However, it should be mentioned that the tracers often are relatively short-lived and need to be produced on-site (such as fluorine-18 with a half-life of just below 2 hours). The usual way of doing so is to use a cyclotron so, in a sense, the cyclotron is used indirectly to "make positrons" by creating the positron emitters.ZapperZ said:Positrons are produced by tracers (radioactive nuclei) that are injector or digested. These positrons do not come from cyclotrons.
Orodruin said:However, it should be mentioned that the tracers often are relatively short-lived and need to be produced on-site (such as fluorine-18 with a half-life of just below 2 hours). The usual way of doing so is to use a cyclotron so, in a sense, the cyclotron is used indirectly to "make positrons" by creating the positron emitters.
Clearly it would not be viable to have a LHC-size accelerator near every hospital as would be required (again, due to the short half-lives involved). A smaller cyclotron works perfectly well for the purpose.
Which is just what I said. I was essentially tracing down where the OP may have gotten the idea.ZapperZ said:The TRACERS may be produced in an accelerator, but not the POSITRONS for PET scans, which is the premise of the OP in the title.
Zz.
The use of positrons in PET scanners allows for better image resolution and less radiation exposure to the patient. Positrons interact with electrons in the body, producing two gamma rays that can be detected by the scanner. This allows for more precise localization of the radioactive tracer and reduces the risk of radiation damage to healthy tissues.
A cyclotron is a type of particle accelerator that uses a magnetic field to accelerate charged particles. In the case of PET scanners, a cyclotron is used to accelerate protons or deuterons, which are then directed at a target material, such as oxygen-18. This process produces positrons through the decay of the unstable oxygen-18 nucleus.
Oxygen-18 is a commonly used target material in PET scanners because it has a relatively short half-life of 2 minutes, which means it decays quickly and does not remain in the body for an extended period of time. This reduces radiation exposure to the patient and allows for multiple scans to be performed in a shorter amount of time.
The positrons produced by the cyclotron interact with electrons in the body, producing two gamma rays that are emitted in opposite directions. These gamma rays are then detected by a ring of sensitive detectors surrounding the patient. By measuring the timing and location of these gamma rays, the scanner can create a 3D image of the distribution of the radioactive tracer in the body.
The use of a cyclotron in PET scanners does not pose any significant risks to the patient. The levels of radiation exposure are carefully controlled and monitored to ensure the safety of the patient and healthcare professionals. Additionally, the short half-life of the isotopes used in PET scanning means that the radiation exposure is brief and minimal. However, pregnant women and individuals with certain medical conditions may be advised to avoid PET scans as a precaution.