Tuesday, December 12, 2023
Monday, December 11, 2023
Applications of indium-111 antimyosin imaging
Applications of indium-111 antimyosin imaging:
Evaluation of the site, extent and quantitation of the severity of myocardial necrosis.
Myocarditis
Uptake after 1 year post-transplant is associated with an increased rejection rate
Anthracycline treatment - unclear role
Molybdenum breakdown limit for technetium at time of administration mnemonic
See video here https://youtube.com/shorts/kCyJ_AYLQcM
Sunday, December 10, 2023
PET crystals
https://youtube.com/shorts/KrYSxeF0CqA?si=LdTNJd2aJc4FK0mc
LSO/LYSO has small decay time
Allows for improved coincidence timing
Friday, December 8, 2023
Linear no-threshold model in radiation safety
The most conservative theory of radiation is the "linear no-threshold" (LNT) model. According to this model, there is no safe threshold for exposure to ionizing radiation, and any amount of radiation, no matter how small, has the potential to cause harm. The LNT model assumes a linear relationship between radiation dose and the risk of adverse health effects, extending this linear relationship down to zero dose.
In other words, the LNT model suggests that the risk of radiation-induced health effects, such as cancer, increases linearly with increasing radiation dose, and there is no level of radiation exposure considered completely without risk.
Deterministic vs Stochastic effects
Deterministic effects (or tissue reactions) of ionizing radiation are related directly to the absorbed radiation dose and the severity of the effect increases as the dose increases.
Example: Cataracts
Mnemonic: DDD Deterministic severity Determined by Dose
Stochastic effects of ionizing radiation are chance events, with the probability of the effect increasing with dose, but the severity of the effect is independent of the dose received. Stochastic effects are assumed to have no threshold.
Example: Cancer
Mnemonic:
Stochastic Severity No
Probability So
Stannous ions in equilibrium radionuclide angiocardiography
A small amount of stannous chloride (SnCl2) is added to a vial containing a radiopharmaceutical precursor, such as pertechnetate (TcO4^-).
The stannous ions act as a reducing agent, converting TcO4^- to a reduced form of technetium (Tc-99m).
The radiotracer, now in the form of Tc-99m, can be easily incorporated into red blood cells or other carriers.
Technetium gamma decay is an example of isomeric transition
Technetium-99m (Tc-99m) undergoes a type of nuclear decay known as an isomeric transition when it emits gamma radiation. Specifically, Tc-99m undergoes an isomeric transition to its more stable state, technetium-99 (Tc-99), through the emission of gamma rays.
The isomeric transition involves a change in the nuclear energy state of the atom without a change in its chemical properties. In the case of Tc-99m, the metastable state (m) refers to a higher-energy state with a relatively short half-life, and the isomeric transition involves the release of a gamma-ray photon as the nucleus transitions to a lower-energy state.
The gamma rays emitted during the isomeric transition of Tc-99m are of diagnostic interest in nuclear medicine. Tc-99m is widely used as a radiopharmaceutical in various medical imaging procedures, including single-photon emission computed tomography (SPECT). The emitted gamma rays are detected by gamma cameras to create images that provide valuable diagnostic information about the structure and function of organs and tissues in the body.
Photolectric effect and Compton scatter
In the Compton effect, a photon interacts with an outer shell electron, resulting in the ejection of the electron and a scattered photon with reduced energy.
Compton scatter is a significant contributor to image noise. It can result in scattered photons reaching the detector and degrading image contrast.
Compton scatter is more likely to occur with higher-energy photons, such as those around 140 keV.
The photoelectric effect is more pronounced at lower energies and is characterized by the complete absorption of a photon by an inner-shell electron, leading to the ejection of the electron.
The Photoelectric Effect is particularly important in medical imaging applications using low-energy X-rays, where it contributes to contrast in radiographic images.
Mnemonic: Compton is with COmpletely More energy PhoTONs (Compton scatter is more likely to occur with higher-energy photon)
photoeLEctric absorbs aLL Lower Energies
Sunday, December 3, 2023
Inaccurate camera settings, incorrect photopeak, flood field
Inaccurate camera settings, incorrect photopeak, flood field for nuclear boards
The pulse height analyzer (PHA) measures in-coming signals and enables signals of a specific energy range ("window") to be recorded while excluding all other signals.
If the window set slightly below the photopeak, the honey comb artifact with "hot" spots over each photomultiplier tube is characteristic.
Friday, December 1, 2023
BGO mnemonic for nuclear medicine boards
See YouTube video here https://youtu.be/JTpj76zUS0I?si=zNhY9zkG3_55XVU1
Nuclear medicine practive question: Inverse square law
A vial containing 32 millicuries is emitting radiation at a rate of 1 roentgen per hour at a distance of 1 meter. If a technologist stands at a distance of 2 meters from the vial, how much radiation (in roentgens) does the technologist receive during a 15-minute period?
Radiation safety in pregnancy
United States Nuclear Regulation Commission (USNRC) also recommends total fetus exposure during pregnancy to be less than 5.0 mSv (500 mrem). The fetus radiation dose below 50 mGy is considered safe and not cause any harm.
See YouTube video https://youtu.be/ajPn17iT0aE?si=2Uz1dZIwfpoIeRjM
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