Use of Scintigraphy for the Diagnosis of Apical Infection of Equine Cheek Teeth

Scintigraphy with 99mTechnetium Methyldiphosphate (99mTc-MDP) can detect changes in bone which precede radiographic changes, and this makes it a very useful imaging modality for the diagnosis of early periapical infection of the equine cheek teeth, where the results of radiography may be equivocal. It is a particularly useful technique for the differentiation of dental sinusitis from other causes of sinusitis. Bone phase images acquired 2 to 4 hours postinjection give the most useful information for the evaluation of dental and sino-nasal lesions. Images should be acquired in sedated horses using dynamic studies which are then motion corrected. Left and right lateral, dorsal, and ventral views are usually sufficient to image the equine skull fully; however, oblique views may occasionally be useful for lesion localization. Periapical infections of the cheek teeth typically result in focal and intense increased radionuclide uptake (IRU) located over the apical region of the affected tooth. In contrast, most cases of primary sinusitis show more diffuse and less marked IRU over the affected region(s). However, some cases of primary sinusitis do exhibit focal areas of moderate to marked IRU, and care should be taken to try and differentiate these from periapical infections by three-dimensional lesion localization.