6130667 Therapeutic Ultrasound

8/2/2019 6130667 Therapeutic Ultrasound

1/18

THERAPEUTIC ULTRASOUND (US) Sagar Naik,P

1

Therapeutic Ultrasound (US)

Sagar Naik,PTSound is defined as the periodic mechanical disturbance of an elastic medium

such as air. Sound requires a medium for its transmission and cannot cross

vacuum. Ultrasound refers to mechanical vibrations, which are essentially the same a

sound waves but of a higher frequency. Such waves are beyond the range of huma

hearing and can therefore also be called ultrasonic. Vibration merges with sound at frequencies around 20 Hz; vibration below th

frequency is often called infrasoundor infrasonic.

Audible sound 20 to 20000 Hz Ultrasound Greater then 20000 Hz Infrasound Less than 20 HzTherapeutic ultrasound 0.5 to 5 MHz

1 to 3 MHz The wavelength is the distance between the closest points on the wave that ar

performing the same motion at any instant in time. Thefrequency is the number of times a particle undergoes a complete cycle in on

second.

The velocity of a wave is the speed at which the wave moves through th

medium, and varies depending upon the physical nature of the medium.

Nature of Sonic (Sound) Waves: Sonic waves are series of mechanical compressions and rarefactions in th

direction of travel of the wave, hence they are called longitudinal waves. The

can occur in solids, liquids, and gases and are due to regular compression an

separation of molecules.

rarefaction compression


2/18


2

The passage of these waves of compression through matter is invisible because

is the molecules that vibrate about their average position as a result of the soni

wave.It is energy that travels and not the matter.

As sound waves pass through any material their energy is dissipated o

attenuated. Sometimes all the energy is absorbed at once; sometimes the sounwave passes with almost no loss.

The molecules of all matter are in constant random motion; the amount o

molecular agitation is what is measured as heat the greater the molecula

movement, the greater the heat.

As the molecules jostle one another energy will be transferred from one t

another so that some will oscillate at higher frequencies and with greate

amplitude because they have gained energy while others will be at lowe

frequencies and amplitudes because their energy has been transferred b

collision. When sonic vibration is applied to a material it is superimposed on the existin

motions and will add to them. The ultimate result is that the regular sonic wav

energy tends to become randomized as the energy it gives to particular molecula

motions becomes spread out in collisions with other molecules. In this way th

sonic energy is steadily converted to heat energy.

The rate at which this exchange occurs will depend on both the nature of thmaterial and the frequency of the sonic wave. Thus the ratio of transmission t

absorption of sonic waves differs in different materials and varies with frequenc

of the sonic energy. Sound waves will pass more rapidly through material in which the molecules ar

close together,thus their velocity is higher in solids and liquids than in gases.

Air 344 m/s Water 1410 m/s Salt water 1500 m/s Muscle 1540 m/s

At other frequencies ultrasound is used for various purposes.

In industry low-frequency ultrasound is used for many cleaning and mixin

processes since efficient vibration of very small particles is achieved.

It can also be used for cutting and engraving as well as detecting cracks i

metal such as welding defects.

The other major medical uses of ultrasound are in body imaging and dentadrills / descalers. These latter usually operate at between 20 to 60 kHz.


3/18


3

Production of Therapeutic Ultrasound:Piezoelectrical transducers are used to achieve the high-frequency ultrasoun

energy needed for imaging and therapy. These are suitably cut crystals, whic

change shape under the influence of an electric charge.

Many types of crystal can be used but the most favored are quartz, which occunaturally, and some synthetic ceramic materials such asbarium titanate and lea

zirconate titanate (PZT). These crystals deform when subjected to a varyin

potential difference a piezo-electric effect.

[Piezo-electric effect: The production of a small e.m.f. across certaisubstances on being subjected to external pressure. Such substances arknown as piezo-electric substances.]The crystal must be cut to suitable dimensions the most important being th

thickness so that it will resonate at the chosen frequency and so achiev

maximum vibration. In order to apply the electric charges, metal electrodes must be fixed to th

crystal.If a suitable metal plate is fixed to one surface of the crystal while th

opposite surface is in air, then almost all the vibrational energy is transmitte

from the crystal to the plate and hence to any solid or liquid to which it applied. This is thetreatment head, which is used to transmit sonic energy to th

tissues. The other essential parts of a therapeutic ultrasound generator are a circuit t

produce oscillating voltages to drive the transducer and s controlling circuiwhich can turn the oscillator on and off to give a pulsed output.

