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"they would be exactly opposite in their center of mass frame but the scanner has no way to know this".
This is unclear. Is it because of relativistic speeds?
If so, perhaps it should be mentioned. — Preceding unsigned comment added by 82.68.94.86 ( talk) 08:31, 22 June 2014 (UTC)
Are the scan times quoted for PET/CT machines correct? The machine I have experience of - it's a couple of years old - requires significantly longer - the CT part takes approximately 10 to 14 minutes for a H&N CT, the slow time mainly being a result of the fact that the CT is very much a low-grade CT scanner. I am not sure what other machines do, and obviously times are very much dependent on the protocol being used, area being imaged, etc., but (in my experience) the CT part takes significantly longer than 30 seconds. zebdee
Answer: With todays multi-detector helical CT scans, the scan time is much faster. We can do an "eyes to thighs" CT scan in less than a minute. NucsDoc
What are the percentages of false positives for PET scans?
Answer: PET is not specific, it merely tells you which areas of the body have faster metabolism than others. This means it picks up inflammation, infection and injuries as well as tumors. For this reason, PET is only suitable for diagnosing tumors in conjunction with other tests. Its other main role is staging of tumors i.e. assessing the extent of a tumor that has already been found by other means.
For example, a CT scan of the chest finds a single nodule in one lung. The question is then, "is this cancer?". PET scanning in this situation can tell you whether this nodule is likely, or unlikely to be tumor.
There was a recent review of PET imaging in lung cancer [1]. In the case of the solitary pulmonary nodule scenario, the specificity of a "positive" PET scan was 82%-94% depending on the precise PET technique used.
For staging of lung cancer - the most important role for PET is determining whether a lung tumor has spread to the center of the chest (the mediastinum). However, even in this case there is a significant false positive rate (PPV : 74-93%; false positive rate: 44.6%). There is also a significant false-negative rate in this situation (up to 11.7%), so PET is usually used in conjuction with other tests, including exploratory surgery (mediastinoscopy). ChumpusRex 15:04, 5 March 2006 (UTC)
Hello, I come from french Wikipedia, I upload a new image for oncology part. Enjoy !
PET Images are measured in different units like Bacqurel per mili litre, SUV (Standard Uptake Value), Percentage and Counts/sec What does each of these units mean?
Answer: Becquerel per mililitre is a measure of the concentration of radioactity within a region. One Bequerel is one count/sec.
The problem with this unit is that the value depends on how much radioactive tracer was given to the patient, the size of the patient, how much time has passed since the injection (due to radioactive decay), etc.
The SUV is a method for partially compensating for this. It corrects for the total amount of radioactivity given, and the approximate volume of the patient (volume is very difficult to measure, so it is estimated from weight).
In words, the SUV is the uptake in the tissue divided by an estimate of the concentration in the body that was available to access the tissue. Concentration is approximated as the injected activity divided by body weight. The idea is to normalize the counts in the tissue to the counts that were available to be taken up by the tissue, or to "standardize" the uptake. Markssss ( talk) 04:52, 28 July 2010 (UTC)
There are a variety of other methods used for calculating SUV, some correct for blood glucose concentration, some use lean body weight instead of total body weight, some estimate body surface area.
Percentage is a cruder method of correction. The voxel with the highest activity is found, and it's activity is called 100%. The activity in other regions is then presented as a fraction of that.
There still some debate as to whether the SUV is a useful measurement, from the point of diagnosis. Some abnormal areas (e.g. tumors), will have a higher uptake (and hence SUV) than normal tissues, and studies have suggested that the higher the activity of an abnormality, the more likely it is to be signficant. Some studies have looked at 'threshold' values of SUV, below which an abnormality is unlikely to be significant (or above which an abnormality is likely to be significant). E.g. if PET can be used to assess a nodule in the lung. If the SUV of the nodule is higher than 2.5, some studies have suggested that it's likely to be cancer.
However, given the different interpretations of SUV, different scan techniques, different times between injection and scanning at different hospitals, etc. some people argue that the SUV is relatively useless - as it's whole point is to allow comparisons between scans done at different times and at different sites.
ChumpusRex 21:43, 10 June 2006 (UTC)
I was just curious why there is a link to antimatter in the "See also" section. I couldn't see how the two were related, so I think there needs to be some mention of antimatter in the article if it relates, or the link should be deleted. cøøki ə Ξ (talk) 04:13, 22 September 2006 (UTC)
right now i am working on a project.the topic is 'Development of a parameter which will distinguish between the TB n cancer' and this has to be done by kinetic analysis of PET-CT scan.
