The prevalence of peripheral arterial disease (PAD) has increased worldwide with an increase in the aging global population and incidence of chronic non-communicable diseases. The risk factors for developing PAD include aging, smoking, diabetes, hypertension, dyslipidemia, and renal insufficiency [1,2]. Moreover, PAD, which is a type of atherothrombosis, is often associated with coronary artery disease (CAD) and cerebrovascular disease (CVD) [3]; hence, the diagnosis of PAD evokes the suspicion of CAD or CVD. Thus, an accurate diagnosis of PAD is crucial for the systemic status as well as the status of the lower extremities.

Duplex ultrasonography (DUS), computed tomography angiography (CTA), and magnetic resonance angiography (MRA) are the commonly employed imaging modalities for evaluating PAD; they exhibit the exact site and extent of stenosis, presence of calcification, and peripheral blood flow. Although DUS provides noninvasive real-time imaging [1], identifying the calcified lumen and visualizing the total length of the lower extremities are challenging. Moreover, DUS is influenced by the skill of the operator. CTA, which has high spatial and temporal resolution, is widely used in clinical practice [4]. However, it is difficult to assess small, calcified arteries below the knee employing ionizing radiation [5]. Moreover, the use of iodine-based contrast agents is contraindicated in patients with renal insufficiency; contrast enhanced-MRA (CE-MRA) is also contraindicated in such patients because gadolinium-based contrast agents can cause nephrogenic systemic fibrosis (NSF) [6].

Thus, the use of non-CE-MRA (NCE-MRA) is considered in patients with iodine or gadolinium allergy and renal insufficiency. Currently, most NCE-MRA methods, such as time-of-flight (TOF) [7] and fresh blood imaging (FBI) [8], require electrocardiography (ECG) or peripheral pulse unit (PPU) triggering, which tend to result in poor arterial visualization in arrhythmic cases owing to poor synchronization. Recently, arterial spin labeling (ASL) or MRA techniques using acceleration selective-motion sensitized gradient (AS-MSG) [[9], [10], [11], [12]], termed enhanced acceleration-selective ASL (eAccASL) [13], have been reported. eAccASL generates MRA without ECG, PPU, or contrast agents, by using the differences in pulsatility between arterial and venous blood flow. The combination of eAccASL and turbo field-echo (TFE) readout was introduced for lower-extremity MRA without ECG, PPU, or contrast agents [14]; however, the arterial depictions of TFE-based eAccASL (TFE-Acc) on distal segments were slightly weaker than those of the NCE-MRA with ECG triggering, such as quiescent-interval single shot [15]. In contrast, MRA with the combination of eAccASL and turbo spin-echo (TSE) readout demonstrated good arterial depictions of the hand [16], which has slower blood flow than that in the lower extremities [17].

Patients with PAD have sluggish arterial blood flow [18]; thus, we hypothesized that TSE-based eAccASL (TSE-Acc) without ECG or PPU triggering and contrast enhancement could obtain better peripheral arterial visualization in the lower extremities than TFE-Acc. This study aimed to compare the diagnostic performance of TSE-Acc and TFE-Acc in the lower extremities with that of triggered angiography non-contrast enhanced (TRANCE) [19], which is considered as the reference standard.