L-14 Shortwave Therapy :L-14 Shortwave Therapy By Dr.Eng WALID TARAWNEH Rehabilitation Engineering


Diathermia :Diathermia Diathermy: “to heat through” Diathermy involves heating deep muscular tissues. When heat is applied to the painful area, cellular metabolism speeds up and blood flow increases. The increased metabolism and circulation accelerates tissue repair. The heat: helps the tissues relax and stretch reduces nerve fiber sensitivity increasing the patient's pain threshold. 19/3/2009 DR.WALID TARAWNEH 2


Methods of Diathermy :Methods of Diathermy There are three methods of diathermy. In each, energy is delivered to the deep tissues, where it is converted to heat. Shortwave Diathermy. The body part to be treated is placed between two capacitor plates. Heat is generated as the high-frequency waves travel through the body tissues between the plates. Shortwave diathermy is most often used to treat areas like the hip, which is covered with a dense tissue mass. It is also used to treat pelvic infections and sinusitis. The treatment can also reduces inflammation. The Federal Communications Commission regulates the frequency allowed for short-wave diathermy treatment. Most machines function at 27.33 MHz Ultrasound diathermy. Here high-frequency acoustic vibrations are used to generate heat in deep tissue. Microwave diathermy. This method uses radar waves to heat tissue. This form is the easiest to use, but the microwaves cannot penetrate deep muscles. Diathermy is also used in surgical procedures. Many doctors use electrically heated probes to seal blood vessels to prevent excessive bleeding. This is particularly helpful in neurosurgery and eye surgery. Doctors can also use diathermy to kill abnormal growths, such as tumors, warts, and infected tissues. 19/3/2009 DR.WALID TARAWNEH 3


Shortwave Therapy Diathermy (SWD) :Shortwave Therapy Diathermy (SWD) SWD is used in medical therapy to produce local heating in tissue through the conversion of electromagnetic energy into thermal energy The shortwave used are non-ionizing electromagnetic radiation 80 watt power , more than 300 million times too weak to produce ionization But this EMR can causes tissue ions to move within tissues SW is used to penetrate deep into the body tissues to : stimulate blood flow heat the treated area SWD is electrical field that is applied to a patient by : capacitor field treatment (Capacitive Electrode) coil field treatment (Induction Electrode) 19/3/2009 4 DR.WALID TARAWNEH


History :History The medical application of electromagnetic energy (EME) dates back to 1892 ( using EM- vibration with f=200-300 Hz by D.Arsonval) The modern application of short wave electrotherapy was developed in the 1930’s by Schliephake using the capacitive method The inductive method was developed in USA in 1934 In 1940 the pulsed short wave electrotherapy was developed by Ginsburg 19/3/2009 5 DR.WALID TARAWNEH


SW as a part of the Electromagnetic Spectrum :SW as a part of the Electromagnetic Spectrum Introduction The shortwave (SW) generate electromagnetic energy at about f= 27.12 MHz , = 11 meter wavelength and 80 watts power This energy is transferred to the environment via a flat coil The electromagnetic field Field : describes the action of force at a distance without direct contact with the field source Generation of electromagnetic fields Electrical field is generated at the end of conducting wire where a it is built of electrical charge Magnetic field is generated at the conducting wire where it is built of stream of stream of electrical charge The electrical field creates a magnetic field and the magnetic field creates electrical field 19/3/2009 6 DR.WALID TARAWNEH


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Slide 8:SW are Non-ionizing EMR that do not have enough energy to change the electrical properties of molecules or to remove electrons from atoms When charges move in a wire it produce an electric current. constantly moving charges forms a magnetic force at right angles to the direction of the charge motion. If an electric charge is accelerated it causes the production of an electromagnetic radiations EMR Effects of electromagnetic field: Electromagnetic field produces circular currents at right angles to the line of force giving eddy currents which leading to friction of tissue particles and produce heat. The heat will concentrate in the tissues of low resistance (blood and muscles). The effect of the electrical part of the EM field on the living tissue is more power than the magnetic part The effect of EMR on living tissues is characterized by the relationship between the wavelength and the depth of penetration (distance at which the field strength reduced by a factor of 0.37) 19/3/2009 8 DR.WALID TARAWNEH


