Andrei Samarin MD, Abstract Co-Author: Nothing to Disclose

Dorothee Rita Fischer MD, Abstract Co-Author: Nothing to Disclose

Michael Betz, Abstract Co-Author: Nothing to Disclose

Norman Espinosa, Abstract Co-Author: Nothing to Disclose

Gustav K. Von Schulthess MD, PhD, Abstract Co-Author: Consultant, ICON plc Grant, General Electric Company Consultant, General Electric Company Consultant, Bayer AG

Katrin Doris Marianne Stumpe MD, Presenter: Nothing to Disclose

Evaluation of unclear ankle and foot pain is a promising indication of 18F-fluoride PET/CT imaging. Being a very sensitive technique for the detection of bone alterations and new bone formation, 18F-fluoride PET/CT often shows multiple sites of focally increased 18F-fluorid uptake with different intensity in the symptomatic and asymptomatic ankle and foot. The aim of this study was to evaluate the value and clinical relevance of 18F-fluoride uptake in the symptomatic and asymptomatic foot.  

20 consecutive patients who underwent clinical 18F-fluoride PET/CT for the evaluation of unclear foot pain were included in the study and their imaging data were retrospectively analyzed. Scanning started 30-45 min after the i.v. injection of a 94-135 MBq of 18F-fluoride.The maximal standard uptake values (SUVmax) of focally increased fluoride uptake were measured in both ankle and foot. Additionally, to account for factors that may influence the intensity of tracer uptake, SUVmax values of fluoride uptake in distal diaphysis of the ipsilateral tibia were measured. The ratio of the uptake in the foot and that in the distal tibia (foot/tibia ratio) was calculated for every foot. Patients were questioned about pain in both feet at the time of PET/CT examination and clinical follow-up (range 2-8 months).

11 of 20 patients showed focally increased 18F-fluoride uptake in the asymptomatic foot at the time of examination. In one patient with healing fracture foot/tibia ratio was 4.5, in all other asymptomatic feet, foot/tibia ratio was below 3.38. Two patients who presented initially with an asymptomatic foot but developed pain at the time of follow-up examination showed a higher foot/tibia ratio of 4 and 5.4, respectively. The foot/tibia ratio in patients with painful foot was significantly higher (range of 3.4 to 20.3).

Focally increased low grade 18F-fluoride uptake in the foot region is common and often present in the asymptomatic foot (foot/tibia ratio < 3.4). Foot/tibia ratio over 3.4 was associated with pain or development of pain during clinical follow-up.

The information provided by 18F-fluorid PET/CT might contribute to early detection of osteoarthritis and other bone disorders preceding morphological alterations.

Samarin, A, Fischer, D, Betz, M, Espinosa, N, Von Schulthess, G, Stumpe, K, Clinical Relevance of 18-Fluoride Uptake in PET/CT in the Asymptomatic and Symptomatic Foot.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11011866.html