I haven't seen anything in this page related to the reconstruction process, which is a very important component of PET, because of the low data quality of the process. Do you think that's worth including here? User:Sjayanthi November 3rd, 2006
I'm not much of an expert in these fields, being a year 9 science student, however in the article under the sub-heading 'How the scanner operates', it reads "the positron travels a few millimetres before encountering and annihilating with an electron." Could somebody clarify for everybody (especially me) which material (the body or any other material) the electron is a part of? Because I had always thought that an annihilation of a sub-atom in the body would result in the atom concerned becoming a positively charged ion, and causing disruption in the atomic structure of the organs being built from these atoms. Thanks. 210.11.82.107 09:28, 19 November 2006 (UTC)
Far, far worse damage comes from the gamma, which is ionizing also, but the damage is not caused by the ion per se (it's called that only because this is how these things were DETECTED originally), but rather from the high energy interactions which provide enough energy to break DNA. A simple ion contacting DNA won't do that. DNA is ionized (lots of negatives) and associates with positively ionized histones to be stored. Lots of ions in water are not bad, and in biology are normal. By the way, the atom the positron come from becomes a negative ion also, but this is soon fixed, as it picks up an H+ from solution and becomes a sugar hydroxyl. Again, no sweat, and generally no damage (due to the very small amounts of stuff made). S B H arris 08:47, 16 November 2006 (UTC)
Great, thanks a million. A+, here I come! 210.11.82.107 09:28, 19 November 2006 (UTC)
There is another interesting potential decay pathway of the positron - instead of annihilating with a free electron, the positron may strip off and then bind with (by coulomb attraction) a weakly bound electron, with the consequent formation of
positronium (Ps), which is also sometimes referred to as "a light hydrogen atom". Ps can exist in either of 2 quasi-stable states - a triplet spin 1 state (3S1) which eventually decays by annihilation with a spin opposed electron from a neighboring atom in a process known as "pick-off annihilation", or in a singlet spin 0 state (1S0) which eventually decays by self combination. Note that with the decay of the spin 0 state, the process occurs in approximately 100 ps with two gamma photons being created and emitted at 180 degrees, while the spin 1 state decay occurs much more slowly in approximately 100 ns, and creates 3 gamma photons.
(see
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=14761021&query_hl=3&itool=pubmed_docsum and
http://www.ph.unimelb.edu.au/photo/people/leighton/thefinalcheck.pdf)
Duedilly
06:12, 11 December 2006 (UTC)
i just want to know about the line that says "the positron travels a few millimetres before encountering and annihilating with an electron." but i thought that as soon as a positron encounters an electron, it annihilates...and electrons are present anywhere and everywhere.so how is that positrons are able to travel upto distances as large as milimeters inside the body...please somebody explain this...urgent ,specialy for me...i have a related project even...
Hi I have a quick question about why the gamma rays emmitted by the positron-electron annihilation does not produce two rays exactly 180 degrees apart? Doesn't this break the law of conservation of momentum? Or does the initial velocity of the positron towards an electron before they annihilate cause the final gamma rays to not be 180 degrees apart? Thanks Ongy 09:41, 28 August 2007 (UTC)
You guessed it, the momentum of the electron and positron at the instance of annihilation causes the angle to not be an exact 180 degrees. The angle is usually close enough to 180 and the diameter of scanner bore is short enough that it doesn't considerably skew localization of the annihilation event. 14:51, 31 August 2007 (UTC)
Thanks for that!!! Ongy 00:49, 8 September 2007 (UTC)
Hello, in the lead paragraph it says PET produces images of "metabolic activity" or something along those lines a couple of times. While this is the most popular use of PET, it is not necessarily the only use correct? PET can be used to image any process providing you can make the right biomolecule into a positron emitter. It is true that FDG is by far the most widely used clinically, and it images metabolism, but theoretically PET can image anything. Is this too specific for the lead paragraph? I understand the desire to state the most popular use, but as it is worded I think it is a bit deceiving. CallipygianSchoolGirl ( talk) 02:27, 11 March 2008 (UTC)
You are absolutely correct, which is why I added something to that effect in the "Radioisotopes" paragraph some time ago. It should be said, however, that not just any molecule can be radiolabeled and turned into a successful PET probe. For example, there are some pretty severe constraints in developing ligands that reversibly bind to neuroreceptors in the brain. The isotope of choice is usually C-11, and so the compound must be able to be synthesized, injected in the subject and reach and pass its peak uptake all in a relatively short time, due to the short half life. Additionally, as the ligand gets metabolized in the liver, the metabolites that contain the C-11 cannot cross the blood brain barrier, or they will create a confound in the analysis of the kinetics. The result is many failed research tracers, but there are many successful ones as well. Markssss ( talk) 05:57, 5 May 2008 (UTC)
Another quibble: The lead states that the PET scan and CT image are done at the "same time." Correct me if I'm wrong but they are still two seperate scans that do not overlap temporally. They are done in one sitting, but it is not like the CT X-Ray tube is firing at the same time the PET scanner is picking up Gamma is it? CallipygianSchoolGirl ( talk) 02:31, 11 March 2008 (UTC)
Right again! I Markssss ( talk) 05:57, 5 May 2008 (UTC)
