Isotope application in the fields other than nuclear energy
Radioisotopes are frequently used in various fields of human health, scientific research, and industry, both as non-sealed radioactive compounds and sealed sources.
Nuclear medicine is an everyday diagnostic modality in health care including in vivo and in vitro methods for identifying various diseases. Most radioisotopic diagnostic imaging examinations are based on the gamma radiation of 99mTc radionuclide, which is capable of being bound to a huge number of biospecific molecules thereby resulting in organ- or tissue-specific radiopharmaceuticals. PET-imaging (Positron Emission Tomography) is performed by using radiopharmaceuticals containing positron emitter F-18, O-15, N-13, C-11 radionuclides; such imaging provides a quantitative evaluation of the physiological processes in the tissues. In vitro diagnostic methods such as radioimmunoassay (RIA) and immunoradiometric assay (IRMA) are based on the radioindication by I-125-labelled tracers of immunoreactions in patients` blood samples.
Nuclear medicine also includes radionuclide therapy, mainly for tumour treatment, when radioactive compounds containing Y-90, I-131, S-153m, Ho-166, Lu-177, Re-186 or Re-188 radionuclides are used as therapeutic radiopharmaceuticals. On the other hand radiology includes external radiation treatment utilising Co-60 or Ir-192 sealed sources, accelerated electrons, protons, or cold neutrons. One special part of this modality is brachytherapy, when radiation sources are placed temporarily (I-125, Ir-192) or permanently (I-125) within the body of the patient.
Although non-sealed radioactive compounds are rarely used in industry, Ir-192 sealed sources are of considerable importance in a number of solid material tests, e.g. mouldings, and welding seams. Co-60 sealed sources provide gamma radiation for laboratory and industrial irradiators and sterilizers.
In pharmaceutical research and development the H-3 and C-14 labelled compounds play a role of considerable importance since biodistribution and pharmacokinetic studies of molecules possessing unknown physiological properties can easily be screened by them. Research in the field of molecular biology and genetics requires radioactive nucleotides labelled with P-32, P-33 and S-35. In addition to this, molecules labelled with stable isotopes (e.g. C-13) can also be used especially in the environmental sciences.