Therapeutic Ultrasound SES Flashcards
What is Ultrasound
Acoustic vibrations propagated in the form of longitudinal compression waves at frequencies too high to be detected by the human ear
Uses of US
- Therapeutic
- Imaging: real time US, pregnancy, MSK
- Dental drills/descalers
- Detecting cracks in metal/bone (stress #’s)
- Cleaning jewellery
How does US affect tissue
Biological Basis 1
- In tissue, US causes; molecules to vibrate (heat) and v
How does US affect tissue
Biological Basis 1
In tissue, US causes;
-Molecules to vibrate (heat)
-Cavitation: gas bubbles expand and contract as the compression waves pass by, changes cell membrane permeability
Biological Basis 2
Acoustic streaming
-Movement of fluid in the US field
-Stimulates cell activity and changes cell membrane permeability
Physiological effects of therapeutic US
- Increase exchanges across capillary walls and cell membranes (stable cavitation and acoustic streaming)
- Increase blood flow (heat)
- Increase soft tissue extensibility (heat)
Therapeutic uses
- Facilitate soft tissue healing
- Facilitate bone healing (first 2/52 post injury)
- Hasten resolution of inflammation
- Pain relief
- Increase flexibility
- Reduce muscle spasm
- (+/- wound healing)
Advantages
- Preferential heating of collagen tissue
- Penetration to deeper structures (6cm)
- Can help with Rheumatoid Arthritis of the hand
- Carpal Tunnel Syndrome
Indications for use of US
Calcific shoulder tendinitis
- Decreased calcium deposits
- Decreased pain and improved quality of life
- PUS, 0.89MHz, 2.5W/cm2, 15min, 24Rx
Fracture healing
- Tibial and distal radius
- Significant decrease in time to healing
- Significant smaller loss of reduction
- Decreased incidence of delayed union
Epicondylosis, tendinosis, tenosynovitis
-Significantly decreased pain and increased pressure tolerance
Lateral epicondylitis/osis
- Improved pain, weight lifting, grip strength
- Requires more investigation
Chronic leg ulcers
- Very low cont. dose and prolonged Rx
- Significant decrease in mean ulcerated area
- Requires more investigation
Perineal trauma
- Positive effect on pain
- Requires effect on pain
Safety issues-dangers for US
Burns
- Relevant for continuous output
- Ensure appropriate application
- Ensure adequate couplant (gel)
- Ensure continuous motion of the sound head
- Keep the sound head perpendicular to the skin
Transient cavitation
- Avoid very high intensities
Standing wave formation
- Ensure continuous movement of the sound head
Destructive vs Constructive interference
Destructive interference:
-Incident and reflected waves exactly out of phase; the resultant is zero
Constructive interference:
-Incident and reflected waves are in phase; the resultant has a maximum amplitude
Hence the need to continuously move the transducer head to minimise local heating and damage to blood vessels
Dangers of US
Periosteal Pain
- Avoid superficial bone
- Move the sound head more quickly
- Decrease the intensity
- Increase the frequency
Contraindications/precautions of US
A factor that may be a CI for continuous ultrasound (CUS) may be a precaution for pulsed ultrasound (PUS)
This is because CUS is a form of deep heating
- Circulatory insufficiency
- Inability to detect heat
- Metal implants (TKR, THR)
- Infective disorders (spread, increase activity)
- Haemorrhagic conditions
- Treatment over an inbuilt stimulator (e.g. cardiac pacemaker)
- Tumours, tuberculosis, oestomyelitis
- Skin disorders
- Neural tissue - superficial or exposed
- Fractures
- Air filled cavities
- Implanted plastics and cements
- Areas treated with radiotherapy in last 6/12
- Eyes or genitals
- Inability to communicate
- Rapidly dividing tissue (e.g. epiphyseal plates, pregnacy)
- Pregnancy
Application principles of US
Continuous or pulsed output
Continuous movement of sound head
- Irregular beam
- Standing waves
Perpendicular to skin surface
Sufficient couplant and direct contact with couplant
-Avoid reflection back into sound head (damage)
Avoid superficial bone
Penetration depths (half values) = the depth at which half the initial energy has been absorbed (1MHz = 6cm, 3MHz = 3cm
Methods of application of US
In contact
Solid gel sheet
- Not used routinely unless treating wounds; more for diagnostics
- Open wounds or irregular areas
- Agar gel approx. 3mm thick
Phonophoresis
-Movement of drugs through the skin using US
Dose guidelines of US
Always use lowest intensities necessary to produce desired therapeutic effect
Based on: Condition/injury -Acute/subacute/chronic (phase of healing; is heating desired or not?) -Whether heating prior to stretching -Depth of target structure -Size of treatment are
Machine parameters:
Continuous/pulse = chronicity
Frequency (0.5 - 3.5 MHz)
- Depth of structure
- Rate of healing
Intensity (W/cm2)
- Size of treatment area (dose
- Chronicity (higher intensity)
- Depth of structure
Duration (minutes)
-1-2 min for every 10cm2 - mid quads
Treatment frequency
- Acute = 1-2x day for 6-8 days
- Chronic = alternative days until symptoms subside or improvement ceases
Basic therapeutic US applications
Non thermal effect
- No temp increase (37.5 degrees baseline)
- Application: acute injury, oedema, healing
Mild thermal effect
- 1 degree temp increase (38.5 degrees)
- Application: Sub-acute injury, haematoma
Moderate thermal effect
- 2 degrees temp increase (39.5 degrees)
- Application: Chronic inflammation, pain, trigger points
Vigorous heating effect
- 4 degrees temp increase (41.5 degrees)
- Application: stretch collagen
