Abstract 17339: Blood Oxygenation Level Dependent Magnetic Resonance Imaging: a Tool for Objective Assessment of Perfusion in the Lower Limb

Aims: No objective method exists for measuring muscle perfusion in the lower leg. We aimed to determine the utility of blood oxygenation level dependent (BOLD) MRI for assessment of lower limb perfusion. Methods: BOLD MRI was performed on the calf of patients with critical limb ischaemia (CLI, before and after successful revascularisation), age-matched controls, and healthy volunteers, using a 3T magnet (Fig 1a). A thigh cuff was inflated to suprasystolic pressure for 5mins then released to provoke reactive hyperaemia. Time to peak (TTP), the rate of increase in signal after decuffing (gradient) and time to half ischaemia (1/2T) were used to measure relative differences in signal intensity for each muscle group (Fig1b). Results: A longer TTP, lower gradient and shorter 1/2T (ANOVA, P<0.001 for all) was measured in the ischaemic leg of CLI patients (n=21) compared with the patient’s contralateral (control) limb (n=21), the limbs of age-matched controls (n=4) and the limbs of healthy volunteers (n=9) in each muscle group (Fig 1c). BOLD MRI was carried out after limb revascularisation (n=5, pre ABPI 0.45 vs. post ABPI 0.79). At 1-7 days post intervention imaging revealed significantly shorter TTP (89.7±5.4s vs. 141.7±7.1s), higher gradient (6.19±0.56 vs. 2.61±0.36) and longer 1/2T (201.6±5.8s vs. 173.5±7.7s) compared with pre intervention values respectively (paired t-test, P<0.001 for all, Fig 1d). In all cases, the soleus and anterior muscle groups discriminated best between ischaemic and control limb perfusion. Conclusions: BOLD MRI can reliably discriminate between well and poorly perfused limbs. Evaluating changes in BOLD signal may better guide lower limb intervention and provide an objective means of quantifying improvements immediately after treatment, which may ultimately lead to improved limb salvage. ![][1] [1]: /embed/graphic-1.gif