Passive microwave resonant sensor for detection of deep tissue injuries

Deep tissue injuries (DTIs) are a perilous class of pressure ulcers in people with reduced mobility and sensation such as the elderly and people with spinal cord injury. DTIs initiate at deep bone-muscle interfaces and progress outwards, causing extensive tissue damage prior to their visual detection at the skin level. Here, we present a wearable sensor for detecting DTIs at their early stages of development. The sensor emits a 0.1 mW microwave to the depth of tissue and its impedance is monitored at different times. The impedance variations are analyzed and a single assessment parameter is generated for monitoring the presence of DTI and its stage of progression. This sensor can detect lesion phantoms as small as 0.5 mL through a layer of tissue which is thicker than 140 mm. The proposed sensor has the potential to be used as a low-cost prognostic device for DTIs, tumors or blood clots.