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Fotonii sunt parte a spectrului Fotonii sunt parte a spectrului electromagneticelectromagnetic

Lumina vizibila

Rad X & Rad GamaUVInfrarosii

Unde radio

Energie suficientapentru a produce

ionizarea

Prefixes and symbolsPrefixes and symbols

pp pico pico 10 10-12-12 a million millionth of a million millionth ofnn nano nano 10 10-9-9 a thousand millionth of a thousand millionth ofmkmk micro micro 10 10-6-6 a millionth of a millionth ofmm milli milli 10 10-3-3 a thousandth of a thousandth ofkk kilo kilo 10 1033 a thousand times a thousand timesMM mega mega 10 1066 a million times a million timesGG giga giga 10 1099 a thousand million times a thousand million times

TT tera tera 10 101212 a million million timesa million million times

GeneralitatiGeneralitati

Generarea radiatiei, transportul si Generarea radiatiei, transportul si interactia cu materia sunt procese fizice:interactia cu materia sunt procese fizice: Desi radiatia nu poate fi vazuta sau simtita, ea Desi radiatia nu poate fi vazuta sau simtita, ea

poate fi foarte bine descrisa si cuantificata din poate fi foarte bine descrisa si cuantificata din punct de vedere fizic;punct de vedere fizic;

Ea poate fi determinata cu precizie folosind Ea poate fi determinata cu precizie folosind mijloace experimentale adecvate.mijloace experimentale adecvate.

Identificarea unui IzotopIdentificarea unui Izotop

Nucleoni

Atomul

Electroni

Henri Henri Becquerel Becquerel

(1852-1908)(1852-1908)

Descoperitorul radioactivitatii , 1896

1. Radioactivitatea1. Radioactivitatea

O proprietate a nucleelorO proprietate a nucleelor Datorita proprietatilor fizice inerente, un nucleu Datorita proprietatilor fizice inerente, un nucleu

s-ar putea sa nu fie stabil si sa fie dispus sa s-ar putea sa nu fie stabil si sa fie dispus sa sufere o transformare nucleara. Acest proces sufere o transformare nucleara. Acest proces poate fi rapid (durata de injumatatire scurta) sau poate fi rapid (durata de injumatatire scurta) sau lent (durata de injumatatire lunga). In oricare lent (durata de injumatatire lunga). In oricare caz, timpul de transformare nu poate fi prevazut caz, timpul de transformare nu poate fi prevazut pentru un nucleu individual - este un eveniment pentru un nucleu individual - este un eveniment intamplator care poate fi descris corespunzator, intamplator care poate fi descris corespunzator, numai folosind statisticanumai folosind statistica

Durata de injumatatire tDurata de injumatatire t1/21/2

0

20

40

60

80

100

120

0 2 4 6 8 10

Descrie cat de rapid Descrie cat de rapid un nucleu particular un nucleu particular se transformase transforma

Este timpul necesar Este timpul necesar pentru jumatate din pentru jumatate din cantitatea de material cantitatea de material radioactiv sa se radioactiv sa se transforme transforme (deseori,timp de (deseori,timp de dezintegrare)dezintegrare)

ActivitateaActivitatea

‘‘Cantitatea’ unui radionuclidCantitatea’ unui radionuclid in SI unitatea este Becquerel (Bq) in SI unitatea este Becquerel (Bq) - -

o transformare nucleara pe o transformare nucleara pe secunda secunda

Vechea unitate este Curie (Ci)Vechea unitate este Curie (Ci)

1 Ci = 37 x 109 Bq = 37 GBq

A(t) = A(0) exp(-t ln2 / tA(t) = A(0) exp(-t ln2 / t1/21/2))

A(t) activitatea la timpul tA(t) activitatea la timpul t A(0) activitatea initiala la timpul 0A(0) activitatea initiala la timpul 0 t timpult timpul tt1/21/2 durata de injumatatire ( fizica ) durata de injumatatire ( fizica )

1 Bq este o cantitate mica1 Bq este o cantitate mica

Potasiul-40 din fiecare persoana > 1000BqPotasiul-40 din fiecare persoana > 1000Bq cele mai multe din sursele radioactive au > cele mai multe din sursele radioactive au >

100,000Bq100,000Bq Sursele radioactive din radioterapie au in Sursele radioactive din radioterapie au in

mod obisnuit > 100,000,000Bqmod obisnuit > 100,000,000Bq

Tipuri de radioactivitateTipuri de radioactivitate

Particule alfa (Nucleu de heliu) - “grea”, Particule alfa (Nucleu de heliu) - “grea”, sarcina pozitiva dubla, interactioneaza sarcina pozitiva dubla, interactioneaza puternic cu materia.puternic cu materia.