I notice that the illustration showing how the process works shows the Sun Microsystems brand name prominently, which bugs me. Would it be possible to redo this picture and remove this text and logo to make it generic and to remove the plug for the computer manufacturer? I'm sure Sun isn't the only one making this equipment. + ILike2BeAnonymous ( talk) 20:51, 12 March 2008 (UTC)
Under description, the picture obscures some of the text. Not sure how to fix it? Nrusse ( talk) 18:04, 29 March 2008 (UTC)
This article duplicates and overlaps with the PET-CT article, with which it should be combined. Fbarw ( talk) 20:09, 22 July 2008 (UTC)
I was under the impression that a PET scan analyzes the patient's entire body, to find areas where the uptake of the tracer indicates possible cancer. A friend of mine has the impression that the scan is like an x-ray, in that it covers only a particular small segment of the body. Perhaps both types of scans are used, depending on the circumstances? I don't see the answer to this question in the article. My guess was that, to the knowledgeable editors working on the article, the answer was so obvious that it didn't occur to anyone to spell it out! JamesMLane t c 04:30, 22 October 2008 (UTC)
James, a PET scan is used to 'give an indication' whether an abnormal lump in the body is or is not an active 'cancer'. It isnt diagnostic. Any cell that takes up a lot of labelled glucose because it is rapidly metabolising sugar will show up as a bright spot on the PET scan. Your brain and liver, for example, use huge amounts of glucose all the time, consequently, both show up as positive on a PET scan. Unfortunately, when a part of the body has an active infection, the area becomes flooded with 'macrophage' cells normally - these are fighting the infection, and perfectly healthy, but will show up as PET positive. The theory goes that 'cancer' cells grow more rapidly than 'normal' cells, so take up more glucose than those surrounding them. In theory, therefore, if you have a CT scan of (say) the lung, and there is an abnormal lump in it, you cannot say whether it is a benign harmless lump or a cancer (unless you are treated on the NHS in the UK, and the MD you see chooses to save money and just guess). You need to actually grab a piece of the 'lump' and examine it under a microscope (ie have a biopsy and tissue diagnosis performed). If you have a CT scan with a lump in it, and then perform a PET scan, you end up with two superimposeable images: if the lump corresponds in space to an area on the PET scan that appears to be PET positive, you have an indication that the lump is undergoing rapid cell division (ie is cancerous) OR that the body has swamped the area with macrophage cells to fight a localised infection: so all in all, PET scans are not 100% diagnostic of cancer - you still need a biopsy. All in all, as they are currently used by HHS practitioners in the UK, PET scans are almost worthless, and tend to be used as an alternative to what NICE and SIGN guidelines describe as the 'gold standards' for diagnosis (ie physical biopsy and immunohistochemical laboratory work), in order to hide a) the general shortage of surgeons to perform biopsies because their waiting lists are too long, and b) the appallingly low standards of NHS Pathology laboratories, many of which lack full CPA Accreditation (Governments ' minimum Quality Control Standards) due to atrocious funding deficits. DrLofhouse —Preceding unsigned comment added by 79.77.93.167 ( talk) 00:54, 29 January 2009 (UTC)
Under safety the article says that a PET scan is non-invasive. Yet the proecdure requires the injection of a radioactive substance on a biologically active molecule. Doesn't that make the procedure invasive? VR talk 16:54, 12 February 2010 (UTC)
It is noninvasive in the sense that it shows internal processes in living animals without surgically exposing the tissues. This is true both in the research and clinical settings. In research, this allows chemical processes to be quantified without having to dissect tissues in order to measure tracers within them. In clinical applications, this means, for example, that tumors can be identified and localized without exploratory surgery. You are correct in the sense that there are some very small risks involved, but obviously not the same as surgical procedures. Markssss ( talk) 04:44, 28 July 2010 (UTC)
http://www.euronews.net/2011/11/23/x-rays-see-pain/ 23/11/11 13:07 CET
Some highlights: Torsetn Gordh of Uppsala University, Radioactive tracer mixed with D-Deprenyl, Rolf Jonsson (whiplash patient and chairman of Swedish Whiplash Society)
99.181.131.33 ( talk) 23:57, 29 November 2011 (UTC)
There's a bunch of good stuff at fluorodeoxyglucose that could be merged here, including a cool animated 3-D PET scan of a human torso. Gbuchana ( talk) 18:42, 11 July 2012 (UTC)
The current history section contradicts some facts, as apparently the first practical models were developed by Ter Pogossian and his team. From the NY Times obit: "Dr. Michel Mathew Ter-Pogossian, who led the research that turned the positron emission tomography (PET) scanner from an intriguing concept to a medical tool used in hospitals and laboratories everywhere... in the search for a workable model, great strides had been made by others over the decades, but it was Dr. Ter-Pogossian and his colleagues in St. Louis who produced a series of machines for commercial production and practical use in the 1970's... Early in his professional life, Dr. Ter-Pogossian built one of the first scanners to detect radioactivity concentrations in living material, as well as a tool for delivering radiation therapy for cancers of the cervix and uterus. In the early 1950's he recognized the potential of short-lived radioactive tracers, and he was one of the first to use them to find brain tumors and measure blood flow." http://www.nytimes.com/1996/06/21/us/michel-m-ter-pogossian-71-led-research-on-pet-scanner.html Thinkfood ( talk) 07:21, 12 July 2012 (UTC)
