Elawadi Abousaleh, Alshanqity Mukhtar, AlHussain Hussain, Mohamed Reham, Orz Yasser, Alqahtani Sultan, Melheim Sayel
King Fahad Medical City, Riyad, Saudi Arabia.
Faculty of Medicine, Mansoura University, Egypt.
Phys Imaging Radiat Oncol. 2022 Jul 2;23:60-65. doi: 10.1016/j.phro.2022.06.014. eCollection 2022 Jul.
Stereotactic Radiosurgery (SRS) is a specialized radiotherapy treatment technique for Arteriovenous Malformations (AVM) in which Computed Tomography (CT) images are used for dose calculations. The purpose of this study was to investigate CT image distortions caused by embolic agents and quantify the influence of these distortions on dose calculations.
Eight AVM patients administered embolic agents prior to SRS were included. Original plans were compared to new recalculated plans using two sets of images. The first set was created by masking the embolic material and artefacts, the second was the diagnostic CT images. In addition, treatment plans were created for an anthropomorphic phantom with water inserts, then with known volumes of embolic materials to study the dosimetric effect of each material.
Relative to patients' original plans, maximum Monitor Unit (MU) difference was -4.4% with whole brain masking, -1.3% with artefact masking, -4.1% with embolic masking, and -4.5% with artefact-free diagnostic images. Calculated dose differences were within ± 3.5% for all plans. In phantom, Gamma pass rate was 96% for both embolic agents with conformal fields and 99.9% with dynamic arcs. Dose and MU differences in phantom plans were negligible.
Relative dose differences between the original plans and the corrected ones were not clinically remarkable. We recommend evaluating the effect of embolic materials on individual patients' plans. The whole brain corrected planning CT images or diagnostic CT images could be utilized to calculate the magnitude of dose reduction caused by embolic materials and correct it if necessary.
立体定向放射外科（SRS）是一种用于治疗动静脉畸形（AVM）的特殊放射治疗技术，其中计算机断层扫描（CT）图像用于剂量计算。本研究的目的是调查栓塞剂引起的CT图像畸变，并量化这些畸变对剂量计算的影响。
纳入8例在SRS治疗前接受栓塞剂治疗的AVM患者。使用两组图像将原始计划与重新计算的新计划进行比较。第一组是通过屏蔽栓塞材料和伪影创建的，第二组是诊断性CT图像。此外，为带有水填充物的人体模型创建治疗计划，然后使用已知体积的栓塞材料来研究每种材料的剂量学效应。
相对于患者的原始计划，全脑屏蔽时最大监测单位（MU）差异为-4.4%，伪影屏蔽时为-1.3%，栓塞屏蔽时为-4.1%，无伪影诊断图像时为-4.5%。所有计划的计算剂量差异在±3.5%以内。在模型中，对于适形野，两种栓塞剂的伽马通过率均为96%，对于动态弧形野为99.9%。模型计划中的剂量和MU差异可忽略不计。
原始计划与校正后计划之间的相对剂量差异在临床上并不显著。我们建议评估栓塞材料对个体患者计划的影响。全脑校正后的计划CT图像或诊断性CT图像可用于计算栓塞材料引起的剂量减少幅度，并在必要时进行校正。
