Section 4&5

Question 1

What are the 3 components of visual perception?

Answer 1

Detection, recognition, interpretation

Question 2

What is the structure of truth table

Answer 2

positive negative, true diagonal and false diagonal

Question 2

Sensitivity

Answer 2

true positive = # pt diag/disease present (TP + FN)

Question 2

Specificity

Answer 2

true negative = # pt correctly identified as no disease//# without the disease

Question 3

Accuracy

Answer 3

correct diagnosis of disease present in patients (TN + TP) //total

Question 4

Prevalence

Answer 4

patients with disease present -TP + FN// total

Question 5

What are the components of instrument?

Answer 5

source, medium, filter, detector, signal processing

Question 6

Current =

Answer 6

amount of charge flowing at a point per unit time

Question 7

Voltage =

Answer 7

energy difference between 2 points

Question 8

Fundamental idea in Band theory

Answer 8

Photon absorption provides energy to electrons to be excited. This causes the electron to sit in the conduction band. As it de-excites, it emits a photon to fall into valence band

Question 9

Scintillation –>

Answer 9

radiation into light

Question 10

Detectors have 3 factors

Answer 10

Intrinsic efficiency/sensitivity
dead time
energy discrimination

Question 11

Intrinsic efficiency (sensitivity)

Answer 11

photons detected//#photons incident to detector

• faster image & reduced dose

Question 12

Dead time is

Answer 12

the amount of time for the detector to record an event and resent ready for next event

Question 13

Paralysable

Answer 13

event is missed so the detector restarts dead time after every miss - very saturated fast - slows/paralyses its measurements

Question 14

Non-paralysable

Answer 14

does not extend its time - just misses event and keeps going - higher rates can be measured

Question 15

Energy discrimination is

Answer 15

the ability to distinguish photons of different energies - measured at full width at half maximum

Question 16

Energy discrimination in detectors helps with

Answer 16

filtering out low scattered radiation

Question 17

In scintillation detector, photomultiplier tube is

Answer 17

responsible for converting light into electrical signals

Question 18

In scintillation detector, crystal density affects

Answer 18

the ability to convert radiation, as more interactions occur frequently and more light is produced - probability is higher and efficiency is increased