Category: H

Cells that have the capacity to develop into red blood cells, white blood cells, and platelets and have a key role in hematopoiesis (producing blood cells). Hematopoietic progenitor cells are located principally in the red bone marrow, which in adults is restricted to the pelvis, ribs, spine, skull, sternum (breastbone), humerus (upper arm bone), and…

A rare brain tumor composed of blood vessel cells. Hemangioblastomas are usually slow growing and benign. They most commonly occur in the cerebellum, retina of the eye, and spinal cord. Treatment requires removing the entire tumor surgically. A tumor of the brain or spinal cord arising in the blood vessels of the meninges or brain.…

The use of an electric heating pad, hot water bottle, hot compresses, a heat lamp, a hot tub, hot baths, or hot showers to promote healing. Heat treatments increase blood flow to an area, which can help augment natural healing. Heat treatments are sometimes used to treat back pain. Care should be taken not to…

A group of physical disorders brought on by prolonged exposure to hot temperatures, insufficient fluid intake, and failure of the body to successfully regulate its internal temperature. Heat disorders, which usually result in hyperthermia, include heat cramps, heat exhaustion, and heat stroke. These conditions can be serious and even life-threatening if prompt action is not…

The field of law that deals with the legal issues associated with health care, including the interrelationships among health care professionals, patients, and the parties who are financially responsible for health care services. Both government (through Medicare and Medicaid) and private organizations (such as the Joint Commission on Accreditation of Healthcare Organizations) heavily regulate the…

The backward flopping of the head when an infant is placed in a sitting position. Weak neck muscles make the baby unable to hold up his or her head until age 4 months. After that, head lag is a sign of possible developmental delay, a failure to develop physical and intellectual skills at the normal…

Repetitive banging of the head against the side of the crib, most common in infants between ages 5 and 11 months. Some normal bruising may occur, but lacerations or skull injuries may indicate child abuse and need to be investigated. Boys are more likely than girls to be head- angers. In some cases, the behavior…

An acute infection caused by the hantavirus, which is transmitted from rodents to humans. Hantaviruses have been found in wild rodents, including deer mice, rats, and moles throughout the world. Rodents transmit hantavirus via the respiratory route, and humans contract it through inhalation of infectious airborne droplets of saliva or urine or through dust from…

A two-step subtraction method for producing digitized x-ray images which uses at least four images. Both energy and temporal subtraction steps are used to mitigate patient motion artifacts.  

The amount of material required to attenuate a beam of radiation to one-half of its original level. Units are given in lengths, such as centimeters. The amount of lead, copper, cement, or other material that would dissipate a beam of radiation by 50%. The number of half value layers required for safety in blocking the…