
Prostate volumes drawn from US images differ from those drawn from CT images with the CT volumes being typically larger than the US volumes. Urethral registration of the prostate volume based on aligning the prostatic urethra generates a dose distribution that best follows the preimplant plan and is geometrically the preferable choice for dosimetry.
The dose distribution and the DVH for the US prostate is sensitive to the mode of registration limiting the ability to determine if acceptable dose coverage has been achieved.
超声（US）引导下的永久性前列腺植入通常使用超声测量的前列腺体积来规划植入过程，并使用CT测量的前列腺体积进行植入物的三维剂量学评估。这样的方案要求CT和超声测量的前列腺体积进行配准。我们研究了前列腺体积配准对接受超声和荧光透视引导下永久性植入联合治疗的低级别前列腺癌患者植入后剂量学的影响。
患者处于截石位时获取超声图像集，以勾勒出随后用于治疗计划的前列腺体积。每个计划都进行了定制和优化，以确保超声测量的前列腺体积得到完全覆盖。植入后，患者仰卧位进行CT扫描以进行植入后剂量学评估。通过交互式创建尺寸略大于源的小立方体的正交图像在CT上定位源，以确保每个籽源的唯一识别。使用以下两种方法之一对超声和CT三维表面进行配准：（a）直肠表面和前列腺底部，或（b） Foley球囊和尿道作为对齐参考。根据CT源分布将剂量分布分配到超声测量的前列腺体积，并计算剂量体积直方图（DVH）。
超声图像绘制的前列腺体积与CT图像绘制的不同，CT体积通常大于超声体积。基于前列腺尿道对齐的前列腺体积尿道配准产生的剂量分布最符合植入前计划，并且在几何上是剂量学的首选。
超声测量的前列腺的剂量分布和DVH对配准模式敏感，限制了确定是否实现可接受剂量覆盖的能力。
