In vivo contrast-enhanced microCT for the monitoring of mouse thoracic, lumbar, and coccygeal intervertebral discs

Mouse models are often used for studies of intervertebral disc (IVD) homeostasis and degeneration, yet the relatively small size of the IVD poses challenges for noninvasive, longitudinal imaging modalities. The recently developed contrast-enhanced microCT (CE mu CT) using Ioversol has been successful in detecting degenerative changes in the murine IVD ex vivo at the micrometer scale. Further leveraging the superior biocompatibility of Ioversol as a contrast agent, we demonstrate the in vivo use of this CE mu CT technique to examine IVDs at multiple spinal sites. Ioversol was administered via tail vein injection (TVI) in growing and adult male FVB/NJ mice (n=5 /group). The animals were anesthetized and underwent in vivo micro-computed tomographic (microCT) at the coccygeal (CC5/CC6), lumbar (L5/6), and thoracic (T12/T13) IVDs. TVI of Ioversol was well-tolerated by all animals. As Ioversol filtered through the kidneys and accumulated in the bladder, the attenuations of the mouse bladder and kidneys increased due to the high molecular weight of Ioversol, confirming that the Ioversol is biological available. Average IVD attenuations increased 3%-15% following TVI (ANOVA; P<.01). The presence of Ioversol in the IVD combined with high-resolution microCT allow for nondestructive visualization of structural features of the IVD. These results demonstrate CECT with Ioversol as a viable strategy for the in vivo monitoring of multiple mouse IVDs during degeneration, disease, and injury.