Wiant David, Manning Matthew, Koch Kyle, Maurer Jacqueline, Hayes Lane, Liu Han, Shang Qingyang, Sintay Benjamin
Department of Radiation Oncology, Cone Health Cancer Center, Greensboro, NC, USA.
J Appl Clin Med Phys. 2017 Sep;18(5):251-258. doi: 10.1002/acm2.12152. Epub 2017 Aug 3.
To determine if the treatment planning computed tomography scan (CT) from an initial intracranial stereotactic radiosurgery (SRS) treatment can be used for repeat courses of SRS.
Twenty-five patients with 40 brain metastases that received multiple courses of SRS were retrospectively studied. Magnetic resonance scans from repeat SRS (rMR) courses were registered to CT scans from the initial SRS (iCT) and repeat SRS (rCT). The CT scans were then registered to find the displacement of the rMR between iCT and rCT registrations. The distance from each target to proximal skull surface was measured in 16 directions on each CT scan after registration. The mutual information (MI) coefficients from the registration process were used to evaluate image set similarity. Targets and plans from the rCTs were transferred to the iCTs, and doses were recalculated on the iCT for repeat plans. The two dose distributions were compared through 3D gamma analysis.
The magnitude of the mean linear translations from the MR registrations was 0.6 ± 0.3 mm. The mean differences in distance from target to skull on a per target basis were 0.3 ± 0.2 mm. The MI was 0.582 ± 0.042. Registration between a comparison group of 30 CT scans that had the same data resampled and 30 scans that were intercompared with different patients gave MI = 0.721 ± 0.055 and MI = 0.359 ± 0.031, respectively. The mean gamma passing rates were 0.997 ± 0.007 for 1 mm/1% criteria.
The rMR can be aligned to the iCT to accurately define targets. The skull shows minimal change between scans so the iCT can be used for set-up at repeat treatments. The dosimetry provided by the iCT dose calculation is adequate for repeat SRS. Treatment based on iCT is feasible.
确定初始颅内立体定向放射外科治疗（SRS）的治疗计划计算机断层扫描（CT）是否可用于SRS的重复疗程。
回顾性研究了25例患有40个脑转移瘤并接受多疗程SRS治疗的患者。将重复SRS（rMR）疗程的磁共振扫描与初始SRS（iCT）和重复SRS（rCT）的CT扫描进行配准。然后对CT扫描进行配准，以找到iCT和rCT配准之间rMR的位移。配准后，在每次CT扫描上的16个方向测量每个靶区到近端颅骨表面的距离。配准过程中的互信息（MI）系数用于评估图像集的相似性。将rCT的靶区和计划转移到iCT上，并在iCT上重新计算重复计划的剂量。通过三维伽马分析比较两种剂量分布。
MR配准的平均线性平移量为0.6±0.3mm。每个靶区到颅骨距离的平均差异为0.3±0.2mm。MI为0.582±0.042。对30例重新采样相同数据的CT扫描和30例与不同患者相互比较的扫描进行比较，其MI分别为0.721±0.055和0.359±0.031。对于1mm/1%标准，平均伽马通过率为0.997±0.007。
rMR可与iCT对齐以准确界定靶区。扫描之间颅骨变化极小，因此iCT可用于重复治疗时的摆位。iCT剂量计算提供的剂量学对于重复SRS是足够的。基于iCT的治疗是可行的。
