SLR - April 2012 - Kristin Burton
Reference: Familiari D, Glaudemans A. W.J.M., Vitale V, Prosperi D, Bagni O, Lenza A, Cavallini M, Scopinaro F, Signore A. Can Sequential F-FDG PET/CT Replace WBC Imaging in the Diabetic Foot? J Nucl Med. 2011;52:1012-1019.
Scientific Literature Review
Reviewed by: Kristin Burton, DPM
Residency Program: Grant Medical Center
Podiatric Relevance:
Pedal ulcerations will develop in up to 15 percent of diabetics with 15-25 percent of these patients requiring amputation. Detection and differentiation between soft tissue infection and osteomyelitis can be difficult. Bone biopsy is the gold standard, but is not always performed due to its invasive nature and loss of accuracy with the contamination from surrounding soft tissue infection. Therefore, imaging can be useful in evaluation and diagnosis of osteomyelitis. Nuclear medicine currently plays a large role in detection and diagnosis of diabetic pedal infections. White blood cell (WBC) labeled scintigraphy is currently considered the nuclear medicine gold standard imaging technique for diagnosing osteomyelitis. Recent publications have suggested 18F-FDG PET/CT may be the future trend for diagnosis of osteomyelitis with advantages including no blood manipulation, higher image resolution and shorter acquisition time. This study aimed to compare accuracy of sequential 18F-FDG PET/CT scanning in differentiating soft tissue infection from osteomyelitis from no infection at all, compared to WBC scintigraphy.
Methods:
Thirteen patients with clinical suspicion of pedal osteomyelitis were included and evaluated with both WBC scintigraphy, sequential 18F-FDG PET/CT scanning and bone biopsy. High clinical suspicion was based on the presence of two or more signs and symptoms of local inflammation or systemic signs of infection, along with purulence. WBC scintigraphy was performed on day one, 18F-FDG PET/CT was performed on day two. Bone biopsy was performed within one week of the scans and sent for histological analysis of neutrophilic infiltration.
Results:
Biopsy results demonstrated osteomyelitis in seven patients, soft tissue infection without bone infection in two patients, and no infection in four patients. WBC scintigraphy correctly identified all four patients without infection, and osteomyelitis in six of the seven patients with proven osteomyelitis. One patient was considered to have soft tissue infection with WBC scintigraphy, but was confirmed as osteomyelitis with bone biopsy. The overall diagnostic accuracy in diagnosing osteomyelitis with WBC scintigraphy was 92 percent. 18F-FDG PET was able to correctly identify three of the four patients who were infection free. One infection free patient was considered to have osteomyelitis which was then negative for osteomyelitis with bone biopsy. Only three of the seven patients with biopsy confirmed osteomyelitis were found to have osteomyelitis by 18F-FDG PET scanning. This correlated to a diagnostic accuracy of 54 percent. After adding 18F-FDG PET scanning with CT images, the overall diagnostic accuracy improved to only 62 percent.
Conclusions:
Although recent literature has popularized the 18F-FDG PET/CT scan as the future diagnostic tool for osteomyelitis, this study provided evidence that the diagnostic accuracy of WBC scintigraphy is greater than F-FDG PET scanning alone and with the addition of CT scanning. WBC scintigraphy remains the gold standard imaging technique for differentiating soft tissue infection from osteomyelitis.