SU-E-T-369: Experience of Using 6D Robotic Couch Top in the Treatment of Intracranial Tumors Utilizing Frameless Stereotactic Radiosurgery (SRS) Technique




To investigate the extent and necessity of 6 DOF corrections for intracranial frameless Stereotactic Radiosurgery


Civco Protura 6D robotic couch top was fitted to the Novalis TX in 2012. The couch enables ± 3 ° rotations in pitch, roll and yaw, ±50 mm in lateral and longitudinal shifts and ±25 mm in vertical shifts. Patient sets up using the room laser; then two orthogonal kV images are taken for confirmation. A CBCT is acquired and registered to the planning CT using two independent systems. The calculated rotational and translational shifts are applied. A second CBCT is acquired to assess the residual translational and rotational errors. The treatment will be carried out if residual rotational shifts are ≤ 0.3 degrees. We treated 113 patients utilizing 6D couch to align a total of 160 targets. Some of the targets were fractionated, with total alignments of 252. Geometrical analysis is performed to assess the system's accuracy and extent of shifts.


After the planar kV images alignment, a CBCT was acquired and registered to the planning CT, the average required rotational shifts were (yaw=1.03 °± 0.8, roll=1.16°± 0.9 and Pitch= 0.9°± 0.7). A second CBCT was taken to verify the match and the previous shifts, the residual rotational errors on average were 0.37°± 0.6, 0.27°± 0.28 and 0.24°± 0.29 in the yaw, roll, and pitch directions, respectively. The translational residual shifts (mm) were 0.68 ± 0.57, 0.68 ± 0.57, 0.68 ± 0.57 in lateral, vertical, and longitudinal directions, respectively.


The 6D couch is capable of aligning targets with an accuracy of ≤ 0.4 ° in any rotational direction and ≤ 0.7 mm in any translational directions, and not applying the rotational corrections could lead to compromised target dose coverage and may lead to excessive dose to OARs.