Digital imaging ch. 8

What year was digital radiography introduced?

1987.

Is digital radiography now more or less common than traditional film?

More common than film.

What are the two types of digital imaging?

Direct digital imaging and indirect digital imaging.

What are the main benefits of digital radiography?

Less radiation, immediate images, use during procedures to see progress, easy storage and sharing, and image manipulation.

Why can digital imaging be useful during dental procedures?

It allows images to be viewed during procedures to see progress.

What is an analog image?

A radiographic image produced on traditional film with continuous shades of gray that blend together.

What type of medium produces an analog radiographic image?

Traditional film.

How are the shades of gray arranged in an analog image?

They are continuous and blend together.

What is a pixel?

A digital unit of information; a small box that holds an electronic charge caused by photons.

How many shades of gray can an individual pixel have?

One shade of gray.

What is a digital image?

A picture composed of many pixels.

What analogy do the slides use to describe a digital image?

A mosaic.

What does digitize mean?

To convert an image into digital information so a computer can process it.

What is bit-depth?

The number of gray-scale combinations possible in an image.

How is digital information transmitted and stored?

As combinations of 0s and 1s called bits.

How many possible colors does a 1 bit-depth image have?

2.

What are the two possible colors in a 1 bit-depth image?

White and black.

In a 1 bit-depth image, what does 0 represent?

White.

In a 1 bit-depth image, what does 1 represent?

Black.

What equation determines the number of possible shades from bit-depth?

2 raised to the power of the bit-depth.

How many possible shades does a 1 bit-depth image have?

2¹ = 2 shades.

How many possible shades does an 8 bit-depth image have?

2⁸ = 256 shades.

What is the first step in the basic digital imaging process?

The sensor is placed in the mouth.

What happens after the sensor is placed in the mouth?

Photons strike the sensor.

What happens when photons strike the sensor?

Electronic information is digitally recorded.

What does the sensor do with the digitally recorded information?

It transmits the information to the computer.

What happens after the information reaches the computer?

Computer software stores the image electronically.

What are the basic steps of digital imaging in order?

Sensor placed in mouth → photons strike sensor → electronic information is digitally recorded → sensor transmits information to computer → software stores image electronically.

What is direct digital imaging?

Digital imaging in which a sensor is used instead of film.

What replaces traditional film in direct digital imaging?

A sensor.

How is image information transferred to the computer during direct digital imaging?

A fiberoptic cable transfers the information directly to the computer.

What are the two sensor types listed for direct digital imaging?

CCD and CMOS/APS.

What does CCD stand for?

Charge-Coupled Device.

What is a CCD?

A solid-state detector used in devices such as fax machines, scanners, and digital cameras.

What does a CCD do with photons?

It processes photons and stores the information in pixels.

What analogy do the slides use to explain how a CCD works?

Like opening your eyes for a second and recording everything you saw.

Which sensor has the lowest "noise" according to the slides?

CCD.

What is a disadvantage of manufacturing CCD sensors?

They are expensive to manufacture.

According to the slides, what is the most common type of sensor?

CCD.

What does CMOS/APS stand for?

Complementary Metal Oxide Semiconductor/Active Pixel Sensor.

How is CMOS/APS similar to CCD?

It performs a similar function but is smaller and requires less power.

How does CMOS/APS differ from CCD?

They differ in how the pixels are read.

Which sensor requires less power, CCD or CMOS/APS?

CMOS/APS.

Which sensor is smaller in size according to the slides?

CMOS/APS.

What resolution advantage do CMOS/APS manufacturers claim?

25% better resolution than CCD because of the APS component.

What are examples of CMOS/APS systems listed in the slides?

Dexis, Schick, and SuniRay.

What equipment is required for direct digital imaging?

A computer with software, x-radiation source, intraoral sensor, receptor holders, and infection-control barriers.

What is the purpose of the computer in direct digital imaging?

It digitizes, processes, and stores information received from the sensor.

What does the computer convert electronic charges in sensor pixels into?

Shades of gray.

How quickly can a digital image be recorded on a computer monitor according to the slides?

0.5 to 120 seconds.

What image capabilities can the computer provide?

Split screen, magnification, and image manipulation.

