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What is Nuclear Medicine?

Nuclear medicine is the branch of medicine that involves the administration of radioactive substances in order to diagnose and treat disease. The scans performed in nuclear medicine are carried out by a radiographer. This speciality of nuclear medicine is sometimes referred to as endoradiology because the radiation emitted from inside the body is detected rather than being applied externally, as with an X-ray procedure, for example.

For nuclear medicine scans, radionuclides are combined with other chemical compounds to form the radiopharmaceuticals that are widely used in this field. When administered to the patient, these radiopharmaceuticals target specific organs or cellular receptors and bind to them selectively. External detectors are used to capture the radiation emitted from the radiopharmaceutical as it moves through the body and this is used to generate an image. Diagnosis is based on the way the body is known to handle substances in the health state and disease state.

The radionuclide used is usually bound to a specific complex (tracer) that is known to act in a particular way in the body. When disease is present, the tracer may be distributed or processed in a different way to when no disease is present. Increased physiological function that may occur as a result of disease or injury usually results in an increased concentration of the tracer, which can often be detected as a “hot spot.” Sometimes, the disease process leads to exclusion of the tracer and a “cold spot” is detected instead. A large variety of tracer complexes are used in nuclear medicine to visualize and treat the different organs, tissues and physiological systems in the body.

What are radioactive tracers?

Radioactive tracers are made up of carrier molecules that are bonded tightly to a radioactive atom. These carrier molecules vary greatly depending on the purpose of the scan. Some tracers employ molecules that interact with a specific protein or sugar in the body and can even employ the patient’s own cells. For example, in cases where doctors need to know the exact source of intestinal bleeding, they may radiolabel (add radioactive atoms) to a sample of red blood cells taken from the patient. They then reinject the blood and use a SPECT scan to follow the path of the blood in the patient. Any accumulation of radioactivity in the intestines informs doctors of where the problem lies.

For most diagnostic studies in nuclear medicine, the radioactive tracer is administered to a patient by intravenous injection. However a radioactive tracer may also be administered by inhalation, by oral ingestion, or by direct injection into an organ. The mode of tracer administration will depend on the disease process that is to be studied.

Different types of Nucelar Medicines Test

The following are brief explanations of the nuclear medicine tests performed at MNAP.

  • Whole body bone scan – used to identify metastatic cancer involving the bone.
  • 3 phase bone scan – used to identify fractures.
  • Thyroid uptake scan – used to visualize the thyroid gland when disease of the thyroid is suspected.
  • Renal scan – used to indicate the perfusion, function and structure of the kidneys. It is also used to indicate the presence of obstruction or renovascular hypertension.
  • Lasix renal scan – records how the kidneys, ureters and the bladder work together.
  • Captopril renal scan – determines the functional significance of a renal artery or arterial stenosis.
  • Hepatobiliary- gallbladder scan – valuable in evaluating patients suspected of having gallbladder disease.
  • Parathyroid scan – done primarily to detect tumors in the parathyroid gland.
  • Gastric emptying scan – used to determine the rate of gastric emptying. It is performed on patients who have postcibal nausea, vomiting, bloating, early satiety or belching.
  • Liver/spleen scan – allows for visualization of the liver and spleen. It is indicated for patients with cancer to rule out metastatic tumor in the liver.
  • MUGA scan – for patients with cancer or poor carotid function.
  • Nuclear Stress Test – please see a detailed explanation of the test in the cardiology section.

What are some common uses of the procedure?

Physicians use radionuclide imaging procedures to visualize the structure and function of an organ, tissue, bone or system within the body.

In adults, nuclear medicine is used to:

  • Heart
  • -visualize heart blood flow and function (such as a myocardial perfusion scan)
    -detect coronary artery disease and the extent of coronary stenosis
    -assess damage to the heart following a heart attack
    -evaluate treatment options such as bypass heart surgery and angioplasty
    -evaluate the results of revascularization procedures
    -detect heart transplant rejection
    -evaluate heart function before and after chemotherapy (MUGA)

  • Lungs
  • -scan lungs for respiratory and blood flow problems
    -assess differential lung function for lung reduction or transplant surgery
    -detect lung transplant rejection

  • Bones
  • -evaluate bones for fractures, infection and arthritis
    -evaluate for metastatic bone disease
    -evaluate painful prosthetic joints
    -evaluate bone tumors
    -identify sites for biopsy

