Intravascular optical coherence tomography is a high-resolution intracoronary imaging modality, providing a microscopic image of intravascular features. However, it has lower penetration depth than intravascular ultrasound. Recently, a second-generation optical frequency-domain imaging (OFDI) technique has been developed to provide greater penetration depth and faster pullback speed. However, there is little evidence supporting the efficacy of OFDI in patients with peripheral artery disease (PAD) undergoing endovascular treatment (EVT). We aimed to evaluate the ability of OFDI to visualize vessel walls from the superficial femoral artery (SFA) to the below-knee (BK) arteries, as well as the coronary arteries. This clinical trial is a single-center, single-arm, open-label study to be conducted in Japan. A total of 20 patients will be enrolled in this study. The primary endpoint is to obtain a clear image of the intravascular features of the SFA and BK arteries, specifically the visualization of ≥ 270° of the vessel lumen in ≥ 16 out of 21 cross sections. Obtaining clear images in ≥ 85% of cases will be regarded as confirmation of the ability of OFDI to visualize vessel walls from the SFA to the BK arteries. This is the first clinical trial to be conducted accordance with good clinical practice to expand the indications of OFDI for PAD patients undergoing EVT in Japan. The result of this study will help provide another imaging option during EVT in daily practice.