In this first instalment, we look at two types of emission imaging: positron emission tomography PET and single-photon emission computerised tomography SPECT. As its name suggests, emission imaging works by detecting radiation emitted from within the patient, enabling clinicians to determine the presence and size of cancerous tumours, and conduct other diagnostic procedures such as coronary perfusion. Both work on the same basic principles - detecting gamma rays and building a three-dimensional picture of, say, a cancerous tumour.
A radioactive tracer radiotracer is injected into the patient. Radiotracers are molecules such as glucose with a radioactive isotope attached. As tumour cells rapidly grow, compared to neighbouring cells, they require large amounts of glucose. Blood carries glucose throughout the patient but it is absorbed mostly at the tumour site, carrying the isotope with it.
The isotope then decays, emitting gamma rays photons that are much higher in energy than visible light and can pass out of the body. By collecting the gamma rays in detectors placed around the patient, we can build up a picture of where they came from, locating the tumour position and shape. Many different detector systems are available.
The simplest is the pinhole camera, which you may have used to observe an eclipse. To do this, you prick a tiny hole in a sheet of card and place a sheet of paper behind it. Cardiovascular diseases have been one of the leading reasons for mortality, even the most developed nations.
In order to identify certain diseases, cardiac imaging becomes a vital technology for every health organization. In the end, the choice is made by the patients or technicians depending on the advantages and shortcomings of both procedures. This sort of imaging provides metabolic and functional information about the cardiac organ.
It involves injecting radiotracers into the bloodstream which depicts the images as and when it flows through various organs. Thank you for updating your details. Log In. Sign Up. Become a Gold Supporter and see no ads. Log in Sign up. Articles Cases Courses Quiz. Molecular imaging is the old principle of nuclear medicine, initially developed by a Jewish-Hungarian scientist called von Hevesy, who received the Nobel Prize in for his discovery that metabolic processes can be studied with radioactive substances.
If you combined that with a PET scan, differentiation of liver tumours might be easier. Basically, MRI is intensively used for brain examinations. However, I should add that, due to the fact that the brain does not change much between the different scans, a rigid retrospective image fusion will do. The brain undergoes no major changes in position and form, no matter how the patient is positioned. But if there were hybrids it would be more interesting to look at regions outside the brain.
But I am sure it will happen one day. Combining imaging modalities is helping to achieve better diagnostic and therapeutic outcomes for heart patients. This website uses cookies to give our readers the best website experience. Please refer to our privacy policy to find out how we use cookies and how you can edit your preferences. How many slices should such a hybrid system have?
The bright enlightened spot is a benign tumour of the parathyroid.
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