Physical and physiological Aspects to heat :Physical and physiological Aspects to heat HEAT: Definition : heat is an increase in the velocity of particles The energy of the EM- field that penetrates into tissues is converted into heat The intensity of the field decrease with increasing the depth The dissipated المبعثرة energy P in tissues P = 0.5  E2 (W/m3)  - the specific electrical conductivity of tissues E – the amplitude of local electrical field strength Table 1 shows that  become greater with increasing f and that muscle conductivity is greater than that for fat tissues The specific absorption rate (SAR) = 0.5  E2/ (W/kg) - specific mass density . For muscle tissues = 1070 kg/m3 while for fat tissues is = 940 kg/m3 Reaction of human body to heat : The human body T0 is controlled by the ventral part of the hypothalamus . The information of this control is provided by the T0 of the blood and the thermo detectors (cold detectors below the skin ) Table 1 19/3/2009 9 DR.WALID TARAWNEH


Slide 10:If T0 of the blood increase or the thermo detectors are stimulated the hypothalamus activates various mechanisms that serve to keep the body T0 within limits ( 36- 37.5)C . These mechanism are : Vasodilation , Sweating and Reduction in heat production Application of heat results increase in local cell metabolism activity and increase in transport through the cell membranes (for each 1C activity increase with 13%) . This lead to increase in pCO2, pO2 and pH. If T0 rise above 420C tissue death occurs Heat and high frequency therapy Non thermal effect : are effects that arise without involvement of CNS or hypothalamus Thermal effect: are effects that arise from an increase of blood T0, stimulation of thermo detectors In muscle tissues the increase in T0 will increase the elasticity factor by 5-10 , while heat reduces the potential in nerve tissues leading to depolarization with not strong enough potential to induce action potential The increase of heat will increase the speed of transmission within nerve 19/3/2009 10 DR.WALID TARAWNEH


Methods for inducing heat by EM-field :Methods for inducing heat by EM-field Methods Capacitive Inductive Capacitive Methods The body part forms the dielectric in a plate capacitor ( two electrodes) If The electrical field is perpendicular to tissue layer the penetration of the field is poor ( the skin /fat layer form a sort of shielding, because the field cause a build up of charges at the interfaces between the tissue layers ) Most energy is absorbed by skin and fat  so the heat is only superficial If the field is parallel to tissue layer the penetration is much better and the specific absorption rate ( SAR) at 27 MHz is 20 -30 times greater in muscle than that in fat Most energy is absorbed by muscle and bone  so the heat will be in the depth of body part electrode body part fat muscle bone 19/3/2009 11 DR.WALID TARAWNEH


Slide 12:Inductive method In this method the magnetic field serves as the carrier of the electrical field The distribution of the field and SAR depended on the shape and the position of the electrode The electrical field close to the coil is strong The faradic screen prevent the passes of the electrical field ,where as the magnetic field can pass unhindered (without resistance) This allows the to induce eddy current in the tissues which leading to friction of tissue particles and produce heat. The heat is max when f and pulse duration is max f= 27MHz , pulse duration approx 50-450 s The effective area of the field is ring shaped When using two coils the pulse of one coil is delivered in the pulse interval of the other coil . This allow treatment of a large area in one session and treatment from both side of the subject (body part) 19/3/2009 12 DR.WALID TARAWNEH


Shortwave Equipment :Shortwave Equipment Principles Short wave unit used for generation thermal and biological effects in the tissues of the human body. High frequency current pass through the body via two plate-electrode Part of the body to be treated is placed between the two electrode. High frequency current is made to flow through the capacitor, whereby heat is generated in the dielectric (part of the body between plates) When a pulsed high-frequency is used, there is less heating. When induction electrode are used eddy-current are induced which cause the thermal and other biological effects in the body. In SW technique there is two main circuits : the machine circuit which produce high frequency current coupled with the patient circuit through inductors to transfer the electrical energy to the patient. To get max transfer of the energy the patient circuit had to be kept tuned to the high frequency of the used in the machine circuit generator This is done by mean of motor –driven tuning capacitor tuning capacitor motor 19/3/2009 13 DR.WALID TARAWNEH


