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Spinal disorders are an increasing cause of disability and a growing therapeutic challenge. CT fluoroscopy is a reliable technology that enables basic spine interventions to be performed with great precision and more difficult procedures to be carried out with safety and confidence. This technique decreases risk and maximizes patient comfort during such procedures.
Spinal disorders are an increasing cause of disability and a growing therapeutic challenge. CT fluoroscopy is a reliable technology that enables basic spine interventions to be performed with great precision and more difficult procedures to be carried out with safety and confidence. This technique decreases risk and maximizes patient comfort during such procedures.1,2
Multislice CT fluoroscopy allows the guidance and placement of needles to be monitored in 3D (Figure 1). Acquisition of three contiguous CT slices of varying thickness (1 to 16 mm) permits a volumetric approach with precise management of the patient's z-axis. A high frame rate (up to eight images per second) and short delay (0.33 sec) between needle movement and reproduction of the movement provides real-time imaging with image stability. Anatomy can be discerned with millimeter precision for needle placement.1
Procedures can be performed quickly, and x-ray exposure to patients is low. Additional benefits include precise needle positioning and a low rate of complications or technical failure. CT fluoroscopy can help patients avoid surgery for conditions such as thoracic and lumbar neurolysis, percutaneous laser disc decompression, and synovial cyst decompression.2-7 The need for general anesthesia and/or sedation is reduced as well.
Practitioners who are interested in this technique should undergo proper training. Hands-on workshops and web-based online training are necessary, practical approaches to complete academic teaching.
The scattered dose to the radiologist performing CT fluoroscopy-guided procedures is reduced significantly when all radiation protection devices and 80 kV protocols are combined. A lead apron and thyroid collar should be worn. Lead gloves can reduce the scattered dose to the fingers by 30% and to the wrist by 50%. Use of a facial screen enables a scattered dose reduction (SDR) of 94% for the upper chest and head. Placing a lead cover on the patient offers an SDR of 97% for the lower part of the body.
Interventions are of two types: basic and advanced. The former are relatively easy to perform; the latter need experience and proper training.
Several basic procedures should present little difficulty to the experienced interventional radiologist:
The procedure begins with an axial scan, with the patient lying prone, from C0 to C3 for targeting and vertebral artery delineation. Posterior puncture is made with a 25-gauge spinal needle. CT fluoroscopy guidance permits fast, correct needle tip placement at the level of the C2 bony facet (trigger zone) followed by steroid injection. If needle contact with the bony facet does not trigger neuralgia, pain may be due to atlas-axis spondylosis (pseudo-Arnold's neuralgia). The main danger with this procedure is vertebral artery puncture.3,4
A perforated dura will cause injected air to wash out. The needle must be pulled back slightly in this case, and the presence of cerebrospinal fluid assessed using aspiration. If dural perforation induces headache, a blood patch can be considered. Punctures to the nerve root, epidural vein, and facet joint can occur on rare occasions.
Injection of contrast or sterile air will cause the facet joint and synovial cysts to opacify. The pressure should be increased with saline to rupture the cyst. The procedure should be stopped if the patient is suffering unbearable pain and direct cystic puncture performed instead. This involves the same technique as that used for lumbar epidural infiltration, with saline cystic rinsing followed by increased pressure to rupture the cyst wall. A steroid injection completes the procedure. 3,10
More difficult interventions also benefit from new technology and techniques:
Local anesthesia from the skin to the pedicle can be used if the patient is anxious. CT fluoroscopy then guides direct puncture (22-gauge needle) from the skin to the pleurovertebral angle. The extrapleural space is widened with saline and the needle tip positioned at the anterior third of the paravertebral space. The tip's extravascular position can be confirmed using 2 to 4 mL contrast.3,4,11,12
Neurolysis of the thoracic ganglion is performed with rapid injection ( < 10 sec) of 8 mL of 8% phenol in glycerine (Figure 3A). The patient should then be moved quickly to a sitting position to avoid diffusion of phenol to the stellate ganglion. This sitting position should be maintained for two hours with the patient awake.
The main danger associated with this procedure is intravenous injection of the phenol in glycerine solution, which may be fatal. Diffusion of phenol to the stellate ganglion can cause Horner syndrome.
Contrast-enhanced abdominal CT is performed with the patient lying prone to delineate the ureters and determine the target slices. Single-sided puncture with CT fluoroscopy guidance is carried out at the L2 and L4 levels, from skin to target, with 22-gauge needles. Injection of 1 mL contrast will prove the extravascular positioning of the needle tip and evaluate diffusion. Lumbar plexus neurolysis is carried out by injecting 10 mL of an 8% phenol in glycerine solution at each level. Needles should be rinsed with 1 mL lignocaine before withdrawal (Figure 3B).
Ureteral puncture is a risk associated with this intervention. The procedure should be stopped if diffusion toward the posterior third of the vertebral body is observed. Potential complications include pain when injecting phenol and orthostatic hypotension.3,4,11,13
Direct disc puncture (18-gauge needle), via a posterolateral approach, is guided by CT fluoroscopy. The needle tip should be centered at the level of the nucleus in all planes. Disc decompression can then be induced using a laser fiber or RF probe, as required (Figure 4). Patients should then rest for four hours. Discitis (infectious or thermal) is the main risk associated with this procedure.11,14,15
The approach will depend on the vertebral level. A transpedicular approach is most commonly required, though sometimes a posterolateral approach may be taken at the lumbar level or an intercostovertebal approach at the thoracic level. Local anesthesia is administered from the periosteum to the skin. CT fluoroscopy-guided vertebral puncture is performed using an 11- or 13-gauge needle. A hammer may be necessary for crossing the cortex.
The needle tip is placed centrally at the anterior third of the vertebral body. Cement (3 to 5 mL) can then be prepared and injected slowly (Figure 5). CT fluoroscopy will help evaluate filling and diffusion. Patients should be confined to bed for four hours after the procedure.
The procedure should be halted if a leak occurs. Practitioners taking a posterolateral approach should avoid the nerve root. Epidural or venous leaks are other possible complications.4,6,11,16,17
Triple-slice CT fluoroscopy, with its real-time volumetric approach, makes it possible to perform nonvascular interventions with the highest precision, safety, speed, and confidence. Spine interventions represent a significant number of patients in practice. Real-time CT fluoroscopy with multiplanar reconstruction, combined with navigation and/or robotics, will allow new minimally invasive treatments to be developed further.
Proper training will help strengthen professionalism in this emerging subspeciality.
DR. BRAT is head of radiology at the Centre Hospitalier Hornu-Frameries in Hornu, Belgium.
Additional procedures are described at www.ctfluoroscopy.org.