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Ultrasound Flashcards

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1
Q

what is a ultrasound?

A

Located in the Acoustical, therapeutic tissue healing, or tissue destruction
Thermal & Non-thermal effects
“Continuous” vs “Pulsed”
We use it for therapeutic effects
Can deliver medicine to subcutaneous tissues (phonophoresis)

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2
Q

what does the transducer do?

A

A device that converts energy

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3
Q

what is the piezoelectric crystal?

A

Piezoelectric crystal: a crystal that produces (+) and (-) electrical charges when it contracts or expands
Crystal of quartz, barium titanate, lead zirconate, or titanate housed within transducer

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4
Q

what is the reverse (indirect) piezoelectric effect?

A

Reverse (indirect) piezoelectric effect: occurs when an alternating current is passed through a crystal resulting in contraction & expansion of the crystal
US is produced through the reverse piezoelectric effect
Vibration results in high-frequency sound waves

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5
Q

what type of Piezoelectronic effect does ultrasound use?

A

Reverse (indirect) piezoelectric effect

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6
Q

what is the frequency?

A

Frequency: number of times an event occurs in 1 second; expressed in Hertz or pulses per second
Hertz: cycles per second
Megahertz: 1,000,000 cycles per second
In the U.S., we mainly use ultrasound frequencies of 1, 2 and 3 MHz

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7
Q

what are the ultrasounds we use for ultrasound?

A

In the U.S., we mainly use ultrasound frequencies of 1, 2 and 3 MHz
1 = low frequency; 3 = high frequency

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8
Q

when frequency decreases what happens to depth of penetration?

A

increases

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9
Q

when frequency decreases what happens to the sound wave?

A

frequency = sound waves are absorbed in more superficial tissues (3 MHz)

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10
Q

what is the equation for frequency?

A

F=1/ℷ

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11
Q

what are the three influences on transmission of energy?

A

reflection, refraction, absorption

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12
Q

what is reflection?

A

occurs when the wave can not pass through the next density

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13
Q

what is refraction?

A

is the bending of the sound wave due to a change in the speed as the wave enters a medium with a different density

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14
Q

what is absorption?

A

occurs when the tissue wave is collecting the waves energy.

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15
Q

what is attention?

A

Decrease in a wave’s intensity resulting from absorption, reflection, & refraction

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16
Q

when frequency increases what happens to the attention?

A

increases due to the molecular friction the waves must overcome to pass through the tissues.

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17
Q

What does US penetrate through and what does it absorb through?

A

US penetrates tissues that are high in water content
US absorbs in tissues that are dense in protein

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18
Q

When absorption is high what is the frequency?

A

frequency increases like at 3 MHz

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19
Q

penetration increases what occurs to the absorption?

A

the absorption decreases (1 MHz)

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20
Q

When penetration is high what is the relationship between frequency and absorption?

A

decreases in frequency and decreases in absorption (1 MHz)

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21
Q

tissues that are higher in water content have what type of absorption rate?

A

low absorption rate
tissue type: fat

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22
Q

tissues that have a high protein content have what type of absorption rate?

A

high

tissue type: peripheral nerve and bone

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23
Q

describe the absorption rate as it passes through tissues with increased tissue protein

A

blood
fat
nerve
muscle
skin
tendon
cartilage
bone
(increasing in density of protein content)

https://www.physio-pedia.com/Therapeutic_Ultrasound#/media/File:Protein_content.jpg,

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24
Q

what is the acoustic impedance for ultrasounds?

A

Determines amount of US energy reflected at tissue interfaces
If acoustic impedance of the 2 materials forming the interface is the same, all sound will be transmitted
The larger the difference, the more energy is reflected & the less energy that can enter the 2nd medium

