Bez názvu155 Lectures on Medical Biophysics Department of Biophysics, Medical Faculty, Masaryk University in Brno massage6small sunburn %E0%A4%C3%D7%E8%CD%A7%A1%C3%D0%B5%D8%E9%B9%E4%BF%BF%E9%D2 ultrazvuk_v Bez názvu155 2 Physical Therapy Hubbard Hydrotherapy Tank, Carlos Andreson, Watercolour, 1943 Lectures on Medical Biophysics Department of Biophysics, Medical Faculty, Masaryk University in Brno Bez názvu155 3 Lecture outline ØMain methods of physical therapy: Ø ØTherapy by mechanical treatment ØNon-electric thermotherapy – (heating and cooling, hydrotherapy) ØElectrotherapy ØUltrasound therapy ØMagnetotherapy ØPhototherapy Ø Ø Bez názvu155 4 Therapy by mechanical treatment - examples ØMassages – manual or instrumental ØChanges in blood circulation, muscular relaxation Ø Ø ØRehabilitative exercises Øincrease of body strength and mobility, psychical effects, improvement of body posture massage6small Lecebny_telocvik Bez názvu155 5 Thermotherapy Ø The application of heat is (from biophysical point of view) an intervention in the body thermoregulation. Heat can be delivered to the organism (positive thermotherapy), or taken away from the organism (negative thermotherapy). ØThe body response depends on: Ø- the way of application - heat conduction, convection or radiation (see electrotherapy and phototherapy) Ø- the intensity, penetration ability and duration of the heat stimulus. Non electric thermotherapy causes mainly changes of body surface temperature (to depths of 2 - 3 cm), with electrotherapy we can heat deeper tissues. Ø- the size and geometry of the application area in the case of local application: The tissue temperature increases when the heat input from outside exceeds the heat output. Cylindrical body parts are heated faster when the radius is small. Considering only conduction, the resistance to heat flow increases linearly with the thickness of tissue layers. In cylindrically shaped tissues it increases non-linearly. Ø- the patient’s health (ability of thermoregulation). Bez názvu155 6 Thermotherapy Ø The following sources of heat are used in thermotherapy: a)Internal (heat produced by the organism itself). b)External. Considering the origin and transfer of heat, the thermotherapeutic methods can be divided into five main groups based on: •- heat conduction •- heat convection •- radiation •- high-frequency electric currents •- thermal action of ultrasound Bez názvu155 7 Heat conduction ØMainly packs and compresses. According to the extent of the covered body part, they can be total or partial, according to the temperature hot, indifferent or cold, and also wet or dry. ØThe compresses can be dry (blankets, bottles), peloids (mud) and paraffin. Their temperature ranges from 45 to 55 ºC in dry compresses up to 60 - 77 ºC in paraffin compresses. Thalasso-Views mud3 Bez názvu155 8 Heat convection – hydrotherapy Øhydrotherapy encompasses, besides heat effects, also mechanical action (buoyancy, hydrostatic pressure, impacts of water streams, water movement). It acts mainly on the cardiovascular system, vegetative nerves and psychology. Heat helps muscles to relax, reduces pain, accelerates resorption of oedemas. The procedures differ from each other in the way of heat transfer, in the ratio of conduction and convection, and in the degree of homogeneity of heat flux: Øcold (less than 18 °C), cool (18 – 24 °C), tepid (24 – 33 °C), warm (33 – 36 °C) or hot (37 – 42 °C). ØOr: hypothermic (10 - 34 °C, 5 min.), isothermal (34 - 36°C, 20 - 30 min), hyperthermic (37 - 42°C, short duration). ØThe effect of the whole-body bath is given mainly by the surface body temperature. After immersion, the body surface is exposed to the actual medium temperature until thermal equilibrium is formed in several millimetres thick water layer, and the effective bath temperature starts to act. Disturbing the layer prevents stabilisation of the effective temperature, that is why the patient should not move during the bath. Bez názvu155 9 Whirling baths, underwater massages, hot and cold water jets hydrotherapy1 hydrof For upper and lower limbs moderately hyperthermic – increasing blood supply and metabolism, skin receptors activated hydrotherapy_02_sm Alternative application of sharp hot and cold water jets – a method with outstanding activation effect. Bez názvu155 10 Sauna ØEffects of hot (80 - 100°C) air of low relative humidity (10-30%) are utilised, followed by cooling in cold water. Outstanding tonic action. Steambath: about 