Ultrasound and Diathermy

Question 1

what is ultrasound

Answer 1

deep-penetrating agent that produces changes in tissue via thermal and nonthermal (mechanical) mechanisms
-uses sound waves

Question 2

uses of ultrasound

Answer 2

-diagnostic imaging (.5-50 mW/cm2)
-therapeutic deep tissue healing (1-3 W/cm2)
-tissue destruction (.2-200 W/cm2)

Question 3

what are the two frequencies of therapeutic ultrasound

Answer 3

1 Hz
3 Hz

Question 4

which ultrasound frequency penetrates deeper

Answer 4

1 Hz

Question 5

ultrasound production

Answer 5

-produced by alternating current through crystal which is housed within the transducer
-AC current enters the crystal causing it to contract and expand, this produces the ultrasound waves
-requires a coupling medium (gel, water, ultrasound pads) in order for energy to pass from transducer into the tissues

Question 6

reverse piezoelectric effect

Answer 6

converts electrical energy to mechanical energy (creates the sound waves)

Question 7

what shape wave are ultrasound waves

Answer 7

sinusoidal (goes up and down in a wavy formation)

Question 8

longitudinal waves

Answer 8

-molecule displacement occurs parallel to direction of sound, travels in the same direction
-can travel thru solid (bone) and liquids

Question 9

how does ultrasound waves pass through soft tissue

Answer 9

via longitudinal waves

Question 10

transverse (shear) waves

Answer 10

-molecule displacement in transverse waves are displaces perpendicular to the direction of energy
-cannot pass thru fluids
-only found when ultrasound waves hit a bone

Question 11

Fresnel zone

Answer 11

portion of the ultrasound beam used for therapeutic purposes

Question 12

treatment area for ultrasound

Answer 12

-area is only slightly larger than the diameter of the sound head
-never cover an entire muscle or limb, it needs to be broken up into smaller groups and focused separately

Question 13

effective radiating area (ERA)

Answer 13

-proportion of the transducers surface area that produces ultrasonic energy (cm2)

Question 14

large ERAs

Answer 14

produce collimated, focused beam
-when treating a trigger point, its like a light saber and only focuses on 1 pinpoint spot

Question 15

smaller ERAs

Answer 15

yields a more divergent beam
-treats a larger area like a muscle strain

Question 16

frequency

Answer 16

MHz
-how deep the wave penetrates
-1 or 3 Hz is commonly used for ultrasound
–1 Hz beam diverges more than 3 Hz

Question 17

what does high-frequency (3MHz) treat and how

Answer 17

treats superficial tissue because energy is rapidly absorbed and heats 3x faster than 1MHz

Question 18

how to calculate treatment time

Answer 18

desired temp/heating rate

Question 19

which frequency has a longer treatment time

Answer 19

1 MHz

Question 20

power

Answer 20

energy, measured in watts (W)

Question 21

intensity

Answer 21

describes the strength of the sound waves at a given location within the tissues being treated

Question 22

spatial average intensity (SAI)

Answer 22

amount of energy passing through the sound heads effective radiating area (W/cm2)

total watts (W)/ERA (cm2) = W/cm2

Question 23

duty cycle

Answer 23

pulse length (on time)/ (pulse length (on) + pulse interval (on+off)) * 100

Question 24

continuous output

Answer 24

100% DC, always on
-causes thermal effects (increase blood flow, viscoelasticity, inflammation, muscle temp)
-used for tissues 5cm or more deep

Question 25

pulsed output

Answer 25

-causes nonthermal (mechanical) effects
-decreases temporal avg intensity, reducing thermal effects and increasing proportion of nonthermal effects

Question 26

spatial average temporal peak intensity (SATP)

Answer 26

-avg intensity during the on time of the pulse
-total amount of energy delivered to the body during the treatment

Question 27

spatial average temporal average intensity (SATA)

Answer 27

-measures the power of utlrasonic energy delivered to the tissues over a given time (total watts/time)
-energy delivered to the tissues per unit of time
SATA = output * duty cycle (decimal)

Question 28

beam nonuniformity ration (BNR)

Answer 28

describes the variation between the peaks, the spatial peak intensity, and valleys
-ratio of the highest intensity to the avg intensity
BNR = spatial peak intensity/spatial avg intensity
-there is going to be an unknown value, use “x”