Nuclear medicine Flashcards
1
Q
What is scintigraphy / nuclear medicine?
A
The use of gamma radiation to form images following the injection of various radiopharmaceuticals
2
Q
Why is imaging in nuclear medicine significantly different from X-ray or US imaging?
A
Radiation is emitted in all directions so different imaging techniques are needed to find the distribution of radiation in the body
3
Q
Why is Technetium-99 the most commonly used radionucleotide?
A
- 140 keV gamma produced (90% of the time) which gives a decent probability of interaction with scintillation detector (gamma camera)
- Cheaply made
- 6 hr half life
- Beta emission is negligible to dose
4
Q
Explain the function of a gamma camera to someone who is not a scientist
A
There are four main components to a GC:
- Collimator
- parallel lead tubes to allow only parallel gammas to
scintillator - trade-off between more counts and better spatial localisation
- parallel lead tubes to allow only parallel gammas to
- Scintillator
- eg. zinc sulphide
- gamma on crystal, many PE, CS or PP interactions
- de-excitation of electrons gives many visible photons
- PMTs
- visible light strikes photocathode to give
photoelectrons by PE - large amplifying voltage accelerates and multiplies electrons –> brief current when hitting anode
- visible light strikes photocathode to give
- Computer
- integrates signals from PMTs, processes and displays image
5
Q
What properties make a good radionuclide?
A
- Single gamma emission
- No beta emission
- Suitable half-life (clear image but not high dose)
- Gamma of suitable energy (150 keV is ideal) - not too low so there is absorption and scatter, not too high to penetrate collimator.
6
Q
What are some advantages of nuclear medicine?
A
- High sensitivity
- Physiological (function) and anatomical information can be shown
7
Q
What are some disadvantages of nuclear medicine?
A
- Ionising radiation means dose to patient
- Expensive
- Non-specificity. This is overcome by combining with CT or MRI
