imaging in inflammatory diseases and infection

Question 1

Outline the scientific basis of positron emission tomography.

Answer 1

Uses radionuclides which decay by positron decay
Proton-neutron+ positron
Most commonly used radionuclide is Fluoride 18 =110 minute half-life
Gamma rays have a high energy, high frequency- similar to X-rays

Question 2

State the properties of the ideal isotope for labelling.

Problems which might arise

Answer 2

• half-life of isotope should be similar to time of examination
• should easily bind to pharmaceutical element
• Radionuclide should be easily prepared in lab
• Gamma rays are produced as a result of decay
• Different isotopes used for different tissues as different amounts of active cell which will absorb gamma rays.

Problems:

• collimator not picking up all gamma rays
• presence of metal objects
• radiation dose limits
• distance from camera

Question 3

Explain detection of gamma radiation and production of digital image by gamma camera, PET and SPECT.

Answer 3

Gamma camera:
- Patient administered radionuclide usually IV. Radionuclide contains nuclear energy in due to nuclear charge
- Cells absorb the radionuclide and as it decays it will release Gamma rays
-Collimator picks up energy and transforms it into light energy
-Gamma camera converts energy into electrical energy so image can be seen
SPECT:
-rotates around area of interest

Question 4

Have a common dose ‘currency’ with which to compare dose from common Imaging procedures.

Answer 4

Gamma rays usually between 50-300 Kev