crdr finals 1 Flashcards by demure u

What is the science of the response of the human eye to visible light?

photometry

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What are photopic and scotopic visions?

Photopic - Bright light vision with cones (peak at 555 nm).

Scotopic - Dim light vision with rods (peak at 505 nm).

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What is the basic unit of photometry?

Lumen

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What organization made the first attempt to quantify human vision in 1924?

Commission Internationale de l’Éclairage (CIE)

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What is the total intensity of light from a source?

luminous flux (lux)

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What describes the intensity of light incident on a surface?

illuminance

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fc = foot candle
cd = candela
lux = luminous flux

meanings teh

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One lumen of luminous flux incident on a single square is a fc

1 fc = 10.8 lux

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What is a property of the source of light, such as a viewbox or a digital display device?

luminance intensity

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luminance intensity is measured in?

lumens/steradian or cd

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What is a quantity that is similar to luminance intensity; another measure of the brightness of a source?

luminance

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luminance is expressed in?

candela per square meter (nit)

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MERONG 2 TABLE DINE ATI

BASAHI NAT D BUMAGSAK

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What are the two fundamental laws of photometry?

*inverse square law
*cosine law

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This is when luminous intensity decreases in proportion to the inverse square of the distance from the source

inverse square law

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This is important when one is describing the luminous intensity of a digital display device

cosine law

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What does “hard copy” mean in medical imaging?

Images presented on film and interpreted on a lighted viewbox

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Until when were most medical images hard copy?

Until the mid-1990s

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What were the first widespread digital medical images?

CT (1974) and MRI (1980)

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How were early CT and MRI images usually interpreted?

film placed on a lighted viewbox

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What devices are used for soft copy viewing?

Digital cathode ray tube (CRT) or active matrix liquid crystal display (AMLCD).

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What are the properties of liquid crystal materials?

Highly ordered molecular structure (like a crystal) and viscosity (like a fluid)

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What type of molecules are liquid crystals?

Linear organic molecules that are electrically charged, forming a natural molecular dipole.

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How are liquid crystals aligned?

Through the action of an external electric field

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How are active matrix liquid crystal displays (AMLCDs) fashioned?

Pixel by pixel

What controls the intensity and color of light in an AMLCD pixel?

Light-polarizing filters and films

How do color and monochrome AMLCDs differ?

*Color AMLCDs use red-green-blue (RGB) filters within subpixels. *Medical flat panel displays are monochrome.

How are medical flat panel digital display devices identified?

By the number of pixels = 1-megapixel = 1000×1000 pixels = 5-megapixel = 2000×2500 pixels)

What is the portion of the pixel face that is available to transmit light. It is a measure of image luminance of AMLCDs?

aperture ratio

What is the efficiency of AMLCDs in transmitting backlight?

About 10% through a monochrome monitor and about 5% through a color monitor.

What causes inefficiency in AMLCDs?

Light absorption in filters and polarizers, and pixel obstruction by the TFT and bus lines

What does "active" mean in AMLCD?

Each pixel can be individually controlled (active read)

What does "passive" mean in AMLCD?

nature of reading a digital image receptor line by line (passive read)

How do AMLCDs handle ambient light?

They are designed to better reduce the influence of ambient light on image contrast

This is designed to produce artifact free digital images.

pre-processing

What is the act of matching a worker to the work environment for maximum efficiency?

ergonomics

What is a principal disadvantage of an AMLCD?

Angular dependence of viewing

What is a major advantage of digital radiographic imaging over screen-film imaging?

The ability to manipulate the image before (pre-processing) and after (post-processing) display

this provides electronic calibration to reduce pixel-to-pixel, row-to-row, and column-to-column response differences.

pre-processing

Is pre-processing manual or automatic?

automatic

What are offset images and gain images?

Offset images - Calibration images generated many times a day. Gain images - Calibration images generated every few months.

This is the pre-processing calibration techniques that make the image receptor response uniform

flat-fielding

What technique is used to reduce noise and improve contrast?

Averaging techniques

What is the residual latent image from a previous exposure that can interfere with new images?

image lag

How are defective pixels corrected?

signal interpolation

How is image lag corrected?

application of offset voltage

What causes trouble when switching from high-dose to low-dose imaging?

Image lag

What is the voltage variations along pixel buses causing linear artifacts?

line noise

How is line noise corrected?

application of voltage correction

This refers to anything that can be done to a digital radiographic image after it is acquired by the imaging system

post-processing

This is performed to optimize the appearance of the image for the purpose of better detecting pathology

post-processing

What is the process of adding text to an image; helpful in informing the clinician about anatomy and diagnosis?

annotation

What is used To make all 65,536 shades of gray visible and amplify image contrast?

window and level

What is used to render the smallest detail visible?

magnification

What is used to bring images into standard viewing order?

image flip

What is used to reverse the contrast: bone appears black, and soft tissue appears white to highlight pathology?

image inversion

What causes misregistration in subtraction imaging?

Patient movement during serial image acquisition

What is used to correct misregistration of an image?

pixel shift

What is used to determine average pixel value for use in quantitive imaging?

region of interest (ROI)

In what areas is quantitative radiology applied?

Bone mineral assay calcified lung nodule detection renal stone identification

What is effective for fractures and small, high-contrast tissues?

edge enhancement

What is used in identifying diffuse, non-focal disease?

highlighting

What allows careful visualization of precise regions of an image?

pan, scroll, zoom

What percentage of medical images today are digitally acquired?

Up to 90%

What enables acquisition, interpretation, and storage of medical images digitally without film?

PACS

Picture Archiving and Communication System

4 principal components of PACS

*Image acquisition system *Display system *Network *Storage system

What is required for quick and easy interaction between imaging systems and PACS?

A microprocessor-controlled workstation connected through a network

What is the process of remote transmission and viewing of images?

teleradiology

What standard ensures compatibility between different imaging systems?

DICOM

Digital Imaging and Communications in Medicine

What replaces a traditional film file room in PACS?

Magnetic or optical memory devices

How much data can optical discs hold?

Tens of gigabytes (GB); when stored in a "jukebox," terabytes (TB)

How fast can images be recalled from PACS storage?

seconds

Where is backup storage typically located?

Offsite at a digital data storage vendor

How does PACS improve imaging efficiency?

By reducing the workflow chart and speeding up image processing, interpretation, and recall