Arterial Spin Labeling MR Imaging Reproducibly Measures Calf Muscle Perfusion

Objectives:This study hypothesized that arterial spin labeling(ASL) magnetic resonance(MR)imaging at 3-T would be a reliable non contrast technique for measuring peak calf skeletal muscle blood flow through ischemia-hyperemia in both healthy volunteers and patients with peripheral arterial disease(PAD) and will discriminate between these groups. Prior work demonstrated the utility of first-pass gadolinium-enhanced calf muscle perfusion MR imaging in patients with PAD. However, patients with PAD often have advanced renal disease and cannot receive gadolinium. One advantage to ASL-based measures of calf muscle perfusion is the avoidance of administering intravenous gadolinium。Methods:Patients with PAD had claudication and an ankle brachial index of 0.4 to 0.9. Age-matched normal subjects(NL) had no PAD risk factors. Fifteen subjects with PAD and thirty age-matched PAD-free subjects were recruited.All performed supine,and we use a tourniquet system with a thigh cuff to create ischemia-hyperemia, then scan in a 3-T MR imaging scanner. After scanning we will get 61 primery ASL images, then through motion correction and signal average, the ASL relative blood flow images generate. Peak perfusion was measured from ASL blood flow images by placing a region of interest in the calf muscle region with the greatest signal intensity. This study we get the value from the soleus. Perfusion was compared between PAD patients and NL and repeat testing was performed in 12 subjects(5 NL, 7 PAD) for assessment of reproducibility.Results: Through analysis the result of the MRI,peak calf perfusion of 30 NL(age: 52±10 years) was higher than in 15 PAD patients(age: 63±9 years, ankle brachial index: 0.68±0.11)( 61±13 ml/min – 100 g vs. 37±9ml/min/100 g), independent sample test result shows the 95% confidence interval does not across the zero value, so the difference is statistically significant. As a measure of reproducibility, intraclass correlation coefficient(ICC) between repeated studies was 0.87(95% confidence interval [CI]:0.80-0.98). Inter observer reproducibility was 0.98(95% CI: 0.96-0.99).Conclusions : ASL is a reproducible non contrast technique for quantifying peak exercise blood flow in calf muscle. Independent of exercise time, ASL discriminates between NL and PAD patients. This technique may prove useful for clinical trials of therapies for improving muscle perfusion, especially in patients unable to receive gadolinium.