R

Radiation oncologist: Doctor specializing in use of radiation to treat cancer.

Radiation therapist: Specially trained operator of equipment that delivers radiation therapy.

Radiation therapy: Cancer treatment that involves high-energy rays (such as x-rays) to kill or shrink cancer cells. Radiation may come from outside of the body (external radiation) or from radioactive materials or "pellets" placed directly in the tumor (internal or implant radiation). Radiation therapy may be used to reduce the size of a cancer before surgery, to destroy remaining cancer cells after surgery, or as the main treatment.

Radical prostatectomy: Surgical removal of the entire prostate gland, the seminal vesicles and nearby tissue.

Radioactive implant: Source of high-dose radiation placed directly into or around a tumor to kill the cancer cells. (See: Brachytherapy.)

Radioactive tracer: An atom made radioactive for the express purpose of makings the atom's course through thru a body traceable.

Radiocystitis: Inflamation of the bladder caused by radiation treatment.

Radiogenic: Caused by radiation.

Radiogram: A picture, usually of internal organs or bones, created by use of Xrays.

Radioisotope: An unstable that is prone to break up (decay). Decay releases small fragments of atoms and energy. Exposure to certain radioisotopes can cause cancer. But radioisotopes are also used to find and kill cancer cells. In certain imaging procedures, for example, radioisotopes are injected into the body where they collect in cancerous areas, showing up as highlighted areas on images.

Radiologic technologist: Health professional (not a doctor) trained to position patients for x-rays, take the images, and then develop and check the images for quality. The films taken by the technologist are sent to a radiologist to be read.

Radiologist: Doctor with special training in diagnosing diseases by interpreting x-rays and other types of imaging studies, such as CT scans and MRIs (magnetic resonance imaging). A physician who specializes in treating and/or diagnosing patients using radioactive substances.

Radionuclide bone scan: Use of a small amount of radioisotope to produce images of the bones.

Radio pathology: The study of radiation induced diseases and illnesses. 

Rarecutter enzyme: See restriction enzyme cutting site.

Recombinant clone: Clone containing recombinant DNA molecules. See recombinant DNA technology.

Recombinant DNA molecules: A combination of DNA molecules of different origin that are joined using recombinant DNA technologies.

Recombinant DNA technology: Procedure used to join together DNA segments in a cell-free system (an environment outside a cell or organism). Under appropriate conditions, a recombinant DNA molecule can enter a cell and replicate there, either autonomously or after it has become integrated into a cellular chromosome.

Recombination: The process by which progeny derive a combination of genes different from that of either parent. In higher organisms, this can occur by crossing over.

Recurrence: Cancer that has returned after treatment. "Local recurrence" means the cancer returned to the same place as the original cancer. "Regional recurrence" means it has come back in the lymph nodes near the first site. "Distant recurrence" is when cancer metastasizes (spreads) after treatment to organs or tissues (such as the lungs, liver, bone marrow, or brain) farther from the original site than the regional lymph nodes.

Rectum: The lower part (about 5 inches) of the large intestine

Rectus abdominus (abdominal) flap procedure: (See: Transverse rectus abdominus muscle flap procedure.)

Red blood cells: Blood cells that contain hemoglobin, the substance that carries oxygen to body tissues.

Regimen: Strict, regulated plan (such as diet, exercise, or other activity) designed to reach certain goals. In cancer treatment, a plan to treat the disease. (See: Protocol.)

Regional involvement: Spread of cancer from original site to nearby areas, but not to distant sites such as other organs.

Rehabilitation, rehab: Activities designed to help a person adjust, heal, and return to a full, productive life after injury or illness. May involve physical restoration such as the use of prostheses as well as physical therapy, counseling, and emotional support.

Regulatory region or sequence: A DNA base sequence that controls gene expression.

Relapse: Recurrence of cancer after a disease-free period. 

Remission: Complete or partial disappearance of the signs and symptoms of cancer in response to treatment; the period during which a disease is under control. (A remission may not signal a long term cure.)

Rescue treatment: Procedures, such as bone marrow transplants, that "rescue" a patient's immune system and blood-forming organs from the effects of high dose chemotherapy.

Resection: A surgical procedure to remove part or all of an organ or other structure.

Respiratory therapist: Under the direction of a physician, a respiratory therapist gives breathing treatments and helps manage patients on ventilators.

Retinoids: Vitamin A and synthetic compounds similar to vitamin A.

Resolution: Degree of molecular detail on a physical map of DNA, ranging from low to high.

Restriction enzyme, endonuclease: A protein that recognizes specific, short nucleotide sequences and cuts DNA at those sites. Bacteria contain over 400 such enzymes that recognize and cut over 100 different DNA sequences. See restriction enzyme cutting site.

Restriction enzyme cutting site: A specific nucleotide sequence of DNA at which a particular restriction enzyme cuts the DNA. Some sites occur frequently in DNA (e.g., every several hundred base pairs), others much less frequently (rarecutter; e.g., every 10,000 base pairs).

Restriction fragment length polymorphism (RFLP): Variation between individuals in DNA fragment sizes cut by specific restriction enzymes; polymorphic sequences that result in RFLPs are used as markers on both physical maps and genetic linkage maps. RFLPs are usually caused by mutation at a cutting site. See marker.

RFLP: See restriction fragment length polymorphism.

Ribonucleic acid (RNA): A nucleic acid found in all cells that transmits genetic messages between structures in the cell. Usually referred to as RNA; A chemical found in the nucleus and cytoplasm of cells; it plays an important role in protein synthesis and other chemical activities of the cell. The structure of RNA is similar to that of DNA. There are several classes of RNA molecules, including messenger RNA, transfer RNA, ribosomal RNA, and other small RNAs, each serving a different purpose.

Ribonucleotide: See nucleotide.

Ribosomal RNA (rRNA): A class of RNA found in the ribosomes of cells.

Ribosomes: Small cellular components composed of specialized ribosomal RNA and protein; site of protein synthesis. See ribonucleic acid (RNA).

Risk factor: Anything increasing the chance of getting a disease such as cancer. Different cancers have different risk factors. Unprotected exposure to strong sunlight is a risk factor for skin cancer, for instance, while smoking is a risk factor for lung, mouth, larynx, and other cancers. Some risk factors, such as smoking, can be controlled. Others, like a person's age, cannot be changed.

RNA: See ribonucleic acid (RNA)