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Radiology Physic Review

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    ADIOLOGY PHYSICS REVIEW

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    hat is a Photon?,Under the photon theory of light a photon

    ( )is a discrete bundle or quantum of( ) .electromagnetic or light energy Photons, ,are always in motion and in a vacuum have a

    ,constant speed of light to all observers at(the vacuum speed of light more commonly

    ) = .just called the speed of light of c 2 998x 108 / .m s

    In physics, a quantum ( :plural quanta) is theminimum unit of any physical entity involved in an.interaction

    A photon, , ,for example is a single quantum of light"and may thus be referred to as a light quantum".

    http://en.wikipedia.org/wiki/Physicshttp://en.wikipedia.org/wiki/Physicshttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Light_quantumhttp://en.wikipedia.org/wiki/Light_quantumhttp://en.wikipedia.org/wiki/Light_quantumhttp://en.wikipedia.org/wiki/Light_quantumhttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Physics
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    Fun Photon Facts,The photon is an elementary particle despite the fact that it

    . ,has no mass It cannot decay on its own although the energy of( )the photon can transfer or be created upon interaction with

    .other particles Photons are electrically neutral and are one of,the rare particles that are identical to their antiparticle the

    antiphoton

    Basic Properties of Photons, . . .According to the photon theory of light photons

    , = .move at a constant velocity c 2 9979 x 108 / ( . . "m s i e the speed of"),light in free space

    .have zero mass and rest energy

    ,carry energy and momentum which are also related to the frequency nu=and wavelength lamdba of the electromagnetic wave by E h nu and p

    = / .h lambda

    / / .can be destroyed created when radiation is absorbed emitted - ( . . )an have particle like interactions i e collisions with,lectrons and other particles such as in the Compton.ffect

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    :Exposure The amount of ionizations-produced in air by x ray or gamma. ,photons The unit is Roentgen the SI unit

    .is the coulomb per kilogram

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    :Activity A measure of theintensity of radioactivity in asample of material quantified by

    the number of radioactivedisintegrations occurring in a

    given quantity of material per. ,unit time Unit is the curie the

    .SI unit is Becquerel

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    ( ):Absorbed Dose D The energy impartedto matter by ionizing radiation per.unit mass of irradiated material The

    absorbed dose is expressed in unit

    ; ( ).rad the SI unit is the gray Gy

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    ( ):Dose equivalent H The product of( : )absorbed dose in rads SI Gray in, ( )tissue a quality factor Q and other

    ( ).modifying factors N Dose equivalent

    is expressed in the unit rem( )ADIATION EQUIVALENT MAN ,the SI unitis the Sievert.

    =Dose Equivalent rads x Q x N

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    a

    Traditional SI Conversion

    Exposure Roentgen (R) Coulomb/kg 1 R= 2.54 x10-4 coul/kg

    Activity Curie (Ci) Becquerel (Bq)1 Ci = 3.7 x

    10

    10

    Bq1Bq=2.7 x 10-11

    AbsorbedDose (D)

    Rad /Gray(Gy)

    Rad/Gray 1 Gy = 100Rad

    Doseequivalent(H)

    Rem/SievertRem = Rad xQF

    Sievert (Sv) =Gray x QF

    1 Sv = 100Rem

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    matter

    nnihilationphotonIncidentphotons

    Secondaryphotons

    Secondaryelectrons

    cattered photonompton effectluorescence photon( )haracteristic radiation

    ecoilelectron

    lectron pair> .1 02 MeV

    Photoelectron( hotoelectric)ffect

    on interactingphotons

    (simplified)representation

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    :Photoelectric Effect Occurs between

    tightly bound inner shell electron and- .incident x ray photon The inner shell

    electron filled by outer shell electronand excess energy is emitted as

    .characteristic radiation Thephotoelectric effect occurs when photon istotally absorbed by the inner shell