45°C, up to 100% humidity. Sauna Bez názvu155 Cryochamber 11 V kryokomoře mráz léčí http://img1.hyperinzerce.cz/x-cz/inz/5302/5302196-kryokomora-za-bezkonkurencni-cenu-1.jpg Action of dry very cold air (up to -160°C) during some minutes followed by aerobic exercise. Bez názvu155 12 Electrotherapy Electrotherapeutic methods utilise - Direct electric current (galvanotherapy, iontophoresis) - Low-frequency alternating current or short impulses of direct current (stimulation) - High-frequency alternating current (diathermy) - High frequency electromagnetic radiation Bez názvu155 13 Conduction of electric currents in tissues ØPassage of electric current through human body obeys the Kirchhoff’s laws. Tissue resistance varies. The ions are current carriers. ØWe can distinguish two types of tissue electric conductivity. Cytoplasm and intercellular medium behaves like conductors whose resistance does not depend on frequency. Membrane structures have properties of capacitors, i.e. their impedance Z depends on frequency: 8-3 Bez názvu155 14 Resistivity (r, rho) of tissues R is the electrical resistance of a conductor (measured in Ω) l is the length of the conductor (measured in m) A is the cross-sectional area of the conductor (measured in m2) Bez názvu155 15 Tissue polarisation ØThe electric charges present in tissues are not always free, they are often bound to macromolecules which are an integral part of cellular structures and their mobility is limited. The macromolecules behave like electric dipoles – variously oriented – their dipole moments are mutually compensated. ØThe electric dipoles are oriented according to the direction of the outer electric field when it is present – their polarisation occurs. So an inner electric field of opposite polarity arises, and the intensity of the outer electric field is lowered. This turning of polar molecules gives rise to the so-called displacement current. Permittivity e is a measure of this ability. Bez názvu155 16 Effects of direct electric current (galvanotherapy, iontophoresis) ØContinuous direct current (DC) does not stimulate, but can change conditions for that. This effect of DC is called electrotonus and is used in galvanotherapy. Ø ØAround cathode (-) an increase of stimulation of motor nerves occurs = catelektrotonus. ØAround anode (+) a decrease of stimulation of sensitive nerves occurs = anelectrotonus. ØApplication in electrotherapy. – ØElectrokinetic phenomena – movement of ions or solvent in electric field – iontophoresis – ions are transported inside the body. electra Bez názvu155 17 Low-frequency AC - electric stimulation ØThe excitability is a general feature of living systems. In mammals, it is best expressed in nerve and muscle tissue. Electric stimulation - ability of tissue to react on electric stimuli. The direct current has stimulating effects only when suddenly changed. ØThe stimulation is a threshold phenomenon, it occurs only after a specific threshold intensity has been reached - the rheobase. ØThe time factor is more important for quantification of stimulation ability: Chronaxie is a time interval necessary for induction of stimulation at the current intensity equal to a two-fold value of rheobase. ØAny skeletal muscle has a characteristics chronaxie. Changes of chronaxie help to determine the degree of excitability impairment and also the degree of muscle impairment. ØThe shortest chronaxie is found in skeletal muscles (< 1 ms), heart muscle (5 ms), the longest one have smooth muscles (50-700 ms). The chronaxie can be read from the so called I/t curve, the dependence of current pulse intensity on its duration. Bez názvu155 18 ØThe skeletal muscle with normal innervations reacts differently on stimulation by electric impulses with rapid onset (rectangular impulses) and with slow onset (triangular impulses). ØIn short impulses below about 10 ms, the I/t curve has the same shape. ØFor longer rectangular impulses the excitability does not change (curve 1) but the excitability for triangular impulses lowers (curve 2). Ø ØThe muscles with damaged innervations (denerved) are not excitable by very short impulses. However, their excitability for long impulses with slow onset increases (curve 3). So arises area of selective excitability („OSD“), which allows stimulation of denerved muscles without stimulation of healthy muscles. The I/t curve Bez názvu155 19 Low-frequency AC - frequency dependence of stimulatory action ØIn very low frequencies (< 100 