Spinal Tuberculosis Evaluated by Means of 18F-FDG PET/CT: Pilot Study

ABSTRACT

Spinal tuberculosis is a serious health care problem and diagnosis is often difficult because many diseases may have similar imaging findings. Hence the need to describe findings of spinal tuberculosis with 2-[fluorine 18]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) when compared to CT.

Sixteen consecutive patients who underwent 18F-FDG PET/CT and known to have or subsequently were proven to have spinal tuberculosis were analyzed. All patients included underwent whole-body 18FFDG PET imaging; none of the patients were on tuberculostatics at the time of the PET investigation. We evaluated 18FFDG uptake visually and semiquantitatively using standardized uptake values (SUVmax) and the ratio of lesion to normal liver (S/L ratio), respectively. The presence of spinal and extraspinal lesions was evaluated histopathologically and by the radiologic findings noted on diagnostic CT. Diagnostic Computed Tomographic (CT) findings were reviewed and compared to 18F-FDG PET/CT.

Only 4 patients had one spinal lesion, while 12 (75%) patients had 2 or more lesions. Those patients that had three or more lesions demonstrated intense FDG uptake with a median of 11.34 (3.8-20.9). Ten (62%) of the patients had both spinal and extraspinal lesions. In most of the cases (75%), the lumbar spine was involved as opposed to the thoracic vertebrae. 18F-FDG PET detected all 39/39 (100%) clinically (sites of disease that resulted in symptoms or signs such as pain, swelling, neurological fallout etc.) and histologically (as reported by the laboratory) observed spinal sites. The median of the SUVmax for spinal lesions was 6.06 (ranging from 2.63 to 16.78). Diagnostic CT reported corresponding morphological changes in only 27 (69%) of the spinal sites identified on 18F-FDG PET/CT. 18F-FDG PET/CT detected 60 of 60 (100%) clinically observed extraspinal sites including pulmonary TB, nodal disease and other musculoskeletal sites versus the 43 of 60 (71%) detected by diagnostic CT only. The median of the SUVmax was 3.61 for nodal sites (ranging from 1.71 to 10.79) and 3.38 for pulmonary sites (ranging from 1.23 to 5.93).

The results suggest that 18F-FDG PET/CT is more effective compared to diagnostic CT only in the identification of sites of active disease and contributes to a better evaluation of extraspinal involvement in TB patients. It also appears to be a very promising imaging modality for the identification of the most appropriate biopsy site, staging disease, predicting multi-drug resistance and monitoring response to therapy.

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