Section 7

Question 1

Gamma rays and xrays are both

Answer 1

high energy electromagnetic radiation (photons)

Question 2

What is the difference between xrays and gamma rays?

Answer 2

Xrays produced by electrons in atoms
Gamma produced by nucleus

Question 3

What are parallels of DR & NM?

Answer 3

Detecting nonvisible radiation; see visible structures in body & give diagnostic info abt patients

Question 4

How is NM different from DR?

Answer 4

NM has source in the patient and uses gamma rays

Question 5

Xrays are an __ source and show __

Answer 5

External source and show anatomy

Question 6

Gamma rays are ___ source and show ___

Answer 6

Internal source and show biofunctionality

Question 7

What is the most common isotope used in NM procedures?

Answer 7

Technicium 99

Question 8

Gamma energy is determined by

Answer 8

the radioisotope, as the energy of the decay is the same - there is no kVp adjustment

Question 9

Radiopharmaceutical is a

Answer 9

radioactive isotope attached to a pharmaceutical molecule

Question 10

Why do we need a detector for gamma rays?

Answer 10

To measure how much gamma radiation; spatial position of source & energy of the radiation

Question 11

Since gamma rays cannot be switched of, what factors must we consider?

Answer 11

• Low Dose Rate
• Small signals from scintillator

Question 12

Photomultiplier tube uses

Answer 12

photoelectric effect to turn light into electrical signal

Question 13

Describe the key properties of NM detectors

Answer 13

PMT, PMT correlation and scintillator

Question 14

Describe the gamma camera

Answer 14

Detect scintillations (flashes of light) produced when gamma rays, resulting from radioactive decay of single photon emitting radioisotopes, interact with a sodium iodide crystal at the front of the camera.

Collimator acts as a lens for our camera - enables the parallel rays to be detected and non-parallel rays to be absorbed

Question 15

Describe the PMT correlation

Answer 15

1. Gamma rays hit the scintillator
2. Multiple visible photons are produced
3. Nearby PMT get high signal and distant PMT have a weak signal
4. SPL works out where gamma rays hits scintillator

Question 16

SPL =

Answer 16

Spatial Position Logic

Question 17

A collimator enables the

Answer 17

gamma source location to be determined

Question 18

What are the collimator walls called?

Answer 18

Septa and are thin as possible to minimise absorption

Question 19

Small Collimator holes =

Answer 19

High resolution

Question 20

Large collimator holes=

Answer 20

Low resolution

Question 21

Larger septa depth =

Answer 21

High resolution

Question 22

Smaller septa depth =

Answer 22

Low resolution

Question 23

Increase in resolution means __ sensitivity?

Answer 23

decrease in sensitivity

Question 24

Pulse Height Analysis is where

Answer 24

we reject scattered photons

Question 25

What are the deteriments of image quality?

Answer 25

- Spatial resolution - Contrast resolution -Sensitivity - Motion

Question 26

Spatial resolution

Answer 26

Better SR means finer details of an object but we have low dose rate and have a short scan time

Question 27

Contrast in NM comes from

Answer 27

functional distribution of radioactive material

Question 28

Detection of scattered radiation

Answer 28

may decrease contrast - use PHA for energy discrimination

Question 29

Sensitivity is how

Answer 29

much radioactivity required for the production of an image - expressed in keps/MBq

Question 30

Decrease in sensitivity =

Answer 30

increase in radioactivity and dose

Question 31

Gating (switching) can be used

Answer 31

to measure only at specific points in a cycle

Question 32

SPL measures

Answer 32

where the gamma ray hit the scintillator/detector

Question 33

What does the height of the PMT pulse indicate?

Answer 33

Greater the height indicates how close gamma absorption was

Question 34

PMT detects

Answer 34

gamma rays

Question 34

PMT correlation works out

Answer 34

where they hit the detector

Question 35

Collimator works out

Answer 35

which direction gamma rays came from and we make sure they came in a straight line