Rad 122: Unit 1 (Part 1 and 2)

What is digital imaging?

The acquisition and display of radiographic images using a computer instead of film.

What does digital imaging use instead of film?

A computer and digital detector.

What type of signal did film-screen imaging use?

Analog signals.

What type of data does digital imaging use?

Digital data.

What is binary code?

Computer language made of 0s and 1s.

What does a 1 represent in binary code?

Signal on.

What does a 0 represent in binary code?

Signal off.

What is the smallest unit of computer information?

A bit.

What is computer hardware?

The physical parts of the computer.

What is the CPU?

The central processing unit, or brain of the computer.

What does RAM stand for?

Random Access Memory.

What is RAM?

Temporary working memory.

What does ROM stand for?

Read Only Memory.

What is ROM?

Permanent memory that stores instructions.

What is an input device?

A device used to enter information into the computer.

What are examples of input devices?

Keyboard and mouse.

What is an output device?

A device that displays or produces information.

What are examples of output devices?

Monitor and printer.

What is application software?

Software used for a specific task.

What is system software?

Software that helps run the computer.

What is an operating system?

The software that controls computer functions.

What does PACS stand for?

Picture Archiving and Communication System.

What is PACS used for?

Storing, retrieving, and sending medical images.

What does RIS stand for?

Radiology Information System.

What does HIS stand for?

Hospital Information System.

What is teleradiology?

Sending radiographic images electronically to another location.

What does LAN stand for?

Local Area Network.

What does WAN stand for?

Wide Area Network.

In film-screen imaging, what did overexposure look like?

Black film.

In film-screen imaging, what did underexposure look like?

White film.

In digital imaging, why can overexposure be harder to recognize?

The computer can adjust brightness and make the image look acceptable.

What is one visible clue of underexposure in digital imaging?

Quantum mottle or noise.

In film-screen imaging, were acquisition and display coupled together?

Yes.

In digital imaging, are acquisition and display coupled together?

No.

What old film-screen term is no longer used for digital image blackening?

Density.

What term replaces density in digital imaging?

Brightness.

What is brightness?

The luminance or lightness of an area displayed on a monitor.

What determines pixel brightness?

The pixel value assigned by the computer.

What does each pixel brightness level show?

A shade of gray, black, or white.

What is image contrast?

The difference between brightness levels in adjacent areas.

What is digital image contrast controlled by?

Exposure factors, subject contrast, software, and hardware.

What software tool mainly controls digital contrast?

The LUT.

What does LUT stand for?

Look-Up Table.

What does the LUT do?

It changes pixel values and controls grayscale or contrast.

What is a processing algorithm?

A computer formula or set of rules used to process an image.

What is window width?

The range of gray shades displayed.

What happens with a wide window width?

More gray shades and lower contrast.

What happens with a narrow window width?

Fewer gray shades and higher contrast.

What is subject contrast?

The difference in x-ray attenuation between tissues.

What creates subject contrast?

Different tissues absorbing x-rays differently.

What interaction mainly contributes to subject contrast?

Photoelectric interaction.

What is the latent image?

The invisible image before computer processing.

What beam carries subject contrast to the detector?

The remnant beam.

What are the 3 factors that determine latent image quality?

Receptor exposure, geometric variables, and subject contrast.

What is receptor exposure?

The amount of radiation that reaches the image receptor.

What are geometric variables?

SID, OID, focal spot size, motion, and alignment.

What is dynamic range?

The range of exposures or pixel values the system can capture or display.

What is exposure latitude?

The range of techniques that produce an acceptable image.

Which has a wider dynamic range: film-screen or digital?

Digital.

Which has a wider exposure latitude: film-screen or digital?

Digital.

What does wide exposure latitude mean?

There is a larger margin of error in technique.

What is dose creep?

Gradual increase in patient exposure because digital images may still look acceptable when overexposed.

Why can digital imaging lead to dose creep?

Because overexposed images may not look too dark or black.

Does more dynamic range automatically mean more image contrast?

No.

What does more dynamic range give the system?

More exposure values or gray levels to work with.

What can more dynamic range improve?

Contrast resolution.

What is contrast resolution?

The ability to see small differences between similar tissues.

Does digital imaging have better contrast resolution than film-screen?

Yes.

Does digital imaging have better spatial resolution than film-screen?

No.

What is one advantage of digital imaging?

Wide dynamic range.

What is another advantage of digital imaging?

Superior contrast resolution.

What is one disadvantage of digital imaging?

Lower spatial resolution compared to film-screen.

What is another disadvantage of digital imaging?

Image quality depends on hardware and software.

What is speed class?

The image system's sensitivity to radiation.

What does a higher speed class mean?

Less radiation is needed for an adequate signal.

What is an exposure indicator?

A number that shows how much exposure reached the image receptor.

What are 3 exposure indicator types?

S-number, EI, and DI.

What does EI stand for?

Exposure Index.

What does DI stand for?

Deviation Index.

What relationship does S-number have with receptor exposure?

Inverse relationship.

If S-number increases, what happened to receptor exposure?

Receptor exposure decreased.

If S-number decreases, what happened to receptor exposure?

Receptor exposure increased.

If S-number doubles from 200 to 400, what happened to exposure?

Exposure decreased by half.

How do you lower the S-number by half?

Double the mAs.

What relationship does EI have with receptor exposure?

Direct relationship.

If EI increases, what happened to receptor exposure?

Receptor exposure increased.

If EI decreases, what happened to receptor exposure?

Receptor exposure decreased.

For EI systems, what does a 300-point increase usually mean?

Exposure doubled.

For EI systems, what does a 300-point decrease usually mean?

Exposure was cut in half.

What is the primary controller of receptor exposure?

mAs.

What does kVp mainly control?

Beam quality and penetration.

What does mAs mainly control?

Receptor exposure.

Can brightness alone prove correct exposure in digital imaging?

No.

What should you check to evaluate exposure in digital imaging?

The exposure indicator.

What is a histogram?

A graph of pixel values in an image.

What is a stored histogram?

The expected histogram for a selected anatomy or projection.

What is an input histogram?

The histogram created from the raw image data.

What creates the input histogram?

Raw data from the image receptor.

What does the computer compare the input histogram to?

The stored histogram.

What is preprocessing?

Computer processing before the image is displayed.