Particule beta/radiatie (electron) - particula Particule beta/radiatie (electron) - particula usoara, interactioneaza lent,parcurs relativ usoara, interactioneaza lent,parcurs relativ netnet

Radiatia gama (fotoni)Radiatia gama (fotoni)

Dezintegrarea alfaDezintegrarea alfa

Dezintegrarea betaDezintegrarea beta

Tranzitia gamaTranzitia gama

Stare excitata

Quantities &Units for Quantities &Units for Radiation MeasurementRadiation Measurement

Exposure

Absorbed Dose

Equivalent Dose

Effective Dose

ExpunereaExpunerea

Numarul de sarcini electrice produse de Numarul de sarcini electrice produse de radiatie in aerradiatie in aer

Este relativ usor de determinat Este relativ usor de determinat Se masoara in C/kg - vechea unitate: Se masoara in C/kg - vechea unitate:

Roentgen Roentgen

1 R = 2.58 x 10-4 C/kg

Doza absorbitaDoza absorbita

Energia depusa in materieEnergia depusa in materie D = E/m (1 Gy = 1 J/kg)D = E/m (1 Gy = 1 J/kg) Unitatea este in relatie directa cu efectele Unitatea este in relatie directa cu efectele

in materiein materie Nu este obligatoriu in relatie directa cu Nu este obligatoriu in relatie directa cu

intensitatea fasciculului de radiatie intensitatea fasciculului de radiatie

Quantities &Units for Radiation Quantities &Units for Radiation MeasurementMeasurement

Exposure EExposure E defined as the amount of defined as the amount of ionisationionisation

created in air created in air only defined for air, and x- and gamma only defined for air, and x- and gamma

radiationradiation measured as Coulomb/kgmeasured as Coulomb/kg old unit the Roentgen R = 2.58 x 10old unit the Roentgen R = 2.58 x 10-4-4 C/kg C/kg

airair

Quantities &Units for Quantities &Units for Radiation MeasurementRadiation Measurement

Absorbed dose DAbsorbed dose D the amount of energy deposited per unit the amount of energy deposited per unit

mass in any target materialmass in any target material applies to any radiationapplies to any radiation measured in Gray (Gy) = 1 Joule/kgmeasured in Gray (Gy) = 1 Joule/kg old unit the rad = 0.01 Gyold unit the rad = 0.01 Gy

Quantities &Units for Radiation Quantities &Units for Radiation MeasurementMeasurement

Absorbed dose can be derived from Absorbed dose can be derived from exposure for x-, gamma radiation, exposure for x-, gamma radiation,

D = E x fD = E x f f f depends on radiation energy and the depends on radiation energy and the

target materialtarget material for soft tissue, 100 keV, 1 Roentgen gives for soft tissue, 100 keV, 1 Roentgen gives

9.5 mGy (0.95 rad) absorbed dose.9.5 mGy (0.95 rad) absorbed dose. for air at all energies 1R = 0.87 radfor air at all energies 1R = 0.87 rad

Quantities & Units for Radiation Quantities & Units for Radiation MeasurementMeasurement

Equivalent Dose HEquivalent Dose H takes into account the effect of the takes into account the effect of the

radiation on tissue by using a radiation on tissue by using a radiation radiation weighting factor Wweighting factor WRR

measured in Sievert Svmeasured in Sievert Sv old unit the Rem = 0.01 Svold unit the Rem = 0.01 Sv H = D x WH = D x WRR