A suitable circuit can maintain a constantly oscillating electric charge to caus

the piezoelectric crystal to change shape at the same frequency and so drive th

metal plate backwards and forwards also at the same high frequency

producing a train of sonic compression waves in any medium with which it

in contact.A suitable resistance circuit is provided to control the amplitude of an electrica

oscillations which in turn controls the magnitude of the mechanical vibratio

of the crystal and hence the amplitude of the sonic wave.This amplitude is referred to as the intensity and is the energy crossing un

area in unit time perpendicular to the sonic beam. It is therefore measured i

watts per square centimeter (i.e., joules/sec/cm2).

Current supplied to the oscillator circuit can be automatically switched on and o

to produce a pulsed output, typically giving ratios 1:1 or 1:4. A meter is often included which measures the electrical oscillations applied to th

crystal but not the vibration of the crystal.


4/18


4

Transmission of Sonic Waves:Due to the fact that the wavelength of these waves is much smaller than th

transducer face; the sonic beam is roughly cylindrical and of the sam

diameter as the transducer.This beam of ultrasound emitted from the transducer is by no means uniform

even in a homogenous medium. The beam non-uniformity ratio (BNR) is th

ratio between peak intensity and average intensity in the beam. The lower th

BNR the more uniform the beam. Waves emitted from the different places on the face of the transducer will trav

to the same point in space in front of the transducer face by different paths an

hence arrive out of phase. Some waves cancel out, others reinforce so that the net result is a very irregula

pattern of the sonic waves in the region close to the transducer face, called thnear fieldorFresnel zone. In the region beyond this, thefar filedorFraunhofe

zone, the sonic field spreads out somewhat and becomes much more regulabecause the differing paths lengths from points on the transducer becom

insignificant at greater distances.

The length of the near field depends directly on the square of the radius of th

transducer face and inversely proportional to the wavelength of the son

waves.

Length of Fresnel zone = r2

/For practical purposes therapeutic ultrasound utilizes the near field and henc

is irregular. There relatively more energy on average, carried in the central pa

of the cross-section of the beam. The intensity of such fields cannot be expressed in a simple way because it varie

from place to place in the ultrasonic beam. Thus the spatial peak intensity or th

spatial average intensity may be specified. If the output is pulsed the intensity over time varies so it can either be expresse

astemporal average intensity ortemporal peak intensity. Thus intensity can be described in four ways:

Spatial average temporal average (SATA) Spatial peak temporal average (SPTA) Spatial peak temporal peak (SPTP) Spatial average temporal peak (SATP)

This irregularity can be ironed out to some extent by continuous movement o

the treatment head during the therapy.


5/18


5

Boundaries between Media: Sonic waves involve vibratory motion of molecules so that there is

characteristic velocity of wave progression for each particular medium.

It depends on the density and elasticity of the medium and together thesspecify what is known as the acoustic impedance of the medium. The acoustic impedance can be found by multiplying the density of th

medium by the velocity of sonic waves through it.

Acoustic impedance = density of medium velocity of wave

The energy carried by a wave also depends on its frequency (the higher th

frequency, the greater the energy)and its amplitude (the larger the amplitud

the greater the energy).

Medium

(High velocity) reflected radiation

incident radiation

Medium(Low velocity) refracted radiation

emergent radiation

When sonic waves come to a boundary, various changes occur:

1) They must travel in the new medium at a velocity characteristic for thamedium and related to its acoustic impedance.

2) The frequency remains the same, so the wavelength must change.


6/18


6

3) Some of the energy is reflected back. The amount of the energy reflecteis proportional to the difference in acoustic impedance between the tw

media.

Water / Glass 63% of energy is reflected

Water / Soft tissue 0.2% of energy is reflected4) If the wave front strikes the boundary at some other angle the reflecte

wave will travel away from the boundary at the same angle; that is, th

angle of incidence of a beam equals the angle of reflection and is in th

same plane.

