al t dmdilphiaccelerators and medical physics...the first publication by roentgen r di h ll d i h li...

A l t d M di l Ph iA l t d M di l Ph iAccelerators and Medical PhysicsAccelerators and Medical Physics

Course 3 : Radioisotopes and related topicsCourse 3 : Radioisotopes and related topics

Saverio BracciniSaverio Braccini

Albert Einstein Albert Einstein Center for Fundamental PhysicsCenter for Fundamental PhysicsLHEPLHEP –– Laboratory for High Energy PhysicsLaboratory for High Energy PhysicsLHEP LHEP Laboratory for High Energy PhysicsLaboratory for High Energy Physics

University of Bern, SwitzerlandUniversity of Bern, Switzerland

EPFL - 11.11.10 - SB - 1/4 1saverio.braccini@cern.chsaverio.braccini@cern.ch

OutlineOutline

1.1. Historical introduction and basics of radiation protectionHistorical introduction and basics of radiation protection1.1. Historical introduction and basics of radiation protectionHistorical introduction and basics of radiation protectionoo The first radiography and the concept(s) of doseThe first radiography and the concept(s) of doseoo Basic quantities in radiation protectionBasic quantities in radiation protection

Fi t f di i t i di iFi t f di i t i di ioo First uses of radioisotopes in medicineFirst uses of radioisotopes in medicineoo NeutronsNeutrons

2.2. Modern medical diagnosticsModern medical diagnostics

3.3. Particle accelerators for radioisotope productionParticle accelerators for radioisotope production

44 Physics and medicine: an ordinary case in modern cardiologyPhysics and medicine: an ordinary case in modern cardiology4.4. Physics and medicine: an ordinary case in modern cardiologyPhysics and medicine: an ordinary case in modern cardiology

Note : all the four modules are correlated with exercises

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Note : all the four modules are correlated with exercises

Fundamental research in particle physics and modern medicineFundamental research in particle physics and modern medicine

Two paths, many crossroadsTwo paths, many crossroads

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The starting point The starting point

•• November 1895 : discovery of X raysNovember 1895 : discovery of X rays

Wilhelm Conrad RöntgenWilhelm Conrad Röntgen

•• December 1895 : first radiographyDecember 1895 : first radiography

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The first publication by RoentgenThe first publication by Roentgen

R di h ll d i h li l t i di t l ft th di

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Radiography allowed saving many human lives almost immediately after the discovery. In particular, portable “Roentgen” devices saved the life of many soldiers in battle fields.

…the real first medical radiography……the real first medical radiography…

Important points:Important points:

•• XX--rays penetrate matterrays penetrate matterXX rays penetrate matterrays penetrate matter

•• XX--rays are differently absorbed by bone and rays are differently absorbed by bone and muscle tissuesmuscle tissues

E ti 15 i tE ti 15 i t•• Exposure time 15 minutesExposure time 15 minutes

•• Exposure nowadays for a hand radiography:Exposure nowadays for a hand radiography:

•• 1/25 to 1/50 second1/25 to 1/50 second1/25 to 1/50 second1/25 to 1/50 second

•• Dose: about <0.1 mSv (natural Dose: about <0.1 mSv (natural background 1background 1--2 mSv/year)2 mSv/year)

Radiography of the hand of Radiography of the hand of

CuriositiesCuriosities

•• Roentgen convinced his wife to participate Roentgen convinced his wife to participate in an experimentin an experiment

Roentgent’s wife BerthaRoentgent’s wife Bertha •• Bertha was horrified and saw in the image a Bertha was horrified and saw in the image a premonition of deathpremonition of death

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The concept(s) of dose The concept(s) of dose •• The The physical dosephysical dose absorbed by matter is measured in Grayabsorbed by matter is measured in Gray

•• 1 Gy = 1 J / 1 Kg1 Gy = 1 J / 1 Kg

•• Used in radiation therapyUsed in radiation therapy•• Used in radiation therapyUsed in radiation therapy

•• In radioprotection the In radioprotection the dose equivalent dose equivalent is measured in Sievertis measured in Sievert

•• Dose Equivalent = (Physical dose) x Wr Dose Equivalent = (Physical dose) x Wr

•• Wr takes into account the biological effects of specific radiationWr takes into account the biological effects of specific radiation

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The concept(s) of dose The concept(s) of dose

•• In radioprotection the In radioprotection the effective doseeffective dose is defined asis defined as

•• Effective dose = (Physical dose) x Wr x Wt Effective dose = (Physical dose) x Wr x Wt

•• Wt takes into account the sensitivity to radiation of different organs for Wt takes into account the sensitivity to radiation of different organs for stochastic effectsstochastic effects

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Dose equivalent and effective doseDose equivalent and effective dose

•• Wr is a multiplicative factor to take into account the “biological effectiveness” Wr is a multiplicative factor to take into account the “biological effectiveness” of radiationof radiation

•• Wt has a different meaningWt has a different meaning

•• Σ Wt = 1Σ Wt = 1

•• If the dose is “full body” If the dose is “full body” dose equivalent = effective dosedose equivalent = effective dose

•• If the irradiation is not homogeneous (ex. The dose is given only to one If the irradiation is not homogeneous (ex. The dose is given only to one ) th ff ti d t th d i l t i t th f ll) th ff ti d t th d i l t i t th f llorgan) the effective dose represents the dose equivalent given to the full organ) the effective dose represents the dose equivalent given to the full

body which produces the same risk. body which produces the same risk.