Can you add an image like http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/imgnuk/petscang.gif or http://www.whatisnuclearmedicine.com/upload/PET-SCAN-Brain.jpg ? It wasn't obvious to me that each detector can pick up activity within a cone, not a cylinder. In other words, each tube detector can see the entire head, not just a single point in the head. Otherwise it could only pick up events that occur in the very center of the circle, and I thought maybe the ring of detectors was translated around to scan other points in the head, or that there were multiple rings each focused on a different point, but now I see that's not how it works. — Preceding unsigned comment added by 71.167.71.24 ( talk) 15:53, 8 October 2012 (UTC)
Maybe remove it or replace it with an appropriate alternate reference? 193.143.201.114 ( talk) 06:51, 5 June 2013 (UTC)
The following articles are proposed for merge;
PET-CT has been proposed as a merge to this article for over a year, but this page hasn't been tagged. I have made this change and also propose that PET/MRI be merged here. This is because I believe the content would be better covered here, as the technology is very similar, as are the indications and outcomes. I think that coverage on this one page would improve the quality of the intended content of all three articles. LT90001 ( talk) 09:30, 30 August 2013 (UTC)
Can someone please help fix? Thanks! Deluxegourmet ( talk) 02:24, 25 March 2014 (UTC)
Cost per scan gives a figure of $1,100 for a PET scan which is woefully low and very misleading despite being properly sourced to a Cancer Care Ontario publication. I think this figure may be the cost to the government itself. In the U.S., I have seen many PET scan bills from multiple hospitals with several insurance co.'s as well as a few for individuals without insurance. The lowest by far was $2,000 for a bill with a 50% discount. However, this is an outlier and the cost typically is $4,000 to $6,000 to the insurance co. Unfortunately, my data falls under the heading of original research. Regardless, something needs to be done to not seriously mislead the reader as to the cost. TL36 ( talk) 02:56, 2 April 2014 (UTC) I agree with TL36. My insurance company and I were just charged $8500 here in central Florida. kolia_w ( talk) 08:33, 15 January 2015
I guess this is purely subjective, but to me, the images of equipment standing empty lack visual interest. I think we should have a picture showing a human being, especially near the top of the article. I would suggest replacing the first one with this image, which shows a patient receiving care: http://en.wikipedia.org/wiki/File:PET_scan_image3699-PH.jpg -- 76.169.116.244 ( talk) 20:21, 21 January 2015 (UTC)
Hello! There appears to be some erroneous text at the end of the first paragraph of the 'Descriptions -> Operations' section:
"To conduct the scan, a short-lived radioactive tracer isotope is injected into the living subject (usually into blood circulation). Each tracer atom has been chemically incorporated into a biologically active molecule. There is a waiting period while the active molecule becomes concentrated in tissues of interest; then the subject is placed in the imaging scanner. The molecule most commonly used for this purpose is fluorodeoxyglucose (FDG), a sugar, for which the waiting period is typically an hour. During the scan, a record of tissue concentration is made as the tracer decays. aghdghsghfvhgf"
Presumably this text was left in by accident?
It's my understanding that the desire to extend the CAT scan to puppies, gerbils, parrots—indeed the entire menagerie of domesticated animal companions—is what led to development of the more general PET scan. I'm puzzled that this isn't mentioned in the article. EEng ( talk) 23:31, 29 December 2015 (UTC)
Moving this here as it is unsourced, per WP:VERIFY:
There are ongoing studies into using potassium 40 as this decays with a positron channel if an inexpensive way could be found to enrich the isotope into a pure form in order to scan human neural pathways for studying neurodegenerative diseases such as Alzheimers disease. The technology is based on new advances in sensing radiation combined with advanced reconstruction algorithms running on a single board teraflop system.
-- Jytdog ( talk) 19:47, 6 April 2016 (UTC)
The Merriam-Webster dictionary says it should be hyphenated.-- Leptictidium ( mt) 12:42, 8 August 2019 (UTC)
Hi, I made few changes as follows:
1. Added a new para on PET for muscles. 2. Divided the section "Musculoskeletal imaging" into two parts: (1) PET for muscles, and (2) PET for bones. 3. Thinking of separating paragraphs for pharmacokinetics and pharmacodynamics paragraphs. I am now trying to re-write the whole article in simple words to be understandable by non-technical audiences. Also, I feel that text related to SPECT should be removed. There should be separate pages on PET-CT, PET-MR, etc..
Senior editors, please keep an eye. Thank you Earthianyogi ( talk) 14:30, 20 April 2020 (UTC)
Dear All, @ ColinFine, Keith D, Sbharris, Kablammo, Joao Sousa (UU), Le Creusot, 202.142.86.208, 190.145.38.136, Kirigiri, Wtmitchell, and LM200:. I have noticed your valuable contribution on this Positron emission tomography article/page. This Positron emission tomography page has reached 108,412 bytes and I have more to write. I propose that section 'Bones' within the article Positron Emission Tomography be split into a separate page called PET for Bone Imaging. The content of the current page seems off-topic and these sections are large enough to make their own page. The page can be accessed here. Thank you Earthianyogi ( talk) 00:06, 26 April 2020 (UTC)
Is this test something like nuclear radioactive iodine treatments like I took for thyroid cancer in 2017 208.82.44.28 ( talk) 23:27, 17 June 2024 (UTC)
This
level-5 vital article is rated B-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | |||||||||||||||||||||||||||||||||||||
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Ideal sources for Wikipedia's health content are defined in the guideline
Wikipedia:Identifying reliable sources (medicine) and are typically
review articles. Here are links to possibly useful sources of information about Positron emission tomography.