5)If some energy is reflected back, but the frequency remains the samthere must be decrease in amplitude of the wave.

6)Refraction also occurs with sonic waves due to the difference in acoustiimpedance. The beam of sonic energy that passes through the secon

medium does not continue in a straight line but changes direction at thboundary because of the different velocities in the two media. If th

acoustic impedances are closely matched little refraction will occur.7) The tuning back of a wave in the same medium has a further consequence

Two waves, the original and the reflected, are traveling in opposit

directions so that at some points they will be combined, producing

much greater amplitude and hence wave energy, and at other points the

will cancel one another out. This tends to produce a stationary wav

pattern, logically called a standing wave.

Absorption of Sonic Waves: Kinetic energy is converted to heat energy as it passes through the material.

The energy will decrease exponentially with distance from the sourcbecause a fixed proportion of it is absorbed at each unit distance so that th

remaining amount will become a smaller and smaller percentage of the initi

energy.

There is an inverse relationship between the amount of energy thapenetrates a material and the amount that is absorbed. Thus if a beam o

ultrasound is passed through the tissues it will be steadily reduced in intensity

This can be expressed as theabsorption coefficient.

Half-Value Depth: The depth or distance at which half the initial energy has been absorbed

known as half-value depth.


7/18


7

The conversion of sonic energy to heat is due to increased molecula

motion it follows that the amount converted will depend on the nature o

those molecules and on the frequency / wavelength of the ultrasound. Thus the half-value depth will be different in different tissues for any give

ultrasound frequency.

Half-value depth of penetration in mm for 1 MHz and for 3 MHz is a

follows:

Tissue 1 MHz 3 MHz

Skin 40 25

Fat 50 16

Muscle 10 20 30 60

Bone 15 5

Absorption of sonic energy is greatest in tissues with largest amounts o

structural protein and lowest water content.

Protein content & absorption of ultrasound in various tissuesBlood Least protein content Least absorption of US

Fat

Nerve

MuscleSkin

Tendon

Cartilage

Bone Greatest protein content Greatest absorption of US

Attenuation of Ultrasound in the Tissues: The loss of energy from the ultrasound beam in the tissues is calle

attenuation and depends on both absorption (the energy of the ultrasonbeam is converted to heat by the tissues)and scattering (the normally parall

beam becomes more dispersed the further it passes into the medium).

Absorption accounts for some 60 80% of the energy lost from the beam

The scattered energy may also be absorbed other than in the region to whic

the ultrasound beam is applied.


8/18


8

Scattering is caused by reflections and refractions, which occur at interface

throughout the tissues. This is particularly apparent where there is a larg

difference in acoustic impedance.

At 1 MHz At 3 MHzFat Muscle Bone Fat Muscle Bone

100 100

80 80

60 60

40 40

20 20

0 0

0 10 20 30 40 50 60 0 10 20 30 40 50 60

depth in tissues (mm) depth in tissues (mm)

Proportional heating of 1 and 3 MHz ultrasound through tissues

Shear waves can also be formed which transmit energy along the periostea

surface at right angles to the ultrasound beam. Due to the fact that threflection is quite large (almost 25%) and that sonic energy is absorbe

almost immediately in bone, there is marked heating at the bone surfac

This mechanism is considered to account for theperiosteal pain that can ariswith excessive doses of therapeutic ultrasound. Differences of acoust

impedance between other soft tissues are much smaller.

Heating in the Tissues due to Ultrasound: The important factor for heating in the tissue due to ultrasound is the rat

of tissue heating, which is, influenced both by theblood flow, whicconstantly carries heat away, andby heat conduction.

In highly vascular tissues such as muscle it is likely that heat would b

rapidly dissipated preventing any large temperature rise; on the othe

hand, less vascular tissue, such as dense connective tissue in the form o

tendon or ligament, may experience a relatively greater temperature rise

Moving the transducer head during the treatment is important because o

following effects:


9/18


9

To smooth out the irregularities of the near field It also reduces some of the irregularities of absorption that migh

occur due to reflection at interfaces, standing waves, refraction, an

differences in tissue thermal conduction or blood flow

It also reduces shear wave formation and thereby reduces chances operiosteal pain

Thus resulting heating pattern is likely to be much more evenly distribute

It has been estimated that for an output of 1 W/cm2

there is a temperatur

rise of 0.8C/min if vascular cooling effects are ignored.

