A Novel Mobile C-Arm Fluoroscopic Imaging of the Foramen Ovale and Its Anatomical Principles

Purpose: Accurate localization of the foramen ovale (FO) is essential for percutaneous balloon compression, radiofrequency thermocoagulation, and glycerol injection in the treatment of trigeminal neuralgia. The mobile C-arm X-ray system is widely used due to its accessibility and low radiation exposure, but achieving optimal positioning to visualize the FO remains challenging. We propose a novel approach using facial surface landmarks to guide rapid and accurate C-arm positioning for FO fluoroscopy. Patients and Methods: Patients were placed in the supine position, and three anatomical reference points were identified: Point A (subnasale), marked with a metal marker, and Points B and C (the intersections of the lateral orbital margins and the superior extensions of the zygomatic arches bilaterally), marked with surgical ink. With the X-ray tube of the C-arm centered above the face, the device was rotated along the transverse axis toward the foot end until Points A, B, and C appeared collinear from the tube's eye view. Fluoroscopy was then used to confirm alignment of Point A with the line connecting the outermost points of the bilateral infraorbital margins. Finally, the tube was tilted 20-25° toward the puncture side along its curved rail to visualize the FO. This method was validated through virtual simulation, intraoperative fluoroscopy, and 3D anatomical modeling. Results: Clear FO images were obtained without additional adjustment in 170 of 200 simulated cases (85.0%) and in 28 of 30 intraoperative cases (93.3%). Simulated imaging showed excellent agreement with the actual osseous FO (Kappa = 0.96, p < 0.001; sensitivity = 0.99; specificity = 1.00), and intraoperative imaging demonstrated perfect agreement with the simulation (Kappa = 1.00, p < 0.001). Conclusion: This technique provides reliable and accurate FO visualization, with excellent agreement between simulated, osseous, and intraoperative imaging. By simplifying the fluoroscopic process, this approach reduces the number of X-ray exposures required, thereby decreasing patient radiation exposure and shortening procedural time.