Israel Medical Association Journal

Fever of unknown origin (FUO) is defined as the repeated occurrence of elevated body temperature above 38.3°C (101°F) lasting for at least 3 weeks with no clear diagnosis despite a thorough investigation of more than one-week duration. FUO cases could be categorized into three major etiologies: infectious, neoplastic, and systemic inflammatory. Despite novel diagnostic modalities, clinicians still encounter a significant number of unresolved FUO cases, accounting for as many as 50% of cases [1]. Prolonged futile FUO investigations may be a source of frustration for many clinicians [2]. We described a unique cause for FUO that shares the complexity of the diagnostic workup and emphasizes the importance of ¹⁸F-fluorodeoxyglucose positron-emission tomography/computed tomography (PET/CT) modality in the process of investigating FUO.

Background: Multiple myeloma (MM) affects the long bones in 25% of patients. The advent of positron-emission tomography/computed tomography (PET/CT) scanners offers the possibility of both metabolic and radiographic information and may help determine fracture risk. To the best of our knowledge, no published study correlates these two factors with long bone fractures.

Objective: To evaluate the impact of PET/CT on fracture risk assessment in multiple myeloma patients.

Methods: We identified all bone marrow biopsy proven multiple myeloma patients from 1 January 2010 to 31 January 2015 at a single institution. We prospectively followed patients with long bone lesions using PET/CT scan images.

Results: We identified 119 patients (59 males/60 females) with 256 long bone lesions. Mean age at diagnosis was 58 years. The majority of lesions were in the femur (n=150, 59%) and humerus (n=84, 33%); 13 lesions in 10 patients (8%) required surgery for impending (n=4) or actual fracture (n=9). Higher median SUVmax was measured for those with cortical involvement (8.05, range 0–50.8) vs. no involvement (5.0, range 2.1–18.1). SUVmax was found to be a predictor of cortical involvement (odds ratio = 1.17, P = 0.026). No significant correlation was found between SUVmax and pain or fracture (P = 0.43).

Conclusions: Improved medical treatment resulted improvement in 8% of patients with an actual or impending fracture. The orthopedic surgeons commonly use the Mirels classification for long bone fracture prediction. Adding PET/CT imaging to study in myeloma long bone lesions did not predict fracture risk directly but suggested it indirectly by cortical erosion.

Background: Implant-related spinal infections are a surgical complication associated with high morbidity. Due to infection, hardware removal may be necessary, which could lead to pseudarthrosis and the loss of stability and alignment.

Objectives: To evaluate the accuracy and diagnostic value of ¹⁸F-fluorodeoxyglucose positron-emission tomography/computed tomography (¹⁸F-FDG PET/CT) in the workup of patients with suspected implant-related infections of the spine and to assess the clinical impact of PET/CT results on the management of these infections.

Methods: The study included nine consecutive patients with a history of spinal surgery who underwent PET/CT for evaluation of suspected spinal implant related infection. All imaging studies were performed between January 2011 and December 2013. All ¹⁸F-FDG PET/CT scans were performed on an 8 slice PET/CT following an ¹⁸F-FDG injection. Images were scored both visually and semi-quantitatively by a radiology expert. Results were compared to additional imaging studies when available, which were correlated to clinical and bacteriological findings allowing calculation of sensitivity, specificity and accuracy.

Results: Among the patients, five experienced hardware-related spinal infection. ¹⁸F-FDG PET/CT sensitivity was 80%, specificity 100%, and accuracy 88.9%. One scan produced a false negative; however, a second PET/CT scan revealed an infection.

Conclusions: PET/CT was found to be valuable for the diagnosis of postoperative hardware-related spinal infection, especially when other imaging modalities were uninformative or inconclusive. As such, PET/CT could be useful for management of infection treatment.