•• Risk for stochastic effects:Risk for stochastic effects:Annual limit for radio exposed workers

Risk for stochastic effects:Risk for stochastic effects:

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Everybody is exposed to radiation !Everybody is exposed to radiation !

EPFL - 11.11.10 - SB - 1/4 10http://www.raddose.ch

Stochastic and deterministic effects of radiationStochastic and deterministic effects of radiation

•• The cancer induction risk factor is estimated at 4% SvThe cancer induction risk factor is estimated at 4% Sv--1 for a population of 1 for a population of workers and at 5 % Svworkers and at 5 % Sv--1 for the general population (children included!)1 for the general population (children included!)

•• The threshold dose of deterministic effects is situated at 0.5 Gy.The threshold dose of deterministic effects is situated at 0.5 Gy.

•• Deterministic effects:Deterministic effects:

•• The aim of radiation therapy is to cure i.e. to produce deterministic effectsThe aim of radiation therapy is to cure i.e. to produce deterministic effects

•• The doses are therefore large (of the order of 60The doses are therefore large (of the order of 60--80 Gy) and there are no limits 80 Gy) and there are no limits g (g ( y)y)for patients coming form laws on radiation protectionfor patients coming form laws on radiation protection

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The ICRU sphere and operational parametersThe ICRU sphere and operational parameters

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XX--rays: what we know today…rays: what we know today…

XX--ray tube : accelerated electrons ray tube : accelerated electrons yyinteract and radiate photonsinteract and radiate photons

==

XX--ray productionray production

XX ray energy spectrumray energy spectrum

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XX--ray energy spectrumray energy spectrum

Photons interact with matterPhotons interact with matterXX--rays interact with matter (material Z) rays interact with matter (material Z) through different mechanisms:through different mechanisms:

•• PhotoPhoto--electric effectelectric effect

•• Compton effectCompton effect ProbabilityProbabilityCompton effectCompton effect

•• Electron Positron pair productionElectron Positron pair production

(Threshold : 2 x 511 keV)(Threshold : 2 x 511 keV)

yy

( )( )

What happens to a photon beam ?What happens to a photon beam ?

II00 I = II = I00 ee--μμss μμ attenuation coefficientattenuation coefficientDepends on:Depends on:pp

•• The material (z)The material (z)

•• The densityThe density

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ss •• The energy of the photonsThe energy of the photons

The attenuation coefficientThe attenuation coefficient

Why water?Why water?Water is the main component of tissuesWater is the main component of tissues

“Water equivalent” a very used concept in“Water equivalent” a very used concept in

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Water equivalent a very used concept in Water equivalent a very used concept in medical applicationsmedical applications

Let’s get back to RoentgenLet’s get back to Roentgen

Almost all XAlmost all X--rays stop in the tissues!rays stop in the tissues!

Dose to the patient!Dose to the patient!Dose to the patient!Dose to the patient!

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The beginning of modern physics andThe beginning of modern physics andmedical radiation physicsmedical radiation physics

Henri Becquerel Henri Becquerel (1852(1852--1908)1908)

1896:1896:

Discovery of naturalDiscovery of natural

radioactivityradioactivity

18981898Thesis of Mme. Curie – 1904

18981898

Discovery of radiumDiscovery of radiumα, β, γ in magnetic field

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MariaMariaSkSkłodowska Curiełodowska Curie

(1867 (1867 –– 1934)1934)

About one hundred years agoAbout one hundred years agoPierre CuriePierre Curie(1859 (1859 –– 1906)1906)

How many “Radium”?How many “Radium”?

At the time of MadameRadium At the time of Madame Curie, there were many substances with different half lives and may be

Radium

Radium emanationhalf lives and – may be –chemical characteristics all “emanated” by Radium !

Radium ARadium F

!

