A digital twin is a digital replica of a living or non-living physical entity with an aim to establish the connection between the physical model and the corresponding virtual counterpart. Digital twin technology has been used in a broad range of applications across aerospace, manufacturing, medical, automotive, and urban planning industries. In medical applications, it can help doctors collect data of patients such as electronic medical records, physiological information, and lifestyle habits for them to perform remote medical services, simulate specific therapies and surgery or drugs, and collect responses from patients. On top of that, it can also assist medical staff to perform simulated training. This report identify key medical care application fields covered by digital twin patents filed to the USPTO (United States Patent and Trademark Office) and points out key technical points involved in these patents.