Slide 14:Type of shortwave therapy Two types available Continuous shortwave therapy Pulsed shortwave therapy continuous SW In continuous SW the subjective feeling of warmth plays the major role. High output approximately of 400 W. Continuous shortwave therapy increases the circulation and stimulation metabolic processes Pulsed SW Maximum output of 1000 W peak power depending on the selected pulse duration. No feeling of warmth. Suited to the treatment of acute condition where heat therapy is contraindicated. Operational Panel Main switch and mains indicating lamp Mode selector switch (continuous/pulsed) Micro-processor timer Time-setting switch Intensity indicator (bar-display) Intensity control Pulsed-mode indicator Tuning indicator Thermal ,safety cut-out 9 19/3/2009 14 DR.WALID TARAWNEH


Block Diagram :Block Diagram Function The power supply give the required voltage to the HF-generator which consist of high tension transformer (HT) that supply the anode of the generator valve (GV) The primary voltage of the HT is controlled by the intensity control unit The HT can be switched on only after the timer is on and it oscillates a 27MHz ,while in pulse mode it give HF current with duration of 400s The bar display indicate the amplitude of the anode current at GV ,which is proportional to output power The energy is extracted inductively from the GV and is give to the patient circuit via the harmonic filter ( to attenuate the harmonics)and the galvanic isolation circuit HT GV TC M 19/3/2009 15 DR.WALID TARAWNEH


Slide 16:The phase detector compares the phases of the current and voltage in the patient circuit and when they are out of phase a signal is generated to the motor (M) control which then energize the tuning capacitor (TC) The fan run directly after setting the treatment time The protection circuit switch of the generator if the treatment mode is switched form continuous to pulse while the HF power is on or when switching from pulse to continuous . The automatic tuning device (ATD) The principle of this device is based on the measurement of phase angle between I and U in the patient circuit The phase is = 0 only if the output circuit is tuned to the generator frequency If not ( the phase  0 ) then the output is not tuned The block diagram of ATD The phase comparator consist of phase angle measurement device amplifier SAMPLE –HOLD CIRCUIT 19/3/2009 16 DR.WALID TARAWNEH


SW –Electrodes :SW –Electrodes Electrodes types capacitive Flexible pads: consist of metal electrode encased in rubber and produce an electrostatic field. Capacitive Space plates: consist of a rigid metal electrode encased in a Perspex cover  electrostatic field Inductive Coil or cable electrode: consists of a wire with plugs at either end electromagnetic field. 1 2 3 Capacitive Space electrode parts 19/3/2009 17 DR.WALID TARAWNEH


Slide 18:The monode electrode : flat, rigid coil encased in Perspex cover electromagnetic field The minode electrode : conical rigid coil encased in Perspex cover electromagnetic field. The diplode electrode or drum electrode: consists of a flat coil electrode encased in a Perspex cover with two wings electromagnetic field The circuplode electrode : an inductive electrode which provided with a faraday screen that eliminates capacitive effect. It give pure magnetic field. No energy absorbed in superficial tissues All these electrodes 4,5,6 and 7 have larger effect in the deeper tissues without having thermal effect . faraday screen 19/3/2009 18 DR.WALID TARAWNEH


Slide 19:The circuplode connection It is connected to the SW-unit via a coaxial cable, where a special adapter is used for this connection The role of the adaptor is to performs the duty of the impedance transformer from high ohmic symmetrical to low ohmic asymmetrical The coupling to the treatment coil L1-L2 IS inductive 19/3/2009 19 DR.WALID TARAWNEH


