Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
25 Cards in this Set
- Front
- Back
|
What is the energy range that is used to be picked up by GC? |
80 - 400 KeV |
|
|
What is GC made out of? |
collimator Thallium-activated NaI crystal Light guide PMT Electronics (position circuit, summation circuit, pulse height analyser, image display/processing units) |
|
|
What are the gamma rays converted to in GC? |
To light photons and then to electrical impulses. |
|
|
Gamma rays are scattered from the patient's body. Which angle of the rays will be picked by the GC for imaging? |
right-angled |
|
|
What is the function of the collimator? |
To filter out scattered (non-perpendicular ) gamma rays and allow only perpendicular rays to pass through. |
|
|
What is scintillator crystal made out of? |
Thallium-activated NaI (Sodium Iodide) |
|
|
What is the function of PMT? |
To convert light photon into electrical impulses and amplify it. |
|
|
The total signal produced by the PMT is proportional to what? |
gamma ray energy |
|
|
What color of light is produced by the scintillator crystal? |
green |
|
|
3 purposed selection of collimator |
Organ size in relation to the crystals diameter crystal thickness required resolution/efficiency |
|
|
2 types of collimator |
Pin hole and multi holes |
|
|
3 types of multi holes collimator |
Converging, diverging, parallel |
|
|
As septa thickness increases, the resolution ?, efficiency? |
Resolution increase, efficiency decrease |
|
|
As collimator is placed further away from patient, the resolution? |
decreases |
|
|
What are the properties of pin hole collimator? Aperture size Image cone length and resolution sites |
aperture 20- 25 cm at pinhole image is inverted and magnified cone length increase, resolution decrease Used for thyroid and small area imaging |
|
|
Diverging collimator, size of converging point image organs |
40 - 50 cm behind the collimator minified, useful area become larger used on large organs |
|
|
Converging collimator, Size of converging point Image Site |
40 - 50 cm in front of collimator Magnifed, not inverted Paediatric cases and small organs |
|
|
What is the standard thickness and diameter for NaI crystal |
1.25 cm, 30 to 50 cm diameter |
|
|
lower crystal thickness, ? intrinsic resolution, ? intrinsic efficiency |
better, lower |
|
|
3 disadvantages of NaI crystal |
hygroscopic fragile large crystals are difficult to grow |
|
|
What is the atomic number of NaI |
3.67 g/cm^3, dense |
|
|
What is the electrical supply for PMT? |
1200 V |
|
|
What is the purpose of magnetic shielding in the PMT? |
To prevent defocusing of electron beam |
|
|
The intensity of light scintillation is ? to the kinetic energy of the electron. |
proportional |
|
|
How many dynodes are typically found in PMT? |
10 |
