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Medical Physics

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  1. Medical Physics Chapter (3) Hot &cold in medicine

  2. Heat Therapy Two primary therapeutic effects take place in a heated area: • 1- There is an increase in metabolismالأيض) )مجموع • العمليات المتصلة ببناء البروتوبلازماresulting in a relaxation • of the capillary systemالشعيرات الدموية • 2- There is an increase in blood flow as blood moves in to cool the heated area.

  3. The relaxation and increased blood flow are beneficial • to damaged tissue, although the details of the • therapeutic action are not well understood. • In this section we briefly consider the physical methods • of producing heat in the body, these methods are • (A)Conductive heating, • (B)Infrared (IR) radiant heating, • (C)Radiowaveheating (diathermy)and العلاج بالانفاذالحراري • 1- Short wave 2- Microwave • (D)Ultrasonic wave heating (ultrasonic diathermy).

  4. [A] The ConductiveMethod • The conductive method is based on the physical • fact that if two objects at different temperatures • are placed in contact, heat will transfer by • conduction from the warmer object to the cooler one. • The total heat transferred will depend upon • (1)the area of contact (2) the temperature difference, • (3) the time of contact (4) the thermal conductivity of • the materials (k).

  5. Hot baths, hot packs, electric heating pads بطانية, and • occasionally hot paraffin applied to the skin , heat the • body by conduction. • Conductive heat transfer leads to local surface • heating since the circulating blood effectively • removes heat that penetratesdeep into the tissue. • Conductive heating is used in treating conditions • such as arthritisإلتهاب المفاصل , neuritis إلتهاب العصب , • sprains إلتواء المفصل بعنف and strains توتر, • contusionsرضة , sinusitis التهاب الجيبand back pain.

  6. [B]RadiantInfrared(IR)Heat • Radiantinfrared(IR)heatisalsousedforsurface • heatingofthebody.Thisisthesameformofheatwe • feelfromthesunorfromanopenflame. • Man-madesourcesofradiantheatareglowingwire • coilsملف من السلكand250wattsincandescentيتوهجlamps. • TheIRwavelengthsusedarebetween600and • 40,000nm.

  7. Thewavespenetratetheskinabout3mmandincrease • thesurfacetemperature. • Excessiveexposurecausesreddening(erythemaإلتهاب جلدى )andsometimesswellingانتفاح او تورم(edema إستسقاء). • Veryprolongedإمتدادexposurecausesbrowningor • hardeningoftheskin. • Radiativeheatingisgenerallyusedforthesame • conditionsasconductiveheating,butitisconsideredto • bemoreeffectivebecausetheheat penetratesdeeper.

  8. [C]RadiowaveHeating(Diathermy) • Theamountofheatthatcanbetransferredtothe bodybyelectricaldiathermyincreasesasthe frequencyofthecurrentincreases. • Short-wave diathermyutilizeselectromagneticwaves intheradiorange(wavelength::10m);microwave diathermyuseswavesintheradarrange (wavelength::12cm). • Heatfromdiathermypenetratesdeeperintothebody thanradiantandconductiveheat.Itisthususefulfor internalheatingandhasbeenusedinthe treatmentofinflammationoftheskeletonإلتهاب الهيكل العظمى ,bursitis إلتهاب كيسى ,andneuralgia الألم العصبي .

  9. 1- Short Wave Diathermy • Twodifferentmethodsusedfortransferringthe • electromagneticenergyintothebodyinshortwave • diathermy. • (I)Thepartofthebodytobetreatedisplacedbetween • twometalplace-likeelectrodesenergizedbythehigh • frequencyvoltage. • Thebodytissuebetweentheplatesactslikean • electrolyticsolution سائل التحليل . • Thechargedparticlesareattractedtooneplateand • thentheotherdependinguponthesignofthe • alternatingvoltageontheplates;theseresultsin • resistive(joule)heating.

  10. Differentbodymaterialsreactdifferentlytothewaves, • andthiseffectprovidessomeselectivityintreatments. Location of capacitor plates for short wave diathermy

  11. (II)Thesecondmethodoftransferringshort-wave energyintothebodyismagneticinduction احداث مجال مغناطيسي . • Ininductiondiathermy,eitheracoilisplacedaroundthe • bodyregiontobetreatedora"pancake"coilis • placednearthatpartofthebody. • Thealternatingcurrentinthecoilresultsinanalternating • magneticfieldinthetissues. Location of induction coil around knee for short-wave diathermy

  12. Consequently,alternatingcurrentsare • induced,producingjouleheatinginthebody • regionbeingtreated. • Short-wavediathermyheatsthedeeptissues • ofthebody. • Ithasbeenusedinrelievingmusclespasms; • تشنجات العضلات painfromproduced • inter-vertebraldiscs, degenerativejointdisease) • andbursitis;andas adeepheatingagentfor • jointswithminimal softtissuecoveragesuch • astheknee,elbowكوعandankle.

