ULTRASOUND Flashcards
(81 cards)
1
Q
convert electrical energy into ultrasonic energy, and vice versa.
A
Piezoelectric transducers
2
Q
Piezoelectric means
A
pressure electricity
3
Q
piezoelectric material
A
crystal or ceramic)
4
Q
Ultrasound transducer materials
A
lead-zirconate-titanate(PZT), plasticpolyvinylidene difluoride (PVDF), and the new monocrystalline transducers.
5
Q
transducer is destroyed if heated above its Curie temperature.
A
piezoelectric effect
6
Q
do not conduct electricity, but each side is coated with a thin layer of ___ that acts as an electrode.
A
Transducer crystals; silver
7
Q
causes the crystal to momentarily change shape
A
electrical energy
8
Q
It converts electrical energy into mechanical (sound) energy by physical deformation of the crystal structure.
A
electrical energy
9
Q
nonconducting crystal changes shape in response to a _____ placed on its electrodes.
A
voltage
10
Q
change in shape of the crystal increases and decreases the ____ in front of the transducer, thus producing ______ (transmitter).
A
pressure ; ultrasound waves
11
Q
natural piezoelectric material
A
quartz crystal
12
Q
ommonly used in watches and other timepieces to provide a mechanical vibration source at ____
A
32.768kHz
13
Q
Ultrasound transducers for medical imaging applications employ a
A
Syntheticpiezoelectric ceramic, most often lead-zirconate-titanate (PZT).
14
Q
Transducers may be operated in either
A
pulsed or continuous-wave mode.
15
Q
Virtually all medical ultrasound makes use of ____
A
pulsed transducers.
16
Q
the distance traveled by the wave per unit time and is equal to the wavelength divided by the period.
A
speed of sound/Velocity
17
Q
The average velocity of sound in soft tissue ____
A
1,540 m/s.
18
Q
is determined by the ratio of the bulk modulus(B) (a measure of the stiffness of a medium and its resistance to being compressed) and the density (ρ) of the medium.
A
wave speed
19
Q
Of major importance are the speed of sound in air (____ m/sec), the average speed for soft tissue (____ m/sec), and fatty tissue (-____m/sec).
A
330 m/sec;1,540 m/sec);1,450 m/sec).
20
Q
velocity of sound in a medium is determined by the ____ and ____ of the medium.
A
density and elastic properties
21
Q
Frequencies are measured in
A
hertz (Hz)
22
Q
The period is the time between successive oscillations
A
Frequencies
23
Q
Ultrasound frequencies are greater than ____.
A
20 kHz
24
Q
Diagnostic ultrasound uses transducers with frequencies ranging from ____
A
1 to 20MHz.
25
Transducers also have different frequencies ranging from a low frequency of ____ to higher frequencies of ____.
1MHz ; 12 to 20 MHz
26
ultrasound is the distance between compressions or rare factions, or between any two points that repeat on the sinusoidal wave of pressure amplitude.
wavelength
27
In soft tissue, the ultrasound wavelength is __
0.39 mm at 4 MHz and 0.15 mmat 10MHz
28
At 2 MHz, the ultrasound wavelength is __ in air and ___ in bone
0.17 mm; 1.7 mm
29
Ultrasound wavelength decreases with increasing ____.
frequency
30
high-frequency ultrasound beam (___ wavelength), depth of penetration is ____. Lower frequency ultrasound has____ wavelength and less resolution, but a ____ penetration depth
small; reduce. longer;greater
31
thick body parts requires ____ frequency, while small body parts requires ___ frequency
lower frequency; higher frequency
32
are pressure disturbance that propagates through a material
Sound waves
33
is the size of pressure difference from the equilibrium value.
amplitude of wave
34
is the distance between successive wave crests
Wavelength (λ)
35
is the number of oscillations in each second.
Frequency (f)
36
_____ waves have vibrations along their travel direction.
Longitudinal waves
37
______ waves have vibrations perpendicular to the travel direction.
Transverse waves
38
is caused by a mechanical deformation induced by an external force(such as a plane piston), with a resultant increase in the pressure of the medium.
Compression
39
is mechanical energy that propagates through a continuous, elastic medium by the compression and rarefaction of "particles" that compose it.
