Postoperative Determination of Directional Deep Brain Stimulation (DBS) Lead Orientation Using Rotational Fluoroscopy: Interobserver Agreement and Comparison with CT-Based Software

Introduction: Commercial software platforms, such as Brainlab Elements™ utilize postoperative Computed Tomography (CT) to estimate deep brain stimulation (DBS) lead orientation. The iron-sight method on rotational fluoroscopy offers a potentially accurate and accessible alternative, but its interobserver agreement and validity in clinical settings remain unverified. Objective: To evaluate inter-observer agreement in estimating lead orientation using the iron-sight method on postoperative rotational fluoroscopy and to compare these estimates with Brainlab Elements™ from postoperative CT. Methods: This prospective study included 70 leads in patients who underwent DBS implantation with directional leads at a tertiary care center between 2022 and 2024. The inter-rater agreement of independent measurements obtained by two observers utilizing the iron-sight method was evaluated. Subsequently, these measurements were compared with those derived from the Brainlab Element™ software. Results: Bland–Altman analysis of measurements between observers revealed a mean bias of 0.68° (95% CI: –0.0678° to 1.4335°), with limits of agreement from –5.49° (CI: –6.79° to –4.19°) to 6.85° (CI: 5.55° to 8.15°). The Preiss–Fisher test confirmed that the agreement was statistically significant and unlikely to be due to chance. (Z = –15.78, P < 0.001). In the method comparison (n = 67), the mean bias was –0.69° (95% CI: –2.48° to 1.10°), with limits of agreement ranging from –14.86° (95% CI: –17.97° to –11.76°) to 13.48° (95% CI: 10.37° to 16.58°). The Watson–Williams test showed no significant difference in circular means (p = 0.7905). Exploratory regression suggested that coronal and polar lead angles modestly influenced interobserver variability, whereas trajectory angles did not affect method agreement. Conclusion: The iron-sight method is a reliable and reproducible tool for estimating directional lead orientation, with excellent interobserver agreement and good concordance with Elements™ estimates.