Hz), the stimulatory action grows linearly with frequency. In high frequencies, the growth of stimulatory action becomes smaller and changes in decrease. In the range of 500 - 3000 Hz, the threshold value of stimulating current depends on Öf. The stimulatory action starts to decrease above 3000 Hz and at about 100 kHz disappears fully. Ø ØHigh frequency currents have no stimulatory action because the duration of one period is much more shorter than the shortest chronaxie. They have no electrochemical effects either. Bez názvu155 20 Electrostimulation %E0%A4%C3%D7%E8%CD%A7%A1%C3%D0%B5%D8%E9%B9%E4%BF%BF%E9%D2 45 The stimulating effects depend on the amplitude, frequency, shape and modulation of pulses, and the kind of tissue!!!!! Bez názvu155 21 Thermal effects of high frequency (HF) currents ØMechanism of the HF currents action is based on transformation of the absorbed electric energy into heat Q according to Joule’s law: Ø Ø Q = UIt Ø Ø where U is voltage, t is the time of current I passage. This mechanism of heat production depends on the way of HF currents application. Ø ØDielectric heating (due to dielectric losses) takes place when applying currents by means of a capacitor field. ØWhen using induction fields, heat is produced by the so called eddy currents. Bez názvu155 22 Utilisation of high-frequency (HF) electric currents ØIn the case of alternating electric HF currents (>100kHz), the heat effects dominate totally. The heat originates directly in tissues due to dielectric heating, eddy currents or absorption of electromagnetic energy. Ø ØFor HF therapy, international agreements specified the following frequencies: Ø –Short-wave diathermy (27.12 MHz, i.e. wavelength of 11.06 m), –Ultra-short-wave diathermy 433.92 MHz (69 cm), –Microwave therapy 2 400 or 2 450 MHz (12.4 or 12.25 cm) . –HF therapy makes possible deep heating. Bez názvu155 23 Three ways of application of HF currents: Ø1. The tissue is connected in the electric circuit as a resistor by means of contact electrodes – classical diathermy. It is not used in practice today. Ø Ø2. Tissue is connected as dielectric placed between insulated electrodes – heating in the capacitor field. The heat produced is proportional to the dielectric loss. Amount of heat arising in subcutaneous fat tissue is lower than in the muscles. Ø Ø3. Use of eddy currents in magnetic field of a coil – inductive heating. An insulated cable is wound round a limb or a coil is laid to the body. The skin is less heated, 2 cm thick muscle layer lowers the heating to one half. Bez názvu155 24 Different ways of HF diathermy Application of HF currents (a- condenser field, b- inductive, c- microwaves) 47 Bez názvu155 25 Short-wave diathermy – heating in capacitor field diatermie Bez názvu155 26 Microwave therapy ØSource: magnetron. The oscillations of electromagnetic field are led to an emitter - a dipole with a reflector. 1 cm of muscle is enough to lower the intensity to one half, the relation between heat production in the skin and the muscles is almost equalised. Microwaves put electrically charged particles (ions, dipoles) into oscillatory motion which is transformed into heat by friction. Bez názvu155 27 Microwave diathermy brd-dthm (older type) mt3d Bez názvu155 28 Potential risks of microwave and radiofrequency radiation ØMainly thermal effects. Ø ØMicrowave sources ØRadars ØCell phones ØRadio and TV transmitters ØElectric mains ØTrolley lines (wires) – ØSome studies showing carcinogenic effects of microwaves or low-frequency electromagnetic fields were not verified sufficiently, but it is prudent to reduce exposures. Bez názvu155 29 Ultrasound therapy ØUltrasound therapy is based on biological effects of ultrasonic oscillations which are not electric. Despite of that, this therapy is sometimes included in the list of electrotherapeutic methods. Ø ØAn ultrasound (US) therapeutic system consists of two main parts: generator of HF electric current and the application probe, the US source itself, which consists of a piezoelectric transducer. Ø ØIn therapy, f = 0.8 - 1 MHz is used, sometimes up to 3 MHz, with intensity of US - typically 0.5 - 1 W·cm-2 . Exposure time is 5 - 15 min., in 5 - 10 repetitions. US can be applied continuously or pulsed. Ø ØThe main therapeutic mechanism is high-frequency massage of tissue. Additional effects are caused by tissue heating (causing hyperaemia) and some physico-chemical effects. Ø ØAcoustic coupling between the probe and the skin is secured