Sound
40
occurs following the compression event; as the backward motion of the piston reverses the force, the compressed particles transfer their energy to adjacent particles, with a subsequent reduction in the local pressure amplitude.
Rarefaction
41
Energy propagation occurs as a wave front in the direction of energy travel
longitudinal wave
42
is formed from numerous pulses of ultrasound reflected from tissue interfaces back to the receiver
Acoustic image
43
is a composite effect of loss by scatter and absorption.
Attenuation
44
Ultrasound has an attenuation in soft tissue of ∼___ dB/cm per MHz.
∼0.5 dB/cm per MHz
45
is the thickness of tissue necessary to attenuate the incident intensity by 50%, which is equal to a 3-dB reduction in intensity(6 dB drop in pressure amplitude).
ultrasound half value thickness (HVT)
46
As the frequency increases, the HVT _____ .
decreases
47
acoustic impedance unit is called the ____
Rayl
48
Air and lungs have ___ acoustic impedance
low
49
Bones has ___ acoustic impedance
high
50
Piezoelectric crystals have ___ acoustic impedance
very high
51
Most tissues have acoustic impedance values of_____
∼1.6 × 10 6 Rayl.
52
the ability of ultrasound to transfer from one material type to another material type depends on the difference in acoustic impedance between two materials.
acoustic mismatch
53
is applied between the transducer and skin to displace the air and minimize large reflections that would interfere with ultrasound transmission into the patient.
gel
54
is a measure of the energy flowing through a given cross-sectional area each second.
ultrasound intensity
55
Negative decibel values correspond to ______.
signal attenuation
56
Positive decibel values correspond to ______.
signal amplification
57
The development of ______ was the precursor to medical ultrasound. ____ equipment was initially constructed for the defense effort during World War II to detect the ____
sonar (Sound Navigation and Ranging) ; presence of submarines.
58
In (year) Dr. ____ positioned two transducers on opposite sides of the head measure ultrasound transmission profile. He also discovered that __ and other ___ could be detected by this technique.
1947; Karl Theodore Dussick ; tumors; intracranial lesions
59
In the late (year) __ , ____, and ___ independently demonstrated that when ultrasound waves generated by a piezoelectric crystal transducer were transmitted into the human body, these waves would be returned to the transducer from tissue interface of different acoustic impedances.
1940s ; Douglas Howry, John Wild, and George Ludwig
60
In (year) ___ developed the first ultrasound scanner, consisting of a cattle watering tank with a wooden rail anchored along the side.
1948; Douglas Howry
61
____ techniques were developed by ___ and ___ in 1954 in Sweden. These investigators were able to distinguish normal heart valve motion from the thickened, calcified valve motion seen in patients with rheumatic heart disease.
Echocardiographic; Carl Hertz and Inge Edler
62
Then in 1957 an ____ scanner was built by ___ and ___ in Scotland. This scanner was used primarily to evaluate the location of the placenta and to determine the gestational age of the fetus.
early obstetric contact-compound scanner; Tom Brown and Ian Donald
63
___ transducers with improved resolution now allow the sonographer to accumulate several images per second at a rate of up to ____
High frequency transducer; 30 frames per second
64
Like therapeutic ultrasound, diagnostic ultrasound involves transmission of ___ into the tissues by a ___ through a ___ with calculation of the time it takes for the ___ to return to the transducer from different interfaces.
high frequency sound waves (5 to 10 MHz) ; transducer; coupling agent (Gel) ; echo
65
The upper abdominal ultrasound examination generally includes a survey of the abdominal cavity from the diaphragm to the level of the umbilicus. Specific protocols are followed to image the texture, borders, anatomic relationships, and blood flow patterns within the liver, biliary system, pancreas, spleen, vascular structures, retroperitoneum, and kidneys.
Abdomen and Retroperitoneum Application
66
such as the thyroid, breast, scrotum, and penis are imaged very well with ultrasound using high-frequency transducers.
