Radiology 2 Digital Radiography

Front 1

What are the benefits of digital x-rays?

Back 1

1. Allows faster image access, open image just by searching pt's neame, can send image to colleague, etc
2. No chemical processing. Once you capture the image you are done
3. Dose reduction
4. Digital image processing - zoom in, enhance contrast, brightness
5. Image database - archive all your patients images
6. Professional image - Pt senses that you are up to date, latest technology
7. Dental marketing
8. Novelty

Front 2

What is data stored as in digital imaging?

Back 2

Bits
BInary digiT
1's & 0's

Front 3

What is the term for when the continuous signal gets sampled then reconstructed using discrete units?

Back 3

Analogue to Digital Conversion

Front 4

What are 4 main components that affect digital image quality?

Back 4

1. The imaging system (image capture) - sensors, phosphor plates (PSP)
2. Display system (the monitor that you are using to display image)
3. Viewing condition - want subdued light. When light is on it is harder to see what's going on. Look at images with dim light conditions
4. Viewer - The more experience you have looking at radiographs, the better you are at interpreting what you see.

Front 5

What are the image quality system components that contribute to the image capture?

Back 5

1. Resolution (spatial resolution)
2. Contrast (contrast-resolution)
3. Bit Depth
4. Signal to Noise Ratio (SNR)
5. Field of View

Front 6

What is the difference between Spatial resolution & Contrast resolution?

Back 6

Spatial resolution - Resolving power of any image-forming device

Contrast resolution - ability to distinguish between smallest differences in the intensity of an image. (usually useal for medical imaging)

Front 7

What is used to test resolution?

Back 7

Line pairs per mm
The higher line pairs, the better your sensors are.
We can see big black lines, (they are metal lines running from top to bottom) and they converge as you go down.
In conventional film we get 20 lines per mm, but when we convert to digital, not all systems are abole to get that resolution.
Digital - zoom in, can still distinguish line pairs at 20. At upper portion of graph, we can see lines much easier, but notice, the blackets you can get is at top, as you go down it becomes fuzzy. Once we get to 20 lines per mm, contrast drops significantly, but can still get resolution (can still see lines)

Front 8

Which image has better bit depth?

Back 8

Left image

Front 9

What is a measure used to quantify how much signal has been corrupted by noise?

Back 9

Signal to Noise Ratio (SNR)

Front 10

In radiography, the more x-ray photons you have, the better signal to noise ratio. How do you get more photons?

Back 10

1. Increase exposure time, increase mA (current)
2. The higher radiation dose the better image quality

Front 11

What effect does noise have on a radiograph?

Back 11

When you have high noise you cannot tell where root ends or where the PDL space or lamina dura is

Front 12

Can short exposure noisy images be useful?

Back 12

If you are trying to locate impacted teeth or root fragments, you don't need full exposure

Front 13

What are two ways of acquiring digital dental imaging?

Back 13

1. Sensors or Solid-State detectors (CCD & CMOS)
2. Receptors or Plates (PSP)

Front 14

What is the purpose of a scintillator?

Back 14

Takes x-ray photon and converts them to light photons

Front 15

What do the fiber optics do for the sensor?

Back 15

Guide photons to the image detector component

Front 16

What is the purpose of CMOS on a sensor?

Back 16

Converts light signal to electrical signal, so computer can process that information

Front 17

What is the purpose of the electronic layer on a sensor?

Back 17

Takes electrical signal and passes the signal to computer through either wireless or usb connector

Front 18

What is the purpose of a protective shield on a sensor?

Back 18

Absorb scattered radiation

Front 19

What type of sensor resembles film, has a thin profile, base layer just like with film and coated with phosphor layer, and there is a protective coating to reduce film scratching

Back 19

Photostimulable Phosphor (PSP) Plates

Front 20

What is the sequence of the PSP cycle?

Back 20

see above

Front 21

What PSP scanner do we currently use at CWRU?

Back 21

ScanX
Old model - after you put sensor on top, it comes out from bottom, then need to expose light.

Front 22

What will the image look like at the foot of the response curve?

Back 22

Underexposed, image will appear white

Front 23

What are the pros and cons of CCD/CMOS vs PSP?

Back 23

Front 24

What are the most useful tools for digital image processing?

Back 24

Contrast, Brightness, Gamma adjustment
Zoom
Rulers

Front 25

What acts as a graphical representation of the tonal distribution in a digital image?

Back 25

Histogram
It plots the number of pixels for each tonal value

Front 26

What are some toys used for image enhancement?

Back 26

LUT inversion
Color conversion
Embossing

Front 27

What will happen to the line pairs when you sharpen the image with a filter?

Back 27

You lose resolution

Front 28

What are some things to take into consideration when selecting a Display system?

Back 28

Monitor resolution
Color vs Grayscale - can go color or grayscale. Color is cheaper. Grayscal for professionals, better gray scale value, but no more intraoral image views.
Bit depth
Contrast
Screen size

Front 29

What is the best image display or viewing system?

Back 29

OLED - 1 mm thickness, best contrast, whitest white, and pitch black

Front 30

What are the best image storage formats?

Back 30

TIFF (compressed/uncompressed)
PNG