ultrasound Flashcards
why use Ultrasound
it delivers energy to cell membrane which forces more membrane to change behaviour, produce membrane excitement. it is a form of mechanical energy- not mechanical
how does US work
sens sound wave into tissues stimulates cells- more stimulation= positive adaptations- produce more collagen tissue for example
limited evidence for this instead of exercise. high frequency sound waves absorbed in the body are pulsed for a low average intensity, average low intensity- tickles cells- higher cellular activity level promotes natural body resources
1mHz- greater depth- less superficial structure, 3 MHz- superficial structures
absorption of US
blood, fat, nerve, muscle skin, tendon (cartilage), bone
best absorption in tendon, ligament, fascia, joint capsule and scar tissue
increasing protein content gives increasing absorption
nature of waves
transverse, longitudinal, have areas of less compression, frequency- the number of times a patient experiences a complete compression cycle in a second
wavelength- the distance between 2 equivalent points on wave form in particular median
nature of waves- velocity
the speed at which the waves (disturbance) travels through the medium, the 3 factors are related- velocity= frequency wavelength
clinical intervention choice
needs coupling gel, US- dense collagen based tissues- lig, tendon, fascia, joint capsule, scar tissue
treatment parameters
time- minutes, frequency- MHz, intensity- watts per cm3, pulse ratio- duration– ms
what is pulse ratio
the time which the machine is on
pulse ratio- acute= 1:4/3, sub-acute- 1:2/1, pulse 1:1 or continuous
frequency
the decision of which frequency to use is based on the depth of the target tissue
superficial (<2cm)- 4 mhZ) deep (2-5cm)- 1 MHz
what is intensity
the intensity of energy supplied by the machine to tissue
acute- 0.1-0.3 W/cm2, sub-acute- 0,2-0.5 W/cm2, chronic- 0.3-0.8 W/cm2
dose calculation
frequency- superficial or deep, pulse factor- add both parts of ratio-severity, intensity- severity, area size- number of times the treatment head fits of the lesion
application time- 1 X (pulse factor) X number of times head fits over lesion
contraindications
Pts who are unable to co-operate or comprehend instruction, not over the uterus in pregnancy, areas of active tumour, areas of current or recent bleeding tissues or haemorrhage, significant vascular abnormalities- DVT, haemophiliacs by factor replacement, not over sensitive organs- eyes, gonalds, advanced heart disease
precautions
over the anterior neck-glands and cells, significant loss of sensation or circulatory impairment over treatment area, devitalised tissue, local acute skin condition
application and mandatory warnings
always use the lowest intensity which procedures a therapeutic response, keep the treatment head moving at all times, test hot and cold if using continuous sensation, caution over pacemaker of another implanted electronic devise, continuous unwise over metal implants
thermal US
most effective in heating the dense collagenous tissue and will require high intensity with continuous mode. it can be used to selectively raise the temperature of particular tissues due to its mode of action.
thermal US- more effective tissues
periosteum, collagenase tissues (lig, tendon, and fascia) and fibrotic muscle
if the temperature of damaged tissue is raised to 45°, then a hyperemia will result- therapeutic. this temp also helps in initiating the resolution of chronic inflammatory status
Non-thermal US
attributed primarily to a combination of cavitation and acoustic streaming
Non-thermal US- cavitation
relates to the formation of gas filled voids, within tissues and body fluids. 2 types: stable- occurs at therapeutic dose of US, this is the formation and growth og has bubbles by accumulation of dissolved gas in medium. Unstable- is the formation of bubbles at low pressure of the US cycle. these bubbles then collapse very quickly releasing large amount of energy which is detrimental to tissue viability
Non-thermal US- acoustic streaming
is described as a small eddying of fluids near vibrating structure such as cell membranes and the surface of stable cavitation gas bubbles. this affects diffusion rates and membrane permeability
combined effect of cavitation and acoustic streaming
in the cell membrane excited (up regulates), increasing the activity of the whole cell
Non-thermal US- micro massage
a mechanical effect which is less important now. the sound wave traveling through the meidum causes molecules to vibrate, possibly enhancing tissue fluid interchange and affecting tissue mobility- little evidence
effects of US on inflammation
stimulating effect on mast cells, platelets, WBC with phagocytic roles and macrophages. by increasing the activity of these cells, the influence is to act as an inflammatory optimiser. it is an ineffective anti-inflammatory, it promotes the normal resolution of the inflammatory events
effects of US on proliferation
stimulates fibroblasts, endothelial cells and myofibroblasts. these cells are normally active during scar production and US is pro-proliferative- maximises efficiently. lose dose increases protein synthesis and increases fibroplasia and collagen synthesis
effects of US on remodelling
the application of therapeutic US can influence the remodelling of the scar tissue in that it appears to be capable of enhancing the appropriate orientation of newly formed collagen and change from typ3 to type 1= increase the repair process