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"they would be exactly opposite in their center of mass frame but the scanner has no way to know this".
This is unclear. Is it because of relativistic speeds?
If so, perhaps it should be mentioned. — Preceding unsigned comment added by 82.68.94.86 ( talk) 08:31, 22 June 2014 (UTC)
Are the scan times quoted for PET/CT machines correct? The machine I have experience of - it's a couple of years old - requires significantly longer - the CT part takes approximately 10 to 14 minutes for a H&N CT, the slow time mainly being a result of the fact that the CT is very much a low-grade CT scanner. I am not sure what other machines do, and obviously times are very much dependent on the protocol being used, area being imaged, etc., but (in my experience) the CT part takes significantly longer than 30 seconds. zebdee
Answer: With todays multi-detector helical CT scans, the scan time is much faster. We can do an "eyes to thighs" CT scan in less than a minute. NucsDoc
What are the percentages of false positives for PET scans?
Answer: PET is not specific, it merely tells you which areas of the body have faster metabolism than others. This means it picks up inflammation, infection and injuries as well as tumors. For this reason, PET is only suitable for diagnosing tumors in conjunction with other tests. Its other main role is staging of tumors i.e. assessing the extent of a tumor that has already been found by other means.
For example, a CT scan of the chest finds a single nodule in one lung. The question is then, "is this cancer?". PET scanning in this situation can tell you whether this nodule is likely, or unlikely to be tumor.
There was a recent review of PET imaging in lung cancer [1]. In the case of the solitary pulmonary nodule scenario, the specificity of a "positive" PET scan was 82%-94% depending on the precise PET technique used.
For staging of lung cancer - the most important role for PET is determining whether a lung tumor has spread to the center of the chest (the mediastinum). However, even in this case there is a significant false positive rate (PPV : 74-93%; false positive rate: 44.6%). There is also a significant false-negative rate in this situation (up to 11.7%), so PET is usually used in conjuction with other tests, including exploratory surgery (mediastinoscopy). ChumpusRex 15:04, 5 March 2006 (UTC)
Hello, I come from french Wikipedia, I upload a new image for oncology part. Enjoy !
PET Images are measured in different units like Bacqurel per mili litre, SUV (Standard Uptake Value), Percentage and Counts/sec What does each of these units mean?
Answer: Becquerel per mililitre is a measure of the concentration of radioactity within a region. One Bequerel is one count/sec.
The problem with this unit is that the value depends on how much radioactive tracer was given to the patient, the size of the patient, how much time has passed since the injection (due to radioactive decay), etc.
The SUV is a method for partially compensating for this. It corrects for the total amount of radioactivity given, and the approximate volume of the patient (volume is very difficult to measure, so it is estimated from weight).
In words, the SUV is the uptake in the tissue divided by an estimate of the concentration in the body that was available to access the tissue. Concentration is approximated as the injected activity divided by body weight. The idea is to normalize the counts in the tissue to the counts that were available to be taken up by the tissue, or to "standardize" the uptake. Markssss ( talk) 04:52, 28 July 2010 (UTC)
There are a variety of other methods used for calculating SUV, some correct for blood glucose concentration, some use lean body weight instead of total body weight, some estimate body surface area.
Percentage is a cruder method of correction. The voxel with the highest activity is found, and it's activity is called 100%. The activity in other regions is then presented as a fraction of that.
There still some debate as to whether the SUV is a useful measurement, from the point of diagnosis. Some abnormal areas (e.g. tumors), will have a higher uptake (and hence SUV) than normal tissues, and studies have suggested that the higher the activity of an abnormality, the more likely it is to be signficant. Some studies have looked at 'threshold' values of SUV, below which an abnormality is unlikely to be significant (or above which an abnormality is likely to be significant). E.g. if PET can be used to assess a nodule in the lung. If the SUV of the nodule is higher than 2.5, some studies have suggested that it's likely to be cancer.
However, given the different interpretations of SUV, different scan techniques, different times between injection and scanning at different hospitals, etc. some people argue that the SUV is relatively useless - as it's whole point is to allow comparisons between scans done at different times and at different sites.
ChumpusRex 21:43, 10 June 2006 (UTC)
I was just curious why there is a link to antimatter in the "See also" section. I couldn't see how the two were related, so I think there needs to be some mention of antimatter in the article if it relates, or the link should be deleted. cøøki ə Ξ (talk) 04:13, 22 September 2006 (UTC)
right now i am working on a project.the topic is 'Development of a parameter which will distinguish between the TB n cancer' and this has to be done by kinetic analysis of PET-CT scan.