    .electron and a photoelectron is emitted

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    PHOTOELECTRIC

    EFFECT

    Incident photon

    Photoelectron

    Characteristic

    x-ray

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    :Compton Scatter In Compton scatterincident photon interact with loosely

    bound outer shell electron resulting

    .is scattered photon This is a causeof most scattered radiation in.diagnostic radiology

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    COMPTON SCATTERING

    Incident photon

    Compton Electron

    Scattered Photon

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    :Coherent scatter - a termsometimes used for Rayleigh;scattering Incident photon changes

    .direction without losing energy

    imilar with that of Bremsstrahlung-ray production

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    Rayleigh Scattering

    Incident photon

    Scatteredphoton

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    :Pair Production High energy photoninteract with the nucleus of an

    .atom The photon disappear andenergy is converted in to an

    .electron and positron

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    PAIR PRODUCTION

    Incident photon

    e-

    e+

    electron

    positron

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    :Photodisintegration When a highenergy photon is absorbed by anucleus resulting in immediate

    .disintegration of the nucleus

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    -Diagnostic x rays are produced when

    electrons with high energies of 20.to 150 Kev are stopped in matter-X rays are produced by two

    :different process known as

    .1 Bremsstrahlung. -2 Characteristic x ray production

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    ( )Bremsstrahlung Breaking or General-X rays are produced when incident

    electrons interact with nuclearelectric fields which slow them down

    .and change their direction Some of the

    -kinetic energy is emitted as x ray

    . -photon Bremsstrahlung x ray produce.continous spectrum of radiation

    -Bremsstrahlung x ray production

    increases with the accelerating

    ( ) ( )voltage KV and atomic number z of.anode

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    :Characteristic radiation Characteristicradiation is produced when the inner shell

    electron of the anode target are ejected by

    .the incident electron The inner shell vacancyare filled by outer shell electrons and theenergy difference is emitted as characteristic

    .radiationExcess energy may also be emitted as Auger

    .electron-K shell electron is emitted only if incident

    -electron have energies greater than K shell.binding energy

    = =For tungsten 70 kv Molybdenum 20 kv- -L shell electron also normally accompanies K. - -shell radiation L shell characteristic x rays

    have very low energies and are absorbed by the-glass of the x ray tube.

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    X Ray tube components

    Cathode: heated filament which is thesource of the electron beam directedtowards the anode

    tungsten filament

    Anode (stationary or rotating): impactedby electrons, emits X Rays

    Metal tube housing surrounding glass (ormetal) X Ray tube (electrons are

    traveling in vacuum) Shielding material (protection againstscattered radiation)

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    Parts of fixed Anode x-ray Tube

    High Tension Generator

    Cathode

    Anode

    The Glass Envelope and VacuumThe Tube shield

    Cooling mechanism

    Filtration mechanism

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    High Tension Generator

    The high tension voltage is applied to anode of x-raytubegives the kinetic energy for the electron to leavecathode and bombard anode.

    For diagnostic radiology 40-120 KVP is used.

    This high voltage are provided by step up transformeror high tension generator.

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    The cathode

    Cathode is negative pole of the x-ray tube. It is a metal structuresupporting the filament, which on heating emits electrons.

    Focusing Cup: Where the filament is located in the cathodeFilament made up of tungsten wire which tolerates high temperatureup to 3370*c

    Has high resistance so as to produce amount of heat needed to boilthe electron

    Shaped in helical or spiral winding to increase surface area foremitting electrons.

    Its size is small so as to produce electron beam covering small area.

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    Cathode structure

    Cathode includes filament(s) andassociated circuitry tungsten material : preferred because of

    its high melting point (3370C)

    slow filament evaporation

    no arcing (spark)

    minimum deposit of W on glass envelope

    To reduce evaporation the emissiontemperature of the cathode is reached justbefore the exposure

    in stand-by, temperature is kept at 1500C so that 2700C emissiontemperature can be reached within a

    second

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    Modern tubes have two filamentsa long one : higher current/lower resolutiona short one : lower current/higher

    resolution

    Coulomb interaction makes the electronbeam divergent on the travel to theanode

    focal spot increased low r m r solut on o l s t on o

    l trons s ru l !

