Peripheral Arterial Disease (PAD) is caused by a reduction of the internal diameters of the arteries in the upper or lower extremities mainly due to atherosclerosis. If not treated, its worsening may led to a complete occlusion, causing the death of the cells lacking proper blood supply, followed by gangrene that may require chirurgical amputation. We have recently performed a clinical study in which good sensitivities and specificities were achieved with dynamic diffuse optical tomography. To gain a better understanding of the physiological foundations of many of the observed effects, we started to develop a mathematical model for PAD. The model presented in this work is based on a multi-compartment Windkessel model, where the vasculature in the leg and foot is represented by resistors and capacitors, the blood pressure with a voltage drop, and the blood flow with a current. Unlike existing models, the dynamics induced by a thigh-pressure-cuff inflation and deflation during the measurements are taken into consideration. This is achieved by dynamically varying the resistances of the large veins and arteries. By including the effects of the thigh-pressure cuff, we were able to explain many of the effects observed during our dynamic DOT measurements, including the hemodynamics of oxy- and deoxy-hemoglobin concentration changes. The model was implemented in MATLAB and the simulations were normalized and compared with the blood perfusion obtained from healthy, PAD and diabetic patients. Our preliminary results show that in unhealthy patients the total system resistance is sensibly higher than in healthy patients.
Dynamic optical tomographic imaging has shown promise in diagnosing and monitoring peripheral arterial disease
(PAD), which affects 8 to 12 million in the United States. PAD is the narrowing of the arteries that supply blood to the
lower extremities. Prolonged reduced blood flow to the foot leads to ulcers and gangrene, which makes placement of
optical fibers for contact-based optical tomography systems difficult and cumbersome. Since many diabetic PAD
patients have foot wounds, a non-contact interface is highly desirable. We present a novel non-contact dynamic
continuous-wave optical tomographic imaging system that images the vasculature in the foot for evaluating PAD. The
system images at up to 1Hz by delivering 2 wavelengths of light to the top of the foot at up to 20 source positions
through collimated source fibers. Transmitted light is collected with an electron multiplying charge couple device
(EMCCD) camera. We demonstrate that the system can resolve absorbers at various locations in a phantom study and
show the system’s first clinical 3D images of total hemoglobin changes in the foot during venous occlusion at the thigh.
Our initial results indicate that this system is effective in capturing the vascular dynamics within the foot and can be used
to diagnose and monitor treatment of PAD in diabetic patients.