MR增强延迟扫描成像在保乳术后俯卧位照射患者瘤床靶区勾画中的应用

目的 基于形变配准探讨保乳术后术腔血清肿不可见或低可见度(CVS≤2)患者行俯卧位照射时MR增强延迟扫描成像在瘤床(LC)勾画中的应用。方法 26例患者入组。分别在俯卧位CT定位图像、俯卧位MR定位T2WI成像及增强延迟2、5、10min的T1WI成像上勾画LC并分别定义为LCCT、LCT2、LC2T1、LC5T1和LC10T1。基于形变配准进行CT与MR图像LC间体积与位置的比较。结果 LCT2、LC2T1、LC5T1、LC10T1体积似均大于LCCT体积,且LC2T1、LC5T1与LCCT间体积差异有统计学意义(均P<0.05)。LC10T1与LCCT间的包含度(DI)、适形指数(CI)、相似度指数(DSC)、靶区中心距离(COM)均似优于LCT2与LCCT、LC2T1与LCCT及LC5T1与LCCT,但差异均无统计学意义(均P>0.05)。结论 基于俯卧位MR定位增强延迟扫描成像勾画低CVS患者LC靶区是可行的,无论是靶区体积大小还是靶区空间位置,基于T1WI增强延迟10min扫描所勾画LC靶区与基于俯卧位CT图像上金属钛夹所勾画的最接近。

Application of delayed-enhancement MRI in lumpectomy cavity delineation for patients after breast-conserving surgery in prone radiotherapy using deformable image registration

Objective To assess the feasibility of delayed-enhancement MRI in contouring the lumpectomy cavity (LC) for patients with invisible seroma or a low cavity visualization score (CVS≤2) in the excision cavity after breast-conserving surgery (BCS). Methods Twenty-six patients with stageT1-2N0M0 who underwent prone radiotherapy after BCS were recruited. The LC delineated on CT simulation images was denoted as LCCT. The LCs delineated on T2WI, as well as on different delayed phases (2-, 5-and 10-minute) of delayed-enhancement T1WI were defined as LCT2, LC2T1, LC5T1 and LC10T1, respectively. Subsequently, the volumes and locations of the LCs were compared between CT simulation images and different sequences of MR simulation images using deformable image registration. Results The volumes of LCT2, LC2T1, LC5T1 and LC10T1 were all larger than that of LCCT. A statistical significance was found between the volume of LCCT and those of LC2T1 or LC5T1, respectively (both P<0.05). The conformal index (CI), degree of inclusion (DI), dice similarity coefficient (DSC) and the distance between the center of mass of the targets (COM) of LCCT-LC10T1 were better than those of LCCT-LCT2, LCCT-LC2T1 and LCCT-LC5T1, however, there was no statistical difference among them (all P>0.05). Conclusions It is feasible to delineate the LC based on prone delayed-enhancement MR simulation images in patients with low CVS after BCS. Meanwhile, the LCs derived from prone delayed-enhancement T1WI of 10-minute are the most similar with those derived from prone CT simulation scans using titanium clips, regardless of the volumes and locations of LCs.