ways radiation is used in medicine

• diagnosis of disease, therapy, and research• Diagnosis covers a wide range of exams from fairly routine x

rays to complex CT scans and the injections of radioactive material for nuclear medicine imaging.

• Radiation therapy involves delivering a large dose of radiation to a small area of the body.

• Therapy is primarily directed to the killing of tumor cells as part of the treatment of cancer.

• Radiation therapy may also be used in the treatment of other diseases, such as coronary artery disease, by applying a large radiation dose to a small area on the inside surface of the vessel to reduce the probability that the artery will close (occlude) in the future.

NUCLEAR MEDICINE

• discovery of x rays in 1895 was a major turning point in diagnosing

• physicians finally had an easy way to "see" inside the body without having to operate

• Newer x-ray technologies such as CT (computerized tomography) scans have revolutionized the diagnosis and treatment of diseases affecting almost every part of the body.

• Other sophisticated techniques have provided physicians with low-risk ways to diagnose heart disease . For example, doctors can now pinpoint cholesterol deposits that are narrowing or blocking coronary arteries, information essential for bypassing or unclogging them.

NUCLEAR MEDICINE

• Half of all people with cancer are treated with radiation, and the number of those who have been cured continues to rise.

• There are now tens of thousands of individuals alive and cured from various cancers as a result of radiotherapy.

• In addition, there are many patients who have had their disease temporarily halted by radiotherapy.

• Radionuclides are also being used to decrease or eliminate the pain associated with cancer--such as that of the prostate or breast--that has spread to the bone.

Radionuclides• a technological backbone for much of the biomedical

research being done today• used in identifying and learning how genes work. • Much of the research on AIDS is dependent upon the use

of radionuclides. • Scientists can engineer, produce and "arm" monoclonal

antibodies in the laboratory to bind to a specific protein on a patient's tumor cells--with radionuclides.

• When such "armed" antibodies are injected into a patient, they bind to the tumor cells, which are then killed by the attached radioactivity, but the nearby normal cells are spared.

• So far, this approach has produced encouraging success in treating patients with leukemia.

USE OF RADIONUCLIDES• Every major hospital in the United States has a nuclear

medicine department • radionuclides are used to diagnose and treat a wide variety

of diseases more effectively and safely by "seeing" how the disease process alters the normal function of an organ.

• To obtain this information, a patient either swallows, inhales, or receives an injection of a tiny amount of a radionuclide.

• Special cameras reveal where the radioactivity accumulates briefly in the body, providing an image that shows normal and malfunctioning tissue.

• Radionuclides -are also used in laboratory tests to measure important substances in the body, such as thyroid hormone.

• Radionuclides are used to effectively treat patients with thyroid diseases, including Graves disease--one of the most common forms of hyperthyroidism--and thyroid cancer.

PET scanning

• another clinical and research tool• positron emission tomography• involves injecting radioactive material into a

person to "see" the metabolic activity and circulation in a living brain.

• PET studies have enabled scientists to pinpoint the site of brain tumors or the source of epileptic activity, and to better understand many neurologic diseases

• For example, researchers were able to learn how dopamine--the chemical messenger (neurotransmitter) that's involved in Parkinson's disease--is used by the brain

PET scanning

• The test involves injecting a very small dose of a radioactive chemical, called a radiotracer, into the vein of your arm.

• The tracer travels through the body and is absorbed by the organs and tissues being studied.

• Next, you will be asked to lie down on a flat examination table that is moved into the center of a PET scanner—a doughnut-like shaped machine.

• This machine detects and records the energy given off by the tracer substance and, with the aid of a computer, this energy is converted into three-dimensional pictures. A physician can then look at cross-sectional images of the body organ from any angle in order to detect any functional problems.

PET scanning

PET scans are most commonly used to detect

cancer

heart problems (such as coronary artery disease and damage to the heart following a heart attack),

brain disorders (including brain tumors, memory disorders, seizures)

other central nervous system disorders.

DIAGNOSIS AND TREATMENT

• The use of ionizing radiation has led to major improvements in the diagnosis and treatment of patients with cancer.

• These innovations have resulted in increased survival rates and improved quality of life.

• Mammography can detect breast cancer at an early stage when it may be curable.

• Needle biopsies are more safe, accurate, and informative when guided by x-ray or other imaging techniques.

• Radiation is used in monitoring the response of tumors to treatment and in distinguishing malignant tumors from benign ones.

• Bone and liver scans can detect cancers that have spread.

Treatment Options

Three-Dimensional Radiation Therapy (3D-CRT) • a nonsurgical cancer treatment procedure • shapes the radiation beams so that they “conform” to the

shape of the tumor• technique allows physicians to accurately treat the

cancerous tumor, as well as areas of potential cancer, while minimizing the amount of radiation that vital organs and healthy tissue adjacent to the tumor receive.

