Positron emission tomography–computed tomography (better known as PET-CT or PET/CT) is a nuclear medicine technique which combines, in a single gantry, a positron emission tomography (PET) scanner and an x-ray computed tomography (CT) scanner, to acquire sequential images from both devices in the same session, which are combined into a single superposed (co-registered) image. Thus, functional imaging obtained by PET, which depicts the spatial distribution of metabolic or biochemical activity in the body can be more precisely aligned or correlated with anatomic imaging obtained by CT scanning. Two- and three-dimensional image reconstruction may be rendered as a function of a common software and control system.[1]
PET-CT has revolutionized medical diagnosis in many fields, by adding precision of anatomic localization to functional imaging, which was previously lacking from pure PET imaging. For example, many diagnostic imaging procedures in oncology, surgical planning, radiation therapy and cancer staging have been changing rapidly under the influence of PET-CT availability, and centers have been gradually abandoning conventional PET devices and substituting them by PET-CTs. Although the combined/hybrid device is considerably more expensive, it has the advantage of providing both functions as stand-alone examinations, being, in fact, two devices in one.
The only other obstacle to the wider use of PET-CT is the difficulty and cost of producing and transporting the radiopharmaceuticals used for PET imaging, which are usually extremely short-lived. For instance, the half-life of radioactive fluorine-18 (18F) used to trace glucose metabolism (using fluorodeoxyglucose, FDG) is only two hours. Its production requires a very expensive cyclotron as well as a production line for the radiopharmaceuticals. At least one PET-CT radiopharmaceutical is made on site from a generator: Ga-68 from a gallium-68 generator.
By diagnosing with the help of a PET-CT, the advantages of the two individual methods are combined, and the result considerably exceeds images obtained by the two devices taken separately.
The method allows identification of all cancerous formations in the body, regardless of their size or degree of development.
The diagnosis time is short, the doctor can thus save precious time in the fight with the disease
The substance used, although it is radioactive, presents a very low degree of risk, it is naturally eliminated by the body within a maximum of 24 hours after administration
PET-MRI, like PET-CT, combines modalities to produce co-registered images.
A – CT image; B – PET image; C – Coregistered PET and CT images. The bright red/yellow masses show hypermetabolic areas of the pelvis with metastases of a previous, surgically removed colon carcinoma in a 69-yr-old woman.Siemens Biograph PET-CT scanner
The combination of PET and CT scanners was first suggested by R. Raylman in his 1991 Ph.D. thesis.[3] The first PET-CT systems were constructed by David Townsend (at the University of Geneva) and Ronald Nutt (at CPS Innovations in Knoxville, TN) with help from colleagues.[4] The first PET-CT prototype for clinical evaluation was funded by the NCI and installed at the University of Pittsburgh Medical Center in 1998. The first commercial system reached the market by 2001, and by 2004, over 400 systems had been installed worldwide.[5]
Procedure for FDG imagingedit
An example of how PET-CT works in the work-up of FDG metabolic mapping follows:
Before the exam, the patient fasts for at least 6 hours.[6]
On the day of the exam, the patient rests lying for a minimum of 15 min, in order to quiet down muscular activity, which might be interpreted as abnormal metabolism.
An intravenousbolus injection of a dose of recently produced 2-FDG or 3-FDG is made, usually by arm vein. Dosage ranges from 3.7 to 7.4 megabecquerels (0.1 to 0.2 mCi) per kilogram of body weight.
After one or two hours, the patient is placed into the PET-CT device, usually lying in a supine position with the arms resting at the sides, or brought together above the head, depending on the main region of interest (ROI).
An automatic bed moves head first into the gantry, first obtaining a tomogram, also called a scout view or surview, which is a kind of whole body flat sagittal section, obtained with the X-ray tube fixed into the upper position.
The operator uses the PET-CT computer console to identify the patient and examination, delimit the caudal and rostral limits of the body scan onto the scout view, selects the scanning parameters and starts the image acquisition period, which follows without human intervention.
The patient is automatically moved head first into the CT gantry, and the x-ray tomogram is acquired.
Now the patient is automatically moved through the PET gantry, which is mounted in parallel with the CT gantry, and the PET slices are acquired.
The patient may now leave the device, and the PET-CT software starts reconstructing and aligning the PET and CT images.