  13. 2-MicrowaveDiathermy • Microwavediathermyisanotherformof • electromagneticenergy.Itisusuallyeasiertoapplythan • short-wavediathermy. • Microwavediathermydevelopedoutofradarresearchin • the1940s. • Themicrowavesareproducedtoaspecialtubecalleda • magnetronandarethenemittedfromtheapplicator • (antenna). • Theantennaisusuallydesignedsothatitcanbeplaced • severalinchesfromtheregiontobetreated. • Themicrowavesfromtheantennapenetratedeep • intothetissues,causingatemperatureriseanddeep • heating.

  14. Microwavediathermyisusedinthetreatmentof • fracturesالكسور,sprainsلى المفصل بعنفandstrains التوتر, • bursitisالإلتهاب الكيسى ,injuriestotendons أذي للاوتار ,and • arthritis إلتهاب المفاصل . • [D]UltrasonicDiathermy • Ultrasonicwavesareusedfordeepheatingofbody • tissue. • Thesewavesarecompletelydifferentfromthe • electromagneticwaves. • Theyproducemechanicalmotionlikeaudiblesound • wavesexceptthefrequencyismuchhigher • (usuallynear1MHz).

  15. Inultrasonicdiathermy,powerlevelsofseveralwattsper • squarecentimeter(watt/cm2)areusuallyusedandthe • soundsourceisdirectlyincontactwiththebody. • Astheultrasonicwavesmovethroughthebodythe • particlesinthetissuesmovebackandforth. • Themovementissimilartoamicro-massageand • resultsinheatingofthetissues. • Ultrasonicheatinghasbeenfoundusefulinrelieving • thetightnessيسكن الألمandscarringندوبthatoftenoccur • injointdisease أمراض المفاصل . • Itgreatlyaidsjointsthathavelimitedmotion. • Itisusefulfordepositingheatinbonesbecausethey • absorbultrasoundenergymoreeffectivelythansoft • tissuedoes.

  16. Use of Cold in Medicine • Cryogenics is the science and technology of producing • and using very low temperatures. • cryobiology : is the study of low temperature effects • in biology and medicine. • It is an active research area. Liquid air (-196 °C) was • produced in 1877; liquid helium (-269 °C) was produced • in 1908 • Dewar Container for Cryogenic Fluids • The storage of cryogenic fluids has always been a • problem. • Most ordinary liquid-storage containers are • unsatisfactory because they absorb a large amount • of heat by conduction, convection and radiation.

  17. A significant improvement is the insulated container • developed by James Dewar in 1962 and named after • him. • This container is made of; glass or thin stainless • steel to minimize conductive losses. • It has a vacuum space to essentially eliminate • convective losses, and the sides are silvered or • polished so that radiation striking the surface is • reflected rather than absorbed. • The container resembles the familiar Thermos bottle • used to store hot and cold drinks. • Dewar vessels with capacities of over 100,000 liters • have been made.

  18. Dewar container forcryogenicfluids.

  19. CryogenicsandPreservationofTissues • Lowtemperatureshavebeenusedforlong-term • preservationofblood,sperm,bonemarrow,and • tissues. • Studiesoftheirrelationshiptothehibernationالبيات الشتوي of animalsareunderway,andthelong-term • preservation ofmanisbeingconsidered. • Muchinteresthasbeenarousedbytheideaofusing • cryogenicmethodstocoolthebodyintoastateof • "suspendedanimationتعطيل الإحياء "sothatitcanpass • timewithoutaging. • Thisscienceiscalledcryonics

  20. Onegoalofcryonicsis: topreserveatalow • temperaturepeoplewithfataldiseaseswiththehope • thatinthefuturetheycouldberevived) bring back to • life ) andtheir diseasescured. • Considerableefforthasbeenexpendedonproblems • associatedwiththepreservationandstorageofvarious • tissues,butsuccesshassofarbeenlimitedtosimple • systems. • Ithasbeenfoundthatforlongtermsurvivalthetissues • shouldbestoredatverylowtemperatures. • Preservationismuchbetteratthetemperatureofthe • liquidnitrogen(-196°C)thanatthetemperatureof • solidcarbondioxide(-79°C).

  21. Anotherimportantfindinginvolvesthefreeze- • Thaw cycle دورة التجمد و الذوبان . • Survival after freezing is more dependent upon • The cooling rate during the freezing cycle • than on the warming rate during the • thawing cycle. • Measurementofthesurvivaloftwo • biomaterialsasa functionofthecoolingrate • afterfreezingandthawing ofthematerials. • Thesurvivalcurvesofdifferentbiomaterialsas • afunctionofcoolingratethatwillensurecell • survivalforallmaterials.

  22. Survivalbehaviorasafunctionofcoolingrateforredbloodcellsandbonemarrow.Survivalbehaviorasafunctionofcoolingrateforredbloodcellsandbonemarrow.