Pulsed Ultrasound: A circuit in the ultrasonic generator is arranged to turn the ultrasound on i

short bursts or pulses.

This reduces the time averaged intensity and hence the amount of energavailable to heat the tissues while ensuring that the energy available in eac

pulse (pulsed averaged intensity) is high enough for mechanical rather tha

thermal effects to predominate. Many therapeutic ultrasound generators produce 2 ms pulses and vary th

intervals between pulses. This can be expressed either as:

The mark : space ratio, which is the ratio of the pulse length to thinterval

The duty cycle, which is the ratio of the pulse length to the total lengtof the pulse plus interval, expressed as percentage.

Pulse IntervalMark:space

ratio

Ratio of pulse

to total period

Duty

cycle

2 ms 2 ms 1:1 1 in 2 50%

2 ms 8 ms 1:4 1 in 5 20%

Effects of Pulsing:If pulsed ultrasound is applied at a mark:space ratio of 1:4 the amount o

introduced energy is one-fifth of that which would be introduced bcontinuous ultrasound applied for the same length of time and at th

same intensity. The same amount of energy could be introduced into the tissues either b

extending the treatment for 5 times the length or giving 5 times th

intensity of the continuous treatment. The effect is not the same becaus

with pulsed treatment there is time for heat to be dissipated by conductio


10/18


10

in the tissues and in the circulating blood. Therefore, higher intensitie

can be safely used in a pulsed treatment because the average heating

reduced. Ultrasound application can increase rates of ion diffusion across ce

membranes; this could be due to increased particle movement on eitheside of the membrane and possibly, increased motion of the phospholipid

and proteins that form the membrane.

Mild mechanical agitation of the tissues has certain effects, which remai

the same no matter how long the agitation, is continued but that short bursof more vigorous agitation have different, more significant effects.

Physical & Physiological Effects of Ultrasound:As oscillation or sonic energy is passed through the body tissue, it cause

transfer of heat energy in the body tissues. If this energy is not dissipated bnormal physiological response, then there is local rise in temperature, whic

accounts for thermal effects.

If heat dissipation equals heat generation there is no net rise i

temperature and any effects are said to be non-thermal. Using low intensities o

pulsing the output achieves non-thermal effects.

Thermal Effects:

The advantage of using ultrasound to achieve heating is due to th

preferential heating of collagen tissue and to the effective penetration othis energy to deeply placed structures.Heating fibrous tissue structures such as joint capsules, ligament

tendons, and scar tissue may cause a temporary increase in the

extensibility, and hence a decrease in joint stiffness.Mild heating can also have the effect of reducing pain and muscle spasm

and promoting healing processes.

Non-Thermal Effects:

1)Cavitation:Cavitation is the formation of tiny gas bubbles in the tissues as a resu

of ultrasound vibration. These bubbles, generally of a micron (10-6

m

or so in diameter. These can be of two types, namely stable cavitation or transien

cavitation.

Stable cavitation occurs when the bubbles oscillate to and fro withi

the ultrasound pressure waves but remain intact.


11/18


11

Transient (or collapse) cavitation occurs when the volume of th

bubble changes rapidly and then collapses (implodes) causing hig

pressure and temperature changes and resulting in gross damage t

tissues.

Stable cavitation associated with acoustic streaming, is considered thave therapeutic value but the transient cavitation, which is only likel

to occur at high intensities, can be damaging.

In practice the danger of tissue damage due to cavitation is minimize

by the following measures:

Using space-averaged intensities below 4W/cm2 Using a pulsed source of ultrasound Moving the treatment head during insonation

2)Acoustic Streaming:Acoustic streaming is a steady circulatory flow due to radiation torque

Additionally, as a result of either type of cavitation there is a localized

unidirectional fluid movement around the vibrating bubble. These ver

small fluid movements also occur around cells, tissue fibres, and othe

boundaries, which is known asmicrostreaming.

