The aim of this study was to evaluate the clinical use of fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) in acute and chronic osteomyelitis and inflammatory spondylitis. The study population comprised 21 patients suspected of having acute or chronic osteomyelitis or inflammatory spondylitis. Fifteen of these patients subsequently underwent surgery. FDG-PET results were correlated with histopathological findings. The remaining six patients, who underwent conservative therapy, were excluded from any further evaluation due to the lack of histopathological data. The histopathological findings revealed osteomyelitis or inflammatory spondylitis in all 15 patients: seven patients had acute osteomyelitis and eight patients had chronic osteomyelitis or inflammatory spondylitis. FDG-PET yielded 15 true-positive results. The tracer uptake correlated with the histopathological findings in each case. Bone scintigraphy performed in 11 patients yielded ten true-positive results and one false-negative result. Follow-up carried out on two patients revealed normal or clearly reduced tracer uptake, which correlated with a normalisation of clinical data. In early postoperative follow-up it was impossible to differentiate between postsurgical reactive changes and further infection using FDG-PET. It is concluded that acute and chronic osteomyelitis of the peripheral as well as the central skeleton can be detected using FDG-PET. Osteomyelitis can be differentiated from soft tissue infection surrounding the bone. Unlike computed tomography and magnetic resonance imaging, FDG-PET is not affected by metal implants used for fixing fractures. FDG-PET demonstrated promising initial results with respect to treatment monitoring. Nevertheless, in the early postoperative phase FDG-PET seems to be of limited value owing to unspecific tracer uptake.

IntroductionThe diagnosis of spine infections can be difficult, because the patient's history, subjective symptoms and physical findings are often inconclusive, particularly in the early stages. Nuclear medicine procedures, which identify pathophysiological reactions preceding morphological changes, can play a useful role in the diagnosis of spondylodiscitis. Specific tracers are used in infectious bone disease: Ga-67, Tc-99m nanocolloid, Tc-99m-HMPAO-and In-111-labeled leukocytes, Tc-99m and In-111 polyclonal human immunoglobulin, and Tc-99m-labeled monoclonal antibodies [10]. However, for diagnosing spine infections, these procedures are still not optimal [10,19]. On white cell imaging, up to 50% of all patients with spondylodiscitis show photopoenic defects, which are not specific for infection [12].Fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) is increasingly playing an important role in the diagnosis, staging and monitoring of malignant tumours [3,5,15]. Not only tumours but also infections show an increased uptake of FDG. The FDG uptake depends on the increased glucose metabolism in activated inflammatory cells such as leukocytes, granulocytes and macrophages [20]. In detecting osteomyelitis with FDG-PET, first studies reported a sensitivity of up to 100% [6,7,9,18]. However, there are limited experiences Abstract Nuclear medicine procedures can be helpful in diagnosing spine infections. The purpose of the study was to evaluate the findings of positron emission tomography with fluorine-18 fluorodeoxyglucose (FGD-PET) in the detection of spondylodiscitis. We performed FDG-PET in 16 patients with suspected spondylodiscitis. All the patients were operated and underwent histopathological examination. The FDG-PET findings were graded and evaluated by two independent nuclear medicine physicians. Of the 16 patients, 12 had a histopathologically confirmed spondylodiscitis. In all these 12 patients, FDG-PET was true-positive. In the four patients without spondylodiscitis, FDG-PET showed three true-negative and one false-positive result. In spondylodiscitis, the mean standard uptake value (SUV) of FDG was 7.5 (SD± 3.8). The PET scans depicted the paravertebral soft tissue involvement in cases of spondylodiscitis. Our first results showed that FDG-PET is a very sensitive imaging procedure in the detection of spondylodiscitis. Compared to other nuclear medicine procedures, PET enables a rapid imaging with acceptable radiation dose and high spatial resolution.

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The aim of this study was to evaluate FDG-PET findings in patients with osteoporosis or preclinical osteoporosis and acute vertebral compression fractures in order to determine whether FDG-PET has a value for distinction of pathological from osteoporotic vertebral fractures. 17 patients with a spontaneous compression fracture of the spine were evaluated by bone scanning with Tc-99m HDP, positron emission tomography with fluorine-18 deoxyglucose (FDG-PET) and magnetic resonance imaging (MRI). Osteoporosis had been established in all cases by X-ray and osteodensitometry. PET and bone scan images were scored independently from 0 (no pathological uptake) to 4 (definitive pathological uptake) by two blinded nuclear medicine physicians. The results of the blinded scoring were compared to MRI findings which served as gold standard. In 13 out of 17 patients, MRI demonstrated a vertebral fracture generating from osteoporosis. In 12 of these 13 cases, PET scans were scored with 0 or 1 and categorized as true negative. Standard uptake values (SUV) ranged between 1.1 and 2.4. In one of the 13 patients, PET was interpreted false positive with an uptake score of 3 (SUV = 2.9). Of the 17 patients, MRI revealed a pathological fracture caused by spondylodiscitis in three patients and by plasmacytoma in one patient. In these patients, all PET scans were highly positive with a score of 3 and 4 and SUV values between 3.8 to 9.8. The bone scans of all 17 patients were positive with scores of 3 or 4 but a differentiation between osteoporotic and pathological fractures was not possible. Our preliminary results indicate that acute vertebral fractures that originated from osteoporosis or preclinical osteoporosis tend to have no pathologically increased FDG uptake. Since a high FDG uptake is characteristic for malignant and inflammatory processes, use of FDG-PET may have potential value for differentiation between osteoporotic and pathological vertebral fractures.

For the medial meniscus, where horizontal and complex tears were more prevalent, 3-Tesla MRI shows a higher accuracy than for the lateral meniscus. Particularly with regard to the medial meniscus, 3-Tesla MRI could be effectively used when a degenerative tear is suspected. Nevertheless, in regard to a remarkable number of false positive and false negative findings the diagnostic value of a 3-Tesla MRI investigation should not be overestimated.