Microwave-induced Thermoacoustic tomography for subcutaneous vascular imaging

Growing demand for bedside medical imaging with increased ease of access has motivated development of more cost-effective ultrasound systems. Multimodal imaging techniques such as Microwave-induced Thermoacoustic (TA) tomography can simplify system design by providing enhanced imaging contrast. The introduction of continuous-wave (CW) TA has made this technique more cost-effective by reducing device size and power requirements. However, this approach is not suitable for imaging the first few millimeters of tissue such as superficial veins. We propose the use of electrical structures that concentrate pulsed microwave excitation near the dermis combined with conventional antennae that radiate CW deeper into tissue for a complete cost-effective imaging platform. With this approach, we have demonstrate proof-of-concept TA imaging of microcapillaries and plant vasculature using substantially reduced pulsed-excitation power, down to 50 W _pk or 42 mW _avg , at a resolution of 300 μm using 5000 averages equivalent to about 1 sec image acquisition time with a transducer array.