Superficial Structures Applications:
67
The premature infant is susceptible to intracranial hemorrhage during the stress of delivery and the struggle to survive. Sonography is the preferred clinical diagnostic tool to evaluate the premature infant for intracranial hemorrhage, infection, or hunt drainage for ventriculomegaly. Ultrasound examination can detect within the neonatal skull include meningomyelocele, Arnold-Chiari deformity, hydrocephalus or ventriculomegaly, Dandy Walker deformity, agenesis of the corpus callosum, and arteriovenous malformation.
Neonatal Neurosonography Applications:
68
A complete transabdominal examination of the female pelvis includes visualization of the distended urinary bladder, uterus, cervix, endometrial canal, vagina, ovaries, and supporting pelvic musculature.
Gynecologic Applications:
69
Endovaginal ultrasound is the procedure of choice during the first trimester of pregnancy to delineate the gestational sac with the embryo, yolk sac, chorion, and amniotic cavities. The gestational sac may be visualized as early as 4 weeks from the date of conception with endovaginal ultrasound. The embryo, heartbeat, and site of the placenta may be seen at 5 weeks of gestation.
Obstetric Applications:
70
The use of ultrasound and color flow Doppler has enhanced the ability to image peripheral vascular structure in the body. The ultrasound facilitates good visualization of the common femoral artery and vein and their branches as they extend into the calf. Thrombus within a distended venous structure is identified when the sonographer is unable to compress the vein with the transducer. Color flow Doppler is also useful for denoting an absence of flow within a vessel.
Vascular Applications:
71
Real-time echocardiography of the fetal, neonatal, pediatric, and adult heart has proven to be a tremendous diagnostic aid for the cardiologist and internist. Echocardiography is used to evaluate many cardiac conditions. Atherosclerosis or previous rheumatic fever may lead to scarring, calcification, and thickening of the valve leaflets. With these conditions, valve tissue destruction continues, causing stenosis and regurgitation of the leaflets and subsequent chamber enlargement. Echocardiography has been used to diagnose congenital lesions of the heart in fetus, neonates, and young children. The cardiac sonographer is able to assess abnormalities of the four cardiac valves, determine the size of the cardiac chambers, assess the interatrial and interventricular septum for the presence of shunt flow, and identify the continuity of the aorta and pulmonary artery with the ventricular chambers to look for abnormal attachment relationships
Cardiologic Applications:
72
may be used for vascular assessment. The full bladder helps to push the small bowel superiorly out of the pelvic cavity, flattens the body of the uterus, and serves as a sonic window to image the pelvic structures. Sonography of the pelvis is clinically useful for imaging normal anatomy, identifying the size of ovarian follicles as part of an infertility workup, measuring endometrial thickness, evaluating the texture of the myometrium, determining if a pregnancy is intrauterine or extrauterine, detecting tumors or abscess formations, and localizing an intrauterine contraceptive device.
A Doppler ultrasound is a test that uses high-frequency sound waves to measure the amount of blood flow through your arteries and veins, usually those that supply blood to your arms and legs. Vascular flow studies, also known as blood flow studies, can detect abnormal flow within an artery or blood vessel.
Doppler ultrasound:
73
The disadvantages of diagnostic ultrasound include ___, __,___,__,____
limited contrast resolution; limited depth of penetration; mall viewing field; lack of penetration of bone.
74
is the ratio of the acoustic power produced by the transducer to the power required to raise tissue in the beam area by 1°C.
The thermal index (TI),
75
is a consequence of the negative pressures (rarefaction of the mechanical wave) that induce bubble formation from the extraction of dissolved gases in the medium.
Cavitation
76
The mechanical index (MI)
is a value that estimates the likelihood of cavitation by the ultrasound beam.
77
At high intensities, ultrasound can cause biologic effects by
thermal and mechanical mechanisms.
78
Relative sound intensity is measured on a logarithmic scale and may be expressed in ____ equal to ___
decibel (dB). ;equal to 10 × log10(I/I0), where I0 is the original intensity and I is the measured intensity.
79
Ultrasound intensitiesare normally expressed in ___
milliwatts per cm2(mW/cm2)
80
Medical diagnostic ultrasound intensity levels are described in units of ____- the amount of energy per unit time per unit area.
milliwatts/cm2
81
When penetration to deeper structures is important, ____ ultrasound transducers must be used, because of the strong dependence of attenuation with frequency
lower frequency
