Radionuclide imaging

Chapter 37 Radionuclide imaging






37.3 Production of artificially produced radionuclides


There are three common ways of producing artificially produced radionuclides which are then used in radionuclide imaging. These are:





37.3.2 The technetium generator


It is not feasible to produce nuclei with very short half-lives at a remote site and then transport these to the hospital. Such radionuclides are produced at the hospital’s radiopharmacy either by the use of a technetium generator or by the use of a medical cyclotron.


The technetium generator used in nuclear medicine is an important example of the production of artificial radionuclides. As mentioned in Section 37.3.1, if molybdenum-98 is placed in a neutron stream, the nuclei of the molybdenum atoms can be made to absorb the neutrons to produce molybdenum-99. The capture of a neutron raises the energy of the resulting molybdenum-99 nuclei and each loses this energy by the prompt emission of a gamma-ray.


A molybdenum-99/alumina column is in the centre of the generator, as shown in Figure 37.2 (see page 272). The molybdenum-99 has a half-life of 67 hours and decays to form technetium-99m by β-particle emission, as shown below:




Equation 37.2 image



The image is eluted (or flushed) from the generator at regular intervals as sodium pertechnetate. This radionuclide, which is in liquid form, may be used for a number of radionuclide imaging situations. The imagedecays to image by the emission of a gamma-ray of energy 140 keV. The metastable radionuclide has a half-life of 6 hours. Clearly, after a period of time, the activity of the molybdenum-99, and hence its ability to produce technetium 99m, will be reduced and the technetium generator must have its molybdenum-99/alumina column replaced.


A number of other radionuclides used in nuclear medicine can be produced from stable materials when they are bombarded with particles but further discussion about their production is beyond the scope of this section




37.4 Clinically useful radionuclides


Radionuclides are used to diagnose and to treat certain conditions. When they are used for diagnosis, they may be labelled (chemically linked) to a certain radiopharmaceutical, thus encouraging their uptake by specific body parts. The labelled radionuclide may then be injected into, or ingested by, the patient. Such diagnostic techniques in nuclear medicine have three main uses:


Mar 6, 2016 | Posted by in GENERAL RADIOLOGY | Comments Off on Radionuclide imaging
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