occluded - Blocked. -

oncologic - Relating to oncology, the study of cancer and the branch of medicine devoted to the diagnosis and treatment of cancer. -

oncologist - A doctor who specializes in treating cancer. Some oncologists specialize in a particular type of cancer treatment. For example, a radiation oncologist specializes in treating cancer with radiation. -

oncology - (ong-kolo-jE) - The study or science dealing with the physical, chemical, and biologic properties and features of neoplasms (abnormal tissue growth or cancer), including causation, pathogenesis, and treatment. -

one thousandth of a rem, the unit for measuring equivalent dose., roentgen (R, r) (rent-gen, rent-chen)

one thousandth of a sievert, the unit for measuring effective dose., - -

opaque - (O-pAk) - Impervious to light; not translucent or only slightly so.

optionally retrievable filters - A device that is temporarily implanted in and then removed from the inferior vena cava, the large vein that returns blood from the legs to the heart, to prevent blood clots in the lower body from traveling to the heart or lungs. -

orbit - The bony cavity containing the eyeball. -

organ Preservation - The principle that using radiation therapy and chemotherapy achieves the same local control and survival that aggressive surgery in the definitive treatment of some malignancies without the need to sacrifice the organ and the function. It is widely use in larynx, head and neck in general, esophageal, anal canal, and other organs. -

orthopaedics - (or-thO-pEdics) - The medical specialty concerned with the preservation, restoration, and development of form and function of the musculoskeletal system, extremities, spine, and associated structures by medical, surgical, and physical methods. -

orthopedic cement - An acrylic cement such as polymethylmethacrylate (PMMA) used to repair bone fractures and in other orthopedic surgeries. -

osmosis - Movement of a solution through the membrane of a cell. -

osteoarthritis - A common condition that usually starts in middle age and is characterized by degenerative changes in the bone and cartilage of one or more joints. -

osteomyelitis - (os-tEo-mI-e-LI-tis) - Inflammation of the bone marrow and adjacent bone.

osteopenia - Reduction in bone volume to below-normal levels; the first stage of bone loss; an early-warning sign pointing to an increased risk of developing full-blown osteoporosis.

osteoporosis - (os-tEo-pOro-sis) - A condition of reduced bone mass, with decreased outer thickness and a decrease in the number and size of the spongy structures in the bone (but normal chemical composition), resulting in increased fracture incidence. Osteoporosis is classified as primary (Type 1, postmenopausal osteoporosis; Type 2, age-associated osteoporosis; and idiopathic, which can affect juveniles, premenopausal women, and middle-aged men) and secondary osteoporosis (which results from an identifiable cause of bone mass loss).-

ovary - One of two female reproductive glands that contain the ova, or eggs, that are released during ovulation; the fallopian tubes connect the ovaries and the uterus. -

ovulation - The release of an ovum, or egg, from the ovary, which then travels through the fallopian tube to the uterus to be fertilized by a sperm -