by an oil or gel (local application) as well as water (underwater application). Ø ØMain indications of US therapy: chronic joint, muscle and neural diseases. Limited success is reported in healing wounds after surgery, healing injuries and varicose ulcers. Bez názvu155 30 Thermal action of ultrasound ØIn US therapy, thermal dissipation of acoustic energy takes place. Tissue heating depends on physical properties of tissue and its blood supply. The highest heating appears at the interfaces between tissues of very different acoustic impedances. ØThe thermal action of US cannot be considered without respect to other healing mechanisms (micromassage etc.) Bez názvu155 31 US - THERAPY ultrazvuk_v sonic15 sonopuls491UZ sonopuls591UZ Bez názvu155 32 Effects of magnetic fields - magnetotherapy ØBasic concepts: magnetic fields: static, alternating and pulsed. Homogeneous and non-homogeneous magnetic fields. ØMagnetic flux density B depends on the magnetic permeability of the medium m: Øm = mr.m0 Ø –Ferromagnetic substances - mr >>1. –Diamagnetic substances - mr is slightly lower than 1 –Paramagnetic substances - mr is slightly higher than 1. –(m0 is permeability of vacuum – 4p·10-7 N·A-2) – ØBody tissues are composed almost only from diamagnetic and paramagnetic substances. Magnetic fields can induce electric voltages and currents in biological medium (due to action of Lorentz force on moving electrical charges, or by action of Faraday force in varying magnetic fields). The induced voltages are, of course, substantially lower than the membrane potentials. Bez názvu155 33 Magnetomechanical and magnetochemical effects ØIn a strong mg field, the diamagnetic and paramagnetic molecules orient themselves to minimise their free energy. In non-homogeneous fields with big gradients, a translation movement of ferromagnetic compounds takes place (in living organisms negligible). A strong mg field (over 1 T) would reduce the flow rate of laminar streaming in a tube. Ø ØFurther, it is necessary to consider indirect action as well, mediated by free radicals arising as a consequence of magnetochemical reactions. Ø ØWe can say that a stable magnetic field of high intensity inhibits metabolic processes, but a varying one stimulates them. These changes are transient. Ø ØThe interactions of magnetic fields with human tissues are utilised in both diagnostics and therapy. Magnetotherapy is an example of healing procedure. Magnetic stimulation of brain can be used both in diagnostics and therapy. Bez názvu155 34 Magnets in medicine ØTranscranial magnetic stimulation biotesla_2000 BiStim Module mesmtub Magnetotherapy Biomagnetism quackery of Franz Messmer 200 years ago Bez názvu155 35 Phototherapy ØUltraviolet (UV), visible (VIS) and infrared (IR) light sources are commonly used in medicine, namely in physical therapy. Ø brdk-uvl solux Bez názvu155 36 Light radiation Øultraviolet (UV) 1- 380 nm: UV-A 380 - 315 nm Ø UV-B 315 - 280 nm Ø UV-C 280 - 190 nm Øvisible (VIS) 380 - 780 nm Øinfrared (IR) 0.780 - 1 mm: IR-A 0.78 – 1.4 µm Ø IR-B 1.4 – 3.0 µm Ø IR-C 3.0 µm – 1.0 mm ØFrom a practical point of view, the ultraviolet range begins from the wavelength of 190 nm. The spectral range 1 - 190 nm is so called vacuum UV radiation. It is attenuated strongly even by air and hence its biological effects are rare. Bez názvu155 37 Sources of light ØThe only natural source is the Sun. ØThe other sources are artificial and each of them emits only one part of the optical spectrum: Ø ØHot objects. The wavelength of radiation depends on source temperature, its spectrum is continuous. Light bulbs and various sources of radiant heat. – ØLuminescent sources (fluorescent lamps and tubes). They are based on excitation processes in atoms and molecules. Spectrum of these sources can consist of individual spectrum lines. – ØBoth these sources emit non-coherent radiation. – ØThe only artificial source of intense coherent light is the laser. Bez názvu155 38 1919%20fremont%20street%20neon Sources of visible light lamps laser-coh http://solarscience.msfc.nasa.gov/predict.shtml http://solarscience.msfc.nasa.gov/images/ssn_predict_l.gif Bez názvu155 39 Molecular mechanisms of biological effects of light ØEnergy of single atoms depends on its electron configuration. Delivery of energy causes electron jumps to higher energy levels (DEe) – an excited state arises. Absorption spectrum is not continuous. The excitation takes place mainly in the valence shell. ØEnergetic states