Flashcards in Ultra Sound Deck (33)
What are the Thermal Effects of US?
Pain relief with anything ending in "itis", pain relief for neuromas, adhesive scars(loosens bonds, stretch after), affects nerve conduction velocity (helps decrease pain), improves extensibility of the connective tissues by loosening bonds
What are the non-thermal effects of US? (less than 20% Duty Cycle)
Cavitation may break down calcium deposits and increase the rate of healing, affects nerve conduction velocity (could change pain perception), phonophoresis drives chemicals through skin via US beam.
What are the contraindications of US?
Where heat is not indicated (when using thermal effects), severe cardiac disease, malignancy, sepsis, Hemophiliac pt, Over deep vein thrombosis, over neoplasm (Will grow faster if US), over pregnant belly, over the eyes, over the heart, near a pacemaker, over growth plates
What are the precautions for using US?
over healing fracture (.1-.2 watt can improve healing), Over Spinal Cord, Over Metal Implants
How far into the skin does 1MHz penetrate? 3MHz?
1MHz - 5cm (2in)
3MHz - 1cm (1/2in)
What is a BNR?
BNR (bean nonconformity ratio)
rates the quality of the head, 1:1 is a perfect ratio, sound is equal all of the head. A BNR 6:1 is the minimum acceptable.
What is the difference in practice when using an US with a good BNR, compared to using an US with a poor BNR?
The worse the BNR => the faster you must move the head. if BNR is 3 or slower, you can move really slow.
What is the difference between continuous, and non continuous US? Why would they be used?
Continuous gives thermal and non-thermal effects. Pulsed US, especially below 10%, gives only non-thermal effects. Typically, if heat is not contraindicated, continuous is used. pulsed may be used to promote healing without heating the area.
10-20% - acute injuries
30-50% - subacute injuries
60-100% - chronic injuries
What determines the intensity of the US?
Maximum intensity is typically determined by the pt. tolerance. Typical maximum intensity is 1.5 w/cm^2, but you have to take the BNR into consideration. (poor BNR, that intensity could hurt). Also, if a deep structure that is not near bone needs to be heated, the pt. may safely tolerate intensities above 1.5
What should the intensity settings be for an acute injury? Subacute? Chronic?
Acute Injury - .1-.2 w/cm^2
Subacute Injury - .3-.8 w/cm^2
Chronic Injury - .9-1.5 w/cm^2
What is the effective radiating area, and how is it applied when using US?
ERA - the area of the sound head which is producing an ultrasonic wave. As a rule of thumb, an 8-10min treatment of US can cover an area twice the area of the sound head. If a larger area is covered, treat in segments, each twice the sound head size.
What should the head movement speed be?
1-4 cm/sec for BNR of 3 or less
4 cm/sec for BNR > 3
What does the "intensity" of an US beam mean?
Strength of the US beam. It is the rate at which energy is delivered per unit area and is expressed in units of watts per cm squared (typically ranging from .5-3.0). The greater the intensity, the greater resulting temperature elevation.
How do you measure intensity?
measuring the total power output (in watts) of the ultrasound applicator and dividing by the area (in cm2) of the applicator face.
What is the Duty Cycle?
duration of pulse (time on) - continuous
pulse period (time on + time off) - pulsed wave
What is the temporal average intensity of the duty cycle?
The average of the intensity of both the on and off periods. Amount of heating depends on the temporal average intensity.
What is the temporal peak intensity of the duty cycle?
The maximum intensity.
When would "pulsing" be of benefit?
when the desired effect is due to non-thermal mechanism and when heating is to be minimized (stasis ulcers, acute injury)
Attenuation (as applied to US)
decrease of energy contained within a sound beam as it travels through a tissue
What are the three processes that occur that effect attenuation?
Reflection, refraction, and absorption.
Pt. is a 34 y/o male w/ the inability to flex mp joints of R hand due to a crush injury 6 weeks ago. Please treat with US underwater. BNR - 5:1. 4 ERA. Use Depth of penetration of .5cm, area to be treated as 3cm.
Is this indicated? - Yes
Duty Cycle? - continuous
Ultrasound Headspeed, based on a BNR?
Area to be treated?
What should your intensity be?
pt. is an 18 y/o who sprained her ankle 2 weeks ago. has continued pain and swelling. please treat with US. BNR - 5:1. ERA - 4. Depth of penetration wanted - 3cm. Area - 6cm.
Frequency - 1MHz
Ultrasound head speed? 4cm/s
Duty cycle - 30-50%
Treatment time? 15min
What is the calculation for depth?
What does a BNR of less than 3 indicate?
That the clinician must move the head at a speed of 1cm/s
What does a BNR of > 3 indicate?
That the clinician must move the head at a speed of 4cm/s
What is the ERA?
Effective Radiating Area. The area of the sound head which is producing the ultrasonic wave. as a rule of thumb, 8-10min can treat 2x the area of the sound head (always multiple the ERA by two!).
What are the ratio #'s for the intensity calculations for 3MHz and 1MHz?
.4/cm for 3MHz
.25/cm for 1MHz
What does Intensity refer to in regards to ultrasound?
the strength of an ultrasound beam. It is the rate at which energy is delivered per unit area and is expressed in W/cm2
What are the non-thermal settings and effects of Ultrasound?
Cavitation (vibrational effect on gas bubbles, pulsation of bubbles cause changes in cellular activity and tissue damage). Causes stretching of cell wall, balloons out, collapses back in, causing nutrients to be absorbed.
Acoustical streaming (Mechanical pressure waves, movement of fluids along the boundries of the cell membranes) pulls on sound walls, opens membranes, allows for nutrients to be absorbed.
Micro-Massage(increase cell membrane permiability, increase cell activity, increase capillary density, and increased protein synthesis).