Slide 20:Some Application 19/3/2009 20 DR.WALID TARAWNEH


Factors influence field distribution in SW Diathermy :Factors influence field distribution in SW Diathermy These factors are : Electrodes spacing : Spacing allows the lines of force in the electrostatic field to divergeللتَبَاعُدbefore entering the tissues. This prevents concentration of heat in the super-facial tissues and ensures more heating through the part Spacing can be provided by: wrapping flexible pads in towel. flat felt spacing pads between pad electrode and skin. air when using space plates. a- Normal spacing even field distribution. b- Increased spacing deep field concentration. c- Decreased spacing superficial concentration. The use of diplode electrode offer different spacing a b c 19/3/2009 21 DR.WALID TARAWNEH


Slide 22:2- Air in cavities التجاويفِ : As sinuses كجيوبor uterus رحم, The lines of force deviate to avoid air as it offers a high resistance. As a result only the sides of air cavity will be heated. 3- Electrode size: If the electrodes are too small than the diameter of treated part line of force will be concentrated superficially. If the electrodes are markedly larger the line of force will be lost in the air. Ideally, the electrodes should be slight larger than the area treated. 4- Metal: Metal causes the lines of force to concentrate on the metal Air 19/3/2009 22 DR.WALID TARAWNEH


Therapeutic Effects of SWD :Therapeutic Effects of SWD Pain relief: of traumatic pain and rheumatic conditions affecting muscles, ligaments and joints. Muscle spasm: may be reduced directly by SWD. Inflammation: resolution of inflammation as a result of increase blood supply. Accelerate wound healing: by increase coetaneous circulation. Infection: increase circulation and increase white blood cells and antibodies. Fibrosis: increase extensibility of fibrous tissues such as tendons, joint capsule and scars. 19/3/2009 23 DR.WALID TARAWNEH


Indications and Therapeutic Uses of SWD :Indications and Therapeutic Uses of SWD 1- Musculo-skeletal disordersاِضطرابات الجهاز العضلي Tendonitisالتهاب الأوتار ,Strainإجهاد ,Sprainإلتواء ,Sub-acute and chronic arthritisالتهاب المفاصل الحاد و المزمن ,Abscesses الدمامل,Post-traumatic conditions as fracture, and contusionبعد الكسر و الكدمات . 2- Cardiovascular disordersاضطرابات الجهاز الدمموي Angina pectoris and Hypertension. النوبة قلبية وإرتفاع ضغط 3- Chest disorders: To relieve muscle spasm in some forms of bronchial disorders,and Sub-acute and chronic bronchitis. 4- Neurological disorders: Neuritis, Sciatica, Migraine. التهاب العصب, عرق نِساء, داء شقيقة 5- Genitourinary disorders: اضطرابات جهاز الرحم 6- Mouth and teeth disorders: ِضطرابات الأسنانَ والفَمَّ: Gingivitis, إلتهاب لثّةCyst كيس 7- Ear, nose and throat disorders: Sinusitis التهاب الجيوب, Laryngitis. إلتهاب حنجرة 19/3/2009 24 DR.WALID TARAWNEH


Contraindications of SWD :Contraindications of SWD 1- Malignant and ischemic tissues. الأنسجة خبيثة. 2- Moderate and excessive edema. وذمة معتدلة ومفرطة 3- Metallic implants. 4- Pacemakers. 5- Tendency of hemorrhage; during menstruation, pregnancy, peptic ulcer and varicose veins. ميل النزفِ؛ أثناء حيضِ، حمل، قرحة معوية وعروق دوالية. 6- Impaired thermal sensation. 7- Unreliable patient. مريض عديم الثقة 8- Recent radio-therapy. 9- Acute infection or inflammation. عدوى أَو إلتهاب حادّ 10- Analgesic therapy. علاج مسكّن 11- Severe cardiac condition and blood pressure abnormalities. الحالات القلبية الحادّة وضغط دمّ 19/3/2009 25 DR.WALID TARAWNEH