DE of a single molecule are, in principle, sums of electron energies DEe corresponding to the electron configuration, vibration energy DEn and rotation energy DEr : Ø ØDE = DEe + DEn + DEr Ø ØAll the three kinds of energy are quantised. The action of the radiation depends on photon energy. The lowest energy have photons of IR-C, it corresponds to the changes of rotation energy of molecules. The energy of IR-B and IR-A photons can influence both the vibration and rotation of molecules. The energy of VIS and UV photons can influence rotation, vibration and also electron configuration. Bez názvu155 40 Effects of visible light ØPhotosynthesis ?biochemistry ØPhotoreception ?biophysics of vision S_rhodopsin 180px-Simple_photosynthesis_overview_svg Photosynthesis splits water to liberate O2 and fixes CO2 into sugar From Wikipedia, the free encyclopedia Bez názvu155 41 Molecular effects of ultraviolet radiation ØConsidering compounds of biological importance, the most sensitive are those with conjugated double bonds. Ø ØIn proteins, the most sensitive amino acids are tyrosin and tryptophan. (abs. maximum around 280 nm). Ø ØIn NA, the N-bases are sensitive. Their absorbance is higher than the absorbance of proteins, maximum at 240-290 nm. Ø ØUV radiation penetrates only into the surface layers of the skin Ø ØThe skin effect of UV light manifests itself as reddening – erythema – followed by melanin pigmentation Þ protecting mechanism against further penetration of UV. Synthesis of vitamin D which controls metabolism of Ca and P (its lack causes rickets - rachitis), is an important positive effect of UV light. We cannot also exclude the carcinogenic effect of UV since almost 90% of skin cancer appears on uncovered areas of the skin. Bez názvu155 42 Sources of ultraviolet radiation ØSun Ø ØMercury discharge tube (used in medicine) Ø ØHydrogen or deuterium discharge tubes (used in research) Ø ØXenon lamp Ø ØElectric arc, lightning etc. Ø ØSome lasers Bez názvu155 43 Penetration of UV radiation fig1 Bez názvu155 44 Effects of ultraviolet radiation on living organisms ØSunburns - erythema ØEffects on eye: blepharospasm (uncontrollable closure of eye lids) – originates due to damage of cornea by UV radiation. Þ protection by goggles with UV filter. Lens cataract can arise (Fig.↓) ØUV-C with wavelength below 280 nm has outstanding bactericidal action. Þ sterilisation of labs, special boxes and surgery rooms. sunburn cataract%20eye 23promo1 Bez názvu155 45 Sources and effects of infrared light ØAll the three ranges of IR radiation have thermal effects. •IR-A is involved in sun light. It passes through glass and is only little absorbed by water. •IR-B is emitted from various lamps and discharge tubes. It passes through glass but is well absorbed by water. •IR-C is emitted from heater, hot bodies, humans…. Absorbed by glass and water. ØAlmost all IR radiation is absorbed by skin. It causes local vasodilatation and thermal erythema which looks like diffuse red patterns and, in contrary to the erythema caused by UV light, its duration is short. Pigmentation is very weak. The irradiation by IR light, however, increases skin sensitivity to the UV light. ØA long exposure of eyes to the IR radiation can cause in some professions (glass-blowers, founders, smelters, steelmen etc.) the so called heat cataract (opacity of the lens). Bez názvu155 46 IR radiation heat transfer ØHeat action of the visible and IR light from artificial sources: Ø ØLamp boxes – radiation heat in enclosed space. Skin receptors are stimulated, whole-body heating occurs. Ø ØIR lamps: Solux, Sirius - high-power lamps with blue or red filters, radiators of IR light. The radiation is absorbed mainly in body surface. Used mainly in dermatology, ORL and dentistry. Skin receptors are stimulated, suggestive feeling of heat, reflex vasodilatation and muscular relaxation takes place. Bez názvu155 47 ØLowering light intensity to 35 % of original value newsf17 Penetration of IR radiation http://www.depilazione.net/news4.htm Bez názvu155 48 Thermal Erythema ØThermal erythema – erythema as a consequence of excessive use of electric pad - BACK: erythema ab igne http://dermatlas.med.jhmi.edu/derm/Display.cfm?ImageName=EAB Bez názvu155 49 Summary – effects of light fig13a Bez názvu155 Author: Vojtěch Mornstein Content collaboration and language revision: Ivo Hrazdira, Carmel J. Caruana Presentation design: Lucie Mornsteinová Last revision and soundtrack addition: November 2020