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0

Near zone length?

F * D2
---------
6

1

Nyquist limit?

1/2 prf

2

What determines the range of brilliancies within a displayed image?

Contrast

3

A television image is made up of how many closely spaced horizantal lines?

525

4

Bistable images , which only appear in black and white have what kind of contrast?

High

5

What determines the brilliance of the displayed image?

Brightness = brilliance

6

Greyscale imaging was first made possible with the use of what?

Scan Converters

7

What does the scan converter do?

Ultrasound info is obtained from pulses emitted by a transducer that penetrates into the body. Multiple penetrations, or spokes, are needed for each two dimensional image. However television displays video infromation as 525 interlaced , horizantal lines divided into two fields. THE SCAN CONVERTER TRANSLATES THE INFORMATION FROM THE SPOKE FORMAT INTO VIDEO FORMAT.

8

The process of storage of information into the scan converter is called what ?

Writing. Image is then read from the scan converter for display on the CRT

9

What are analog #'s?

Real world numbers that are found in our everyday lives

10

What are digital numbers?

associated with a computer device

11

What is Spacial Resolution?

Image detail

12

What are the four limitations of analog scan converters?

image fade

image flicker

instability

deterioration

13

Digital scan converters use computer technology to convert images into numbers using a process called?

digitizing

14

What is a pixel?

The smallest building block of a digital picture?

15

What is the number of picture elements per inch?

Pixel density

16

Higher pixel density is achieved what?

smaller pixels

17

Spacial resolution is improved with high or low pixel density?

High

18

Low pixel density = ?

Larger pixels

19

What is the smallest amount of computer memory?

Bit 0's and 1's

20

What is a byte?

A group of 8 bits of computer memory
10011111
A word of computer memory is made up of 2 bytes or 16 bits

21

More shades of grey appear on an image with more what?

More bits per pixel.

22

Images that have many shades of grey have superior what?

Contrast resolution

23

More shades of grey = ?

IMPROVED CONTRAST RESOLUTION
MORE BITS PER PIXEL

24

How do you determine the number of shades of grey there are in an image?

Multiply 2 by itself the same number of times as there are bits

2 to the (number of bits) power)

25

How many possible shades of grey are displayed with 5 bits of memory?

32
mulitpling 2 by itself 5 times yield 32
2x2x2x2x2 = 32

26

Any processing of the reflected signals before storage is called what?

pre-processing.Pre processing alters the image data forever and cannot be reversed or "un-done".

27

What is the manipulation of an image after storage in the scan converter, a process that can be reversed or applied to a frozen image?

Post Processing

28

Read magnification occurs during what stage of processing?

Post processing. It can be catorigized by the number of pixels or scan lines in the magnified image is the same as the original image. MAGGING AFTER YOU HAVE ALREADY AQUIRED.

29

Write magnification occurs during what processing stage?

pre processing. It is applied during data aquisition. Mag'ing DURING SCANNING