Microstreaming exerts viscous stress on the cell membrane and thu

may increase membrane permeability.

This may alter the rate of ion diffusion causing therapeutically usefu

changes, which includes increased secretion from mast cellincreased calcium uptake, and greater growth factor production b

macrophages. All these effects could account for the acceleration of repair followin

ultrasound therapy.

3)Standing Waves:Standing waves are due to reflected waves being superimposed on th

incident waves. The result is a set of standing or stationary waves with peaks of hig

pressure (antinodes), half a wavelength apart, between which arezoneof no pressure (nodes). Gas bubbles collect at the antinodes, and cells collect at the nodes.

This pressure pattern causes stasis of cells in blood vessels at th

pressure nodes.The endothelium of the blood vessels exposed to standing waves ca

also be damaged leading to thrombus formation.


12/18


12

Erythrocytes can be lysed if they are swept through the arrays of bubble

situated at the pressure antinodes. There is also the possibility of marked local heating where th

amplitude of the combined waves is high.

If transducer head is moved during the treatment, then standing waveare unlikely to form.

4) Micromassage:The micromassage effect of ultrasound occurs at a cellular level wher

the cells are alternately compressed and then pulled further apart.

The waves of compression and rarefaction may produce a form o

micromassage, which could reduce oedema. Ultrasound has been found to be effective at reducing recent traumat

oedema andchronic indurated oedema.

Effects of Ultrasound on Inflammation & Tissue Repair:Acute Stage:

Stable cavitation and acoustic streaming increases calcium ion diffusio

across the cell membrane, which works as a cellular secondary messenger

and thereby increases the production and release of wound-healing factors. These include the release of histamine from mast cells and growth factor

released from macrophages.

In this way, ultrasound has the potential to accelerate normal resolution oinflammation providing that the inflammatory stimulus is removed.

This acceleration could also be due to the gentle agitation of the tissue fluid

which may increase the rate of phagocytosis andmovement of particles an

cells. Thus, ultrasound has a pro-inflammatory, not an anti-inflammatory action.

Proliferative (Granulation) Stage: This begins approximately 3 days after injury and is the stage at which th

connective tissue framework is laid down by fibroblasts for the new bloovessels. During repair, fibroblasts may be stimulated to produce more collagen

ultrasound can promote collagen synthesis by increasing cell membran

permeability, which allows the entry of calcium ions, which control cellulaactivity.

Not only is more collagen formedbut it is also ofgreater tensile strengt

after ultrasound treatment.


13/18


13

Ultrasound encourages the growth of new capillaries in chronic ischaemitissue and the same could happen during repair of soft tissues after injury. The enhanced release of growth factors from macrophages followin

exposure to therapeutic ultrasoundmay cause proliferation of fibroblasts.

It has been suggested that ultrasound treatment given during the first weeks after injury accelerates bony union, but, if given to an unstabl

fracture during the phase of cartilage formation, it may result in thproliferation of the cartilage and consequently delay of bony union.

Remodelling Stage: This stage last months or years until the new tissue is as near in structure a

possible to the original tissue.

Ultrasound is considered to improve the extensibility of mature collagesuch as is found in scar tissue, which occurby promoting the reorientatio

of the fibres (remodelling), which leads to greater elasticity without loss o

strength.

Therapeutic Uses of Ultrasound:Varicose Ulcers:

Ultrasound promotes healing of varicose ulcers and pressure sore

(decubital ulcer).

[Varicose Ulcer: Ulcer (circumscribed depressed lesion on the skin o

mucous membrane of any internal organ following sloughing of necrotinflammation) in the leg associated with varicose veins is known avaricose ulcer.Pressure Sore: A bed sore; a decubital ulcer appearing on dependensites usually on lumbosacral region, most commonly in bed-ridden elderpersons is known as pressure sore.]

Pain relief:Ultrasound is used in herpes zoster, low backache, prolapse

intervertebral disc (PIV) and many other conditions.[Herpes Zoster: Shingles (band-like involvement of neurocutaneoutissues) caused by varicellazoster virus. It involves posterior root gangliand presents with severe continuous pain in the distribution of thaffected nerve.Prolapsed Intervertebral Disc: Abnormal descent of intervertebral disbetween the vertebra is known as prolapsed intervertebral disc.]

