Lecture 21 Flashcards
Radioactive decay
Spontaneous change in the atomic nucleus
Elementary particles and electronic magnetic radiation
Radionuclides
Unstable radioactive nuclei
Alpha decay
The parameters that are changed include mass, charge and energy.
The emission is alpha particles and gamma rays
Beta negative decay (B-)
A neutron in the nucleus is converted into a proton and electron. The parameters changed in this one are mass and energy.
Electron capture
The nucleus captures an electron from the K shell and a proton is converted into a neutron. The parameters changed are charge and energy.
Isometric transition
Transition of the excited nucleus to the ground state. The energy of the nucleus changes and gamma rays are emitted.
Activity A of a radioactive source
A radioactive source is any substance containing radionuclides. Radioactivity A is the average number of decaying nuclei per unit of Time.
A=-dN/dt
Half life
The time taken for the radioactive nuclei of a specific type in the source to decay.
Biological half life
The time taken for the nuclei of one type in the body to decrease to one half of the initial amount due to the excretion from the body.
Radiopharmaceuticals.
Radioactive active chemical compounds introduced into the body for the diagnosis or treatment of the body
Localisation diagnostics
Investigate where accumulation takes place in the body.
Planar nuclear scintigraphy
A radio pharmaceutical is introduced into the body, the detector scans the investigated region and the intensity of the emitted ÿ rays is recorded.
SPECT and PET
For the SPECT the gamma camera rotates around the patient and the data is presented as a 2D or 3D.
Whereas for the PET the substance is introduced into the body and the protons are detected by pairs of detectors on opposite sides of the body.
Radiation therapy
Tumor cells are more sensitive to ionizing radiation than healthy cells and the biological effect depends on the total absorbed dose and the dose distribution over time.
Radiation therapy must provide maximum protection to the surrounding healthy tissue.
