Image Perception, Photometry, Visual Physiology, Display Devices

Question 1

The CIE recognized the difference between photopic and scotopic vision. Photopic vision uses:
a) Rods in dim light
b) Cones in bright light
c) Rods and cones equally
d) Peripheral retina only

Answer 1

b) Cones in bright light — Photopic vision is cone-mediated and used for daylight and image interpretation.

Question 2

Scotopic vision is characterized by:
a) Cone activity in bright light
b) Rod activity in dim light
c) Color discrimination
d) High spatial resolution

Answer 2

b) Rod activity in dim light — Scotopic vision is low-light, low-detail vision.

Question 3

The basic unit of photometry is the:
a) Candela
b) Lux
c) Lumen
d) Nit

Answer 3

c) Lumen — The lumen is the fundamental unit describing light output.

Question 4

Luminous intensity decreases according to which law?
a) Cosine law
b) Inverse cube law
c) Inverse square law
d) Linear law

Answer 4

c) Inverse square law — Light intensity decreases with the square of distance.

Question 5

The cosine law is important because it describes:
a) Radiation dose
b) X-ray intensity
c) Luminous intensity relative to viewing angle
d) Image noise

Answer 5

c) Luminous intensity relative to viewing angle — Displays appear brightest when viewed straight on.

Question 6

The best viewing angle for a digital display device is:
a) 45 degrees
b) From below
c) From the side
d) Straight on

Answer 6

d) Straight on — Perpendicular viewing maximizes luminance and contrast.

Question 7

Spatial resolution of a digital display improves with:
a) Lower resolution monitors
b) Higher megapixel displays
c) Increased ambient light
d) Lower luminance

Answer 7

b) Higher megapixel displays — More pixels allow finer image detail.

Question 8

Aperture ratio in LCDs is a measure of:
a) Pixel size
b) Contrast resolution
c) Image luminance
d) Noise

Answer 8

c) Image luminance — Aperture ratio affects brightness.

Question 9

A phosphor is defined as:
a) A light detector
b) A material that emits light when stimulated
c) A charge collector
d) A display pixel

Answer 9

b) A material that emits light when stimulated — Emitted light is called luminescence.

Question 10

An LED emits light when it is:
a) Heated
b) Magnetized
c) Electrically stimulated
d) Exposed to x-rays

Answer 10

c) Electrically stimulated — LEDs produce light via electrical excitation.

Question 11

Modern video monitors are best described as:
a) CRTs
b) Plasma displays
c) LCDs with LED backlighting
d) Film-based displays

Answer 11

c) LCDs with LED backlighting — LEDs replaced older backlight technologies.

Question 12

Preprocessing of digital images is:
a) Operator controlled
b) Largely automatic
c) Performed by the radiologist
d) Performed after interpretation

Answer 12

b) Largely automatic — Preprocessing occurs before image display.

Question 13

Postprocessing of digital images:
a) Is automatic
b) Requires operator manipulation
c) Occurs before acquisition
d) Is not adjustable

Answer 13

b) Requires operator manipulation — Windowing and leveling are postprocessing tasks.

Question 14

Annotation refers to:
a) Image subtraction
b) Contrast adjustment
c) Adding text and labels to an image
d) Image compression

Answer 14

c) Adding text and labels to an image — Helps identify anatomy and clinical details.

Question 15

The primary purpose of image subtraction is to:
a) Reduce noise
b) Reduce dose
c) Enhance image contrast
d) Improve spatial resolution

Answer 15

c) Enhance image contrast — Subtraction removes background structures.

Question 16

Photometry knowledge is essential because:
a) All imaging is analog
b) Digital displays rely on light perception
c) It controls patient dose
d) It determines kVp

Answer 16

b) Digital displays rely on light perception — Proper viewing requires photometric understanding.

Question 17

Ambient light affects digital imaging because it:
a) Improves contrast
b) Has no effect
c) Can degrade display visibility
d) Reduces resolution

Answer 17

c) Can degrade display visibility — Excess ambient light reduces perceived contrast.

Question 18

The principal system for viewing digital images is the:
a) CRT
b) Plasma display
c) Active-matrix LCD
d) Film viewbox

Answer 18

c) Active-matrix LCD — This is the standard clinical display.

Question 19

The brightness of a digital display device is measured as:
a) Illuminance
b) Luminance
c) Exposure
d) Intensity

Answer 19

b) Luminance — Luminance describes emitted brightness.

Question 20

Illuminance refers to:
a) Brightness emitted by a display
b) Intensity of light incident on a surface
c) Image contrast
d) Pixel value

Answer 20

b) Intensity of light incident on a surface — Measured falling onto the display.

Question 21

Which device is used to measure luminance and illuminance?
a) Dosimeter
b) Photometer
c) Densitometer
d) Ion chamber

Answer 21

b) Photometer — Used for display QC measurements.

Question 22

“Two common types of photometers are:
a) Ion and solid-state
b) Near-range