Acute tissue injury:


14/18


14

Ultrasound is used in soft tissue and sport injuries, in occupationa

injuries and post-natal injuries. It is used for perineal post-natal pain, fo

painful shoulders and for both neurogenic & chronic pain.

Scar tissue:

Ultrasound improves quality of scar tissue and excessive fibrous tissue. is used in conditions likeDupuytrens contracture andplantar fasciitis.

[Dupuytrens contracture: Thickening and contracture of palmar fasciatypically affects the ring finger and may involve years later incompletelittle finger is called Dupuytrens contracture.Plantar fasciitis: Tenderness under the heel from plantar fibromatosis otear of plantar fascia is called plantar fasciitis.]

Bony injury:

Ultrasound therapy in the first 2 weeks after bony injury can increasbony union, but, given to an unstable fracture during the phase of cartilag

proliferation, it may result in the proliferation of cartilage and therefore decreasbony union. Ultrasound has also been used in the early diagnosis of stres

fractures.

Chronic Indurated Oedema:The mechanical effect of ultrasound has an effect on chronic oedema an

helps in its treatment. It also breaks down adhesions formed between adjacen

structures.

Dangers of Ultrasound:There are very less evidences of dangers of ultrasound but it may occur i

some conditions only.

Burns could occur if the heat generated exceeded the physiological ability t

dissipate it.Tissue destruction would result from transient cavitation.Blood cell stasis and endothelial damage may occur if there is standing wav

formation.These dangers would be more likely with high-intensity continuous outp

with a stationary head or over bony prominences.


15/18


15

Contraindications of Ultrasound:Rapid dividing tissues:

Since ultrasound affect tissue repair it is possible that it could affe

abnormal tissue activity so that it might encourage neoplastic growth an

provoke metastases. Therefore, treatment over tumours or over tissue i

precancerous states should be avoided.

Pregnant Uterus:To the rapidly dividing and differentiating cells of the embryo and fetu

should be avoided by not applying treatment over the pregnant uterus. Diagnost

ultrasound is entirely safe and it is probable that low doses of therapeuti

ultrasound would have no ill effects.

Epiphyseal Plates:Avoid giving ultrasound on cartilaginous epiphyseal plates becaus

growth of the bone is impeded.

Spread of Infection:Bacterial or viral infection could be spread by ultrasound, presumably b

facilitating microorganism movement across membranes and through the tissue

The low-grade infections of venous ulcers, or similar, would seem to be safe t

treat.

Tuberculosis:Due to the possible risk of reactivating encapsulated lesions tuberculou

regions should not be treated.

Vascular Problems:Circumstances in which hemorrhage might provoke should not be treate

For example, where bleeding is still occurring or has only recently bee

controlled, such as an enlarginghaemarthrosis orhaematoma or uncontrollab

haemophilia.

Severely ischaemic tissues should be avoided because of the poor he

transfer and possible greater risk of arterial thrombosis due to stasis anendothelial damage.

Treatment over recent venous thrombosis might extend the thrombus o

disrupt its attachment to the vein wall forming an embolus. Areas o

atherosclerosis are best avoided for the same reason.

[Haemarthrosis: Bleeding into the joint usually from an injury, whicresults in a swelling of the joint, is known as haemarthrosis.


16/18


16

Haematoma: A collection of blood inside the body, caused by bleedinfrom an injured vessel is called haematoma.Haemophilia: An inherited coagulation defect characterized by permanent tendency to hemorrhages due to a defect in the coagulation o

blood is known as haemophilia.Atherosclerosis: A condition caused by intramural deposition of LowDensity Lipoprotein (LDL), secondary to exposure of smooth muscles tlipid, resulting in platelet induced smooth muscle proliferation, formation ofibrotic plaques and calcification is known as atherosclerosis.]

Radiotherapy:Areas that have received radiotherapy in the last few months should no

be treated because of the risk of encouraging pre-cancerous changes.

Nervous System:Where nerve tissue is exposed, e.g. over a spina bifida or after

laminectomy, ultrasound should be avoided. Treatment over the cervical gangli

or vagus nerve might be dangerous in cardiac disease.

