Lower extremity artery disease (LEAD) is characterized by low awareness rate and high missed diagnosis rate, leading to low treatment rate and high disabling mortality rate. However, none of the current examination methods can comprehensively and thoroughly evaluate the vascular structure and blood oxygen status of the lower extremity at the same time. Photoacoustic imaging can display millimeter-scale microvessels without the need for contrast agents. The investigators developed photoacoustic tomography (PACT) technology, which wass able to provide three-dimensional and high-resolution photoacoustic images of the target area.The investigators plan to recruit LEAD patients in different disease conditions and healthy volunteers to receive the PACT examination on the feet using this imaging system, and to evaluate the potential clinical role of the imaging system in LEAD, and its added value to current imaging methods.

Inclusion Criteria:

1. Inclusion of the case group 1) LEAD patients; 2) Patients voluntarily take part in the study and write informed consent.
2. Inclusion of the control group 1) Patients without LEAD by ultrasound and clinical diagnosis; 2) Patients voluntarily take part in the study and write informed consent.

Exclusion Criteria:

1. age <18 years;
2. pregnant women, nursing mothers and pregnant women in preparation;
3. with laser operation contraindication (for example, received a photodynamic therapy in the last month);
4. with metal implants in lower legs or feet;
5. with a history of mental illnesses or abuse of drug and alcohol;

7) with blood phobia or pathological hypotension; 8) with cerebral hemorrhage or peripheral vascular bleeding risk, or history of stroke; 9) with wounds in lower legs or feet; 10) unable or uncooperative with the experimenter.

The LEAD patients are diagnosed as LEAD by computed tomography angiography or ultrasound.