Unit 7 Exam - Image Display

Aspect Ratio

The ratio of width to height of an object; used to describe the shape of the monitor

Spatial Resolution

Ability to distinguish two adjacent details as being separate from each other

Pixel Pitch

Thee distance between the centers of any two adjacent pixels

What is another name for pixel pitch?

Dot pitch

Smaller pixel pitch = _________ spatial resolution

Increased

American College of Radiology (ARC) requires a minimum brightness capability for radiologic display of _______ lumens  

250

Brightness (luminance)

The black level of a display screen

Contrast Resolution

Ability of the display system to distinguish between multiple densities in the radiographic image

What factor determines contrast resolution?

Bit depth

How many phosphors per pixel are in color monitors?

3

How many phosphors per pixel are in monochrome monitors?

1

Color monitors

Uses alternating intensities of red, green and blue to produce the different color variations; monochrome images can be viewed

Monochrome monitors

Color images will appear as shades of gray, produces sharper text and image; has ability to change brightness

Pixel

The smallest element of the matrix or device that can represent all pixel values within the system’s dynamic range

With LCD monitors, a single pixel consists of _____ individual bar-like segments

18

Hardware pixel in monitor

Intersections of flat, transparent wires crossing over each other to form an overall square shape

A dead pixel appears as:

A permanant white spot

If there is more than ____ defective pixels, the monitor needs to be replaced.

15

What color are stuck pixels?

Black

What does LCD stand for?

Liquid Crystal Diodes

Liquid Crystal Diodes (LCD)

Consists of a layer of nematic liquid crystal between two pieces of polarized glass

A LCD requires at least _____ minutes warm up to reach full luminance

15

If all 3 colors (red, green, blue) were set at 0, what color would be seen on a color monitor?

Black

If all 3 colors (red, green, blue) were set at 255, what color would be seen on a color monitor?

White

If red was set at 255 and blue/green were set at 0, what color would be seen on a color monitor?

Red

Polarized Glass

Long chains of iodine molecules; aligned parallel to each other like grid strips in a grid

With perpendicular sheets of glass, all light is _________.

Blocked

Nematic Liquid Crystal

A crystalline arrangement of molecules that have a long linear shape and tend to align parallel to each other

Each junction of flat wire forms a single _________________.

Hardware pixel

When there is no electrical current applied to a pixel within an LCD, the pixel is in an _________ state.

On

“On” State

Scratches on electrode are perpendicular causing the liquid crystals to line up in a spiral pattern that twist 90 deg. between the glass plates; light waves pass through the nematic liquid crystal and follow the spiral

When an electrical charge is being applied, pixel is in an ________ state.

Off

“Off” state

Crystals align to the charge and all point the same direction; light passing through us blocked by second polarizing glass leaving a dark spot on the screen

Without a ____________, an LCD display device will remain black, rendering it unviewable.

Backlight

Type of Backlight

Fluorescent bulbs or LEDs

What is the most common backlight?

LEDs

Each pixel possess its own ______________.

Thin-film transistor (TFT)

What cleaners should not be used on monitors?

Acetone cleaners

What cleaners should be used on monitors?

Water cleaners

Minimum monitor matrix size for an acceptable digital radiograph is a _____________________?

1536 x 2048 (3 MP)

Grayscale Standard Display Function (GSDF)

Allow medical images to be transferred according to the DICOM standard to be displayed on any DICOM-compatible display device with a consistent gray scale appearance

Luminance

The rate of light (brightness) emitted from a source such as an LCD monitor

Maximum Luminance (maximum brightness)

Checked at same monitor setting over a period of time with a photometer

Luminance Response

Monitors ability to accurately display different shades of brightness from a test pattern

Luminance Ratio

Compares maximum luminance to the minimum luminance

Luminance Uniformity

Consistency of a single brightness level displayed across the area of the screen

Luminance Color

Measure to describe the perceived brightness of a color

Luminance Ratio

Luminance Response

ACR and AAPM minimum spatial resolution for electronically displayed images of _______________.

2.5LP/mm

What is a good viewing angle?

120-170 degrees

Ambient Lighting

Light present in an environment from all light sources

What is the #1 cause of degraded display performance in a system?

Ambient lighting

Specular Reflection

Diffuse Reflection

Veil Glare

Unexposed borders around the collimation edges allow excess light to enter the eye

What post-processing eliminates veil glare?

Shuttering or black surround mask

While diagnosis is taking place, the maximum ambient lighting in a reading room should never be more than ___________ lux.

25