The application of single photon emission computed tomography to the diagnosis of ankylosing spondylitis of the spine.

Single Photon Emission Computed Tomography (SPECT) has been used to examine the spine in a prospective long-term study with the aim of assessing the value of bone scintigraphy in the detection and diagnosis of ankylosing spondylitis (AS). Sites of increased uptake of 99Tcm-MDP were observed in three of the eleven patients examined so far. By carefully optimising the SPECT system (rotating gamma camera), as well as the examination procedure, with respect to high spatial resolution, it was possible to relate these sites precisely to anatomical sites in sectional images of the spine. The advantages of SPECT are demonstrated in all three cases in which the areas of increased uptake in sagittal and transverse sections can be related to specific anatomical sites of the spine characteristically affected by AS. The findings in each of these cases are quite distinct from those of a normal case and correlate with the radiographic appearances. It is concluded that SPECT will make it easier to observe, localise and evaluate regions of increased uptake in patients with AS compared with conventional scintigraphy.