Electromagnetic tracking for CT-guided spine interventions: phantom, ex-vivo and in-vivo results

Abstract

An electromagnetic-based tracking and navigation system was evaluated for interventional radiology. The electromagnetic tracking system (CAPPA IRAD EMT, CASinnovations, Erlangen, Germany) was used for real-time monitoring of punctures of the lumbar facet joints and intervertebral disks in a spine phantom, three pig cadavers and three anaesthesized pigs. Therefore, pre-interventional computed tomography (CT) datasets were transferred to the navigation system and puncture trajectories were planned. A coaxial needle was advanced along the trajectories while the position of the needle tip was monitored in real time. After puncture tracts were marked with pieces of wire another CT examination was performed and distances between wires and anatomical targets were measured. Performing punctures of the facet joints mean needle positioning errors were 0.4 +/- 0.8 mm in the spine phantom, 2.8 +/- 2.1 mm ex vivo and 3.0 +/- 2.0 mm in vivo with mean length of the puncture tract of 54.0 +/- 10.4 mm (phantom), 51.6 +/- 12.6 mm (ex vivo) and 50.9 +/- 17.6 mm (in vivo). At first attempt, intervertebral discs were successfully punctured in 15/15 in the phantom study, in 12/15 in the ex-vivo study and 14/15 in the in-vivo study, respectively. Immobilization of the patient and optimal positioning of the field generator are essential to achieve a high accuracy of needle placement in a clinical CT setting.

Robot arm based flat panel CT-guided electromagnetic tracked spine interventions: phantom and animal model experiments

“…Electromagnetic tracking provides an elegant and accurate way to control the position of an instrument's tip based on imaging data [4,8,9]. However, while CT based imaging provides the large data volumes with high spatial and temporal resolution [4], C-arm based CT approaches seem advantageous for EMT based interventions as a metal free environment during interventions rules out any magnetic field disturbances caused by e.g.…”

“…Working either by triangulating infrared markers attached to the needle's end (optical tracking) or measuring the induced current in small sensor coils integrated in the instrument's tip when placed in an electromagnetic field (electromagnetic tracking, EMT) no additional radiation is needed during the tracking procedure, reducing radiation exposure to the interventionalist and the patient [4,5]. Optical tracking provides robust tracking with the drawback of only indirectly tracking the instrument's tip by calculating it from the rear mounted markers.…”

Image Guidance for Spinal Facet Injections Using Tracked Ultrasound

“…Tracking technology is relatively inexpensive compared to 3D US systems or fluoroscopy, making it a viable option for any clinical setting. Bruners et al have demonstrated a system that combines interventional CT with tracked needles to facilitate lumbar facet needle guidance [4], while Galiano et al have shown that ultrasound (US) can be used instead of fluoroscopy or CT for lumbar facet joint injections [5]. US technology is both ubiquitous and considerably less expensive than fluoroscopy or CT, and eliminates radiation dose to both patient and clinician.…”

Musculoskeletal imaging: current and future trends

“…Spinal phantom-and animalstudies using navigation systems for facet joint injections and intervertebral disc punctures have been promising [19]. However, further clinical studies are required to assess the benefit of these novel techniques in clinical practice.…”