Computed Tomography Neurography for Visualization of the In Vivo Nervous System: A Proof of Concept

The human peripheral nervous system embodies anatomical, physiologic, and diagnostic perplexities that remain unexplained. Yet in the course of human history, there are no mechanisms, such as computed tomography (CT) or radiography, by which to image the peripheral nervous system in vivo using a contrast agent that is identified by ionizing radiation, which would aid in surgical navigation, diagnostic radiology, and basic science thereof.

A novel class of contrast was created by linking iodine to lidocaine. The radiodensity of 0.5% experimental contrast molecule was compared with a control of 1% lidocaine by placing 1.5-mL aliquots of each liquid into centrifuge tubes and performing micro-computed tomography (micro-CT) synchronously under identical settings. Physiologic binding to the sciatic nerve was evaluated by injecting 10 mg of the experimental contrast and 10 mg of the control into the contralateral sciatic nerve, and documenting loss of hindlimb function and recovery. In vivo visualization of the sciatic nerve was evaluated by injecting 10 mg of experimental contrast or control into either sciatic nerve and imaging the hindlimbs under identical conditions using micro-CT.

The mean Hounsfield unit of the contrast was 56.09 compared with -0.48 for control (116-fold increase, P = .0001). Hindlimb paresis revealed similar degree of paresis, baseline recovery, and time to recovery. In vivo enhancement between the contralateral sciatic nerves was similar.

Iodinated lidocaine offers a viable mechanism for in vivo peripheral nerve imaging using CT; however, it requires modification to improve in vivo radiodensity.