System theory in medical diagnostic devices: an overview.

Medical diagnostics refers to testing conducted either in vitro or in vivo to provide critical health care information for risk assessment, early diagnosis, treatment, or disease management. Typical in vivo diagnostic tests include the computed tomography scan, magnetic resonance imaging, and blood pressure screening. Typical in vitro diagnostic tests include cholesterol, Papanicolaou smear, and conventional glucose monitoring tests. Historically, devices associated with both types of diagnostics have used heuristic curve fitting during signal analysis. However, since the early 1990s, a few enterprising engineers and physicians have used system theory to improve their core processing for feature detection and system identification. Current applications include automated Pap smear screening for detection of cervical cancer and diagnosis of Alzheimer's disease. Future applications, such as disease prediction before symptom onset and drug treatment customization, have been catalyzed by the Human Genome Project.