Potential for reduction of radiation dose in the assessment of the lead orientation in directional deep brain stimulation electrodes.

Purpose: Directional deep brain stimulation (dDBS) relies on electrodes steering the stimulation field in a specific direction. Post implantation, however, the intended and real orientation of the lead frequently deviates e.g. due to torque of the electrode. The orientation is assessed by postoperative imaging such as C-arm cone-beam CT (CBCT) using 3D rotational fluoroscopy and multi-slice CT (MSCT). The objective is to determine the effect of different X-ray systems such as CBCT and MSCT, and scan acquisition parameters on effective radiation doses.

Material And Methods: We retrospectively investigated the dose area product (DAP) and dose length product (DLP) of patients who underwent both CBCT and MSCT after dDBS surgery. These metrics were then converted into the effective dose by established conversion coefficients. For CBCT, the feasible dose optimization by collimation was virtually assessed. Univariate analysis was performed to determine differences.

Results: Among 88 patients median effective dose was 0.20 ± 0.07 mSv in CBCT and 2.11 ± 0.33 mSv in MSCT (p < 0.001). The field of view (FOV) in CBCT can be collimated in craniocaudal orientation by 33.6 % and mediolaterally by 60.8 %. This optimized collimation implies an effective dose reduction of 76 % (p < 0.001). Comparison of the effective dose of MSCT vs. CBCT revealed a significant dose reduction by 90.3 % (p < 0.001), whereas optimal collimation by 97.7 % (p < 0.001).

Conclusions: For assessment of dDBS orientation, CBCT had significantly lower radiation doses compared to MSCT. Optimized collimation in CBCT allows for a further substantial dose reduction. Moreover, the proposed approach is applicable on other neuroimaging procedures such as 3D visualization of treated intracranial aneurysm.