Northern Sydney Cancer Centre, Radiation Oncology Department, Royal North Shore Hospital, St Leonards, NSW, 2065, Australia.
Northern Clinical School, University of Sydney, St Leonards, NSW, 2065, Australia.
Radiat Oncol. 2021 Jan 22;16(1):20. doi: 10.1186/s13014-020-01743-9.
To measure intra-fraction displacement (IFD) in post-prostatectomy patients treated with anisotropic margins and daily soft tissue matching.
Pre-treatment cone beam computed tomography (CBCT) scans were acquired daily and post-treatment CBCTs for the first week then weekly on 46 patients. The displacement between the scans was calculated retrospectively to measure IFD of the prostate bed (PB). The marginal miss (MM) rate, and the effect of time between imaging was assessed.
A total of 392 post-treatment CBCT's were reviewed from 46 patients. The absolute mean (95% CI) IFD was 1.5 mm (1.3-1.7 mm) in the AP direction, 1.0 mm (0.9-1.2 mm) SI, 0.8 mm (0.7-0.9 mm) LR, and 2.4 mm (2.2-2.5 mm) 3D displacement. IFD ≥ ± 3 mm and ≥ ± 5 mm was 24.7% and 5.4% respectively. MM of the PB was detected in 33 of 392 post-treatment CBCT (8.4%) and lymph nodes in 6 of 211 post-treatment CBCT images (2.8%). Causes of MM due to IFD included changes in the bladder (87.9%), rectum (66.7%) and buttock muscles (6%). A time ≥ 9 min between the pre and post-treatment CBCT demonstrated that movement ≥ 3 mm and 5 mm increased from 19.2 to 40.5% and 5 to 8.1% respectively.
IFD during PB irradiation was typically small, but was a major contributor to an 8.4% MM rate when using daily soft tissue match and tight anisotropic margins.
测量前列腺切除术后接受各向异性边缘和每日软组织匹配治疗的患者的分次内位移（IFD）。
每天获取治疗前锥形束计算机断层扫描（CBCT）扫描，并在第 1 周和第 46 名患者的每周进行治疗后 CBCT。通过回顾性计算扫描之间的位移来测量前列腺床（PB）的 IFD。评估了边缘错过（MM）率以及成像之间时间的影响。
共回顾了 46 名患者的 392 份治疗后 CBCT。AP 方向的绝对平均（95%CI）IFD 为 1.5 毫米（1.3-1.7 毫米），SI 为 1.0 毫米（0.9-1.2 毫米），LR 为 0.8 毫米（0.7-0.9 毫米），3D 位移为 2.4 毫米（2.2-2.5 毫米）。IFD≥±3 毫米和≥±5 毫米的比例分别为 24.7%和 5.4%。在 392 份治疗后 CBCT 中有 33 份（8.4%）和 211 份治疗后 CBCT 图像中的 6 份（2.8%）检测到 PB 的 MM。由于 IFD 导致 MM 的原因包括膀胱（87.9%）、直肠（66.7%）和臀部肌肉（6%）的变化。治疗前和治疗后 CBCT 之间的时间≥9 分钟表明，运动≥3 毫米和 5 毫米的比例分别从 19.2%增加到 40.5%和从 5%增加到 8.1%。
在使用每日软组织匹配和严格各向异性边缘时，PB 照射过程中的 IFD 通常很小，但却是 MM 率为 8.4%的主要原因。
