Nuclear medicine Flashcards
What is β- decay and what happens to the atomic number and mass number of the nucleus undergoing this decay?
β- decay is a type of radioactive decay where an unstable, neutron-rich nucleus transforms a neutron into a proton, emitting an electron (beta particle) and an electron antineutrino. The atomic number increases by one while the mass number remains unchanged.
Explain β+ decay and its impact on the atomic number and mass number of the nucleus.
β+ decay is a radioactive decay where a proton-rich nucleus transforms a proton into a neutron, emitting a positron (antimatter counterpart of an electron) and an electron neutrino. The atomic number decreases by one while the mass number remains unchanged.
Electron Capture
This process reduces the atomic number by one while the mass number remains unchanged.
Excess energy release from β decay:
Excess energy from β decay can be released through either Isomeric Transition or Gamma Emission.
Isomeric Transition involves decay to an excited metastable state followed by emission of a gamma photon, while Gamma Emission directly transitions the nucleus from an excited state to a lower energy state.
Mathematical relationship for decay rate
The decay rate of an isotope is described by the exponential decay equation: A = A0 * e^(-λt).
This equation is related to the half-life, given by T1/2 = ln(2) / λ, which is the time required to reduce the activity by one-half.
Appropriate half-life
The radioisotope’s half-life should match the intended application. Shorter half-lives are preferred for medical imaging to minimize patient exposure, while longer half-lives are necessary for radiometric dating of ancient events.
Type of emitted radiation
The emitted radiation type (alpha, beta, or gamma) determines the radioisotope’s suitability for specific applications. Gamma emitters are ideal for imaging and non-destructive testing due to their high penetrating power, while alpha or beta emitters are used in targeted radiation therapy for cancer treatment.
Chemical properties
The radioisotope should possess chemical properties that enable it to react, bond, or accumulate in the desired target or system. This is crucial for tracer studies or targeted medical treatments.
Availability
A useful radioisotope should be readily available or producible in sufficient quantities for the intended application. Production often occurs in nuclear reactors or particle accelerators.
Detection
The emitted radiation should be easily detectable and measurable with standard equipment, enabling accurate quantification or visualization of the radioisotope’s behavior.
What is gamma imaging, and what is its primary purpose in medical diagnostics?
non-invasive diagnostic technique in nuclear medicine.
It aims to obtain detailed images of the body’s internal structures and functions using radioisotopes emitting gamma radiation, which can be detected by specialized equipment.
Describe the process involved in gamma imaging, including the role of radiopharmaceuticals.
A patient receives a small amount of a radiopharmaceutical, a decaying isotope chemically bound to target nuclides.
The radiopharmaceutical targets specific tissues or organs, accumulates there, and emits gamma photons.
A gamma camera detects these emitted gamma photons, processing the signals to create a two-dimensional image (scintigram) depicting the distribution and concentration of the radiopharmaceutical within the body.
What components make up a gamma camera, and what are their functions?
A gamma camera consists of a collimator, a scintillation crystal, and photomultiplier tubes.
The collimator shields and guides gamma photons emitted from the patient’s body to ensure only linearly traveling photons reach the scintillation crystal, enhancing image precision.
The scintillation crystal converts incoming gamma photon energy into visible light, enabling detection and measurement of the radiation.
how to improve the gamma camera signal?
centroiding
energy scatter rejection
What role do photomultiplier tubes (PMTs) play in gamma imaging, and what are their main components?
PMTs are highly sensitive light detectors that convert light photons emitted by the scintillation crystal into electrical signals for image creation.
A PMT comprises three main components: the photocathode, the electron multiplier, and the anode.
