radiation Any form of energy that spreads or radiates from its source, including heat, light (visible, ultraviolet and infrared), gamma rays and x-rays . Only a few forms of radiation are radioactive.

radiation oncologist A doctor who specialises in the use of x-rays and other forms of radiation to treat cancers as well as other conditions. Previously called radiotherapist, which term is now used to describe the technician (not a doctor) who delivers or plans radiotherapy.

radiation therapist The health professional (not a doctor) who administers radiotherapy . Sometimes called a therapy radiographer.

radiation therapy see radiotherapy .

radical cystectomy Surgery for people with bladder cancer. For women, the operation removes the bladder and may also remove the uterus, Fallopian tubes, ovaries, front of the vagina and urethra. In men, it removes the bladder, prostate gland and urethra.

radical neck dissection An operation that removes the lymph nodes in the neck and some of the surrounding structures (including muscle), usually as part of surgery for cancer of the mouth, throat (pharynx ) or voice box (larynx ).

radical nephrectomy The main form of treatment for kidney cancer. It removes the diseased kidney and-if they are also diseased-the adrenal gland, surrounding fatty tissue and nearby lymph nodes .

radical surgery An operation that removes a tumour plus surrounding tissue and lymph nodes . The term usually refers to extensive surgery aimed at completely curing the disease.

radioactivity [ra-di-o ac-tiv-i-ty]The nuclei of some atoms are unstable and break down to form simpler, more stable nucleii, and in the process, they release energy (radiation ). This activity is known as radioactivity, and substances that act in this way are said to be radioactive.

radioactive implant [ra-di-o ac-tive im-plant] A radioactive substance (a radioisotope) that is placed directly into or around a cancer within the body to enable the radiation it gives off to kill the cancer cells. Implants are most commonly used for cancers of the cervix , uterus (womb ), breast , mouth, and prostate .

radioactive iodine Iodine that gives off radiation.

radiographer [ra-di-o-gra-pher] A technician trained in taking x-ray pictures of parts of the body to diagnose illnesses and disorders.

radiologist [ra-di-ol-o-gist] A doctor who specialises in the use and interpretation of x-ray photographs and other imaging devices (CT scans ) in diagnosing disorders and diseases.

radiology [ra-di-ol-o-gy] The branch of medicine concerned with the use of radiation , (including x-rays ) and radioactive substances in diagnosing and treating disease. Some radiology departments are now called medical imaging departments, as they may employ techniques such as magnetic resonance imaging that do not use radiation.

radio-opaque [ra-di-o o-paque] Having the ability to block x-rays . Because x-rays will not pass through a radio- opaque substance (eg barium ) such substances show up as clear white on x-ray photographs (in contrast to flesh, which appears grey or black). Radio-opaque substances or dyes are given to patients in many specialised x-ray tests (barium x-rays, angiography, intravenous pyelogram, lymphogram) in order to show up structures within the body.

radioresistant [ra-di-o re-sis-tant] Resistant to the effects of radiation . A cancer is said to be radioresistant if it does not respond adequately to radiotherapy , that is, if it is not sufficiently damaged or destroyed by radiotherapy.

radiosensitive [ra-di-o sen-si-tive] Sensitive to the effects of radiation . A cancer is said to be radiosensitive if it responds to radiotherapy , i.e. the radiation makes it smaller or totally destroys it.

radiotherapy [ra-di-o ther-a-py] The use of particular forms of radiation , usually x-rays or gamma rays , to kill cancer cells or injure them so they cannot grow and multiply. Radiation can be directed at a cancer from outside the body, or a radioactive source may be implanted into the cancer and the area around it. Sometimes called radiation therapy.

receptors see hormone receptors .

reconstructive surgery Surgery to rebuild part of the body that has been destroyed or removed using the patient'sown tissues. It may involve moving skin, cartilage, muscle or bone from other parts of the body. Reconstructive surgery is often used to create a new breast following surgery for breast cancer, or to rebuild parts of the face, nose or mouth following cancer surgery. It is usually carried out by a plastic surgeon: see plastic surgery, breast reconstruction .

rectum [rec-tum] The last 12-15 cm of the large bowel, which opens to the outside at the anus.

recurrence [re-cur-rence] The reappearance of the cancer after a period of remission .

red blood cells One of the two main types of cells present in the blood . Red blood cells make up 45 per cent of blood volume. Their main function is to receive oxygen from the lungs to carry it to tissues throughout the body, and carry carbon dioxide back to the lungs to be breathed out. The red colour comes from haemoglobin, the substance that actually carries the oxygen: see blood cells . Also known as erythrocytes.

regional involvement The spread of cancer from its original site to nearby areas, for example, where a breast cancer has spread to the lymph nodes in the armpit.

registrar In a hospital, the registrar is an experienced doctor responsible for the care of a number of patients with the assistance of junior doctors (residents). A registrar may work with one or more senior surgeons, physicians or consultants.

regression In cancer, the stage when the signs and symptoms are disappearing and the person is recovering. It generally means that the tumour is getting smaller, or that tests (scans, blood counts ) are showing improvement.

rehabilitation Programs that help restore people to independence and a full, productive life after illness or injury. Rehabilitation may involve physical restoration such as the use of prostheses, physiotherapy, occupational therapy programs and/or speech pathology, counselling and emotional support, and employment retraining.

relapse The return of a disease after a period of improvement or remission .

remission A complete remission is a period of good health when all signs or symptoms of the disease have gone, although if the disease is cancer, there may still be some cancer cells in the body. A partial remission means that some of the signs and symptoms are gone. Sometimes called stable disease .

renal cell carcinoma [re-nal cell car-ci-no-ma] The most common cancer of the kidney, it is a type of adenocarcinoma . The cancer may be present for some time before the person notices any symptoms, which include fever , pain and blood in the urine. Also called hypernephroma.

renal sarcoma A rare form of cancer that affects the connective tissues of the kidney.

renal tissue Kidney tissue.

resection The surgical removal of part of an organ or another structure.

respiratory system The parts of the body involved in breathing, including the nose, mouth, throat, trachea(windpipe), and lungs . The purpose of the respiratory system is to get oxygen from the air into the bloodstream and so to the tissues of body, as well as to get rid of the waste carbon dioxide.

risk A measure of how likely a person is to develop a particular disease. Where people are at high risk of developing a particular disease, this does not mean that the disease is certain to develop, but that they have a greater-than-average chance of getting it. Similarly, people at low risk are less likely than others to develop it, though it could still occur. Therefore, risk factors are any action that increases a person's chance of developing a particular disease, for example, overexposure to the sun is the major risk factor for skin cancer, and risk reduction describes techniques to reduce the chances of developing a particular disease, for example, not smoking will reduce the risk of getting lung cancer .

RNA (ribonucleic acid) [ri-bo nu-cle-ic a-cid] One of the two nucleic acids (the other is DNA) found in the nucleus of every cell . RNA's function is to make proteins .