    Cathode structure

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    The Anode

    A piece of tungsten in a form of plate of 2mm thick ,rectangular or circular in shape larger than the focal area is

    embedded on a thick copper rod.

    This is essentially a metal plate to receive the electronwhich bombard it.It is so designed the that bombarded electron gives great

    amount of heat(99%) and small amount of x-ray(1%)Anode has relatively larger surface area so produced heatcan be dissipated and tube damage can be prevented.

    Tungsten and copper is used for this purpose but why?

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    Tungsten As a target:-Highmelting point, high atomic number (efficient

    to produce x-ray), good conductor of heat, can be shaped andmade smooth as required.As a filament:-High thermionic emission, can be convertedinto wire, high melting point and does not vaporize easily.

    Copper-Good conductor of heat so dissipates heat to outside to outsideof tube and also serves as electrode of positive pole (anode)where high KV current is connected.

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    -H o w to p ro d u ce fa ste r a n d p o w erfu l x ra y?

    T h e la rg e r th e d iffe re n ce b e tw e e n in th e( )ch a rg e p o te n tia l d iffe re n ce b e tw e e n a n o d e

    a n d ca th o d e th e fa ste r th e e le ctro n.a cce le ra te to w a rd s th e a n o d e

    ,T h e fa ste r th e e le ctro n g o e s th e h a rd e r th e y-co llid e w ith th e a n o d e a n d m o re p o w erfu l x

    .ray are produced

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    -W h a t is th e e ffe ct o f kV P a n d m A s on x ra y

    p ro d u ctio n ?

    m A s In cre a sin g th e m A s it in cre a se th e- .q u a n tity o f th e x ra y p ro d u ctio n

    kV p In cre a se in kV P it in cre a se s th e q u a lity- .o f th e x ra y p ro d u ctio n

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    X Ray tube characteristics

    Anode mechanical constraints : , , ,

    Focal spot : surface of anode impacted by

    electrons Anode angle

    Disk and annular track diameter (rotationfrequency 3,000 10,000 / )

    Thickness ( ) Anode thermal constraints

    Instantaneous power load (heat unit) Heat loadin time curve

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    Focusing of the electron beam

    The electron spreading away from the filament are brought togetherby means of an electric field which exist between anode and cathode.

    The filament sits in a slot in the cathode.

    The filament and slot are carefully designed in shape, size andposition so that the emitted electron can only leave the filament

    through the slot.

    By this electron leaving the filament comes together in a beam so asto cover small area on the anode, also called FOCAL SPOT of x-raytube.

    Focal Spot:The exact area of the anode where the electron hit theanode.

    oca spo s ze an mag ng

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    oca spo s ze an mag nggeometry

    Focal spot Large image unsharpened Improving sharpness small focal spot size

    For mammography focal spot size 0.4

    Small focal spot size ( )

    Large focal spot allows high output (shorter

    exposure time) Balance depends on organ movement (fast moving

    organs may require larger focus)

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    Anode angle

    The Line-Focus principle :

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    Anode heel effect

    Anode angle (from 7 to 20) induces avariation of the X Ray output in theplane comprising the anode-cathodeaxis

    Absorption by anode of X photons withlow emission angle

    The magnitude of influence of the heeleffect on the image depends on factors

    such as : anode angle size of film

    focus to film distance

    Anode aging increases heel effect

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    The heel effect is not always a negative factor

    It can be used to compensate for differentattenuation through parts of the body

    For example:

    thoracic spine (thicker part of the patient towardsthe cathode side of the tube)

    mammography

    Anode heel effect

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    Conditions necessary for theproduction of x-rays

    There must be a High Voltage (potentialdifference)

    There must be Fast Moving Electrons.

    There must be a Target.

    It must be in Vacuum.

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    % W h a t is 1 5 ru le for kV P ?%If th e kV P is in cre a se d b y 1 5 th e

    .d e n sity is d o u b le d

    W h a t is sa n te s s R u le o r e q u a tio n ?