What is used as the x-radiation source for digital radiography?

A conventional dental x-ray unit.

Why must the x-ray unit timer be adapted for digital imaging?

To allow exposures in a time frame of 1/100 of a second.

What exposure time frame is needed for digital imaging according to the slides?

1/100 of a second.

How is traditional film exposure measured according to the slides?

In impulses of 1/60 of a second.

Are typical digital sensors more or less sensitive to x-rays than conventional film?

More sensitive.

What does the greater sensitivity of digital sensors mean for patients?

Less radiation exposure.

According to the slides, what radiation reduction is associated with D-speed film comparison?

80% radiation reduction.

According to the slides, what radiation reduction is associated with F-speed film comparison?

20% radiation reduction.

What is indirect digital imaging?

Digital imaging performed by scanning traditional radiographs or using storage phosphor imaging.

What are the two methods of indirect digital imaging listed in the slides?

Scanning radiographs and storage phosphor imaging.

How can a traditional radiograph be digitized during indirect imaging?

A CCD camera scans and digitizes the traditional radiograph.

What analogy is used for scanning a traditional radiograph?

It is similar to scanning a photograph.

What is storage phosphor imaging described as?

A hybrid of film and digital sensors.

What does PSP stand for?

Photo-stimulable phosphor.

What are other names for storage phosphor imaging?

Photo-stimulable phosphor (PSP) imaging or phosphor plate imaging.

What type of image plates does storage phosphor imaging use?

Thin, reusable, wireless image plates.

Are storage phosphor plates wired or wireless?

Wireless.

How do storage phosphor plates compare physically with traditional film?

They are as thin and flexible as traditional film.

What does the phosphor coating on a PSP plate do?

It converts photons into light and energizes the phosphor.

How is the information on a PSP plate transferred to the computer?

A special scanner reads the plate and sends the image to the computer.

What happens to PSP plates before they are reused?

They are erased using a light box through processing.

Can PSP plates be reused?

Yes.

What is the major difference between direct digital imaging and PSP indirect imaging?

Direct imaging transfers information directly from a sensor to the computer, while PSP uses a plate that must be scanned.

Which digital imaging method uses a fiberoptic cable?

Direct digital imaging.

Which digital imaging method uses thin, flexible, wireless plates?

Storage phosphor (PSP) indirect imaging.

Which digital imaging method requires a special scanner to read the receptor?

Storage phosphor (PSP) imaging.

Which imaging method uses a sensor instead of film?

Direct digital imaging.

Which method is described as a hybrid between film and digital sensors?

Storage phosphor imaging.

What is digital subtraction?

A method of reversing the gray scale as an image is viewed.

What can digital subtraction eliminate?

Distracting background information.

How can digital subtraction help compare two series of images?

It can remove normal anatomy that has not changed so disease progression can be identified more easily.

What can digital subtraction help identify?

Subtle changes that are otherwise difficult to detect.

Why is digital subtraction useful for monitoring disease?

It makes changes between image series easier to identify by removing unchanged anatomy.

How many shades of gray can traditional film display according to the slides?

16 to 25 shades of gray.

How many shades of gray can digital imaging display?

Up to 256 shades of gray.

What do shades of gray determine in an image?

Contrast.

Approximately how many shades of gray can the trained human eye detect?

About 100.

Approximately how many shades of gray can a novice detect?

About 32.

How many line pairs per millimeter can traditional film provide?

12–20 line pairs per millimeter.

How many line pairs per millimeter can digital imaging provide?

6–22 line pairs per millimeter.

What do line pairs per millimeter determine?

Resolution, or detail, in the image.

What does resolution refer to in a digital image?

The amount of detail.

Approximately how many line pairs per millimeter can the human eye distinguish?

8–10 lp/mm.

Which has more possible shades of gray: traditional film or digital imaging?

Digital imaging.

Traditional film has how many shades of gray?

16–25.

Digital imaging has up to how many shades of gray?

256.

Traditional film has what resolution range?

12–20 lp/mm.

Digital imaging has what resolution range?

6–22 lp/mm.

What is one way digital radiography can be used for patient education?

It allows patients to view their dental health on a computer.