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...
... middle of paper ...
...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.
Works Cited
Jaroff, Leon. “A Winning Combination.” Time 156:23 4 Dec 2000.
Mullen, Robyn J. “Positron Emission Tomography.” 5 Dec 1995. http://www.bae.ncsu.edu/bae/courses/bae590F/1995/mullen/. Yahoo. 25 Mar 2001.
“PET Scans.” 15 Jan 2001. http://www.lifeimage.com/techdata.htm. Yahoo. 25 Mar 2001.
“UIHC Positron Emission Tomography Imaging Center.” 14 Aug 2000. http://www.pet.radiology.uiowa.edu/. Yahoo. 25 Mar 2001.
The careful familial and patient history is imperative for this exam and procedure. And as the video indicated, is this really an effective screening tool for a healthy person more so than seeing the primary care physician. According to the research in the Indian Journal of Medical Research, the “PET/CT doses were found to be higher than many other conventional diagnostic radiology examinations suggesting that all efforts should be made to clinically justify and carefully weigh the risk-benefit ratios prior to every 18FDG whole body PET/CT investigation” (Kaushik et al,
How does the X-ray work? Well first off let me tell you the difference of light rays and X-rays. The light rays are visible light waves and x-rays is a light that is smaller than atoms in your body. You can’t see them with the naked eye like sun rays. X-rays will only pick up items and body parts that are hard and also made of calcium. That light will then project your muscle that would look like a light gray and your bone structure that will be white onto a black piece of radio graphic film.
Other testing procedures that are commonly employed, in order to gain a better visual image of the excitatory activity in the brain are the PET scan and the MRI. According to Kalat (2004), these methods are non-invasive, meaning that they don’t require the insertion of objects into the brain, yet they yield results that allow researchers to record brain activity. The PET scan (positron emission tomography) involves the researcher injecting a radioactive chemical into the patient’s body, which is then absorbed mainly by the brain’s most active cells. With the use of radioactive detectors, placed around the patient’s head, a map is produced that shows which areas of the brain are most active.
Spectral CT imaging has a lot of potential in the future; it is only a matter of developing the current ideas into better methods than they are now. The Dual-layer detector method is showing promise in its investigative trials. Olszewski says, “With the IQon Spectral CT, there is potential to identify the iodinated contrast within the image and allow for its selective visualization, thus allowing the elimination of the first step” (Lentz 2014), the first step being the non-contrast exam before hand. He goes on to say, “you have the ability to remove the contrast agent after the scan…”(Lentz 2014). If the claims Olszewski is making are true, it could cause large reductions in radiation doses to patients, shorter exam times for patient, and increased work efficiency for departments.
Functional Magnetic Resonance Imaging (fMRI),which is one of the most exciting recent developments in biomedical magnetic resonance imaging, allows the non-invasive visualisation of human brain function(1).
Computed Tomography (CT) is a biomedical imaging technique which produces cross-section images also called "slices" of anatomy of the human body. Radiographic beams are made incident on the human body. The reflected radio beams create a detailed computerized picture taken with a specialized X-ray machine. CT is more precise than a standard X-ray, and provides a clearer image. Fig.1 shows a CT scan of transverse view of the brain. The cross-sectional images are used for a variety of diagnostic and therapeutic purposes.
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 ...
Pet Therapy A bus carrying several clinical students from the local college pulls up in front of the nursing home. The students begin to unload some boxes which contain puppies and kittens ranging in age from three to six months. Once inside, the students begin to pass the puppies and kittens out to the patients that are waiting expectantly in the recreation room. Some patients are alone, some are in groups, but all are delighted to see the animals arrive.
...om the radiation, the source of radiation comes from beneath the patient. Spot fluoroscopy should be utilized to minimize radiation to the patient, radiologist, and radiologic technologist. Radiologist and radiologic technologist must wear a lead apron and thyroid shield. A lead shield is put on the front to protect the radiologist and the tech. (Statkiewicz-Sherer, 1983)
Brain scans -These tests can identify strokes, tumors, and other problems that can cause dementia. Scans also identify changes in the 19 brain’s structure and function. The most common scans are computed tomographic (CT) scans and magnetic resonance imaging (MRI). CT scans use X-rays to produce images of the brain and other organs. MRI scans use a computer, magnetic fields, and radio waves to produce detailed images of body structures, including tissues, organs, bones, and nerves. Other types of scans let doctors watch the brain as it functions. Two of these tests are single photon-emission computed tomography, which can be used to measure blood flow to the brain, and positron emission tomography (PET), which uses radioactive isotopes to provide
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.
Since the brain is extremely fragile and difficult to access without risking further damage, imaging techniques are used frequently as a noninvasive method of visualizing the brain’s structure and activity. Today's technology provides many useful tools for studying the brain. But even with our highest technology out there we do not know everything definitely. We do have fallbacks at times and these fallbacks can lead to serious problems.
Gamma cameras and Single Photon emission computerized Tomography (SPECT) scanners are used for planer and tomographic imaging of gamma
e) Ghosh, P. & Kelly, M. (2010). Expanding the power of PET with PERCIST. [Siemens Healthcare White Paper]. URL http://usa.healthcare.siemens.com/siemens_hwem-hwem_ssxa_websites-context-root/wcm/idc/groups/public/@us/@imaging/@molecular/documents/download/mdaw/nduz/~edisp/white_paper_10_percist-00309714.pdf