Lavelle Michael J, Kaza Evangelia, Guthier Christian V, O'Farrell Desmond A, Harris Thomas C, Cormack Robert A, Devlin Phillip M, Buzurovic Ivan M
Department of Radiation Oncology, Dana-Farber/Brigham and Women's Cancer Center, Harvard Medical School, USA.
J Contemp Brachytherapy. 2024 Feb;16(1):48-56. doi: 10.5114/jcb.2024.135647. Epub 2024 Feb 23.
Best practices for high-dose-rate surface applicator brachytherapy treatment (SABT) have long relied on computed tomography (CT)-based imaging to visualize diseased sites for treatment planning. Compared with magnetic resonance (MR)-based imaging, CT provides insufficient soft tissue contrast. This work described the feasibility of clinical implementation of MR-based imaging in SABT planning to provide individualized treatment optimization.
A 3D-printed phantom was used to fit Freiberg flap-style (Elekta, The Netherlands) applicator. Images were taken using an optimized pointwise encoding time reduction with radial acquisition (PETRA) MR sequence for catheter visualization, and a helical CT scan to generate parallel treatment plans. This clinical study included three patients undergoing SABT for Dupuytren's contracture/palmar fascial fibromatosis imaged with the same modalities.SABT planning was performed in Oncentra Brachy (Elekta Brachytherapy, The Netherlands) treatment planning software. A geometric analysis was conducted by comparing CT-based digitization with MR-based digitization. CT and MR dwell positions underwent a rigid registration, and average Euclidean distances between dwell positions were calculated. A dosimetric comparison was performed, including point-based dose difference calculations and volumetric segmentations with Dice similarity coefficient (DSC) calculations.
Euclidean distances between dwell positions from CT-based and MR-based plans were on average 0.68 ±0.05 mm and 1.35 ±0.17 mm for the phantom and patients, respectively. The point dose difference calculations were on average 0.92% for the phantom and 1.98% for the patients. The D and D DSC calculations were both 97.9% for the phantom, and on average 93.6% and 94.2%, respectively, for the patients.
The sub-millimeter accuracy of dwell positions and high DSC's (> 0.95) of the phantom demonstrated that digitization was clinically acceptable, and accurate treatment plans were produced using MR-only imaging. This novel approach, MRI-guided SABT, will lead to individualized prescriptions for potentially improved patient outcomes.
高剂量率表面敷贴近距离放射治疗（SABT）的最佳实践长期以来一直依赖基于计算机断层扫描（CT）的成像来可视化病变部位以进行治疗计划。与基于磁共振（MR）的成像相比，CT提供的软组织对比度不足。本研究描述了在SABT计划中临床实施基于MR的成像以提供个体化治疗优化的可行性。
使用3D打印体模适配弗赖贝格皮瓣式（荷兰医科达公司）敷贴器。使用优化的逐点编码时间减少与径向采集（PETRA）MR序列进行图像采集以实现导管可视化，并进行螺旋CT扫描以生成平行的治疗计划。这项临床研究纳入了3例因掌腱膜挛缩/掌筋膜纤维瘤病接受SABT治疗的患者，采用相同的成像方式进行成像。在Oncentra Brachy（荷兰医科达近距离放射治疗公司）治疗计划软件中进行SABT计划。通过比较基于CT的数字化与基于MR的数字化进行几何分析。对CT和MR的驻留位置进行刚性配准，并计算驻留位置之间的平均欧几里得距离。进行剂量学比较，包括基于点的剂量差异计算和使用骰子相似系数（DSC）计算的体积分割。
对于体模和患者，基于CT的计划与基于MR的计划的驻留位置之间的欧几里得距离平均分别为0.68±0.05毫米和1.35±0.17毫米。体模的点剂量差异计算平均为0.92%，患者为1.9八%。体模的D和D DSC计算均为97.9%，患者平均分别为93.6%和94.2%。
体模驻留位置的亚毫米精度和高DSC值（>0.95）表明数字化在临床上是可接受的，并且仅使用MR成像即可生成准确的治疗计划。这种新颖的方法，即MRI引导的SABT，将为潜在改善患者预后带来个体化的处方。