Radiation Weighting FactorsRadiation Weighting Factors

Type of Radiation WR

beta 1alpha 20x-rays 1gamma rays 1neutrons <10 keV 5neutrons (10 keV – 100 keV) 10neutrons (100 keV – 2 MeV) 20neutrons (2 meV – 20 MeV) 10neutrons >2 MeV 5


Effective Dose EEffective Dose E Takes into account the varying sensitivity Takes into account the varying sensitivity

of different tissues to radiation using the of different tissues to radiation using the Tissue Weighting Factors WTissue Weighting Factors WTT

Measured in Sievert SvMeasured in Sievert Sv Used when multiple organs are irradiated Used when multiple organs are irradiated

to different dose, or sometimes when one to different dose, or sometimes when one organ is irradiated aloneorgan is irradiated alone

Tissue Weighting FactorsTissue Weighting Factors

Tissue WT

Gonads 0.2Red bone marrow 0.12Colon 0.12Lung 0.12Stomach 0.12Bladder 0.05Breast 0.05Liver 0.05Oesophagus 0.05Thyroid 0.05Skin 0.01Bone surfaces 0.01Remainder 0.05TOTAL 1


Effective dose is used to better describe Effective dose is used to better describe the biological relevance of a radiation the biological relevance of a radiation exposure where different tissues/organs exposure where different tissues/organs receive varying absorbed dosesreceive varying absorbed doses

Effective Dose = SUMEffective Dose = SUMtissuestissues (equivalent dose x (equivalent dose x WWRR x W x WTT))


Collective DoseCollective Dose this is used to measure the total impact of this is used to measure the total impact of

a radiation practice or source on all the a radiation practice or source on all the exposed personsexposed persons

for example, diagnostic radiology or for example, diagnostic radiology or nuclear medicinenuclear medicine

measured as man-sievert (man-Sv)measured as man-sievert (man-Sv)

Biological Processes of Radiation Biological Processes of Radiation EffectsEffects

StageStage ProcessProcess DurationDurationPhysicalPhysical Energy absorption, ionisationEnergy absorption, ionisation 10 10-16-16 s s

Physico-chemicalPhysico-chemical Interaction of ions with molecules, Interaction of ions with molecules, 10 10-6-6 s sformation of free radicalsformation of free radicals

ChemicalChemical Interaction of free radicals with Interaction of free radicals with seconds seconds molecules, cells, and DNAmolecules, cells, and DNA

BiologicalBiological Cell death, change in genetic data tens of minutesCell death, change in genetic data tens of minutes in cell, mutationsin cell, mutations to tens of years to tens of years

Tipuri de radiatie (1)Tipuri de radiatie (1)

radiatiile X si radiatia gama = fotoniradiatiile X si radiatia gama = fotoni electronii si particulele beta - sarcina electronii si particulele beta - sarcina

negativanegativa neutroniineutronii protonii - sarcina pozitivaprotonii - sarcina pozitiva paticule alfa si particule incarcate grele paticule alfa si particule incarcate grele

FotoniiFotonii Radiatia gama:radiatie Radiatia gama:radiatie

monoenergetica (una monoenergetica (una sau mai multe linii)sau mai multe linii)

Radiatia X: spectru Radiatia X: spectru continuucontinuu

Diferenta apare privind Diferenta apare privind calea de producere :calea de producere : Gama in nucleuGama in nucleu Radiatia X-nivel atomic Radiatia X-nivel atomic

CW Roentgen, discoverer of X-rays

Producerea radiatiei XProducerea radiatiei X

Electroni de mare energie lovesc o tinta Electroni de mare energie lovesc o tinta (metalica) unde o parte a energiei lor este (metalica) unde o parte a energiei lor este convertita in radiatieconvertita in radiatie

tinta

electroni

Radiatii X

Energie joasa sau medie

(10-400keV)

Energieinalta > 1Me

Tubul de radiatie X pentru Tubul de radiatie X pentru producerea de radiatie X joasa producerea de radiatie X joasa

si mediesi medie

Acceleratorul linear pentru Acceleratorul linear pentru producerea de radiatie X de producerea de radiatie X de

energie inalta energie inalta

target

electrons

X-rays

Interactia Interactia fotonilorfotonilor

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