Cancer: The Enemy from Within by Carolyn Compton

Author:Carolyn Compton
Language: eng
Format: epub
ISBN: 9783030406516
Publisher: Springer International Publishing

Radiological imaging techniques merely detect anomalous physical objects or shapes that disrupt normal anatomy. Nuclear scans, in contrast, take advantage of biological differences in tissue chemistry and metabolism. A tumor, for example, might produce either a “cold” or a “hot” spot on a nuclide scan depending on its avidity for the tracer. Nuclear medicine scans are “whole-body” studies and can be useful in surveying the body for metastases. They are especially helpful in detecting metastases that are difficult to see on radiological imaging, such as those in the bone marrow.

One specialized and highly useful form of functional imaging uses PET technology to detect and measure glucose uptake by cancers. The images are based on the “sugar addiction” of rapidly dividing tumors cells, a hallmark of cancer discussed in ► Chap. 3. The PET tracer used is fluorodeoxyglucose (FDG), labeled with radioactive fluoride (18F), and the technique is known as FDG-PET. The glucose is taken up to varying degrees by the cancer cells depending up their metabolic rate. The PET scanner’s gamma ray sensors, which encircle the body during the scan, detect the radiation emitted by the tracer that has been absorbed. A three-dimensional image is produced and typically shows a glucose-loving cancer as a hot spot (◘ Fig. 7.5). Variations in the amount of glucose uptake in different regions of the tumor also can be visualized as color gradients. FDG-PET can be combined with CT or magnetic resonance imaging (MRI) (see below), and the co-registration of images provides both metabolic and anatomic information.

Fig. 7.5Positron emission tomography (PET) scan. (Scanner diagram adapted from Wikipedia (► https://​en.​wikipedia.​org/​wiki/​Positron_​emission_​tomography). Source: Wikipedia user Jens Maus. This is an open-access image in the public domain. Scan of lung cancer metastasis from medical records of David Luckenbach, reprinted with kind permission of Alison Luckenback in memory of David (► http://​www.​sailingtexas.​com/​Cancer/​cancer7.​html))

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