  • Brain
  • -investigate abnormalities in the brain in patients with certain symptoms or disorders, such as seizures, memory loss and suspected abnormalities in blood flow
    -detect the early onset of neurological disorders such as Alzheimer's disease
    -assist in surgical planning and localize seizure foci
    -evaluate for abnormalities in a chemical in the brain involved in controlling movement in patients with suspected Parkinson's disease or related movement disorders
    -evaluation for suspected brain tumor recurrence, surgical or radiation planning or localization for biopsy

  • Other Systems
  • -identify inflammation or abnormal function of the gallbladder
    -identify bleeding into the bowel
    -assess post-operative complications of gallbladder surgery
    -evaluate lymphedema
    -evaluate fever of unknown origin
    -locate the presence of infection
    -measure thyroid function to detect an overactive or underactive thyroid
    -help diagnose hyperthyroidism and blood cell disorders
    -evaluate for hyperparathyroidism
    -evaluate stomach emptying
    -evaluate spinal fluid flow and potential spinal fluid leaks

In adults and children, nuclear medicine is also used to:

  • Cancer
  • -stage cancer by determining the presence or spread of cancer in various parts of the body
    -localize sentinel lymph nodes before surgery in patients with breast cancer or skin and soft tissue tumors
    -plan treatment
    -evaluate response to therapy
    -detect the recurrence of cancer
    -detect rare tumors of the pancreas and adrenal glands

  • Renal
  • -analyze native and transplant kidney blood flow and function
    -detect urinary tract obstruction
    -evaluate for hypertension related to the kidney arteries
    -evaluate kidneys for infection versus scar
    -detect and follow-up urinary reflux

In children, nuclear medicine is also used to:

    -investigate abnormalities in the esophagus, such as esophageal reflux or motility disorders
    -evaluate the openness of tear ducts
    -evaluate the openness of ventricular shunts in the brain
    -assess congenital heart disease for shunts and pulmonary blood flow

What are the benefits vs. risks?

  • Benefits

    • Nuclear medicine examinations provide unique information—including details on both function and anatomic structure of the body that is often unattainable using other imaging procedures.

    • For many diseases, nuclear medicine scans yield the most useful information needed to make a diagnosis or to determine appropriate treatment, if any.

    • Nuclear medicine is less expensive and may yield more precise information than exploratory surgery.

    • Nuclear medicine offers the potential to identify disease in its earliest stage, often before symptoms occur or abnormalities can be detected with other diagnostic tests.

    • By detecting whether lesions are likely benign or malignant, PET scans may eliminate the need for surgical biopsy or identify the best biopsy location.

    • PET scans may provide additional information that is used for radiation therapy planning.

  • Risks

    • Because the doses of radiotracer administered are small, diagnostic nuclear medicine procedures result in relatively low radiation exposure to the patient, acceptable for diagnostic exams. Thus, the radiation risk is very low compared with the potential benefits.

    • Nuclear medicine diagnostic procedures have been used for more than five decades, and there are no known long-term adverse effects from such low-dose exposure.

    • The risks of the treatment are always weighed against the potential benefits for nuclear medicine therapeutic procedures. You will be informed of all significant risks prior to the treatment and have an opportunity to ask questions.

    • Allergic reactions to radiopharmaceuticals may occur but are extremely rare and are usually mild. Nevertheless, you should inform the nuclear medicine personnel of any allergies you may have or other problems that may have occurred during a previous nuclear medicine exam.

    • Injection of the radiotracer may cause slight pain and redness which should rapidly resolve.

    • Women should always inform their physician or radiology technologist if there is any possibility that they are pregnant or if they are breastfeeding. See the Safety page for more information about pregnancy, breastfeeding and nuclear medicine exams.

Medical Applications

Nuclear medicine and radiology are the whole of medical techniques that involve radiation or radioactivity to diagnose, treat and prevent disease. While radiology has been used for close to a century, “nuclear medicine” began approximately 50 years ago. Today, about one-third of all procedures used in modern hospitals involve radiation or radioactivity. These procedures are among the best and most effective life-saving tools available, they are safe and painless and don’t require anesthesia, and they are helpful to a broad span of medical specialties, from pediatrics to cardiology to psychiatry.

While both nuclear medicine and radiology are used in diagnostic procedures (to determine a patient’s health, monitor the course of an illness or follow the progress of treatment) and therapeutic procedures (to treat illnesses), they are implemented differently. In nuclear medicine, radioisotopes are introduced into the body internally, whereas in radiology X-rays penetrate the body from outside the body.

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