  23. Thisputsaseverelimitationonpreserving • biomaterialscomposedofmanydifferentcell • types. • Formanymammaliancellsخلايا الثديياتonlya • fewpercentsurvive;thusfreezingand • thawing offerslittlehope asageneralmeansof • longtermbiologicalstorage.

  24. Bloodpreservation Bloodpreservationcanbedonebyseveral methods: • Byaddingaprotectiveagentsuchasglycerol.Theuseofadditivestoenhancesurvival • sometimespresentsproblemsthataremorecomplicatedthantheoriginalonesinvolvedwiththefreeze thawcycle.Forexample,theremovalofglycerolfrombloodissufficientlycomplicatedtolimittheprocesstoafewlargehospitals.

  25. (2)Mixingwholebloodwithananticoagulantتخثر andstoringitat 40c.About1%ofthered blood • ceilshemolyze(break)eachday,sothebloodis • notusableafter about21days. • (3)Bloodcanbestoredforamuchlongertime • ifisrapidlyfrozen.Twotechniquesareused • forthis;oneusedthin-walledcontainers; • theotheristheblood sandmethod.

  26. Thin-walledcontainers: • Thecontainerwiththinmetalwallsisconstructedsothatthebloodvolumebetweenthewallsissmall.Afteritisfilledwithblooditisquicklyinsertedintoaliquidnitrogenbath.Thefrozenbloodcanbestoredatthetemperatureofliquidnitrogen(-190°C). • Bloodsandmethod: • Intheblood-sandmethod,bloodissprayedرشontoaliquidnitrogensurfaceandfreezesintosmalldropletsقطرات.Thedropletsareaboutthesizeofgrainsofsand-hencethenameblood-sand.Thedropletsarecollectedandthenstoredinspecialcontainers,usuallyatthetemperatureofliquidnitrogen

  27. Organsbanks • Experimentalworkisunderwaytoformbanksforskin, • bone,muscleandorgans.Thesesubstancesare • hardertopreservethansimplecellssuchasred • bloodcellsforanumberofreasons: (1)Thelargephysicaldimensionslimitthecoolingrate (2)Addingandremovingprotectiveagentsوقايةis difficult. • Evenso,someworkhassuccessfullybeencarriedout • withcorneaالقرنيةandskinpreservation. • Organpreservationandre-useisstillintheexperiment • stage.

  28. Cryosurgery Cryogenicmethodsarealsousedtodestroycells; applicationiscalledcryosurgery. Cryosurgeryhasseveraladvantages. (1)Thereislittlebleedinginthedestroyedarea, (2)Thevolumeoftissuedestroyedcanbecontrolled bythetemperatureofthecryosurgicalprobe,and (3) Thereislittlepainsensationbecauselow temperaturestendtodesensitizeيضعف او يزيل حساسية العصب thenerves.

  29. Oneofthefirstusesofcryosurgerywasinthe • Parkinson'sdisease(shakingpalsyالشلل الرعاش ), • a diseaseassociatedwiththebasalganglionمركز النشاط ofthebrain. • Parkinson'sdiseasecausesuncontrolledtremorsإرتعاش in thearmsandlegs. • Itispossibletostopthetremorsbysurgically • destroyingthepartofthethalamusinthebrainthat • controlsthetransmissionofnerveimpulsestoother • partsofthenervoussystem.

  30. Acryosurgicaltreatmentwasinitiallyundertakenby • Dr.IrvingCooperinNewYorkduringtheearly1960s. • CoopersoughtthehelpoftheunionCarbideCompany • indevelopingacryoknifetouseincryosurgery. • HedesiredtotreatParkinson'sdiseasebydestructively • freezingtheappropriateregioninthethalamus. • InthetreatmentofParkinson'diseasethetipofthe • probeiscooledto-10°Candmovedintothe • appropriateregionsofthethalamus,causingtemporary • freezingoftheseregions.

  31. Thefrozenareasrecoveriftheprobetipis • removedinlessthan30sec. • Thepatientmustbeconsciousواعي duringthe • proceduresothatthesurgeoncanobservewhen • theshakingstops;thismeansthattheprobehas • reachedthecorrectregionofthethalamus. • Thisregionisthendestroyedbyfreezingforseveral • minutesattemperaturesnear-85°C. • Afterthefreezing,thetip iswarmedandremoved.

  32. Thedestroyedtissueformsacystكيس afterthawinganddoes • notinterferewithnormalfunctions. • Thepatientalmostalwaysshowsimmediatebenefit,andthe • post-operativerecoveryperiodدورة الشفاء بعد العملية isvery • shortcomparedtothat foramajorbrainoperation. • Successfulresultswereobtainedinmorethan90%ofthecases • inwhichcryosurgerywasused. • Onecommonuseofcryosurgeryisinthetreatmentoftumors. • Cryogenicmethodshavealsobeenusedinseveraltypesofeye • surgery,suchastherepairofadetachedretina إنفصال شبكية العين andcataractsurgery(theremovalofadarkenedlens).