A whole body scan, which usually is made from mid-thighs to the top of the head, takes from 5 minutes to 40 minutes depending on the acquisition protocol and technology of the equipment used. FDG imaging protocols acquires slices with a thickness of 2 to 3 mm. Hypermetabolic lesions are shown as false color-coded pixels or voxels onto the gray-value coded CT images. Standardized Uptake Values are calculated by the software for each hypermetabolic region detected in the image. It provides a quantification of size of the lesion, since functional imaging does not provide a precise anatomical estimate of its extent. The CT can be used for that, when the lesion is also visualized in its images (this is not always the case when hypermetabolic lesions are not accompanied by anatomical changes).
FDG doses in quantities sufficient to carry out 4–5 examinations are delivered daily, twice or more per day, by the provider to the diagnostic imaging center.
For uses in image-guided radiation therapy of cancer, special fiducial markers are placed in the patient's body before acquiring the PET-CT images. The slices thus acquired may be transferred digitally to a linear accelerator which is used to perform precise bombardment of the target areas using high energy photons (radiosurgery).
^Raylman, Raymond Robert (1991). Reduction of positron range effects by the application of a magnetic field: For use with positron emission tomography. deepblue.lib.umich.edu (Thesis). hdl:2027.42/128772. Retrieved 2020-11-19.
^Townsend, David W. (2008), "Combined PET/CT: the historical perspective", Semin Ultrasound CT MR, 29 (4): 232–235, doi:10.1053/j.sult.2008.05.006, PMC2777694, PMID 18795489.
^NHS Choices: PET scan. Retrieved 11 November 2016.
External linksedit
Wikimedia Commons has media related to PET-CT.
Human Health Campus, The official website of the International Atomic Energy Agency dedicated to Professionals in Radiation Medicine. This site is managed by the Division of Human Health, Department of Nuclear Sciences and Applications
How PET CT works 2008-05-12 at the Wayback Machine – from Harvard Medical School
PET CT for evaluation of Lung Cancer 2008-02-19 at the Wayback Machine – from Harvard Medical School
Benefits of PET-CT - from Medicai
April 11, 2024
this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, citations, reliable, sources, unsourced, material, challenged, removed, find, sources, news, newspapers, books, scholar, jstor, september, 2014, learn, whe. This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources PET CT news newspapers books scholar JSTOR September 2014 Learn how and when to remove this template message Positron emission tomography computed tomography better known as PET CT or PET CT is a nuclear medicine technique which combines in a single gantry a positron emission tomography PET scanner and an x ray computed tomography CT scanner to acquire sequential images from both devices in the same session which are combined into a single superposed co registered image Thus functional imaging obtained by PET which depicts the spatial distribution of metabolic or biochemical activity in the body can be more precisely aligned or correlated with anatomic imaging obtained by CT scanning Two and three dimensional image reconstruction may be rendered as a function of a common software and control system 1 PET CTA complete body PET CT Fusion imageOPS 301 code3 75PET CT has revolutionized medical diagnosis in many fields by adding precision of anatomic localization to functional imaging which was previously lacking from pure PET imaging For example many diagnostic imaging procedures in oncology surgical planning radiation therapy and cancer staging have been changing rapidly under the influence of PET CT availability and centers have been gradually abandoning conventional PET devices and substituting them by PET CTs Although the combined hybrid device is considerably more expensive it has the advantage of providing both functions as stand alone examinations being in fact two devices in one The only other obstacle to the wider use of PET CT is the difficulty and cost of producing and transporting the radiopharmaceuticals used for PET imaging which are usually extremely short lived For instance the half life of radioactive fluorine 18 18F used to trace glucose metabolism using fluorodeoxyglucose FDG is only two hours Its production requires a very expensive cyclotron as well as a production line for the radiopharmaceuticals At least one PET CT radiopharmaceutical is made on site from a generator Ga 68 from a gallium 68 generator Benefits of PET CT 2 By diagnosing with the help of a PET CT the advantages of the two individual methods are combined and the result considerably exceeds images obtained by the two devices taken separately The method allows identification of all cancerous formations in the body regardless of their size or degree of development The diagnosis time is short the doctor can thus save precious time in the fight with the disease The substance used although it is radioactive presents a very low degree of risk it is naturally eliminated by the body within a maximum of 24 hours after administrationPET MRI like PET CT combines modalities to produce co registered images Contents 1 History 2 Procedure for FDG