Morton Daniel, Hilts Michelle, Batchelar Deidre, Crook Juanita
Department of Medical Physics, BC Cancer Agency, Centre for the Southern Interior, Kelowna, British Columbia, Canada; Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, Canada.
Department of Medical Physics, BC Cancer Agency, Centre for the Southern Interior, Kelowna, British Columbia, Canada; Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, Canada.
Int J Radiat Oncol Biol Phys. 2016 Jul 1;95(3):1050-1057. doi: 10.1016/j.ijrobp.2016.01.049. Epub 2016 Feb 2.
To evaluate seed placement accuracy in permanent breast seed implant brachytherapy (PBSI), to identify any systematic errors and evaluate their effect on dosimetry.
Treatment plans and postimplant computed tomography scans for 20 PBSI patients were spatially registered and used to evaluate differences between planned and implanted seed positions, termed seed displacements. For each patient, the mean total and directional seed displacements were determined in both standard room coordinates and in needle coordinates relative to needle insertion angle. Seeds were labeled according to their proximity to the anatomy within the breast, to evaluate the influence of anatomic regions on seed placement. Dosimetry within an evaluative target volume (seroma + 5 mm), skin, breast, and ribs was evaluated to determine the impact of seed placement on the treatment.
The overall mean (±SD) difference between implanted and planned positions was 9 ± 5 mm for the aggregate seed population. No significant systematic directional displacements were observed for this whole population. However, for individual patients, systematic displacements were observed, implying that intrapatient offsets occur during the procedure. Mean displacements for seeds in the different anatomic areas were not found to be significantly different from the mean for the entire seed population. However, small directional trends were observed within the anatomy, potentially indicating some bias in the delivery. Despite observed differences between the planned and implanted seed positions, the median (range) V90 for the 20 patients was 97% (66%-100%), and acceptable dosimetry was achieved for critical structures.
No significant trends or systematic errors were observed in the placement of seeds in PBSI, including seeds implanted directly into the seroma. Recorded seed displacements may be related to intrapatient setup adjustments. Despite observed seed displacements, acceptable postimplant dosimetry was achieved.
评估永久性乳腺籽源植入近距离放射治疗（PBSI）中籽源放置的准确性，识别任何系统误差并评估其对剂量学的影响。
对20例PBSI患者的治疗计划和植入后计算机断层扫描进行空间配准，用于评估计划和植入的籽源位置之间的差异，即籽源位移。对于每位患者，在标准房间坐标系和相对于针插入角度的针坐标系中确定平均总籽源位移和方向籽源位移。根据籽源与乳腺内解剖结构的接近程度对其进行标记，以评估解剖区域对籽源放置的影响。评估评估靶体积（血清肿 + 5毫米）、皮肤（此处原文skin后似遗漏了相关内容，推测可能是如skin dose等）、乳腺和肋骨内的剂量学，以确定籽源放置对治疗的影响。
对于所有籽源总体，植入位置与计划位置之间的总体平均（±标准差）差异为9 ± 5毫米。在整个群体中未观察到明显的系统方向位移。然而，对于个体患者，观察到系统位移，这意味着在手术过程中患者体内存在偏移。不同解剖区域中籽源的平均位移与所有籽源总体的平均值无显著差异。然而，在解剖结构内观察到小的方向趋势，这可能表明在植入过程中存在一些偏差。尽管观察到计划和植入的籽源位置之间存在差异，但20例患者的中位（范围）V90为97%（66% - 100%），关键结构的剂量学达到了可接受水平。
在PBSI中，包括直接植入血清肿的籽源，在放置过程中未观察到明显趋势或系统误差。记录的籽源位移可能与患者体内的设置调整有关。尽管观察到籽源位移，但植入后的剂量学仍达到了可接受水平。
