Schneider Frank, Bludau Frederic, Clausen Sven, Fleckenstein Jens, Obertacke Udo, Wenz Frederik
Department of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Germany.
Orthopaedic and Trauma Surgery Center, University Medical Center Mannheim, University of Heidelberg, Germany.
Phys Med. 2017 May;37:82-87. doi: 10.1016/j.ejmp.2017.04.017. Epub 2017 Apr 28.
To the present date, IORT has been eye and hand guided without treatment planning and tissue heterogeneity correction. This limits the precision of the application and the precise documentation of the location and the deposited dose in the tissue. Here we present a set-up where we use image guidance by intraoperative cone beam computed tomography (CBCT) for precise online Monte Carlo treatment planning including tissue heterogeneity correction.
An IORT was performed during balloon kyphoplasty using a dedicated Needle Applicator. An intraoperative CBCT was registered with a pre-op CT. Treatment planning was performed in Radiance using a hybrid Monte Carlo algorithm simulating dose in homogeneous (MCwater) and heterogeneous medium (MChet). Dose distributions on CBCT and pre-op CT were compared with each other. Spinal cord and the metastasis doses were evaluated.
The MCwater calculations showed a spherical dose distribution as expected. The minimum target dose for the MChet simulations on pre-op CT was increased by 40% while the maximum spinal cord dose was decreased by 35%. Due to the artefacts on the CBCT the comparison between MChet simulations on CBCT and pre-op CT showed differences up to 50% in dose.
igIORT and online treatment planning improves the accuracy of IORT. However, the current set-up is limited by CT artefacts. Fusing an intraoperative CBCT with a pre-op CT allows the combination of an accurate dose calculation with the knowledge of the correct source/applicator position. This method can be also used for pre-operative treatment planning followed by image guided surgery.
到目前为止，术中放射治疗（IORT）一直是在没有治疗计划和组织异质性校正的情况下靠肉眼和手动操作进行的。这限制了应用的精度以及组织中位置和沉积剂量的精确记录。在此，我们展示一种设置，即我们使用术中锥形束计算机断层扫描（CBCT）进行图像引导，以实现精确的在线蒙特卡罗治疗计划，包括组织异质性校正。
在球囊椎体后凸成形术期间使用专用针状施源器进行IORT。术中CBCT与术前CT进行配准。在Radiance中使用混合蒙特卡罗算法在均匀介质（MCwater）和非均匀介质（MChet）中模拟剂量来进行治疗计划。将CBCT和术前CT上的剂量分布相互比较。评估脊髓和转移灶的剂量。
MCwater计算显示出预期的球形剂量分布。术前CT上MChet模拟的最小靶剂量增加了40%，而最大脊髓剂量减少了35%。由于CBCT上的伪影，CBCT和术前CT上MChet模拟之间的剂量比较显示差异高达50%。
图像引导的IORT和在线治疗计划提高了IORT的准确性。然而，当前的设置受到CT伪影的限制。将术中CBCT与术前CT融合，能够将准确的剂量计算与正确的源/施源器位置的信息相结合。这种方法也可用于术前治疗计划，随后进行图像引导手术。
