Positron Emission Tomography
Positron Emission Tomography is a scanning technique that allows us to measure in detail the functioning of distinct areas of the human brain while the patient is comfortable, conscious and alert. PET represents a type of functional imaging, unlike X-rays or CT scans, which show only structural details within the brain. The differences between these types of imaging don’t end there.
In both X-rays and CT scans, a form of radiation is emitted and travels through the body, and a detector receives the unabsorbed rays and transmits them to a computer. The physics behind PET scanning is quite different. Basically, a person is injected with a radioactive substance. This substance begins the process of radioactive decay inside of the person and interacts with the tissue to produce gamma radiation. These gamma rays are detected by scintillation crystals and transmitted to a computer, where images are produced. But how does this all take place?
The description of PET scans in detail requires the understanding of the radioactive substance injected into the subject. First, a small amount of a biochemical substance is tagged with a positron-emitting radioisotope. A positron is an “anti-electron.” Positrons are given off during the decay of the nuclei of the radioisotope. When the positron emitted collides with an electron in the tissue of the subject, both the positron and the electron are annihilated. When this happens, the collision produces two gamma rays having the same energy (511 KeV), but going in opposite directions.
These gamma rays, produced by the annihilation of a positron and an electron, leave the patient’s body and are detected by the PET scanner. The detection of positron-annihilation events forms the heart of any PET scanner. In most systems, the Gamma detector is a BGO (bismuth germinate oxide) crystal, a high-density scintillator. When it is combined with high performance photomultiplier tubes (PMTs), the detection of 511 KeV gamma rays is possible.
These BGO crystals are arranged into 64 distinct segments so that the scintillation light from each of the segments can be distributed onto the photocathodes of four photomultiplier tubes to be amplified. These “block detectors” are placed into modules of four arranged as eight columns of 32 rows of crystals each. A ring of these detectors surrounds the patient during...
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...kinson’s disease, or schizophrenia.
Recently, new advances have been made in PET technology. A pair of American scientists working in Switzerland came up with a combination PET/CT scanner, which effectively pairs the two techniques. This new combination will be very useful in cancer diagnosis. With the PET/CT, both anatomical and functional imaging can be done and reproduced on the same image. This will be helpful in pinpointing the location of tumors, and also for the early identification of tumors too small to be of concern in CT scanning.
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“UIHC Positron Emission Tomography Imaging Center.” 14 Aug 2000. http://www.pet.radiology.uiowa.edu/. Yahoo. 25 Mar 2001.
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Radiology is one of the few so-called “physical-science”-based fields of medicine, making it a challenging and rewarding application of an academic interest in science. It combines advanced knowledge of human physiology with principles of atomic physics and nuclear decay, electricity and magnetism, and both organic and inorg...
Driver, (2013), described the DEXA scanner as a machine that produces two x-ray beams of high and low energy levels. Much like fluoroscopy, the x-ray from the DEXA scanner comes from underneath the patient, and the scanner has a very low x-ray dose. Earlier versions of the DEXA scanner emitted radiation which required up to five minutes to scan an area of interest, but the more advanced machines can take as ...
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Preparing a patient for a nuclear medical procedure, a radioactive tracer material (or radioactive dye) is either injected or huffed through a mask. The camera monitors the dye and sees how it processes in your body, which the dye eventually collects in the part of the body which is to be scanned and because the tracer material gives off gamma rays, which are used as energy, the energy is then detected by the scanner. The devices work together to measure the amount of tracer active in your body to help produce special pictures to detail the structuring and functioning of your organs and inner body works (MassGeneral,2014).
Nuclear Medicine is the use of radioisotopes for diagnosis, treatment, and research. Radioactive chemical tracers emit gamma rays which provides diagnostic information about a person's anatomy and the functioning of specific organs. Radioisotopes are also utilizes in treatments of diseases such as cancer. It is estimated that approximately one in two people in Western countries are likely to experience the benefits of nuclear medicine in their lifetime.
CTscans stands for “Computed Tomography”. It is a way of looking inside your body using a special camera. It is an advanced scanning x-ray and computer system that makes detailed pictures of horizontal cross-sections of the body, or the part of the body that is x-rayed. A CT scan is a diagnostic test that combines the use of x-ray with computer technology. A series of x-beams from many different angles are used to get these cross-sectional images of the patient’s body. In a computer, these pictures are assembled into a 3-dimentianal picture that can display organs, tissues, bones, and any such thing. It can even show ducts, blood vessels and tumors. One of the advantages of CT is that it clearly shows soft tissue structures (such as brain), as well as dense tissue structure (such as bone). The pictures of a Ctscanner are a lot more detailed than the pictures of a regular X-ray machine. It can make pictures of areas protected or surrounded by bones, which a regular X-ray machine can not. Because of this, a CT scanner is said to be 100 times as affective and clever as an ordinary X-ray, and can therefore diagnose some diseases a lot earlier and quicker. It is recent technology that has made it possible to accurately scan objects into a computer in three dimensions, even though the machines and ideas were developed in the 1970s. In the 70s doctors started to use this new type of machine that could give detailed pictures of organs that the older type of x-ray, machine could not give.
It typically uses radio active drug/tracer to show this activity. The tracer is typically injected, swallowed, or inhaled depending on which organ(s) is being studied by the PET scan. PET scans are used when revealing or evaluating several conditions which include: cancers, heart diseases and brain cancers. PET scans provide information different from that uncovered by other types of scans. Cancer shows up as bright spots on PET scans, because they have a higher metabolic rate than normal cells. The only health risk associated with this particular scan is related to the tracer. It may cause a major allergic reaction, which is rare in many cases. It exposes your unborn baby ( if pregnant) to radiation. If your breast feeding, it may expose your child to radiation as
Radioisotopes have helped create advanced imaging techniques. Beforehand, X rays could only provide so much information such as broken bones, abnormal growths, and locating foreign objects in the body. Now it is possible to obtain much more information from medical imaging. Not only can this advanced imaging give imaging of tiny structures in the body, but it can also provide details such as cancerous cells and damaged heart tissue from a heart...
Bushong, S. C. (2008). Radiologic science for technologists: Physics (9th ed.). St. Louis, MO: Mosby, Elsevier.