Single photon emission computed tomography and positron emission tomography in cancer imaging

Article Abstract:

The modern imaging techniques of computed tomography (CT) and magnetic resonance imaging (MRI) can produce remarkable images, but the images are of a static subject. The internal anatomic structure is rendered for the eye to see, but the ongoing physiological and biochemical processes within the structures remain invisible. The related techniques of positron emission tomography (PET) and single photon emission computed tomography (SPECT) promise to change this, and permit the evaluation of malignant tumors in a way that complements the images obtained by CT and MRI. The two techniques known as PET and SPECT build an image by localizing the source of radioisotopes within the body. The difference between the techniques is that PET utilizes isotopes that emit positron particles as their radioactive atoms decay, while SPECT utilizes substances that emit gamma rays. The key to the usefulness of these techniques lies in the ability of chemists to synthesize appropriate molecules containing the radioactive atoms. For example, fluorodeoxyglucose (FDC) synthesized with radioactive fluorine-18 is treated like glucose by the cells in the body. The cells that are actively taking glucose from the blood take the FDC as well, thus the area of highest metabolic use of glucose appears the brightest on the PET scan. In principle, any molecule that becomes involved in some aspect of blood flow or cellular metabolism may be imaged by these techniques. One example of how this information may be put to use is demonstrated in determining the degree of malignancy of a brain tumor. While the infiltration of tumor cells into the surrounding brain tissue is largely invisible by conventional imaging methods, if the metabolism of these cells is greater than the surrounding tissue, they will show up as bright spots on the PET scan. A similar example of the use of PET scanning would be to distinguish between an area of necrosis, which has little metabolic activity, and an area of recurrent tumor, which has higher metabolic activity. PET scanning and SPECT will not replace CT scanning or MRI. What they will do, however, is provide insight into the dynamic aspects of the tissues that only appear as grey outlines on images obtained by other techniques. (Consumer Summary produced by Reliance Medical Information, Inc.)

Methods, Usage, Physiological aspects, Cancer, PET imaging, Positron emission tomography, Diagnostic imaging, Medical imaging equipment, Radionuclide imaging, Radioisotope scanning, SPECT imaging, Single photon emission computed tomography

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Sensorineural hearing loss in combined modality treatment of nasopharyngeal carcinoma

Article Abstract:

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Science & research, Care and treatment, Research, Complications and side effects, Risk factors, Radiotherapy, Hearing loss, Cisplatin, Combined modality therapy, Nasopharyngeal cancer

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