Gong Lixin, Cho Paul S, Han Ben H, Wallner Kent E, Sutlief Steve G, Pathak Sayan D, Haynor David R, Kim Yongmin
Department of Electrical Engineering, University of Washington, Seattle, WA 98195, USA.
Int J Radiat Oncol Biol Phys. 2002 Dec 1;54(5):1322-30. doi: 10.1016/s0360-3016(02)03754-9.
To investigate the feasibility of performing postimplant and intraoperative dosimetry for prostate brachytherapy by fusing transrectal ultrasound (TRUS) and fluoroscopic data.
Registration of ultrasound (prostate boundary) and fluoroscopic (seed) data requires spatial markers that are detectable by both imaging modalities. In this study, the needle tips were considered as such fiducials. Prostate phantoms were implanted with the seeds, and four localization needles were inserted. In the TRUS frame of reference, the longitudinal coordinate of the needle tip was determined by advancing the needle until the echo from its tip just registered at a known probe depth. The tip's transverse coordinates were determined from the associated TRUS slice. The three-dimensional needle tip positions were also calculated in the fluoroscopic coordinate system using a seed reconstruction method. The transformation between the TRUS and fluoroscopy coordinate systems was established by the least-squares solution using the singular value decomposition.
With three of four needle tips as fiducials and the one remaining needle as a test target, the mean fiducial registration error was 0.8 mm and the test target registration error was 2.5 mm. When all four points were used for registration, the errors decreased to 1.1 mm. A comparison between the proposed method and CT-based dosimetry yielded a percentage of prostate volume receiving 100% and 150% of the prescribed minimal peripheral dose and minimal dose received by 90% of the prostate gland that agreed within 0.4%, 2.7%, and 4.2%, respectively.
The combination of TRUS and fluoroscopy is a feasible alternative to the currently used CT-based postimplant dosimetry. Furthermore, because of online imaging capability, the method lends itself to real-time intraoperative applications.
通过融合经直肠超声（TRUS）和荧光透视数据，研究前列腺近距离放射治疗术后植入及术中剂量测定的可行性。
超声（前列腺边界）和荧光透视（粒子）数据的配准需要两种成像方式均可检测到的空间标记物。在本研究中，针尖被视为此类基准标记。将粒子植入前列腺模型，并插入四根定位针。在TRUS参考坐标系中，通过推进针直到其尖端的回波刚好记录在已知探头深度处来确定针尖的纵向坐标。针尖的横向坐标由相关的TRUS切片确定。还使用粒子重建方法在荧光透视坐标系中计算三维针尖位置。通过使用奇异值分解的最小二乘解建立TRUS和荧光透视坐标系之间的变换。
以四根针尖中的三根作为基准标记，将剩余的一根针作为测试目标，平均基准标记配准误差为0.8毫米，测试目标配准误差为2.5毫米。当使用所有四个点进行配准时，误差降至1.1毫米。将所提出的方法与基于CT的剂量测定法进行比较，结果显示接受规定最小周边剂量100%和150%的前列腺体积百分比以及前列腺90%所接受的最小剂量，其一致性分别在0.4%、2.7%和4.2%以内。
TRUS和荧光透视的结合是目前使用的基于CT的术后植入剂量测定法的一种可行替代方法。此外，由于具有在线成像能力，该方法适用于实时术中应用。