I haven't seen anything in this page related to the reconstruction process, which is a very important component of PET, because of the low data quality of the process. Do you think that's worth including here? User:Sjayanthi November 3rd, 2006
I'm not much of an expert in these fields, being a year 9 science student, however in the article under the sub-heading 'How the scanner operates', it reads "the positron travels a few millimetres before encountering and annihilating with an electron." Could somebody clarify for everybody (especially me) which material (the body or any other material) the electron is a part of? Because I had always thought that an annihilation of a sub-atom in the body would result in the atom concerned becoming a positively charged ion, and causing disruption in the atomic structure of the organs being built from these atoms. Thanks. 210.11.82.107 09:28, 19 November 2006 (UTC)
Far, far worse damage comes from the gamma, which is ionizing also, but the damage is not caused by the ion per se (it's called that only because this is how these things were DETECTED originally), but rather from the high energy interactions which provide enough energy to break DNA. A simple ion contacting DNA won't do that. DNA is ionized (lots of negatives) and associates with positively ionized histones to be stored. Lots of ions in water are not bad, and in biology are normal. By the way, the atom the positron come from becomes a negative ion also, but this is soon fixed, as it picks up an H+ from solution and becomes a sugar hydroxyl. Again, no sweat, and generally no damage (due to the very small amounts of stuff made). S B H arris 08:47, 16 November 2006 (UTC)
Great, thanks a million. A+, here I come! 210.11.82.107 09:28, 19 November 2006 (UTC)
There is another interesting potential decay pathway of the positron - instead of annihilating with a free electron, the positron may strip off and then bind with (by coulomb attraction) a weakly bound electron, with the consequent formation of
positronium (Ps), which is also sometimes referred to as "a light hydrogen atom". Ps can exist in either of 2 quasi-stable states - a triplet spin 1 state (3S1) which eventually decays by annihilation with a spin opposed electron from a neighboring atom in a process known as "pick-off annihilation", or in a singlet spin 0 state (1S0) which eventually decays by self combination. Note that with the decay of the spin 0 state, the process occurs in approximately 100 ps with two gamma photons being created and emitted at 180 degrees, while the spin 1 state decay occurs much more slowly in approximately 100 ns, and creates 3 gamma photons.
(see
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=14761021&query_hl=3&itool=pubmed_docsum and
http://www.ph.unimelb.edu.au/photo/people/leighton/thefinalcheck.pdf)
Duedilly
06:12, 11 December 2006 (UTC)
i just want to know about the line that says "the positron travels a few millimetres before encountering and annihilating with an electron." but i thought that as soon as a positron encounters an electron, it annihilates...and electrons are present anywhere and everywhere.so how is that positrons are able to travel upto distances as large as milimeters inside the body...please somebody explain this...urgent ,specialy for me...i have a related project even...
Hi I have a quick question about why the gamma rays emmitted by the positron-electron annihilation does not produce two rays exactly 180 degrees apart? Doesn't this break the law of conservation of momentum? Or does the initial velocity of the positron towards an electron before they annihilate cause the final gamma rays to not be 180 degrees apart? Thanks Ongy 09:41, 28 August 2007 (UTC)
You guessed it, the momentum of the electron and positron at the instance of annihilation causes the angle to not be an exact 180 degrees. The angle is usually close enough to 180 and the diameter of scanner bore is short enough that it doesn't considerably skew localization of the annihilation event. 14:51, 31 August 2007 (UTC)
Thanks for that!!! Ongy 00:49, 8 September 2007 (UTC)
Hello, in the lead paragraph it says PET produces images of "metabolic activity" or something along those lines a couple of times. While this is the most popular use of PET, it is not necessarily the only use correct? PET can be used to image any process providing you can make the right biomolecule into a positron emitter. It is true that FDG is by far the most widely used clinically, and it images metabolism, but theoretically PET can image anything. Is this too specific for the lead paragraph? I understand the desire to state the most popular use, but as it is worded I think it is a bit deceiving. CallipygianSchoolGirl ( talk) 02:27, 11 March 2008 (UTC)
You are absolutely correct, which is why I added something to that effect in the "Radioisotopes" paragraph some time ago. It should be said, however, that not just any molecule can be radiolabeled and turned into a successful PET probe. For example, there are some pretty severe constraints in developing ligands that reversibly bind to neuroreceptors in the brain. The isotope of choice is usually C-11, and so the compound must be able to be synthesized, injected in the subject and reach and pass its peak uptake all in a relatively short time, due to the short half life. Additionally, as the ligand gets metabolized in the liver, the metabolites that contain the C-11 cannot cross the blood brain barrier, or they will create a confound in the analysis of the kinetics. The result is many failed research tracers, but there are many successful ones as well. Markssss ( talk) 05:57, 5 May 2008 (UTC)
Another quibble: The lead states that the PET scan and CT image are done at the "same time." Correct me if I'm wrong but they are still two seperate scans that do not overlap temporally. They are done in one sitting, but it is not like the CT X-Ray tube is firing at the same time the PET scanner is picking up Gamma is it? CallipygianSchoolGirl ( talk) 02:31, 11 March 2008 (UTC)
