Physics Chapter 15 - 17 Flashcards
A word of computer memory consists of:
2 bytes
One of the limitations of an analog scan converter is:
image fade
Analog numbers can have an unlimited and continuous range of values. TRUE or FALSE.
True.
The 2 important elements of digital scan converters are:
Pixel and Bit
The spatial resolution of an analog scan converter is excellent because the large number of storage elements with the ______.
matrix
Decimal numbers are based on ten choices which range from
0-9
How many possible shades of gray are displayed with 4 bits of memory?
16
Any processing of the reflected signals BEFORE storage is
preprocessing
With regards to read magnification, is the ROI rescanned. YES or NO.
NO
The FDA has put a limit on the maximum peak intensity levels for sound beams, this is called
coded excitation
This is a method of describing the extent to which a signal can vary and still maintain accuracy.
dynamic range
PACS stands for
Picture Archiving and Communications System
DICOM stands for
Digital Imaging and Computers in Medicine
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
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
Harmonic frequency sound waves arise from linear behavior. True or False
False
If you are scanning in fundamental frequency at 4 MHz, what would it be in harmonics?
8 MHz
Would you get a better image in harmonics scanning in superficial or deeper tissues?
deeper
. Beams that are most likely to create harmonics are more likely to create artifacts. TRUE or FALSE
False
Contrast agents must meet all of these requirements except which one:
large enough to pass through the capillaries
Which of the following does not belong for the low mechanical index
resonance
Which of the following does not belong for the highest mechanical index
linear behavior
Where are harmonics created
in the tissues
Contrast harmonics created by microbubbles are much stronger than tissue harmonics. TRUE or FALSE.
True
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
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
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
With frequency compounding how many pulses are transmitted down each scan line?
1
What is the primary storage device on a PACS system?
hard disc drives
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
Which of the following is not a form of magnetic media?
laser discs
What is not an advantage of paper media?
bulky
What is a disadvantage of optical media?
no standardized format from image display and storage
Which of the following scan converters will provide the best spatial resolution?
1000 X1000 pixels
This imaging technique continues to display information from older images.
temporal compounding