imaging 3 See also 4 References 5 External linksHistory edit nbsp A CT image B PET image C Coregistered PET and CT images The bright red yellow masses show hypermetabolic areas of the pelvis with metastases of a previous surgically removed colon carcinoma in a 69 yr old woman nbsp Siemens Biograph PET CT scannerThe combination of PET and CT scanners was first suggested by R Raylman in his 1991 Ph D thesis 3 The first PET CT systems were constructed by David Townsend at the University of Geneva and Ronald Nutt at CPS Innovations in Knoxville TN with help from colleagues 4 The first PET CT prototype for clinical evaluation was funded by the NCI and installed at the University of Pittsburgh Medical Center in 1998 The first commercial system reached the market by 2001 and by 2004 over 400 systems had been installed worldwide 5 Procedure for FDG imaging editAn example of how PET CT works in the work up of FDG metabolic mapping follows Before the exam the patient fasts for at least 6 hours 6 On the day of the exam the patient rests lying for a minimum of 15 min in order to quiet down muscular activity which might be interpreted as abnormal metabolism dd dd dd dd dd dd dd dd dd dd An intravenous bolus injection of a dose of recently produced 2 FDG or 3 FDG is made usually by arm vein Dosage ranges from 3 7 to 7 4 megabecquerels 0 1 to 0 2 mCi per kilogram of body weight After one or two hours the patient is placed into the PET CT device usually lying in a supine position with the arms resting at the sides or brought together above the head depending on the main region of interest ROI An automatic bed moves head first into the gantry first obtaining a tomogram also called a scout view or surview which is a kind of whole body flat sagittal section obtained with the X ray tube fixed into the upper position The operator uses the PET CT computer console to identify the patient and examination delimit the caudal and rostral limits of the body scan onto the scout view selects the scanning parameters and starts the image acquisition period which follows without human intervention The patient is automatically moved head first into the CT gantry and the x ray tomogram is acquired Now the patient is automatically moved through the PET gantry which is mounted in parallel with the CT gantry and the PET slices are acquired The patient may now leave the device and the PET CT software starts reconstructing and aligning the PET and CT images A whole body scan which usually is made from mid thighs to the top of the head takes from 5 minutes to 40 minutes depending on the acquisition protocol and technology of the equipment used FDG imaging protocols acquires slices with a thickness of 2 to 3 mm Hypermetabolic lesions are shown as false color coded pixels or voxels onto the gray value coded CT images Standardized Uptake Values are calculated by the software for each hypermetabolic region detected in the image It provides a quantification of size of the lesion since functional imaging does not provide a precise anatomical estimate of its extent The CT can be used for that when the lesion is also visualized in its images this is not always the case when hypermetabolic lesions are not accompanied by anatomical changes FDG doses in quantities sufficient to carry out 4 5 examinations are delivered daily twice or more per day by the provider to the diagnostic imaging center For uses in image guided radiation therapy of cancer special fiducial markers are placed in the patient s body before acquiring the PET CT images The slices thus acquired may be transferred digitally to a linear accelerator which is used to perform precise bombardment of the target areas using high energy photons radiosurgery See also editSingle photon emission computed tomography NeuroimagingReferences edit Shriwastav Ravi Gupta Ravi Kant Mittal Ravi Kumar Rakesh Poudel Sagar Yadav Prakash Chand 2022 01 17 Evaluation of Skeletal and Extra Skeletal Tuberculosis by FDG PET CT with Clinical Correlation doi 10 5281 zenodo 5866467 a href Template Cite journal html title Template Cite journal cite journal a Cite journal requires journal help PET CT Scan Purpose Procedure Benefits Raylman Raymond Robert 1991 Reduction of positron range effects by the application of a magnetic field For use with positron emission tomography deepblue lib umich edu Thesis hdl 2027 42 128772 Retrieved 2020 11 19 Townsend David W 2008 Combined PET CT the historical perspective Semin Ultrasound CT MR 29 4 232 235 doi 10 1053 j sult 2008 05 006 PMC 2777694 PMID 18795489 Kalender Willi Computed Tomography Publicis 2011 pp 79 NHS Choices PET scan Retrieved 11 November 2016 External links edit nbsp Wikimedia Commons has media related to PET CT Human Health Campus The official website of the International Atomic Energy Agency dedicated to Professionals in Radiation Medicine This site is managed by the Division of Human Health Department of Nuclear Sciences and Applications How PET CT works Archived 2008 05 12 at the Wayback Machine from Harvard Medical School PET CT for evaluation of Lung Cancer Archived 2008 02 19 at the Wayback Machine from Harvard Medical School Benefits of PET CT from Medicai Retrieved from https en wikipedia org w index php title PET CT amp oldid 1182252507, wikipedia, wiki, book, books, library,
