Oximetric angiosome imaging in diabetic feet

Purpose: To develop a noncontrast oximetric angiosome imaging approach to assess skeletal muscle oxygenation in diabetic feet. Materials and Methods: In four healthy and five subjects with diabetes, the feasibility of foot oximetry was examined using a 3T clinical magnetic resonance imaging (MRI) scanner. The subjects' feet were scanned at rest and during a toe-flexion isometric exercise. The oxygen extraction fraction of skeletal muscle was measured using a susceptibility-based MRI method. Our newly developed MR foot oximetric angiosome model was compared with the traditional angiosome model in the assessment of the distribution of oxygen extraction fraction. Results: Using the traditional angiosome during the toe-flexion exercise, the oxygen extraction fraction in the medial foot of healthy subjects increased (4.9 ± 3%) and decreased (–2.7 ± 4.4%) in subjects with diabetes (difference = 7.6%; 95% confidence interval = –13.7 ± 1.4; P = 0.02). Using the oximetric angiosome, the percent difference in the areas of oxygen extraction fraction within the 0.7–1.0 range (expected oxygen extraction fraction during exercise) between rest and exercise was higher in healthy subjects (8 ± 4%) than in subjects with diabetes (4 ± 4%; P = 0.02). Conclusion: This study demonstrates the feasibility of measuring skeletal muscle oxygen extraction fraction in the foot muscle during a toe-flexion isometric exercise. Instead of assessing oxygen extraction fraction in a foot muscle region linked to a supplying artery (traditional angiosome), the foot oximetric angiosome model assesses oxygen extraction fraction by its different levels in all foot muscle regions and thus may be more appropriate for assessing local ischemia in ulcerated diabetic feet. J. Magn. Reson. Imaging 2016. J. MAGN. RESON. IMAGING 2016;44:940–946.