Test 2 Part1 Flashcards
(33 cards)
What deep heating modality uses sound waves at high frequencies, penetrates the skin and subcutaneous fat, and also has mechanical effects?
Ultrasound
What is the second most common heating modality used among chiropractors (63%)?
Ultrasound (moist hot packs is #1)
What is the frequency range of most Ultrasound machines?
0.8-3.3 MHz
How is the duty cycle for US calculated?
time sound is delivered divided by total treatment time
Duty cycle of 100% =?
50% or 20%?
continuous US;
pulsed US
What is the purpose of continuous Ultrasound? of Pulsed?
tissue healing;
mechanical/nonthermal effects
Mechanical deformation of a crystal causes an electrical current to form…
Piezoelectric effect
Alternating current is passed through a crystal resulting in very fast contraction and expansion of the crystal producing high frequency sound waves…
Reverse piezoelectric effect
What is the ERA?
BNR?
Effective Radiating Area;
Beam Nonuniformity Ratio
What is the term for the area of the sound head that produces sound energy which is always smaller than the size of the US head?
Effective Radiating Area
What is the term for the ratio between the peak intensity of the US beam divided by the average intensity of the US beam?
Beam Nonuniformity Ratio
What is the BNR used to determine?
comparison of the quality of different US machines
What is the ideal BNR?
1:1 but within the range of 2:1-8:1 is acceptable
T/F: The lower the BNR, the less uniform the intensity of the sound wave.
False; lower ratio equals more uniform
What does PAMBNR stand for? and what does it describe?
Peak Area of the Maximum Beam Nonuniformity; describes the area of the sound head covered by the peak intensity
T/F: Larger PAMBNR means less uniform heating.
True (peak intensity covers a larger area)
T/F: Air is a poor conductor of US.
True, hence the use of gel and gel pads
T/F: Underwater ultrasound is considered indirect ultrasound and should only be done in plastic buckets, not metal due to reflection.
True
T/F: With US, more watts equals greater penetration.
False; equals more heating
Frequency of US dictates depth of heating. What is the typical range?
1-3 MHz
T/F: High frequency US (3MHz) is absorbed at a slower rate and therefore affects deeper tissues.
False; This is true of Low freq (1MHz), High freq is absorbed more rapidly affecting superficial tissues.
T/F: More tissue healing occurs with continuous US than with pulsed.
True
What is the difference b/w reflection and refraction?
reflection: reversal of direction
refraction: change from a straight path when passing obliquely from one medium to another
T/F: The bending of US energy within tissue can lead to concentration of US at the point of reflection, such as where tendon joins bone.
False; should say point of REFRACTION