    = )kV P 2 x th icken d d o f th e b od y p art in cm

    +40

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    Production ofx-ray

    anodecathode

    PHOTOELECTRIC

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    PHOTOELECTRIC

    EFFECT

    Incident photon

    Photoelectron

    Characteristic x-ray

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    The gas envelope and vacuum

    The electron that leave the cathode have unimpeded passage tothe anode.

    If there is no vacuum it collide with the gas with in the tube asa result of which they loose the energy before colliding with

    the anode.

    The end result would be production of less intense and lesspenetrating x-ray .

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    The tube shield

    Made up of cylindrical aluminum or aluminum-lead alloy.

    It will not allow any x-ray to escape out of the x-ray tube expectthrough the glass window which is provided to allow only the

    primary beam from focal spot.

    Metallic casearound the x-ray tube that provides protectionagainst radiation risk and electrical risk. Theoretically it should

    be ray proof and shock proof.

    Ray proof is impossible according to physic of x-ray

    absorption but significantly reduces amount of radiationcoming through the absorber within he safety limit.

    Cooling Mechanism of x ray tube

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    Cooling Mechanism of x-ray tube

    Amount of heat production=KV x mA x Seconds

    The greater the factor are used the more heat are produced.

    If the dissipation of heat were not to take place simultaneouslywith heat production, the melting point of tungsten(3360*c)will

    be soon reached.

    Heat dissipation occurs by-1.Conduction-through the solid part of anode-copper

    2.Convection-through the oil surrounding the tube(glass andcopper block transmit the heat to oil in which tube is immersed.

    3.Radiation-occur through the vacuum of the tube to glassenvelope.

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    Filtration in the x-ray tube

    X-ray beam comprises many wavelength in it.A filter acts by

    absorbing preferably the useless but harmful longerwavelengths in the beam.There by only shorter wavelength x-ray leaves the tube whichwould cast sharp radiographic image.

    This useful beam still has to pass through:1.Thin window in the glass envelope2.Oil within the shield3.Lead lined plastic cover aperture call the portal.(these are also called inherent filtration of x-ray tube.)

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    Scattered Radiation

    When x-ray strikes the body part ,secondary radiation areproduced which have longer wavelength than the primary beam.

    These secondary radiations are scattered in all direction andproduce a veil of fog on the diagnostic x-ray film.Scattered radiation affect the image of part at a distance from thefilm by fogging.

    Small parts like hands and feet shows negligible scattering butpelvic and trunk shows maximum scattering.

    Control of scattered radiation

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    Control of scattered radiationSome radiographic accessories are used to cut down the secondaryradiation fog:1.Shutters/diaphragms:-The shutter diaphragm have lighting

    arrangement above them, incorporated inside the tube shield whichshows the field size (after operating the shutters) on the patients body.2.Cones:Cones of different sizes and shapes are available to restrict fieldof radiography to the obsolete required size.eg-mastoid cone , PNS cone

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    . :3 G rid T h e se a re th e d e vice s w h ich co n sist o f( )se rie s o f a lte rn a te strip e s o f le a d o r tu n g ste n a n d

    ( ). -w o o d o r sim ila r ra d io lu ce n t m a te ria l T h e x ra yp e n e tra te s g rid a n d fa ll o n th e film to p ro d u ce

    . -im a g e T h e sca tte re d x ra y a re cu t o ff b y le a d.strip e s

    - : (Ty p ica lly 2 5 tim e s B u cky fa cto r o r g rid ra tio T h ere la tio n o f th e h e ig h t o f th e le a d strip s to th e w id th.o f th e n on op a q u e m ate ria lb etw e en th em

    : , : , : )C om m on g rid ratio s a re 2 8 2 1 2 a n d 2 1 6

    :G rid s a re m a in ly tw o ty p e s. : ( )1 S ta tin o n a ry g rid s LY S H O LM G rid. : . - .2 M o v in g G rid a Po tte r b u cky g rid b O scilla tin g g rid.c C ro ss g rid

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    A Scattered and primary x-ray photons reachingthe same point Pon film. B Scattered photon isremoved by antiscatter grid, while primary

    photon gets through.

