Appropriate strength of acceleration selective-motion sensitized gradient for non-triggered, non-contrast enhanced magnetic resonance angiography of the lower extremities.

Non-contrast enhanced magnetic resonance angiography (MRA) is useful for diagnosing peripheral arterial disease, especially in patients with renal insufficiency. Recently, non-triggered, non-contrast enhanced MRA using acceleration selective-motion sensitized gradient (AS-MSG), known as enhanced acceleration-selective arterial spin labeling (eAccASL), has been introduced. We aimed to investigate the appropriate strength of the AS-MSG for this technique in the lower extremities. Non-triggered eAccASL with four acceleration encodings (AENCs; 0.17, 0.29, 0.58, and 0.87 m/s²) was compared with electrocardiography (ECG)-triggered eAccASL (AENC: 0.87 m/s²). In the flow phantom, signal intensities (SIs) were calculated. A higher SI was observed with a smaller AENC on non-triggered eAccASL. In eight volunteers, vessel-background contrasts (VBCs) were calculated, and arterial visibility and venous artifacts were assessed by two radiologists. A higher VBC was observed with a smaller AENC on non-triggered eAccASL. The VBCs of non-triggered eAccASL 0.87 were lower than those of ECG-triggered eAccASL 0.87 in the peroneal, and anterior and posterior tibial arteries (all p < 0.05). Subjective scores for arterial visibility did not differ, with median scores within acceptable levels. The venous artifacts score of non-triggered eAccASL 0.17 was lower than those of non-triggered eAccASL 0.29, 0.58, and 0.87 and ECG-triggered eAccASL 0.87 (p < 0.01, p < 0.05, p < 0.001, and p < 0.01, respectively). In two clinical patients, arterial visibility on non-triggered eAccASL 0.29 was comparable or superior to that on ECG-triggered eAccASL 0.87. An AENC of 0.29-0.58 m/s² was considered appropriate for non-triggered, non-contrast enhanced lower-extremity MRA using eAccASL.