In patients with peripheral artery disease (PAD), plaque is accumulating in arteries which leads to a reduction in blood supply to the extremities. In advanced stages, surgical intervention is required to reopen the arteries and restore limb perfusion. During this procedure, it is important to correctly identify which areas of the foot lack perfusion. The standard procedure to obtain this information is X-ray angiography, which is performed repeatedly during the intervention. The disadvantage of this procedure is the relatively high radiation dose and extensive use of contrast agents. To reduce this problem, we evaluate in this pilot study (involving 4 patients) the ability of vascular optical spectroscopy (VOS) to detect the X-ray contrast agent permeating the angiosomes in the foot. We show that the contrast agent can be detected by optical measurements as it temporarily replaces the blood in the different angiosomes, which leads to a 1% to 5% change in the signal amplitude. In addition, measurements of the blood pooling in the foot were performed before the intervention. We observed a strong correlation between the angiosomes that showed a worsen state in the measurement done before the intervention and the absence of angiographic contrast agent signals during the intervention itself. Among the 4 patients monitored, 2 showed a response to the contrast agent in their angiosomes and they corresponded to the patients with a relatively better perfusion in the pre-intervention measurements.