Right again! I Markssss ( talk) 05:57, 5 May 2008 (UTC)
I notice that the illustration showing how the process works shows the Sun Microsystems brand name prominently, which bugs me. Would it be possible to redo this picture and remove this text and logo to make it generic and to remove the plug for the computer manufacturer? I'm sure Sun isn't the only one making this equipment. + ILike2BeAnonymous ( talk) 20:51, 12 March 2008 (UTC)
Under description, the picture obscures some of the text. Not sure how to fix it? Nrusse ( talk) 18:04, 29 March 2008 (UTC)
This article duplicates and overlaps with the PET-CT article, with which it should be combined. Fbarw ( talk) 20:09, 22 July 2008 (UTC)
I was under the impression that a PET scan analyzes the patient's entire body, to find areas where the uptake of the tracer indicates possible cancer. A friend of mine has the impression that the scan is like an x-ray, in that it covers only a particular small segment of the body. Perhaps both types of scans are used, depending on the circumstances? I don't see the answer to this question in the article. My guess was that, to the knowledgeable editors working on the article, the answer was so obvious that it didn't occur to anyone to spell it out! JamesMLane t c 04:30, 22 October 2008 (UTC)
James, a PET scan is used to 'give an indication' whether an abnormal lump in the body is or is not an active 'cancer'. It isnt diagnostic. Any cell that takes up a lot of labelled glucose because it is rapidly metabolising sugar will show up as a bright spot on the PET scan. Your brain and liver, for example, use huge amounts of glucose all the time, consequently, both show up as positive on a PET scan. Unfortunately, when a part of the body has an active infection, the area becomes flooded with 'macrophage' cells normally - these are fighting the infection, and perfectly healthy, but will show up as PET positive. The theory goes that 'cancer' cells grow more rapidly than 'normal' cells, so take up more glucose than those surrounding them. In theory, therefore, if you have a CT scan of (say) the lung, and there is an abnormal lump in it, you cannot say whether it is a benign harmless lump or a cancer (unless you are treated on the NHS in the UK, and the MD you see chooses to save money and just guess). You need to actually grab a piece of the 'lump' and examine it under a microscope (ie have a biopsy and tissue diagnosis performed). If you have a CT scan with a lump in it, and then perform a PET scan, you end up with two superimposeable images: if the lump corresponds in space to an area on the PET scan that appears to be PET positive, you have an indication that the lump is undergoing rapid cell division (ie is cancerous) OR that the body has swamped the area with macrophage cells to fight a localised infection: so all in all, PET scans are not 100% diagnostic of cancer - you still need a biopsy. All in all, as they are currently used by HHS practitioners in the UK, PET scans are almost worthless, and tend to be used as an alternative to what NICE and SIGN guidelines describe as the 'gold standards' for diagnosis (ie physical biopsy and immunohistochemical laboratory work), in order to hide a) the general shortage of surgeons to perform biopsies because their waiting lists are too long, and b) the appallingly low standards of NHS Pathology laboratories, many of which lack full CPA Accreditation (Governments ' minimum Quality Control Standards) due to atrocious funding deficits. DrLofhouse —Preceding unsigned comment added by 79.77.93.167 ( talk) 00:54, 29 January 2009 (UTC)
Under safety the article says that a PET scan is non-invasive. Yet the proecdure requires the injection of a radioactive substance on a biologically active molecule. Doesn't that make the procedure invasive? VR talk 16:54, 12 February 2010 (UTC)
It is noninvasive in the sense that it shows internal processes in living animals without surgically exposing the tissues. This is true both in the research and clinical settings. In research, this allows chemical processes to be quantified without having to dissect tissues in order to measure tracers within them. In clinical applications, this means, for example, that tumors can be identified and localized without exploratory surgery. You are correct in the sense that there are some very small risks involved, but obviously not the same as surgical procedures. Markssss ( talk) 04:44, 28 July 2010 (UTC)
http://www.euronews.net/2011/11/23/x-rays-see-pain/ 23/11/11 13:07 CET
Some highlights: Torsetn Gordh of Uppsala University, Radioactive tracer mixed with D-Deprenyl, Rolf Jonsson (whiplash patient and chairman of Swedish Whiplash Society)
99.181.131.33 ( talk) 23:57, 29 November 2011 (UTC)
There's a bunch of good stuff at fluorodeoxyglucose that could be merged here, including a cool animated 3-D PET scan of a human torso. Gbuchana ( talk) 18:42, 11 July 2012 (UTC)
The current history section contradicts some facts, as apparently the first practical models were developed by Ter Pogossian and his team. From the NY Times obit: "Dr. Michel Mathew Ter-Pogossian, who led the research that turned the positron emission tomography (PET) scanner from an intriguing concept to a medical tool used in hospitals and laboratories everywhere... in the search for a workable model, great strides had been made by others over the decades, but it was Dr. Ter-Pogossian and his colleagues in St. Louis who produced a series of machines for commercial production and practical use in the 1970's... Early in his professional life, Dr. Ter-Pogossian built one of the first scanners to detect radioactivity concentrations in living material, as well as a tool for delivering radiation therapy for cancers of the cervix and uterus. In the early 1950's he recognized the potential of short-lived radioactive tracers, and he was one of the first to use them to find brain tumors and measure blood flow." http://www.nytimes.com/1996/06/21/us/michel-m-ter-pogossian-71-led-research-on-pet-scanner.html Thinkfood ( talk) 07:21, 12 July 2012 (UTC)
