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Radionuclides

In nuclear medicine, a particular radionuclide is administered to the patient, in order to investigate a specific physiological phenomenon by a special detector, generally a gamma camera, outside the body. The injected radionuclide is selectively deposited in certain organs (thyroid, kidney, etc.) can be seen from the gamma camera the size, shape and function of these bodies. Most of these procedures are diagnostic, although some radionuclides are administered for therapeutic purposes.

Useful radionuclides in nuclear medicine are as follows:

  • Diagnosis "in life" emitting: gamma short half-life (technetium-99 metastable, indium-111, iodine-131, xenon-133 and thallium-201) and positron emitters average life ultrashort (carbon-11, oxygen -15. fluorine-18 and Rubidium-82).
  • Diagnosis " in vitro ": gamma emitters (iodine-125, chromium-51 and cobalt-57) and beta emitters (tritium and sodium-24).
  • Therapy: beta emitters (iodine-131, yttrium-90 and estrocio-90).

Nuclear Medicine "in life": use of radiopharmaceuticals

Radiopharmaceuticals are substances that can be administered to the living body for diagnostic or therapeutic purposes, investigating the functioning of an organ. Currently used for diagnostic radiopharmaceuticals 100 to 300.

The isotopes used have short half-lives of minutes, hours or days and are prepared in radiopharmacy laboratories thus ensuring their properties and purity.

Radiopharmaceuticals are usually given as part of or attached to single molecules to be distributed more complex organs you wish to explore molecules.

Positron emitting radionuclides are used in the technique known as positron emission tomography (PET). The positrons emitted by these radionuclides are annihilated with the atomic electrons, giving rise to two gamma propagating in opposite directions and are detected with a gamma camera having sensors located on either side of the patient rays. This method is used to assess, among others, the function of the heart and brain.

The quality of the images obtained with these devices is higher than that of conventional equipment. Currently, due to its high cost and high technology, there are only marketed in countries with high medical technology equipment. The high cost and high technology required due to that to produce these isotopes must have a cyclotron.

Another important technique is the scan, which detects the gamma radiation emitted by the radiopharmaceutical attached to the organ to be studied, on a computer called a gamma camera, the detector is placed on the body, receiving photons from the radiopharmaceutical.

These signals are transformed into electrical impulses that are amplified and processed by a computer. This transformation allows the spatial representation on a screen or x-ray, on paper or displaying successive images of the organ for later study.

Currently, gamma cameras allow to obtain three-dimensional organ courts, improving the quality of studies and diagnostic sensitivity.

Thyroid scan involves obtaining the image of the thyroid gland, the patient administering an isotope such as iodine-131 and technetium-99, which is fixed on this gland cells. It is used to diagnose the presence of alterations in shape, volume or thyroid function, as goiters, hyperthyroidism, thyroid cancers, etc.

The adrenal scintigraphy provides information on the form and function of the adrenal glands, whose dysfunctions may trigger the onset of diseases such as Addison's disease, Cushing's syndrome, etc.

With different isotopes and dosage forms can be studied cardiovascular disease (angina and myocardial infarction), digestive (cysts or tumors from digestive disorders or intestinal absorption) and lung (tumorous involvement of the lungs).

The bone scan to diagnose infections and bone tumors, by detecting the accumulation of the radiopharmaceutical injected into the patient in the affected areas.

The study of central nervous system (CNS) scan these techniques are useful for evaluating the various dementias, epilepsy and vascular disease or tumor that can not be detected by magnetic resonance imaging or computed tomography (CT) .

Nuclear Medicine " in vitro "

The analytical technique called radioimmunoassay, to detect and quantify existing substances in blood and urine, which are difficult to detect by conventional techniques. It is performed by combining the antibody-antigen binding with the labeled with an isotope, generally iodine-125, one of these two components, usually the antigen.

To perform this type of analysis, the patient does not come into contact with radioactivity, because the tests are carried out on blood taken from the patient. For this reason, the specialty of nuclear medicine is called " ". in vitro

It is a technique of great sensitivity, specificity and accuracy, applied to various fields:

  • Endocrinology: determinations of thyroid, adrenal, gonadal hormones and pancreatic stimulation test and dynamic braking.
  • Hematology: determinations of vitamin B12, folic acid, etc.
  • Oncology: determinations of tumor markers for the diagnosis and monitoring of tumors.
  • Virology determinations markers for hepatitis B and C.
  • Pharmacology and Toxicology: drug determinations in blood, detecting sensitization potential of the organism to allergies.
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References

Last review: October 2, 2015