Medical applications of nuclear energy
The applications of radionuclides related to human health emerged quickly after the discovery of X-rays At present, most of the hospitals and health centers have a Radiologíay Department of Nuclear Medicine Department, and radiochemical laboratory methods used for diagnosis and investigation of a variety diseases.
In nuclear medicine, a particular radionuclide is administered to the patient, in order to investigate a specific physiological phenomenon by means of a special detector, a gamma camera generally located outside the body. The injected radionuclide is deposited selectively in certain organs (thyroid, kidney, etc.) Can be seen from the gamma camera the size, shape and function of these organs. Most of these procedures are diagnostic, although some radionuclides are administered for therapeutic purposes. Radionuclides useful in nuclear medicine are as follows:
- Diagnosis "in vivo" gamma emitting short half-life (metastable technetium-99, indium-111, iodine-131, xenon-133 and thallium-201) and positron emitting ultrashort half-life (carbon -11, oxygen-15. fluorine-18 and rubidium-82).
- Diagnosis "in vitro": gamma emitters (Iodine-125, and cobalt-51 chromium-57) and beta emitters (tritium and sodium-24).
- Therapy: beta emitters (iodine-131, yttrium-90 and estrocio-90).
Nuclear Medicine "in vivo": Using radiopharmaceuticals
Radiopharmaceuticals are substances that can be administered to the living body for diagnostic or therapeutic investigating organ function. Currently used for diagnostic radiopharmaceuticals of 100 to 300.
The isotopes used have a short half-life of minutes, hours or days and are prepared in radiopharmacy laboratories ensuring their properties and purity.
Usually administered as part of simple molecules or more complex molecules bound to be distributed in organs you wish to explore.
Positron emitting radionuclides are used in the technique known as positron emission tomography (PET). The positrons emitted by these radionuclides are annihilated with atomic electrons, resulting in two gamma rays which propagate in opposite directions and are detected with a gamma camera having detectors located on both sides of the patient. This method is used to assess, among others, the operation of the Heart and Brain.
The quality of the images obtained with this equipment is superior to conventional equipment, but now, because of its high cost and high technology, as to produce these isotopes must have a ciclotró No, there are only equipment sold in countries with high level of medical technology. Spain has several teams of these features in their units oncology, neurology cardiologíay.
Another important technique is the scan, which detects gamma radiation emitted by the radiopharmaceutical attached to 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 converted into electrical pulses that are amplified and processed by a computer, enabling the spatial representation on a display or x-ray, on paper or displaying successive images of the body for further study.
Currently, gamma cameras allow to obtain three-dimensional organ cuts, improving the quality of the studies and the diagnostic sensitivity.
Thyroid scintigraphy consists in obtaining the image of the thyroid gland, the patient administering an isotope such as iodine-131 and technetium-99, which is fixed in the cells of this gland. It is used to diagnose the presence of alterations in shape, volume or thyroid function, as goiters, hyperthyroidism, thyroid cancers, etc.
Adrenal scintigraphy provides information on the form and function of the adrenal glands, which can cause malfunctions diseases like Addison's disease, Cushing's syndrome, etc. .
With different isotopes and administration forms can be studied cardiovascular disease (angina pectoris and myocardial infarction), digestive (cysts or tumors from digestive or intestinal absorption) and lung (tumorous involvement of the lungs).
The bone scan to diagnose infections and tumors in bone, by detecting the accumulation of the radiopharmaceutical injected into the patient in the affected areas.
Studies of the central nervous system (CNS) scans these techniques are useful for evaluating the various types of dementias, epilepsy and vascular diseases or tumors, which can not be detected by nuclear magnetic resonance or by Computed tomography (CT).
Nuclear Medicine "in vitro"
The analytical technique called radioimmunoassay, to detect and quantify existing substances in blood and urine, and are difficult to detect by conventional techniques. It is performed through the combination of the antibody-antigen binding with isotope labeled, generally iodine-125, one of these two components, generally the antigen.
To perform this type of analysis, the patient does not come into contact with radioactivity, since the analysis is performed on the blood taken from the patient.
It is a technique of great sensitivity, specificity and accuracy, which is applied to various fields:
- Endocrinology: determinations of thyroid hormones, adrenal, gonadal and pancreatic stimulus to test dynamic and braking.
- Hematology: determinations of vitamin B12, folic acid, etc..
- Oncology: determinations of tumor markers for the diagnosis and monitoring of tumors.
- Virology determinations of markers of hepatitis B and C.
- Farmacologíay toxicology: determination of drugs in blood, detecting possible sensitivities of organisms to allergies.
therapeutic nuclear medicine
The specialty of nuclear medicine employing ionizing radiation for the treatment of malignant tumors known as radiotherapy.
When using unsealed radioactive sources discussing metabolic radiotherapy, which involves injecting or do eat a relatively large dose of a radioactive substance in liquid form, to accumulate in the body you want treat, where it acts by means of radiation emitted on fabrics in contact therewith, producing the desired effect of destroying tumor cells.
This type of therapy is used to treat hyperthyroidism, thyroid cancer, bone metastases from prostate and breast tumors and can be used alone or in combination with other therapeutics as cirugíao chemotherapy.
In the case of thyroid cancer iodine-131 is used, that being gamma emitter, patient Entering special units radioproteccióny units have specialized medical care. Once the patient has been discharged, is performed periodically dosimetric control to monitor and verify that, by low doses of gamma radiation, the patient can live with his family and rest of the population.
Applications of radiation therapy may include the following:
- Teletherapy: a technique in which the radioactive source is not in direct contact with the tumor being treated. Among gamma emitters used, stresses the encapsulated source of cobalt-60, contained in the pump called cobalt, which prevents the exit of the radiation except for one orifice which provides a directed radiation. Produces high energy radiation (1.2 MeV) capable of irradiating large tumors located deep. Teletherapy also be administered with electron beam emitting sources and neutron.
- Brachytherapy is a technique in which the radioactive source is in direct contact with the tumor. When radioactive material plates are placed over the tumor area is called brachytherapy surface, if this source is introduced into the patient temporarily in natural cavities, intracavitary brachytherapy spoken and often used encapsulated sources of cesium-137, and if placed radioactive sources in certain tissues is known as interstitial brachytherapy. One of the problems of this therapy, also known as Curietherapy is possible unnecessary exposure of the patient and medical personnel to radiation sources, therefore, the source is placed in the positions n correct at the patient and medical personnel employ remote control commands to prepare, transport and handle radioactive sources.
Diagnostic techniques consist of body imaging using X-ray equipment, which cross the exploratory field to be studied. At present, there are many developments in this field emphasizing ultrasound techniques, which use ultrasound or magnetic resonance imaging uses no ionizing radiation.
Thanks to radiology X, may be studies of skeleton, thorax, abdomen, nervous system, gastrointestinal tract, urinary tract, heart, etc. The radiographic image is obtained when crossing the X-ray beam to explore the area and X-rays being absorbed differently depending on the tissue, obtaining an emergent beam having intensity variations visible on a screen, disclosed that results in a radiograph.
Diagnostic Another important technique is computed tomography (CT), which is to obtain a three-dimensional computer projection from overlapping cuts organ to study, produced by a thin collimated X-ray beam that revolve around it.
Mammography is the imaging technique used for the exploration of the breasts, allowing to study the soft tissues with high contrast and diagnosis of benign and malignant breast lesions, even of small dimensions.
The dental radiology, uses special equipment like pantomografías intraoral films (panoramic radiographs of the mouth) that improve the diagnosis of dentist.