Accuracy evaluation of real-time body surface imaging guided system in spinal stereotactic radiosurgery: a phantom study

Accuracy of position setup and monitoring is a key element in the success of spinal stereotactic radiosurgery. We investigated the reposition and target accuracies of a proposed complementary surface imaging guided (SIG) application to infrared (IR) fiducial marker system for patient setup in the spinal radiosurgery. Among the iterative closest point (ICP) and normal distribution transformation (NDT) algorithm, the appropriate method for SIG system was selected by measuring the reposition accuracy. To evaluate the performance of SIG and marker systems, the reposition and target accuracies was measured by dividing into three groups; Group 1 (infrared (IR)-fiducial marker system alone), Group 2 (SIG alone), and Group 3 (combination of Group1 and 2). Overall, six degrees of freedom (DOF) and the root-mean-square (RMS) values were calculated to evaluate the performance of reposition and target accuracies. The RMS value of ICP and NDT was 3.18 ± 1.80 mm and 0.88 ± 0.71 mm, respectively. The real-time reposition accuracy using NDT algorithm were 0.29 ± 0.50 mm in Group 1, 0.79 ± 0.62 mm in Group 2 and 0.13 ± 0.05 mm in Group 3. Target accuracy of Group 3 (RMS of 0.90 ± 0.62 mm) was superior to that of Group 1and 2 (1.23 ± 0.81 mm and 1.93 ± 1.26 mm, respectively). The positioning and target accuracy were statistically significantly improved by implementing real-time SIG system complementary to conventional IR—fiducial marker-guided system in stereotactic body radiosurgery.