Cao M, Cao N, Cardenes H, Fakiris A, Desrosiers C, Das I
University of California Los Angeles, CA.
Purdue University, West Lafayette, IN.
Med Phys. 2012 Jun;39(6Part8):3691-3692. doi: 10.1118/1.4735009.
To evaluate the patient positioning accuracy and reproducibility of two commercially available immobilization systems for Stereotactic Body Radiotherapy (SBRT) treatment.
Forty one patients with lung (n=21) or liver (n=20) malignancies were assigned to one of the two immobilization devices: Elekta stereotactic body frame (SBF) with built-in stereotactic coordinate system and Civco modular indexing based frame (MIF) without stereotactic reference. All patients underwent the same simulation and planning procedure followed by cone beam CT (CBCT) guided treatment setup. A total of 151 CBCT images were analyzed. The systematic and random isocenter setup errors of the two systems were calculated and compared based on the daily setup corrections under CBCT guidance.
There was not statistically significant difference between the two systems in terms of systematic setup errors in all three translational directions, for both lung and liver patients. The random errors for the lung patients under SBF setup were 1.8mm, 2.0mm and 2.9mm for the vertical, longitudinal and lateral directions, respectively compared to 3.6mm, 4.1mm, and 4.2mm for MIF. A similar trend was also observed for liver patients. The random errors of liver MIF setup reached 3.5mm, 6.1mm and 5.7mm for the vertical, longitudinal and lateral directions, respectively, with relatively smaller errors 1.7mm, 3.4mm and 2.6mm with SBF setup. Repeated CBCTs occurred for MIF system in 42.4% and 40.7% of the lung and liver treatment to verify couch corrections based on the institutional tolerance, resulting in prolonged setup time. Only 25% and 13.6% of the lung and liver treatment with SBF required with repeated CBCT.
Without stereotactic coordinate reference, the body frame system tended to have larger random setup errors and patient positioning accuracy inevitably relies on the volumetric imaging guidance. Patient comfort and reproducibility should be clearly considered for selecting a system.
评估两种市售的立体定向体部放射治疗（SBRT）固定系统的患者摆位准确性和可重复性。
41例患有肺部（n = 21）或肝脏（n = 20）恶性肿瘤的患者被分配到两种固定装置中的一种：带有内置立体定向坐标系的医科达立体定向体架（SBF）和没有立体定向参考的Civco模块化索引框架（MIF）。所有患者均接受相同的模拟和计划程序，随后进行锥形束CT（CBCT）引导的治疗摆位。共分析了151张CBCT图像。根据CBCT引导下的每日摆位校正，计算并比较了两个系统的系统等中心摆位误差和随机等中心摆位误差。
对于肺部和肝脏患者，在所有三个平移方向上，两个系统的系统摆位误差没有统计学上的显著差异。在SBF摆位下，肺部患者在垂直、纵向和横向方向上的随机误差分别为1.8mm、2.0mm和2.9mm，而MIF分别为3.6mm、4.1mm和4.2mm。肝脏患者也观察到类似趋势。肝脏MIF摆位在垂直、纵向和横向方向上的随机误差分别达到3.5mm、6.1mm和5.7mm，而SBF摆位的误差相对较小，分别为1.7mm、3.4mm和2.6mm。MIF系统在42.4%的肺部治疗和40.7%的肝脏治疗中需要重复进行CBCT，以根据机构耐受性验证治疗床校正，导致摆位时间延长。使用SBF进行的肺部和肝脏治疗中，分别只有25%和13.6%需要重复进行CBCT。
在没有立体定向坐标参考的情况下，体架系统往往具有较大的随机摆位误差，患者摆位准确性不可避免地依赖于容积成像引导。选择系统时应充分考虑患者舒适度和可重复性。
