D-18F-fluoromethyl tyrosine imaging of bone metastases in a mouse model

1632 Objectives With the small bones of the foot and ankle, bone scan (Bo) is often requested to evaluate any swelling or chronic ulcers. Labeled leukocyte (WBC) imaging is often reserved for abnormal Bo. This study evaluated the utility of 3-phase Bo (3Pbo), and WBC/Bo imaging for diagnosing complicating osteomyelitis in the foot and ankle. Methods Images of 27 pts presenting with 24 ulcers involving the ankle (n= 15), heel (n=4), toe (n= 4) and midfoot (n=1) and 3 swelling in Charcot joints were evaluated. Criteria for osteomyelitis: 3Pbo, abnormal on all phases, WBC/Bo, ROI abnormal activity on both images. In 11 pts with ankle ulcers, WBC and marrow images (WBC/Ma) were also evaluated for discordant distribution of activity and compared with 3Pbo and WBC/Bo. Imaging results were compared with histopathologic/microbiologic confirmation for all cases. Results In the group of 27 pts, 4 had osteomyelitis, 3 acute and 1 chronic, the rest only had soft tissue infection. In the 11 pts with ankle ulcers, there was 1 case of chronic osteomyelitis and 10 with soft tissue infection. 3Pbo and WBC/Bo were false negative in a patient with chronic osteomyelitis in a Charcot joint. WBC/Ma was false negative in a patient with chronic osteomyelitis and marrow hyperplasia. Imaging results are presented in the table: Conclusions Bone imaging alone or in combination with WBC imaging is not very specific for diagnosing complicating osteomyelitis in the ankle and foot. For the ankle, WBC/Ma may offer better accuracy due to high specificity; however, this needs to be confirmed with larger patient population