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    X-ray Film Cassette. Diagram demonstrating asheet of x-ray film between two fluorescentscreens within a light-proof cassette.

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    :Emulsion Film consist of an approximately 10micrometer thick emulsion supported by mylar

    .base which is 150 micrometer thickThe emulsion contains silver halide grains

    which can be sensitized by radiation or

    .light to hold a latent image( )Several light photon approximately 4 must.be absorbed to sensitize each grain

    P i f Fil

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    Processing of Films1.Proper mixing of the chemical solutionaccording to manufacture instruction.

    2.Unloading of the exposed film from thecassette, writing patient ID with copying penciland then mounting it on to proper hanger.

    3.Developing Process4.Rinsing process5.Fixing process6.Washing Process

    7.Drying process

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    :Developing Development of radiographic film-is a chemical process which reduces x ray

    -exposed silver bromide of the x ray film into

    ,plain metallic silver in a finely divided.form to bring out the latent image

    Sensitized grains are reduced in the.developer by the addition of electron

    A developed grain results in a speck of.silver that appears black on the film Grainswith no latent image are also developed but

    at a much slower rate

    Contains 4 main chemical mixed with

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    distilled water. / :1 Developing Reducing agent 2 main chemicals. -a Hydroquinone slowly build up back tones

    and contrast. b Elon quickly builds up gray tones.2 Preservative agent contains sodium

    sulfite which protects the rapid oxidation

    of the developing agent. : ,3 Activator Contains sodium carbonate also

    called alkalizer which provides necessary.alkaline medium

    . :4 Restrainer Contain potassium bromide

    restrain the developing agent fromdeveloping the unexposed silver halide.crytals

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    Oth 2 h i l

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    :Other 2 chemicals. :1 Wetting agent A form of detergent

    which reduces surface tension andhelps the film to dry faster

    . :2 Cutting agent A combination ofpotassium ferrocyanide and fixer

    which can be used in an emergencyto lighten film that have been

    accidentally overexposed or

    .overdeveloped

    What is difference between Spatial resolution and

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    What is difference between Spatial resolution andcontrast resolution?

    Spatial resolutionis a measure of the ability of animaging technique to demonstrate that two nearby

    , , .objects are indeed separate objects It is measured" ,"in line pairs per millimeter referring to theability of a modality to demonstrate that very small

    pairs of lines are indeed separatelines and not a. - ,single line Of the digital cross sectional modalities

    .CT has the highest spatial resolution-Contrast resolution The density difference between the.two adjacent area on the radiograph

    Refers to the ability of an imaging modality torender different objects or tissues as different

    . -shades of gray Of the digital cross sectional

    , .modalities MRI has the highest contrast resolution

    Radiation from Natural

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    Normally 1-3 mSv/year

    In areas of high background, 3-13

    mSv/yearLD 50/60 = 4 Gy (The LD50/60 isthat dose at which 50%of the

    exposed population will die within60 days)

    Radiation from NaturalSources

    O ti l di l d bli

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    Occupational, medical and publicexposures

    Occupational exposure All exposures of workers incurred:

    in the course of their work, with the exception ofexposures excluded from the Standards

    exposures from practices or sources exempted by the

    Standards

    O ti l di l d bli

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    Occupational, medical and publicexposures

    Medical exposure: Exposure incurred by patients

    as part of their own medical or dental diagnosis ortreatment;

    by persons, other than those occupationally exposed,knowingly while voluntarily helping in the support andcomfort of patients;

    by volunteers in a programme of biomedical researchinvolving their exposure

    O ti l di l d bli

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    Occupational, medical and publicexposures

    Public exposure: Exposure incurred by:

    members of the public from radiation sources,

    excluding any occupational or medical exposure and

    the normal local natural background radiation but including exposure from authorized sources and

    practices and from intervention situations.

