In vivo feasibility of real-time MR-US fusion imaging lumbar facet joint injections

Abstract

Objectives: Traditionally, facet joint injections (FJI) are performed under fluoroscopic or computed tomography (CT) guidance, mainly due to the deep anatomical location and the presence of bony landmarks. Fusion imaging technology, which couples the ultrasound scan with the corresponding CT or magnetic resonance (MR) image obtained from the diagnostic examination and reformatted in real time according to the ultrasound scanning plane, allows to combine the panoramic view and the elevated anatomical detail of MR or CT with the ease of use of ultrasound without patient exposure to ionizing radiation.

Methods: Thirty eight patients (24 females; mean age ± SD: 64 ± 9 years) received MR fusion-assisted ultrasound-guided FJI of 1 ml of a mixture of local anaesthetic and corticosteroid using a ultrasound machine (Logiq E9, GE Healthcare) equipped with a GPS-enhanced fusion imaging technology which couples real-time B-mode images with those of the previous recent diagnostic MR examination. Low-dose CT needle positioning confirmation was performed in the first 28 patients. Patients' pain was recorded using a visual analogue scale (VAS), at baseline and at 2, 4 and 8 weeks.

Results: All fusion imaging-guided injections were performed successfully. Out of 112, 96 FJI had optimal intra-articular needle positioning (accuracy: 85.7%). Patients VAS significantly decreases after the procedure with no differences among who received CT needle positioning control and who did not receive it. No major complications were observed.

Conclusions: Ultrasound needle guidance with MR fusion assistance allows for safe and effective injection of degenerative facet joint disease.

Keywords: Facet joint; Fusion imaging; Injection; Magnetic resonance; Ultrasound.

Fig. 1

Standard ultrasound probe with bracket fitting the position sensor unity (a). Patient in prone position on the CT bed ready to perform the fusion imaging MR–US infiltration and the post-procedure low-dose CT scan. The low-field magnetic generator is visible in the foreground (b)

Fig. 2

MR–US fusion imaging setting procedure, showing the MR images in axial (a) and sagittal (b) orientation before alignment confirmation. You can appreciate the spinous process both on US and MR image

Fig. 3

L5–S1 level-fused images. Green crosses represent accuracy points set by operator on the MR image and automatically replicated on the US image. Pv paravertebral muscles, Star spinous process, VA vertebral arch, Ps psoas muscles

Fig. 4

Biopsy guide is positioned over the green cross target allowing a precise needle placement

Fig. 5

Post-needle insertion CT scan showed a precise needle tip position relative to intra-articular space

Fig. 6

Chart showing pain reduction using VAS scale with no significant difference between post procedure CT-scan group (blue line) and only MR–US fusion guidance group (red line)

Fig. 7

Learning curve of MR–US fusion-guided FJ injection. In one year procedure, time decreased from 36 to 25 min