Real-time ultrasound-computed tomography image fusion for transforaminal lumbar approach: a lumbosacral spine phantoms study.

PURPOSE: Ultrasound (US) is increasingly used for transforaminal approaches. We evaluated whether fusing computed tomography (CT) images with dynamic US could be based on bony and surface landmarks in two phantom models.
METHODS: Recordings were performed in a gelatin-based sonographic phantom and in a computerized imaging reference system training phantom. Three anesthesiologists performed 10 US and CT image fusions via three different techniques: (1) using locations of the fifth lumbar vertebra (L5) spinous process and the two posterior superior iliac spines in both images, (2) using the two lateral edges of the laminae rather than posterior superior iliac spines, and (3) using skin landmarks. Techniques were compared using values of precision (High quality of fusion: VP inferior to 10). Three punctures targeting the L4-L5 right foramina were made, and needle positions were checked using X-ray.
RESULTS: Sixty fusions were performed in the gelatin phantom and 90 in the training phantom. VPs values of the 150 fusions were inferior to 5. Technique 2 was superior to one [operator 1: VP: 1.12 ± 0.54 vs. 2.38 ± 1.49; operator 2: 0.6 ± 0.39 vs. 3.66 ± 1.22; operator 3: 0.89 ± 0.31 vs. 1.23 ± 0.63 (p < 0.001)] with the gelatin phantom. There were no differences with the second phantom. X-ray examinations confirmed L4-L5 needle positioning.
CONCLUSION: Bony and surface landmarks allowed for accurate fusion of CT and US images of the lumbar spine. These techniques, performed on phantoms, allowed for precise localization and puncturing of lumbar neural foramina.