    D li it ( ti l

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    Dose limits (occupationalexposure)

    The occupational exposure of any worker shouldbe controlled so that the following limits be notexceeded:

    500 mSvThe hands and feet

    500 mSvThe skin

    150 mSvThe lens of the eye

    Annual equivalent dose in:

    20 mSv per year, averaged overdefined periods of 5 years

    50 mSv in any single yearEffective dose

    Occupational dose limitApplication

    PUBLIC O ti i ti d

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    PUBLIC - Optimization underConstraints

    DOSE LIMITS effective dose of 1 mSv in a year

    in special circumstances, effective dose of 5 mSvin a single year, provided that the average over

    five consecutive years in less than 1mSv peryear

    equivalent dose to lens of the eye 15 mSv in ayear

    equivalent dose to skin of 50 mSv in a year.

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    Dose limits (public)

    50 mSvThe skin

    15 mSvThe lens of the eyeAnnual equivalent dose in:

    1 mSv in a year(*)Effective dose

    Public dose limitApplication

    (*) In special circumstances, an effective dose of up to 5 mSvin a single year provided that the average dose over fiveconsecutive years does not exceed 1 mSv per year.

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    Dose Limits (ICRP 60) OccupationalPublicEffective dose 20 mSv/yr averaged* 1 mSv in a

    yr

    over 5 yrs.

    Annual equivalent

    dose to Lens of eye 150 mSv 15 mSv

    Skin 500 mSv 50 mSv

    Hands & Feet 500 mSv

    * with further provision that dose in any single yr > 30mSv (AERB) and =50 mSv (ICRP)

    N.B.: M.P.D. 1931 = 500 mSv, 1947=150 mSv, 1977=50mSv&

    in 1990=20 mSv

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    We live with

    1-3 mSv

    Can kill

    4000 mSv

    Radiation

    Where to stop, where is the safe point?What are the effects of radiation?

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    Radiation health effects

    DETERMINISTICSomaticClinically attributablein the exposedindividual

    CELL DEATH

    STOCHASTICsomatic & hereditaryepidemiologicallyattributable in largepopulations

    ANTENATALsomatic andhereditary expressedin the foetus, in the liveborn or descendants

    BOTH

    TYPEOF

    EFFECTS

    CELL TRANSFORMATION

    o og ca e ec s o on z ngradiation

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    radiation

    Deterministic e.g. Lens opacities,

    skin injuries,

    infertility,epilation(hairremoval), etc

    Stochastic

    Cancer, geneticeffects.

    Deterministic effects

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    Deterministic(Threshold/non-stochastic)

    Existence of a dosethreshold value (belowthis dose, the effect is notobservable)

    Severity of the effectincreases with dose

    A large number of cells areinvolved

    adiation injury from an industrial sou

    Deterministic effects

    Threshold Doses for DeterministicEffects

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    Cataracts of the lens of the eye 2-10 Gy

    Permanent sterility

    males 3.5-6 Gy

    females 2.5-6 GyTemporary sterility

    males 0.15 Gy

    females 0.6 Gy

    dose

    everity ofeffect

    threshold

    Effects

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    Radiosensitivity

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    Radiosensitivity

    Muscle

    Bones

    Nervous

    system

    Skin

    Mesodermorgans (liver,

    heart, lungs)

    Bone Marrow

    Spleen

    Thymus

    Lymphaticnodes

    Gonads

    Eye lensLymphocytes(exception to the RS laws)

    Low RSMedium RSHigh RS

    Factors affecting the

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    radiosensitivity

    G1

    S

    G2

    M

    G0

    LET

    LET%survivorcells

    MM

    Physical LET (linear energy transfer): RS Dose rate: RS

    Chemical Increase RS: OXYGEN, cytotoxic drugs. Decrease RS: SULFURE (cys, cysteamine)

    Biological Cycle status:

    RS: G2, M

    RS: S Repair of damage (sub-lethal damage

    may be repaired e.g. fractionated dose)

    Effects of antenatal exposure

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    Effects of antenatal exposure

    Lethal effects can be induced by relatively

    small doses (such as 0.1 Gy) before orimmediately after implantation of the embryointo the uterine wall. They may also beinduced after higher doses during all the

    stages during intra-uterine development.

