positron emission tomography tomography (better known as PET-CT or PET/CT ) is a nuclear medicine technique that combines, in one gantry, positron scanner emission tomography (PET) and computed tomography (CT) computed tomography scanners, to obtain sequential images from both devices in the same session, combined into a single, accompanying image (listed together). Thus, functional imaging obtained by PET, which describes the spatial distribution of metabolic or biochemical activity in the body may be more precisely aligned or correlated with the anatomical imaging obtained by CT scan. Reconstruction of two- and three-dimensional images can be provided as a function of general software and control systems.
PET-CT has revolutionized medical diagnosis in many areas, by adding anatomical localization precision to functional imaging, which was previously less than pure PET imaging. For example, many diagnostic imaging procedures in oncology, surgical planning, radiation therapy and cancer stages have rapidly changed under the influence of PET-CT availability, and centers gradually abandon conventional PET devices and replace them with PET-CT. Although hybrid/hybrid devices are much more expensive, it has the advantage of providing both functions as a stand-alone check, because, in fact, two devices are in one device.
The only other obstacle to the wider use of PET-CT is the difficulty and cost of producing and transporting radiopharmaceuticals used for PET imaging, which is usually very short-lived (eg, half the life of radioactive Fluorine-18 ( 18 F) is used to track glucose metabolism (using fluorodeoxyglucose, FDG) is only two hours.The production requires a very expensive cyclotron and a production line for radiopharmaceuticals.
PET-MRI, like PET-CT, combines the modalities to produce the images listed together.
Video PET-CT
Histori
The PET-CT system was originally proposed by David Townsend (at the University of Geneva at the time) and Ronald Nutt (at CPS Innovations in Knoxville, TN) with help from colleagues. The first PET-CT prototype for clinical evaluation was funded by NCI and installed at the University of Pittsburgh Medical Center in 1998. The first commercial system reached market in 2001, and by 2004, more than 400 systems had been installed worldwide.
Maps PET-CT
Procedure for FDG imaging
Examples of how PET-CT works in the preparation of the FDG metabolism mapping are as follows:
- Before the exam, the patient fasts for at least 6 hours.
- On the day of the exam, the patient rests by lying down for at least 15 minutes, to calm muscle activity, which may be interpreted as abnormal metabolism.
- Injection of intravenous bolus from doses recently produced 2-FDG or 3-FDG is made, usually by a vein in one arm. Doses range 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 a PET-CT device, usually lying in a supine position with a sleeve on the side, or placed overhead, depending on the main area of ​​interest (ROI).
- An automatic bed moves the first head to the gantry, first getting the topogram, also called the scout or surview view, which is a type of intact sagittal part of the body, obtained with a fixed X-ray tube to the top position.
- The operator uses the PET-CT computer console to identify patients and checks, limits caudal and rostral bounds from body scanning to the Scout view, chooses the scanning parameters and starts the image acquisition period, which follows without human intervention.
- The patient automatically moves the first head to the CT gantry, and an x-ray tomogram is obtained.
- Now the patient is automatically transferred via a PET gantry, which is paralleled with a CT gantry, and a PET piece is obtained.
- Patients can now leave the device, and PET-CT software begins reconstructing and aligning PET and CT images.
The whole body scan, which is usually made from the middle thigh to the top of the head, takes 5 minutes to 40 minutes depending on the acquisition protocol and the equipment technology used. The FDG imaging protocol obtains slices of 2 to 3 mm thickness. Hypermetabolic lesions are shown as pixels or voxel-coded false colors to a CT image coded in gray value. Standard Absorption Value is calculated by software for each detected hypermetabolic region in the image. This gives the quantification of the size of the lesion, since functional imaging does not give an accurate estimate of anatomy to what extent. CT can be used for it, when the lesion is also visualized in the picture (this is not always the case when hypermetabolic lesions are not accompanied by anatomic changes).
The dose of FDG in sufficient quantities to perform 4-5 examinations is delivered daily, twice or more per day, by the provider to the diagnostic imaging center.
For use in radiation therapy guided by cancer images, special fiduciary markers are placed in the patient's body before obtaining PET-CT images. The slices obtained can be digitally transferred to the linear accelerator used to carry out the exact bombardment of the target area using high-energy photons (radiosurgery).
See also
- Positron emission tomography
- Nuclear medicine
- Single photon emission Tomography
- Neuroimaging
- Imaging in cancer
References
External links
- Human Health Campus, Official Website of the International Atomic Energy Agency dedicated to Professionals in Radiation Treatment. This site is managed by the Division of Human Health, the Department of Nuclear Science and Applications
- How PET CT works - from Harvard Medical School
- PET CT for Lung Cancer evaluation - from Harvard Medical School
Source of the article : Wikipedia
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