Therapeutic ultrasound

Question 1

How is ultrasound used as therapy?

Answer 1

used to generate heat in the tissues and transfer energy to materials.

Question 2

what is frequency?

Answer 2

number of times a particle experiences a complete compression/refraction cycle.

Question 3

what is wavelength?

Answer 3

distance between two equivalent points on the waveform.

Question 4

How do you get maximum transmission of energy from one medium to another?

Answer 4

must have similar impedance. The greater impedance difference, the greater refraction and the less energy transferred.

Question 5

Why do we need coupling mediums?

Answer 5

As if any air is between the transducer and the skin there will be no effective transmission

Question 6

Which tissues are capable of higher absorption rate?

Answer 6

tissues with higher protein content
tissues with high collagen content e.g. ligament, tendon, fascia, joint capsule and scar tissue

Question 7

Which tissues have lower absorption rate?

Answer 7

tissues high in water and low in protein

Question 8

What is the thermal mode of therapeutic effects?

Answer 8

• most effective at heating dense tissues.
• requires relatively high intensity in continuous mode
• if temperature raised to 40-45º then hyperaemia will occur. this is therapeutic

Question 9

what are the non-thermal therapeutic effects of US attributed to?

Answer 9

cavitation and acoustic streaming

Question 10

what is stable cavitation?

Answer 10

the formation and growth of gas bubbles by accumulation of dissolved gas in the medium. This cavity then acts to enhance acoustic streaming.

Question 11

what is cavitation?

Answer 11

• relates to formation of gas filled voids within tissues and body fluids.
• stable and unstable.

Question 12

What is unstable cavitation?

Answer 12

formation of bubbles at the low pressure part of the ultrasound cycle and these can collapse very quickly, releasing a large amount of energy that is detrimental to tissue viability.

Question 13

what is acoustic streaming?

Answer 13

• circular movement of fluids near a vibrating structure.
• affects diffusion rate na permeability
• cell membrane becomes excited increasing activity of the cell

Question 14

contraindications of therapeutic ultrasound

Answer 14

• Cancerous lesions on or near treatment area
• Current infection
• Areas of growing bones
• Pacemaker- shouldn’t be used in thoracic area
• Healing fracture
• Eyes
• Uterus region in pregnancy
• Vascular disease and ischemic tissue
• Spinal surgery- avoid spine area

Question 15

How is US used in inflammatory phase?

Answer 15

• Ultrasound has stimulating effect on mast cells, platelets, white blood cells and macrophages.
• pro-inflammatory and acts as an inflammatory optimiser.

Question 16

How is US used in proliferative phase?

Answer 16

• Stimulative effect on fibroblasts, endothelial cells and myofibroblasts.
• Pro-proliferative as these tissues already contribute to scar production.

Question 17

How is US used in remodelling phase?

Answer 17

• Can influence the remodelling of scar tissue . Appears to enhance the appropriate orientation of newly formed collogen fibres.
• Enhances functional capacity of scar tissues.