Intravenous contrast-free standardized exercise perfusion imaging in diabetic feet with ulcers.

Background: Impaired foot perfusion is a primary contributor to foot ulcer formation. There is no existing device nor method that can be used to measure local foot perfusion during standardized foot muscle exercise in an MRI environment.

Purpose: To develop a new MRI-compatible foot dynamometer and MRI methods to characterize local perfusion in diabetic feet with ulcers.

Study Type: Prospective.

Population/subjects: Seven participants without diabetes and 10 participants with diabetic foot ulcers.

Field Strength/sequence: 3.0T, arterial spin labeling (ASL).

Assessments: Using a new MRI-compatible foot dynamometer, all participants underwent MRI ASL perfusion assessment at rest and during a standardized toe-flexion exercise. The participants without diabetes were scanned twice to assess the reproducibility of perfusion measurements. The absolute perfusion and perfusion reserve values were compared between two groups and between regions near ulcers (peri-ulcer) and away from ulcers (away-ulcer).

Statistical Tests: Bland-Altman methods for the calculation of coefficient of repeatability (CR) and two-sided and unpaired Student's t-test to compare multiple differences.

Results: The perfusion reserves measured had the best reproducibility (CR in medial region: 1.6, lateral region: 0.9). The foot perfusion reserve was significantly lower in the participants with diabetes compared with the participants without diabetes (1.34 ± 0.32, 95% confidence interval [CI]: 1.1, 1.58 vs. 1.76 ± 0.31, 95% CI: 1.53, 1.98, P = 0.02). Both peri-ulcer exercise perfusion (8.7 ± 3.9 ml/min/100g) and perfusion reserve (1.07 ± 0.39, 95% CI: 0.78, 1.35) were significantly lower than away-ulcer exercise perfusion (12.7 ± 3.8 ml/min/100g, P = 0.02) and perfusion reserve (1.39 ± 0.37, 95% CI: 1.11, 1.66, P = 0.03), respectively.

Data Conclusion: This study demonstrates intravenous contrast-free methods for local perfusion in feet with ulcers by standardized exercise-based MRI. Ischemia regions around foot ulcers can be quantitatively distinguished from normal perfused muscle regions.

Level Of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:474-480.