Key Terms Week1/Lecture2

Question 1

Dynamic Range

Answer 1

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

units: decibels(dB)

It is a comparison, a relative measurement, or ratio, between the largest and smallest signals that are measured accurately

component dynamic range transducer 120dB reciever 100-120dB scan converter 40-50dB display 20-30dB archive 10-30dB

Question 2

Switch

Answer 2

found in the beam former

protects the sensitive electrical components in the receiver from the high voltages created during transmission

Question 3

Beam Former

Answer 3

receives the single electrical spike from the pulser and distributes it to the numerous active elements of an array transducer

creates and distributes the delay patterns for array transducers during transmission

Question 4

Receiver

Answer 4

transforms the electrical signals from the transducer(produced by the reflected sound) into a form suitable for display on the system’s monitor

Five functions must be completed in this order: 1)amplification 2)compensation 3)compression 4)demodulation 5)reject

Question 5

Amplification

Answer 5

all signals are treated identically

entire image gets brighter or darker

It is adjustable (Gain/Overall Gain Knob)

Question 6

Gain/Overall Gain(amplification)

Answer 6

controls the degree of echo amplification, or brightness of the image

measured indB

too much gain-image is too bright

too little gain-image is too dark

Question 7

Compensation

Answer 7

creates an image of uniform brightness from top to bottom of the image

compensates for the sound wave as it weakens(attenuates) as it travels

operator controlled

AKA-TGC(time gain compensation), DGC(depth gain compensation)

Question 8

TGC(time gain compensation)

DGC(depth gain compensation)

Answer 8

compensates for the loss of energy through attenuation of the sound beam as it passes through the tissue

structure will be the same brightness regardless what depth it is

Question 9

Compression

Answer 9

keeps the image’s grayscale content within the range of detection of the human eye (aprox 20 shades of gray)

keeps the electrical signal level within the accuracy range of the system’s electronics

units: dB

operator controlled

AKA-log compression or dynamic range(DR)

Question 10

Decibels

Answer 10

a relative unit that compares one signal to another

important in quantifying the strength of the sound beams, electrical strength, and brightness of the image

notation is logarithmic

Question 11

Demodulation

Answer 11

two part process that changes the electrical signals in the receiver into a form more suitable for the CRT monitor

rectifies and smooths the electrical signal

cannot be adjusted by sonographer

Question 12

CRT Monitor

Answer 12

displays the receiver’s info from the returning electrical signal

2 users controls: contrast and brightness

Question 13

Reject

Answer 13

controls whether low level signals will be displayed on the image

low level echoes can be diagnostic or noise

Question 14

Persistence

Answer 14

frame averaging function that allows echo info to be accumulated over a longer period of time

Increasing persistance-subtle tissue texture differences will be enhanced

decreasing persistence-user is able to evaluate moving structures more easily

Question 15

Zoom(magnification)

Answer 15

allows image magnification by increasing the pixel size-results in image degradation

two type: read and write

Question 16

Read Zoom

Answer 16

occurs after image data is stored in scan converter

number of pixels is same as original image-results in blurry image

Question 17

Write Zoom(RES)

Answer 17

scanning in real time, the box is placed on image and image is expanded

no degradation occurs

Question 18

calipers

Answer 18

markers available to measure distance

can be linear, ellipsoid, and trace

Question 19

annotation

Answer 19

allows labeling of the image

may be a keyboard or preprogrammed keys

may be voice activated

Question 20

Dual Image/Quad Image

Answer 20

allows the screen to be split in two or four

able to compare the anatomy of the abnormal side with the normal side

Question 21

Acoustic Power/Transmit Power

Answer 21

varies the amount of energy the transducer transmits to the patient

power should be used at the lowest level consistent with satisfactory image quality

Question 22

ALARA(As Low As Reasonably Achievable)

Answer 22

when modifications to the output power of the receiver gain need to be made to improve the quality of the image, the first and best choice is the one that minimizes the patient’s exposure

image too dark-increase receiver gain first, no increase to patient’s exposure

image too bright-decrease output power first, decreases patient’s exposure

Question 23

Pulser

Answer 23

creates electrical signals that excite the transducer’s PZT crystals(elements) to create the sound beams

Pulser only functions during the transmission

operator controlled

ranges from near 0-500 volts

Important in bioeffects

Question 24

TI(Thermal Index)

MI(Mechanical Index)

Answer 24

attempts to standardize transducer output have resulted in these two measurements being seen on the monitor

TI-useful predictor of max temp increase under most clinically relevant conditions

MI-related to the likelihood of harmful bioeffects from cavitation

Question 25

Noise

Answer 25

random and persistant degrading of the ultrasound image

unwanted low-level echoes

output power is increased-signal to noise ratio is increased

image quality improves as the signal dominates the image, and the noise disappears