■超小分割的在线自适应磁共振引导放射治疗(MRgRT)有望用于前列腺癌。然而,在线适应对目标覆盖率和危险器官(OAR)在累积剂量水平下的节省的影响尚未报告.使用基于可变形图像配准(DIR)的累积,我们比较了给药适应剂量和模拟非适应剂量.
■23名前列腺癌患者在两个诊所接受0.35T磁共振引导直线加速器(MR-linac)治疗,遵循相同的治疗方案(5×7.5Gy保留尿道和每日适应)。将部分MR图像可变形地配准到计划MR图像。非适应和适应的分数剂量都与相应的矢量场一起累积。实施了两种DIR方法。PTV*(计划目标体积减去尿道+2mm)D95%,CTV*(临床目标体积减去尿道)D98%,和OAR(尿道+2mm,膀胱,和直肠)D0.2cc,进行了评估。从双尾Wilcoxon符号秩检验推断统计学显著性(p<0.05)。
■归一化到基线,通过适应,累积的PTV*D95%显著增加了2.7%([1.5,4.3]%),CTV*D98%为1.2%([0.1,1.7]%)。对于适应后的OAR,累积膀胱D0.2cc下降0.4%([-1.2,0.4]%),尿道+2mmD0.2cc下降0.8%([-1.6,-0.1]%),而直肠D0.2cc增加2.6%([1.2,4.9]%)。对于所有患者来说,直肠D0.2cc仍低于临床限制。两种DIR方法的结果平均相差不到0.2%。
■MRgRT的在线适应改善了目标覆盖率,并且OAR在累积剂量水平上有所保留。
UNASSIGNED: Ultra-hypofractionated online adaptive magnetic resonance-guided radiotherapy (MRgRT) is promising for prostate cancer. However, the impact of online adaptation on target coverage and organ-at-risk (OAR) sparing at the level of accumulated dose has not yet been reported. Using deformable image registration (DIR)-based accumulation, we compared the delivered adapted dose with the simulated non-adapted dose.
UNASSIGNED: Twenty-three prostate cancer patients treated at two clinics with 0.35 T magnetic resonance-guided linear accelerator (MR-linac) following the same treatment protocol (5 × 7.5 Gy with urethral sparing and daily adaptation) were included. The fraction MR images were deformably registered to the planning MR image. Both non-adapted and adapted fraction doses were accumulated with the corresponding vector fields. Two DIR approaches were implemented. PTV* (planning target volume minus urethra+2mm) D95%, CTV* (clinical target volume minus urethra) D98%, and OARs (urethra+2mm, bladder, and rectum) D0.2cc, were evaluated. Statistical significance was inferred from a two-tailed Wilcoxon signed-rank test (p < 0.05).
UNASSIGNED: Normalized to the baseline, the accumulated PTV* D95% increased significantly by 2.7 % ([1.5, 4.3]%) through adaptation, and the CTV* D98% by 1.2 % ([0.1, 1.7]%). For the OARs after adaptation, accumulated bladder D0.2cc decreased by 0.4 % ([-1.2, 0.4]%), urethra+2mmD0.2cc by 0.8 % ([-1.6, -0.1]%), while rectum D0.2cc increased by 2.6 % ([1.2, 4.9]%). For all patients, rectum D0.2cc was still below the clinical constraint. Results of both DIR approaches differed on average by less than 0.2 %.
UNASSIGNED: Online adaptation in MRgRT improved target coverage and OARs sparing at the level of accumulated dose.