    Time

    %

    Pre-implantation Organogenesis Foetus

    Lethality

    0.1 Gy

    Effects of antenatal exposure

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    Effects of antenatal exposure

    Mental retardation:

    ICRP establishes that mental retardation can beinduced by radiation (Intelligence Quotient score< 100).

    It occurs during the most RS period: 8-25 week of

    pregnancy.

    Risks of antenatal exposure related to mentalretardation are:

    Severe mental retardation

    with a risk factor of

    0.1/Sv

    Severe mental retardationwith a risk factor of

    0.4/Sv

    15-25 week8-15 week

    Exam.

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    Relative Dose Received

    number of chest x-rays

    0 50 100 150 200

    , , & ( )rm head ankle foot 1& ( )ead Neck 3( )ead CT 10 ( )horacic Spine 18, ( )ammography Cystography 20( )elvis 24, , & ( )bdomen Hip Upper lower femur 28( )a Swallow 30 ( )bsteric abdomen 34- ( )umbo sacral area 43( )holangiography 52 ( )umber Myelography 60 ( )ower abdomen CT male 72( )pper Abdomen CT 73( )a Meal 76- , - ( )ngio head Angio peripheral 80( )rography 87- ( )ngio abdominal 120( )hest CT 136. . ( )ower Abd CT fem 142( )a enema 154 . ( )ymphan 180

    mSv

    .050.15

    0.49

    0.92

    1.0

    1.22

    1.4

    1.5

    1.72.15

    2.59

    3.0

    3.61

    3.67

    3.8

    4.0

    4.366.0

    6.8

    7.13

    7.69

    9.0

    Exam.(as multiple of chest x-ray)

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    Typical effective doses from

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    Typical effective doses fromdiagnostic medical exposures

    : . ,Fro m R e fe rra lC rite ria Fo r Im a g in g C E.2 0 0 0

    Diagnostic

    procedure

    Typical effective

    dose (mSv)

    Equiv. no. of

    chest x-rays

    Approx. equiv. period of

    natural backgroundradiation

    Chest (single PAfilm)

    0.02 1 3 days

    Skull 0.07 3.5 11 days

    Thoracic spine 0.7 35 4 months

    Lumbar spine 1.3 65 7 months

    Typical effective doses from

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    Typical effective doses fromdiagnostic medical exposures

    Diagnostic

    procedure

    Typical effective

    dose (mSv)

    Equiv. no. of

    chest x-rays

    Approx. equiv. period of

    natural backgroundradiation

    Hip 0.3 15 7 weeks

    Pelvis 0.7 35 4 months

    Abdomen 1.0 50 6 months

    IVU 2.5 125 14 months

    : . ,Fro m R e fe rra lC rite ria Fo r Im a g in g C E.2 0 0 0

    Typical effective doses from

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    Typical effective doses fromdiagnostic medical exposures

    Diagnostic

    procedure

    Typical effective

    dose (mSv)

    Equiv. no. of

    chest x-rays

    Approx. equiv. period of

    natural backgroundradiation

    Barium swallow 1.5 75 6 months

    Barium meal 3 150 16 months

    Barium followthrough

    3 150 16 months

    Barium enema 7 350 3.2 years

    : . ,Fro m R e fe rra lC rite ria Fo r Im a g in g C E.2 0 0 0

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    How to measure doses

    Absolutemethods

    Relativemethods

    Calorimetry

    Chemical(Fricke dosimeter)

    Ionometry(ionization chamber)

    Photography

    Scintillation

    TL

    Ionometry

    They needto know a

    characteristic

    parameter

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    hankyou.


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