Department of Radiation Oncology, University of Virginia Health System, Charlottesville, Virginia.
Department of Radiation Oncology, University of Virginia Health System, Charlottesville, Virginia.
Int J Radiat Oncol Biol Phys. 2018 Nov 15;102(4):895-902. doi: 10.1016/j.ijrobp.2018.05.042. Epub 2018 May 24.
To determine the magnitude and reason for discrepancies between frame- and cone beam computed tomography (CBCT)-determined stereotactic coordinates, we reviewed frame-based Gamma Knife radiosurgery procedures in which CBCT was performed before treatment.
Clinical and treatment documentation was reviewed for 150 frame placements for which stereotactic coordinates were defined via both frame and fiducials on computed tomography imaging and CBCT. Treatment planning system-reported rotational and translational differences and standard deviations (SDs) between frame-based and CBCT-based stereotactic coordinates were recorded. Potential clinical predictors for increased differences were collected. Multiple linear regressions were performed to evaluate for associations with increased translations and rotations.
The absolute mean of the measured pitch, yaw, and roll shifts was 0.14 degrees (range -0.71-0.63 degrees, SD 0.19 degrees), 0.16 degrees (range -0.50 to 0.83 degrees, SD 0.21 degrees), and 0.12 degrees (range 0.37-0.51 degrees, SD 0.15 degrees), respectively. The absolute mean of the measured shifts in the left-right, anteroposterior, and superior-inferior direction was 0.29 mm (range -1.29 to 0.82 mm, SD 0.35 mm), 0.24 mm (range -0.59 to 0.33 mm, SD 0.19 mm), and 0.24 mm (range -0.69 to 0.91 mm, SD 0.27 mm), respectively. Three cases (2.0%) exceeded 1 mm in translational difference, all in the left-right direction (1.05, 1.13, and 1.29 mm). Lower Karnofsky Performance Scale status was associated with greater translational differences (vector magnitude, P = .023) and rotation (pitch, P = .044; yaw, P = .002). Usage of longer total pin length (sum of all 4 fixation pin lengths) was associated with increased rotation but not with translation (P < .001 and P = .56, respectively).
CBCT imaging in this cohort of frame-based cases suggests that the discrepancy in stereotactic coordinates is less than 1 mm or degree in most cases. Low Karnofsky Performance Scale status and longer total pin length correlate with larger differences between frame-defined and CBCT-defined stereotactic coordinates.
为了确定框架和锥形束 CT（CBCT）确定的立体定向坐标之间的差异的大小和原因，我们回顾了在治疗前进行 CBCT 的基于框架的伽玛刀放射外科手术。
对 150 个基于框架的伽玛刀放射外科手术进行了临床和治疗记录，这些手术的立体定向坐标是通过框架和 CT 成像上的基准点定义的。记录了治疗计划系统报告的基于框架和基于 CBCT 的立体定向坐标之间的旋转和平移差异以及标准差（SD）。收集了潜在的临床预测因素，以评估增加差异的可能性。进行了多元线性回归分析，以评估与平移和旋转增加的关联。
测量的俯仰、偏航和滚转偏移的绝对平均值分别为 0.14 度（范围为-0.71 度至 0.63 度，SD 为 0.19 度）、0.16 度（范围为-0.50 度至 0.83 度，SD 为 0.21 度）和 0.12 度（范围为 0.37 度至 0.51 度，SD 为 0.15 度）。左右、前后和上下方向的测量偏移的绝对平均值分别为 0.29 毫米（范围为-1.29 毫米至 0.82 毫米，SD 为 0.35 毫米）、0.24 毫米（范围为-0.59 毫米至 0.33 毫米，SD 为 0.19 毫米）和 0.24 毫米（范围为-0.69 毫米至 0.91 毫米，SD 为 0.27 毫米）。有 3 例（2.0%）的平移差异超过 1 毫米，均在左右方向（1.05、1.13 和 1.29 毫米）。较低的 Karnofsky 表现量表状态与更大的平移差异（向量幅度，P=0.023）和旋转（俯仰，P=0.044；偏航，P=0.002）相关。总固定针长度（所有 4 个固定针长度之和）较长与旋转增加有关，但与平移无关（P<0.001 和 P=0.56）。
在这个基于框架的病例队列中，CBCT 成像表明，在大多数情况下，立体定向坐标的差异小于 1 毫米或 1 度。较低的 Karnofsky 表现量表状态和较长的总固定针长度与框架定义和 CBCT 定义的立体定向坐标之间的较大差异相关。