Slide 26:Pulsed Shortwave Diathermy General Is short wave at the frequency of 27.12 MHz, which is pulsed at a rate, selected by the therapist. The pulse frequency range is from 15 to 200 Hz. The maximum intensity is 1000 watts. The pulse duration is constant at 0.4 ms in square pulse. The advantage of pulsed S.W.D. is that a very high intensity of power can be administered with minimal effect. 19/3/2009 26 DR.WALID TARAWNEH


Slide 27:Biological Effects 1-Increased metabolism. 2-Relief of pain. 3-Stimulated wound healing. 4-Relaxed muscle spasm. 5-Accelerated wound healing. 6-Decreased haematoma formation. Indications 1- Sprains. 2- Contusions. 3- Haematoma. 4- Bursitis. 5- Sinusitis. Contraindications 1- Pacemakers. 2- High fever. 3- Tumour. 4- Metal. 19/3/2009 27 DR.WALID TARAWNEH


Therapeutic Variation In The Field Distribution :Therapeutic Variation In The Field Distribution 1- Application using two flexible pads or space plates: A- The electrodes should be slightly larger than the area treated and spaced from the skin by approximately 25 mm. B- To concentrate heat on one aspect of the part the electrode should be unequal in size (smaller one placed over the area where concentration of heat is required). C- You can produce concentration of heat by using equal size electrodes but with unequal spacing (25 mm over concentrated area and more than 30 mm on other electrode). D- Coplaner application to treat structures on one aspect of the body. If the spacing is less than 25 mm more concentration in the superficial tissue. If spacing increases more depth achieved. The distance between adjacent ends (x) must be greater than the sum of skin electrode distance (A+B) otherwise the line of force will pass directly between electrodes rather than tissues. 19/3/2009 28 DR.WALID TARAWNEH


Slide 29:Application using a combination of flexible pad and space plate: Use a space plate over the top of the foot, because there is less soft tissue around the ankle joint than elsewhere in the lower leg, the line of force concentrates at the ankle and the sensation of heat is felt by the patient in the region. Application using a coil electrode: The coil wound evenly firmly heat superficial tissue. Pancake application heat superficial tissues Application using a flexible pad and coil: Useful for the treatment of hip and shoulder to localise heating to the joint, the proximal end of the cable is attached to the machine electrostatic field is produced between the pad and the proximal loop of coil, electromagnetic field is produced around the proximal loops of the coil. To treat hip joint with referred pain down the thigh, the distal end of the coil is attached to the machine and the proximal end of coil is insulated. An electrostatic field is produced between the pad and the proximal loop and electromagnetic field is produced around all loops of the coil. 19/3/2009 29 DR.WALID TARAWNEH


Dangers and Precautions in SWD :Dangers and Precautions in SWD 1- Burn can be avoided by: Checking all contra-indications and area to be treated. Test of thermal skin sensation. Taking care during application over a bony prominence. Never apply S.W. over clothing. Making sure that the skin is dry. If you apply over two skin surfaces in contact, they must be separated by absorbent material towel. Making sure that the leads from the machine are not touching or within 25 mm electromagnetic field around the lead. Making sure that there is adequate spacing between the electrodes and the skin. Allowing 2 or 3 minutes on each intensity setting maximum heat. 2- shock can be avoided by: Not increasing intensity unless the leads and electrodes are connected to machine. Making sure that the machine is earthed. Not touching the machine. Making sure that there is no metal within the range of 300mm. If the patient is wearing a hearing aid switch it off. 19/3/2009 30 DR.WALID TARAWNEH


Maintenance :General check and tests Check the shortwave therapy annually. Check electrical wiring for safety . Check all the component are properly fastened. check that the fuses have the specified range. Check that all accessories are in good condition. Functional test (front panel test, grid current check, output power check, frequency check , tuning device check, timing check…) The dummy load meter Special for SWD 70 ohms , 600 watts , 6 lamps (carbon filaments-220 V) The radiation power is measured by a photo –electrical cell The meter measures the out put current/ voltage Maintenance 19/3/2009 31 DR.WALID TARAWNEH


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SWD Environments :SWD Environments 19/3/2009 33 DR.WALID TARAWNEH


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