[Spina bifida: Failure of closure of the spinal canal due to defectivfusion of the vertebral arch in the lumbosacral region and is associatewith depression, pigmentation or presence of hair is known as spinbifida.Laminectomy: Surgical removal of the entire lamina of a vertebra as

reatment of herniation of intervertebral disc is known as laminectomy.tSpecialized Tissue:

Thefluid-filled eye offers exceptionally good ultrasound transmission an

retinal damage could occur.

Treatment over thegonads is not recommended.

Implants:Smaller and superficial implants, like metal bone-fixing pin

subcutaneously placed; as a precaution, low doses should be used in thes

circumstances.Plastics used in replacement surgery, such as high-density polyethylen

and acrylic should be avoided.

Treatment over implanted cardiac pacemakers should not be give

because the sonic vibration may interfere with the pacemakers stimulatin

frequency.


17/18


17

Anaesthetic areas:High doses should not be given over anaesthetic areas.

Precautions of Ultrasound:1)Use ultrasound only if adequately trained to do so2)Use ultrasound to treat only those patients with conditions known to respon

favorably to this treatment3)Use the lowest intensity that produces the required effect, because highe

intensities may be damaging

4)Move the applicator constantly throughout the treatment, to avoid the damagineffects of standing waves

5)If the patient feels any additional pain during treatment, either reduce th

intensity to a pain-free level or abandon the treatment6)Use properly calibrated and maintained equipment7)If there is any doubt, do not irradiate

Phonophoresis:Phonophoresis is the movement of drugs through skin into the subcutaneou

tissues under the influence of ultrasound. Many drugs are absorbed through the skin only very slowly; high-frequency soni

vibration may accelerate this process. It is also known as sonophoresis o

ultrasonophoresis. Phonophoresis relies on perturbation of the tissues causing more rapid particl

movement and thus encouraging absorption of the drug.

The effects of phonophoresis are those of the particular drug employed, combine

with the effects of ultrasound. Theoretically phonophoresis is possible utilizing the acoustic streaming force

which exist in the ultrasound field. Phonophoresis will be dependent not only on the frequency, intensity, duty cycl

and treatment duration of the ultrasound, but also on the nature of the drug molecu

itself. In phonophoresis:

Ultrasound facilitates the passage of some drugs into and through the skin The effects are due both to absorption of the drug and to the ultrasound Lower ultrasonic frequencies appear to lead to deeper drug penetration Pulsing ultrasound may lead to better drug penetration


18/18


18

The quality of drug entering the skin is proportional, in general, to the timand intensity of ultrasound application

Drugs used in Phonophoresis:Phonophoresis of hydrocortisone has been used in the treatment of many ski

conditions includingpsoriasis,scleroderma, andpruritus.

A lotion containing zinc oxide, tannic acid, urea, and mentholhas been applie

by phonophoresis to treat herpes simplex virus type II in both oral and genita

infections.Antibiotics such as penicillin have been given by phonophoresis for treatment o

skin infections.

Product Active ingredients

Steroids1) Cobadex cream

2) Locoid lipocream

Hydrocortisone, Dimethicone

Hydrocortisone Butyrate

Anti-inflammatory drugs1) Intralgin gel

2) Movelat cream

Benzocaine Salicylamide

Corticosteroids, heparinoid,

salicylic acid

Local anaesthetics1) Emla cream

2) Xylocaine ointment

Lignocaine, Prilocaine

Lignocaine Hydrochloride

[Psoriasis: A chronic disorder characterized by well defined, scalyerthematous plaques on the extensor surfaces of the extremities like elbowand knees, trunk, back and scalp is called psoriasis. It may be localized ogeneralized and is considered as an autoimmune disease.Scleroderma: Widespread thickening and fibrosis of the skin due t

accumulation of excess collagen and polyglycans, a manifestation o

systemic sclerosis (an induration of tissue due to excess fibrosis) is knowas scleroderma.Pruritus: Severe itching is known as pruritus.]

6130667 Therapeutic Ultrasound

Documents

Transcript of 6130667 Therapeutic Ultrasound