Physics Chapter 15 - 17 Flashcards Preview

OB Ultrasound > Physics Chapter 15 - 17 > Flashcards

Flashcards in Physics Chapter 15 - 17 Deck (35):
1

A word of computer memory consists of:

2 bytes

2

One of the limitations of an analog scan converter is:

image fade

3

Analog numbers can have an unlimited and continuous range of values. TRUE or FALSE.

True.

4

The 2 important elements of digital scan converters are:

Pixel and Bit

5

The spatial resolution of an analog scan converter is excellent because the large number of storage elements with the ______.

matrix

6

Decimal numbers are based on ten choices which range from

0-9

7

How many possible shades of gray are displayed with 4 bits of memory?

16

8

Any processing of the reflected signals BEFORE storage is

preprocessing

9

With regards to read magnification, is the ROI rescanned. YES or NO.

NO

10

The FDA has put a limit on the maximum peak intensity levels for sound beams, this is called

coded excitation

11

This is a method of describing the extent to which a signal can vary and still maintain accuracy.

dynamic range

12

PACS stands for

Picture Archiving and Communications System

13

DICOM stands for

Digital Imaging and Computers in Medicine

14

This technique is used to image the changes in tissue when they are deformed differently and following the application of force. The stiffness data and ultrasound reflections are combined into images. It is called

elastography

15

This is a processing method that makes pictures look sharper. The computer identifies and emphasizes sharp edge boundaries in the image. It is called

edge enhancement

16

Harmonic frequency sound waves arise from linear behavior. True or False

False

17

If you are scanning in fundamental frequency at 4 MHz, what would it be in harmonics?

8 MHz

18

Would you get a better image in harmonics scanning in superficial or deeper tissues?

deeper

19

. Beams that are most likely to create harmonics are more likely to create artifacts. TRUE or FALSE

False

20

Contrast agents must meet all of these requirements except which one:

large enough to pass through the capillaries

21

Which of the following does not belong for the low mechanical index

resonance

22

Which of the following does not belong for the highest mechanical index

linear behavior

23

Where are harmonics created

in the tissues

24

Contrast harmonics created by microbubbles are much stronger than tissue harmonics. TRUE or FALSE.

True

25

In this imaging technique, the reflections from the first pulse are doubled and then subtracted from the second reflection. The fundamental portions of the 2 reflections completely cancel each other out, leaving only the harmonic portion of the second reflection. The remaining harmonics form an image with less distortion than the fundamental image. This is called

power modulation harmonics

26

An uncompressed signal has a dynamic range of 85 dB. The signal undergoes 40 dB of compression. What is the dynamic range of the compressed signal?

45 dB

27

A signal within a system’s receiver has a dynamic range of 70 dB after compression. The original signal was compressed by 40 dB. What is the dynamic range of the original, uncompressed signal?

110 dB

28

With frequency compounding how many pulses are transmitted down each scan line?

1

29

What is the primary storage device on a PACS system?

hard disc drives

30

Are the following procedures usually pre or postprocessing
a. modifying a frozen image-------PRE or POST
b. read zoom ------PRE or POST
c. write zoom ----PRE or POST
d. adjusting the brightness on the monitor----PRE or POST
e. increasing the receiver gain----PRE or POST

a-Post b-Post c-Pre d-Post e-Pre

31

Which of the following is not a form of magnetic media?

laser discs

32

What is not an advantage of paper media?

bulky

33

What is a disadvantage of optical media?

no standardized format from image display and storage

34

Which of the following scan converters will provide the best spatial resolution?

1000 X1000 pixels

35

This imaging technique continues to display information from older images.

temporal compounding