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25
what is the ERA?
effective radiating area: area of the sound wave that produces the waves. expressed in cm2 measured 5 mm from the face of the sound head: but represents all the areas where the sound wave is producing more than 5% of max power output. always a smaller area than the size of the sound head.
26
what do the beams look like with differing diameter heads?
Large diameter heads – column beam Small diameter heads – more divergent beam
27
what is power in relation to us?
it measured in watts and is the amount of energy being produced by the transducer
28
what is intensity in relation to US?
strength of the sound waves at a given location within the tissues being treated.
29
What is spacial average intensity (SAI) as it pertains to US?
amount of US energy passing through the US head’s ERA; expressed in watts per square centimeter (W/cm2) (power/ERA)
30
what is the spacial peak intensity (SPI) in relation to ultrasound?
max. output (power) produced within an ultrasound beam
31
What is the BNR?
Beam Nonuniformity Ratio (BNR) ratio between the SPI spatial peak intensity (SPI) to the average output as reported on the units meter.
32
The lower the BNR the _________.
the lower the BNR the more uniform the beam is.
33
what is the cut off BNR for safety?
BNR greater than 8.
34
Why is it important to know the BNR when it comes to application?
because of "hot spots" in the beam it is pessary to keep the US head moving.
35
what is the Duty cycle?
percentage of time tat the US is actually being emitted from the head.
36
when using a pulse mode what does the duty cycle consist of and what is the equation?
when using a pulse mode the duty cycle is between the pulse length and the pulse interval. equation: pulse length/ (pulse length+pulse interval)x100
37
what would a 100% duty cycle mean?
there is constant sound waves being produced. CONSTANT OUTPUT
38
How would one place the duty cycle for non thermal effects?
lower duty cycle. under 20%
39
What are the methods for a coupling medium?
It is required for US. it should be water based so that there is low absorption and good penetration. coupling medium must conform to the body area. the body area should be clean and relativity hair free.
40
what is direct coupling
using a gel or cream. only use approved agents apply liberally to the area remove air bubbles by passing the head over the area. MOVE SLOWLY 4CM/SEC, in circles moving the head faster will decrease the heat. if the patient reported discomfit, decrease the output intensity.
41
How slow should you move the US head?
4cm/sec moving in circles
42
How might one treat an irregularly shaped area?
Immersion technique the limb will be immersed in degassed water he transducer will be placed 1" from the body part. avoid the formation of air bubbles
43
If you are using the immersion technique with tap water, how should you change the intensity.
If tap water is used, increase the output intensity by 0.5 w/cm2
44
What is the pad (bladder method) for ultrasound?
massive conductive gel conforms to the treatment area commercial pads help limit the size of the treatment area.
45
what are the indications of US?
soft tissue healing & repair joint contractures & scar tissue muscle spasms joint contraction post-acute reduction of myositis ossificans acute inflammatory conditions (pulsed) SJM-PA
46
What are the contraindications for US?
Acute conditions (continuous output) Ischemic areas or impaired circulation areas Tendency to hemorrhage Over/Around eyes, heart, skull, or genitals Over pelvic or lumbar areas in pregnant or menstruating females Cancerous tumors Spinal cord or large nerve plexus (high doses) Anesthetic areas/Diminished Sensation Stress fracture sites or over fracture site before healing is complete (continuous); epiphysis??? Acute infection
47
what are the thermal effects of US?
Increased: blood flow sensory & motor NCV extensibility of structures (collagen) collagen deposition macrophage activity decreased: joint stiffness muscle spasm pain + all Nonthermal effects
48
what are the non thermal effects of US?
increased:  cell membrane permeability  vascular permeability  blood flow  fibroblastic activity decreased:  edema Altered rates of diffusion across cell membrane Stimulation of phagocytosis Production of granulation tissue Synthesis of protein Tissue regeneration
49
what is the pathophysiology for pulsed ultrasound (non-thermal) ultrasound?
Stimulates phagocytosis (assists w/ decrease of chronic inflammation) & increases # of free radicals (increases ionic conductance on cell membrane)
50
what is cavitation for pulsed ultrasound/non thermal ?
Cavitation: formation of gas bubbles that expand & compress due to pressure changes in tissue fluids Stable – occurs when bubbles compress during the -press. peaks followed expansion of bubbles during -press. troughs Unstable (transient) – compression of bubbles during -press. Peaks, but is followed by total collapse during trough (BAD!)
51
what is acoustical streaming when it comes to pulsed ultrasounds?
stable cavitation leads to this; unidirectional flow of tissue fluids, & is most marked around cell membranes
52
what does acoustic streaming help to facilitate?
Facilitates passage of calcium potassium & other ions, etc. in/out of cells Collagen synthesis, chemotactics secretion, increases update of calcium in fibroblasts, increases fibroblastic activity
53
what does the length of US treatment time depend on?
size of the area output intensity goals of treatment frequency
54
How big should the treatment area be?
no larger than 2-3x the surface areas ERA if the area is to larger split the treatment into smaller treatment zones.
55
How long should you perform ultrasound to reach vigorous heating?
1mhz: 10-12 min 3 mhz: 3-5 min
56
what is vigorous heating defined as temperature size?
Vigorous heating is defined as an increase of ~7°F (4°C)
57
what is the depth of penetration for 1 MHz?
5 or more cm
58
what's the depth of penetration for 3 mhz
0.8 to 3cm
59
what is the beam profile for 1mhz and 3mhz
1 mhz: relativity divergent 3 mhz: relatively collimating
60
what is the maximum heating rate for 1mhz vs 3 mhz
1mhz: 0.2 degrees c per minute per w/cm2 "slow" 3 mhz: 0.6 degrees c per minute per w/cm2 "fast" 3-4 faster than 1 mhz
61
what frequency leaves the tissue heater longer?
1mhz is 2x as 3mhz
62
what is the general rule for depth of the tissue and frequency?
General Rule: 1 MHz = Tissues ≥ 1” Deep (2.5cm) 3 MHz= Tissues ≤ 1” Deep
63
what is the process used for inducing medications when performing ultrasounds?
phonophoresis
64
what are the common drugs with phonophoresis
hydrocortisone dexamethasone benzydamine Salicylates various anesthetics
65
what is acoustical streaming?
opens pathways to drive molecules into the tissues using ultrasounds heating process.
66
what is the law that phonophoresis uses?
Based on theory that drug diffuses through skin (Fick’s law)
67
67
what does ultrasound do for the medication phonophoresis?
Ultrasound initiates increases in metabolic rate, enzymatic activity, cellular permeability, ion flux, and diffusion With physiologic enhancement via ultrasound, subsequent increase in efficacy of topical medication

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