PET
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tomography
[to-mog´rah-fe]Since its introduction in 1972, the use of this modality has grown rapidly. Because it is noninvasive and has high contrast resolution, it has replaced some radiographic procedures using contrast media. It also has a better spatial resolution than scintillation imaging (about 1 mm for CAT compared to 15 mm for a scintillation camera).
A CAT scan is divided into a square matrix of pixels (picture elements). The newer CAT scanners use a high resolution matrix with 256 × 256 or 512 × 512 pixels. The region of the tissue slice corresponding to a pixel has a cross-sectional area of 1 × 1 mm to 2 × 2 mm; because of the thickness of the slice, it has a finite height and is therefore referred to as a voxel (volume element).
The actual measurements made by the scanner are the x-ray attenuations along thousands of rays traversing the slice at all angles. The attenuation value for a ray is the sum of the values for all of the voxels it passes through. A computer program called a reconstruction algorithm can solve the problem of assigning attenuation values for all the pixels that add up to the measured values along each ray.
The attenuation values are converted to CAT numbers by subtracting the attenuation value of water and multiplying by an arbitrary coefficient to produce values ranging from −1000 for air to +1000 for compact bone with water as 0. CT numbers are sometimes expressed in Hounsfield units, named after Godfrey Hounsfield, the inventor of the CT scanner; Hounsfield and Allan Cormack were co-winners of the Nobel Prize in physiology or medicine in 1979 for the development of computerized axial tomography.

Most of the isotopes used in PET scanning have a half-life of only 2 to 10 minutes. Therefore, they must be produced by an on-site cyclotron and attached chemically to the tracer and used within minutes. Because of the expense of the scanner and cyclotron, PET is used only in research centers. However, PET is important because it provides information that cannot be obtained by other means. By labeling the blood with 11C-carbon monoxide, which binds to hemoglobin, images can be obtained showing the regional perfusion of an organ in multiple planes. By using labeled metabolites, images can be obtained showing metabolic activity of an organ. 15O-oxygen and 11C-glucose have been used for brain imaging and 11C-palmitate for heart imaging. 81Rb, which is distributed like potassium, is also used for heart imaging. By using labeled neurotransmitters, hormones, and drugs the distribution of receptors for these substances in the brain and other organs can be mapped.
PET
PET
Abbreviation for:pancreatic endocrine tumour
paraffin-embedded tissue
partial-exchange transfusion
peak ejection time
peritoneal equilibration test
photosynthetic electron transport
positron emission tomography
post-exposure treatment
pre-eclamptic toxaemia
Project Executive Team
psychiatric emergency team
PET
PET
PET scan, positron emission transaxial tomography Imaging A non-invasive imaging modality in which emission computed axial tomography is used to detect positron-emitting isotopes–radionuclides that reflect biochemical and pathologic defects in tissues and evaluate blood flow and metabolism in the cerebral cortex, heart, whole body scanning; PET scans may be used to evaluate AIDS-related neuropathology–response to AZT by local ↑ of glucose metabolism, gliosis, differentiating among Alzheimer's, multi-infarct, and other forms of dementia, Huntington's disease, tardive dyskinesia, epilepsy for localization of seizure focus, making surgical therapy viable, malignancy–gliomas, residual tumor, pituitary adenomas, Parkinson's disease–↓ dopamine, psychiatric disease–depression, schizophrenia, and analysis of radiopharmaceuticals; PET scanning may be used in cardiology to evaluate coronary arteriosclerosis, differentiate between benign and malignant tumors, stage CA, detect CA recurrence and metastases, monitor response to therapy and target biopsy sites, assess myoardial viability, regional myocardial blood flow, and ischemia, using 15CO2; after an AMI, there is an severely attenuated vasodilator response in the resistance vessels in both the infarcted myocardium and in the myocardium perfused by normal vesselsPET
tomography
(to-mog'ra-fe) [ tomo- + -graphy]computed axial tomography
Abbreviation: CATSee: computed tomography
computed tomography
Abbreviation: CTCAUTION!
CT scans expose patients to radiation on the order of 10 mSv per scan. Educational materials about the potential risks and benefits of scanning should be provided to patients to ensure that scans are performed safely and carefully.computerized axial tomography
Abbreviation: CATSee: computed tomography
electrical impedance tomography
electron-beam tomography
Ultrafast computed tomographyfull body computed tomography
Abbreviation: FBCTCAUTION!
The test exposes patients to high levels of radiation, reveals more false positive findings than true positives, and is expensive.Heidelberg retinal tomography
Abbreviation: HRThelical computed tomography
optical coherence tomography
Abbreviation: OCTpanoramic tomography
Zonography.positron emission tomography
Abbreviation: PETThe images produced by PET are in colors that indicate the degree of metabolism or blood flow. The highest rates appear red, those lower appear yellow, then green, and the lowest rates appear blue. The images in various disease states may then be compared to those of normal subjects. Three- and four-dimensional reconstructions are often achieved through the use of computed tomography (CT) with the same machine. See: illustration
quantitative computed tomography
Abbreviation: QCTsingle photon emission computed tomography
Abbreviation: SPET, SPECTspiral computed tomography
Helical computed tomography.ultrafast computed tomography
xenon-enhanced computed tomography
positron emission tomography
Abbreviation: PETThe images produced by PET are in colors that indicate the degree of metabolism or blood flow. The highest rates appear red, those lower appear yellow, then green, and the lowest rates appear blue. The images in various disease states may then be compared to those of normal subjects. Three- and four-dimensional reconstructions are often achieved through the use of computed tomography (CT) with the same machine. See: illustration
Positron emission tomography (PET)
PET
Patient discussion about PET
Q. Can a pet allergy cause your nose to plug, give you a sore throat and a bad cough? I recently adopted a puppy. I felt fine for about a week an a half, but 2 days ago I began to sneeze a lot. My nose plugged and I had to blow almost constantly. I also came down with a sore throat and a bad cough. Is this a result of a pet allergy or did I just come down with a cold? I've been around dogs all my life and I don't ever recall reacting like this before.
Q. What kind of dogs are considered "low allergy" breeds? My son really wants a dog and I am allergic. Not severely but... Promised to look into getting a low allergy one. Appreciate any info including how to source free/low cost as money is tight.