• Therefore, the target radiation dose can be increased without exposing healthy parts f the body to increased levels of toxicity.

• used to treat prostate cancer, lung cancer and certain head and neck cancers.

Treatment Options

Intraoperative Radiation Therapy (IORT)• combines surgery and radiation therapy• allows a large, single dose of radiation to be delivered to

the tumor site while reducing the level of radiation exposure to normal adjacent tissue

• Usually, surgery is performed first; the surgeon removes as much of the tumor as possible. Then a dose of radiation is given directly to the remaining cancer as well as nearby areas where cancer cells may have spread.

• The radiation dose is controlled and is allowed to penetrate only as far as needed to treat the tumor.

• In general, nearby normal tissue and organs do not receive radiation.

Treatment Options

Brachytherapy and Interstitial Implantation• an advanced cancer treatment • radioactive materials known as “seeds” or

“sources” are placed directly inside or very near the tumor, giving a high radiation dose to the tumor while reducing the radiation exposure to adjacent healthy tissues

• provides both low dose rate (LDR) and high dose rate (HDR) brachytherapy.

• Both procedures deliver appropriate doses of ionizing radiation to the treatment area.

some specific radioisotopes used to cure various cancers

• Iodine-131 is administered orally as a liquid or capsule in the treatment of thyroid cancer.

• Phosphorus-32 is instilled either in an intraperitoneal or intrapleural space to treat malignant effusions.

• Radioactive Sr-89 and Sm-153 are injected intravenously to relieve pain from bone cancers.

• Many radioisotopes are used as sealed sources to treat cancer such as Cs-137, Ir-192, Sr-90, and I-125.

• Cobalt-60 is used in a machine (teletheraphy unit) as a source of intense gamma radiation for the treatment of a variety of cancers.

Radiation Therapy

• also called radiotherapy • highly targeted, highly

effective way to destroy cancer cells in the breast that may stick around after surgery.

• Radiation can reduce the risk of breast cancer recurrence by about 70%.

• Despite what many people fear, radiation therapy is relatively easy to tolerate and its side effects are limited to the treated area.

Two different ways to deliver radiation to the tissues to be

treated:• a machine called a linear accelerator that

delivers radiation from outside the body

• pellets, or seeds, of material that give off radiation beams from inside the body

Tissues to be treated might include the breast area, lymph nodes, or another part of the body.

Magnetic resonance imagingmri

• most commonly used in radiology to visualize detailed internal structure and limited function of the body

• provides much greater contrast between the different soft tissues of the body than computed tomography (CT) does

• especially useful in neurological (brain), musculoskeletal, cardiovascular, and oncological (cancer) imaging

• Unlike CT, it uses no ionizing radiation, but uses a powerful magnetic field to align the nuclear magnetization of (usually) hydrogen atoms in water in the body.

• Radio frequency (RF) fields are used to systematically alter the alignment of this magnetization, causing the hydrogen nuclei to produce a rotating magnetic field detectable by the scanner.

• This signal can be manipulated by additional magnetic fields to build up enough information to construct an image of the body.

Saggital views of knee and human head

Mri scanner

Herniated disc

• MRI scans can display more than 250 distinct shades of grey, each reflecting slight variations in tissue density or water content.

• It is in those subtle shades that radiologists unlock the secrets of the tissues.

• For example, abnormal tissue, such as a brain tumor, will look different than the normal tissue surrounding it.

• The technologist and radiologist have the ability to alter imaging parameters (like the timings of the RF pulse and gradients) to emphasize areas of injury or disease or to acquire higher image resolutions.

X-ray computed tomography

• Tomography is imaging by sections or sectioning, through the use of waves of energy.

• In conventional medical X-ray tomography, clinical staff make a sectional image through a body by moving an X-ray source and the film in opposite directions during the exposure.

• Consequently, structures in the focal plane appear sharper, while structures in other planes appear blurred.

• By modifying the direction and extent of the movement, operators can select different focal planes which contain the structures of interest.

Ct scans

• A computerized axial tomography scan is an x-ray procedure that combines many x-ray images with the aid of a computer to generate cross-sectional views and, if needed, three-dimensional images of the internal organs and structures of the body.

• Computerized axial tomography is more commonly known by its abbreviated names, CT scan or CAT scan.

• A CT scan is used to define normal and abnormal structures in the body and/or assist in procedures by helping to accurately guide the placement of instruments or treatments.

A large donut-shaped x-ray machine takes x-ray images at many different

angles around the body.• These images are

processed by a computer to produce cross-sectional pictures of the body.

• In each of these pictures the body is seen as an x-ray "slice" of the body, which is recorded on a film.

• This recorded image is called a tomogram.