Can you add an image like http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/imgnuk/petscang.gif or http://www.whatisnuclearmedicine.com/upload/PET-SCAN-Brain.jpg ? It wasn't obvious to me that each detector can pick up activity within a cone, not a cylinder. In other words, each tube detector can see the entire head, not just a single point in the head. Otherwise it could only pick up events that occur in the very center of the circle, and I thought maybe the ring of detectors was translated around to scan other points in the head, or that there were multiple rings each focused on a different point, but now I see that's not how it works. — Preceding unsigned comment added by 71.167.71.24 ( talk) 15:53, 8 October 2012 (UTC)
Maybe remove it or replace it with an appropriate alternate reference? 193.143.201.114 ( talk) 06:51, 5 June 2013 (UTC)
The following articles are proposed for merge;
PET-CT has been proposed as a merge to this article for over a year, but this page hasn't been tagged. I have made this change and also propose that PET/MRI be merged here. This is because I believe the content would be better covered here, as the technology is very similar, as are the indications and outcomes. I think that coverage on this one page would improve the quality of the intended content of all three articles. LT90001 ( talk) 09:30, 30 August 2013 (UTC)
Can someone please help fix? Thanks! Deluxegourmet ( talk) 02:24, 25 March 2014 (UTC)
Cost per scan gives a figure of $1,100 for a PET scan which is woefully low and very misleading despite being properly sourced to a Cancer Care Ontario publication. I think this figure may be the cost to the government itself. In the U.S., I have seen many PET scan bills from multiple hospitals with several insurance co.'s as well as a few for individuals without insurance. The lowest by far was $2,000 for a bill with a 50% discount. However, this is an outlier and the cost typically is $4,000 to $6,000 to the insurance co. Unfortunately, my data falls under the heading of original research. Regardless, something needs to be done to not seriously mislead the reader as to the cost. TL36 ( talk) 02:56, 2 April 2014 (UTC) I agree with TL36. My insurance company and I were just charged $8500 here in central Florida. kolia_w ( talk) 08:33, 15 January 2015
I guess this is purely subjective, but to me, the images of equipment standing empty lack visual interest. I think we should have a picture showing a human being, especially near the top of the article. I would suggest replacing the first one with this image, which shows a patient receiving care: http://en.wikipedia.org/wiki/File:PET_scan_image3699-PH.jpg -- 76.169.116.244 ( talk) 20:21, 21 January 2015 (UTC)
Hello! There appears to be some erroneous text at the end of the first paragraph of the 'Descriptions -> Operations' section:
"To conduct the scan, a short-lived radioactive tracer isotope is injected into the living subject (usually into blood circulation). Each tracer atom has been chemically incorporated into a biologically active molecule. There is a waiting period while the active molecule becomes concentrated in tissues of interest; then the subject is placed in the imaging scanner. The molecule most commonly used for this purpose is fluorodeoxyglucose (FDG), a sugar, for which the waiting period is typically an hour. During the scan, a record of tissue concentration is made as the tracer decays. aghdghsghfvhgf"
Presumably this text was left in by accident?
It's my understanding that the desire to extend the CAT scan to puppies, gerbils, parrots—indeed the entire menagerie of domesticated animal companions—is what led to development of the more general PET scan. I'm puzzled that this isn't mentioned in the article. EEng ( talk) 23:31, 29 December 2015 (UTC)
Moving this here as it is unsourced, per WP:VERIFY:
There are ongoing studies into using potassium 40 as this decays with a positron channel if an inexpensive way could be found to enrich the isotope into a pure form in order to scan human neural pathways for studying neurodegenerative diseases such as Alzheimers disease. The technology is based on new advances in sensing radiation combined with advanced reconstruction algorithms running on a single board teraflop system.
-- Jytdog ( talk) 19:47, 6 April 2016 (UTC)
The Merriam-Webster dictionary says it should be hyphenated.-- Leptictidium ( mt) 12:42, 8 August 2019 (UTC)
Hi, I made few changes as follows:
1. Added a new para on PET for muscles. 2. Divided the section "Musculoskeletal imaging" into two parts: (1) PET for muscles, and (2) PET for bones. 3. Thinking of separating paragraphs for pharmacokinetics and pharmacodynamics paragraphs. I am now trying to re-write the whole article in simple words to be understandable by non-technical audiences. Also, I feel that text related to SPECT should be removed. There should be separate pages on PET-CT, PET-MR, etc..
Senior editors, please keep an eye. Thank you Earthianyogi ( talk) 14:30, 20 April 2020 (UTC)
Dear All, @ ColinFine, Keith D, Sbharris, Kablammo, Joao Sousa (UU), Le Creusot, 202.142.86.208, 190.145.38.136, Kirigiri, Wtmitchell, and LM200:. I have noticed your valuable contribution on this Positron emission tomography article/page. This Positron emission tomography page has reached 108,412 bytes and I have more to write. I propose that section 'Bones' within the article Positron Emission Tomography be split into a separate page called PET for Bone Imaging. The content of the current page seems off-topic and these sections are large enough to make their own page. The page can be accessed here. Thank you Earthianyogi ( talk) 00:06, 26 April 2020 (UTC)
Is this test something like nuclear radioactive iodine treatments like I took for thyroid cancer in 2017 208.82.44.28 ( talk) 23:27, 17 June 2024 (UTC)