High-resolution magnetic resonance imaging of rat masticatory system

Abstract

Objectives: In orofacial research, there is an increasing demand for high-resolution magnetic resonance imaging (HR-MRI) to study and perform follow-up experiments on animal models. Tracking cells (stem cells, lymphocytes and macrophages), labeled with paramagnetic beads, injected in animal models is one of the examples in which HR-MRI can be used. The present study was set up to describe normal dentomaxillofacial structures using HR-MRI. Methods: Post mortem magnetic resonance imaging (MRI) was performed on the dentomaxillofacial area and on the temporomandibular joint (TMJ) of healthy 8 week old Lewis Rats. Image acquisitions were done on a 9.4T vertical bore magnet (Varian 400 spectrometer) in three orthogonal planes. HR-MRI images were obtained using a proton density weighted spin echo sequence [TR=2500ms/TE=18ms (TR=repetition time/TE=echo time)]. All orthogonal directions were acquired as contiguous 1-mm-thick slices with an in-plane resolution of 30 ́30 microns and a 2.5 ́2.5 or 3.5 ́2.5 cm field of view. Results: Based on natural contrast differences, it is possible to identify very precisely anatomical structures in the dentomaxillofacial area. TMJ was clearly demonstrated on HR-MRI images with fine delineation. The HR-MRI scanning revealed a detailed view of teeth and bony structures. Soft tissues, like tooth pulps, oro-facial muscles and neuro-vascular bundles, were also clearly visualized. Conclusions: These findings suggest that HR-MRI may be an interesting imaging technique to examine minute changes in orofacial structures in small animal (rat) research.