Department of Radiation Oncology, Mayo Clinic, 4500 San Pablo Road South, Jacksonville, FL, 32224, USA.
Alaska Cancer Treatment Center, Anchorage, AK, USA.
J Neurooncol. 2020 Jun;148(2):273-279. doi: 10.1007/s11060-020-03463-2. Epub 2020 May 30.
To investigate the frequency, magnitude and possible causes of frame-shifts that may occur between treatment planning and treatment delivery when performing Gamma Knife radiosurgery with rigid frame-based immobilization.
Differences between computed tomography (CT) framed fiducial stereotactic coordinate reference and cone beam computed tomography stereotactic coordinates after image registration were recorded for 49 frame-based GK radiosurgery cases performed using the Gamma Knife Icon. Parameters recorded include rotational shifts, translational shifts, and the GK-computed Maximum Shot Displacement (MSD) between the two stereotactic coordinate spaces. Other patient-specific parameters were collected and linear regression analysis was performed to evaluate predictors of increased displacement.
The median values of rotational shifts were: pitch 0.14°, yaw 0.17°, and roll 0.13°. The median absolute values of translational shifts were: left-right 0.39 mm, anteroposterior 0.14 mm, and superior-inferior 0. 22 mm. The median value of MSD was 0.71 mm. Twelve cases (24.5%) had a MSD of greater than 1.0 mm. Male gender was associated with increased MSD (p = 0.013) and translational shifts (root-mean-squared value, p = 0.017). Cases with large differences between right and left sided pin lengths were also associated with increased MSD (p = 0.011).
The use of CBCT image guidance in frame-based GK radiosurgery allows unintended frame shifts to be identified and corrected. A significant fraction (24.5%) of patients had large enough shifts to result in a MSD of greater than 1.0 mm. Male gender and eccentrically placed frames were associated with increased MSD, and particular care should be taken in these cases.
研究在使用刚性框架固定进行伽玛刀放射外科手术时，从治疗计划到治疗实施过程中可能发生的移码频率、幅度和可能原因。
记录了 49 例使用伽玛刀 Icon 进行的基于框架的 GK 放射外科手术中，计算断层摄影术（CT）框架基准点立体定向坐标参考与图像配准后的锥形束 CT 立体定向坐标之间的差异。记录的参数包括旋转偏移、平移偏移以及两个立体定向坐标空间之间的伽玛刀计算的最大射束位移（MSD）。收集其他患者特定参数，并进行线性回归分析以评估增加位移的预测因子。
旋转偏移的中位数分别为：俯仰角 0.14°，偏航角 0.17°，和滚转角 0.13°。平移偏移的绝对值中位数分别为：左右 0.39 毫米，前后 0.14 毫米，和上下 0.22 毫米。MSD 的中位数为 0.71 毫米。12 例（24.5%）的 MSD 大于 1.0 毫米。男性与较大的 MSD（p=0.013）和较大的平移偏移（均方根值，p=0.017）相关。左右两侧销钉长度差异较大的病例也与较大的 MSD 相关（p=0.011）。
在基于框架的 GK 放射外科手术中使用 CBCT 图像引导，可以发现和纠正意外的框架偏移。相当一部分（24.5%）患者的偏移量足够大，导致 MSD 大于 1.0 毫米。男性和偏心放置的框架与较大的 MSD 相关，因此在这些情况下应特别注意。