Radium B

Radium C Radium E

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Radium B

Radium D

A big step forward…A big step forward…

…in physics and in…in physics and in

•• Medical diagnostics Medical diagnostics

•• Cancer radiation therapyCancer radiation therapyCancer radiation therapyCancer radiation therapy

due to the development of threedue to the development of threeM. S. Livingston and E. LawrenceM. S. Livingston and E. Lawrence

with the 25 inches cyclotronwith the 25 inches cyclotron

due to the development of three due to the development of three fundamental toolsfundamental tools

•• Particle acceleratorsParticle accelerators

P i l dP i l d•• Particle detectorsParticle detectors

•• ComputersComputers

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GeigerGeiger--MMüller counter built byüller counter built byE. Fermi and his group in RomeE. Fermi and his group in Rome

1930: invention of the cyclotron1930: invention of the cyclotron1930: the beginning of 1930: the beginning of four other magnificent four other magnificent

yearsyears

Spiral trajectory of an Spiral trajectory of an accelerated nucleusaccelerated nucleus

Ernest Lawrence Ernest Lawrence

(1901 (1901 –– 1958)1958)

Modern cyclotronModern cyclotron A copy is on display at A copy is on display at CERN MicrocosmCERN Microcosm

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CERN MicrocosmCERN Microcosm

The invention of the cyclotronThe invention of the cyclotron

•• Magnet of 9 inches = 22.8 cm Magnet of 9 inches = 22.8 cm

•• Magnetic field of 15 000 gauss = 1.5 TMagnetic field of 15 000 gauss = 1.5 Tg gg g

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E. O. Lawrence and M. S. Livingston, Physical Review, 38 (1931) 834.

The Lawrence brothersThe Lawrence brothers

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Ernst Lawrence and his brother John Lawrence   at the control panel of the 60‐inch (152 cm) cyclotron shortly. 

The Lawrence brothersThe Lawrence brothers

John Lawrence, brother of John Lawrence, brother of Ernest, was a medical doctorErnest, was a medical doctor

They were both working in They were both working in BerkleyBerkley

First use of artificially produced First use of artificially produced isotopes for medical diagnostics isotopes for medical diagnostics p gp gand therapyand therapy

Beginning of nuclear medicineBeginning of nuclear medicineBeginning of nuclear medicineBeginning of nuclear medicine

An interdisciplinary An interdisciplinary environment helps environment helps

innovation!innovation!

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Discovery of the neutronDiscovery of the neutron

19321932

James ChadwickJames Chadwick

(1891 (1891 –– 1974)1974)

Neutrons are used today toNeutrons are used today to

Student of Student of

Ernest RutherfordErnest Rutherford

•• Produce isotopes for medical diagnostics Produce isotopes for medical diagnostics and therapyand therapy

•• Cure some kind of cancer Cure some kind of cancer

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Ernest RutherfordErnest Rutherford

Matter and antimatter...Matter and antimatter...

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1932 1932 –– discovery of antimatter: the positrondiscovery of antimatter: the positron

Slowed-down

ti lparticleCLOUD

CHAMBER

Positive fast particle

Lead layer

Carl D. Anderson Carl D. Anderson -- CaltechCaltech

pcoming from below

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The positron is at the basis of Positron Emission Tomography (PET)The positron is at the basis of Positron Emission Tomography (PET)

Discovery of the effectiveness of slow neutronsDiscovery of the effectiveness of slow neutrons

O. D’Agostino E. Segrè E. Amaldi F. Rasetti E. FermiO. D’Agostino E. Segrè E. Amaldi F. Rasetti E. FermiO. D Agostino E. Segrè E. Amaldi F. Rasetti E. FermiO. D Agostino E. Segrè E. Amaldi F. Rasetti E. Fermi

19341934First radioisotope of IodineFirst radioisotope of Iodine

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among fifty new artificial speciesamong fifty new artificial species

Also for physicists, patents are important!Also for physicists, patents are important!

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Fermi and the use of radio isotopes in medicineFermi and the use of radio isotopes in medicine

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George de HevesyGeorge de Hevesy

Born in Budapest in 1885

He studied chemistry in Budapest, Berlin, Freiburg

PhD in physics 1908 in Freiburg

He worked in many European Universities (Zürich, Manchester - with Rutherford -, Copenhagen Stockholm Karlsruhe Gent)Copenhagen, Stockholm, Karlsruhe, Gent)

1923 discovered the element 72: Hafnium (Hf)György Hevesy

1943 Nobel Prize in Chemistry "for his work on the use of isotopes as tracers in the study of

(1885-1966)

the use of isotopes as tracers in the study of chemical processes”

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George de HevesyGeorge de HevesyIn 1911 he was given a task by Rutherford …– "My boy, if you are worth your salt, you separate Radium D from all that

nuisance lead."

He proved that “Radium-D” cannot be chemically separated from lead (Pb 207) since it is(Pb-207) since it is…

… just Pb-210 !just b 0

He invented isotope dilution analysis and – using heavy water - proved h h lf f h b d ’ d 9 d !that half of the body’s water turned over every 9 days !

First use of radioisotopes to study metabolism:First use of radioisotopes to study metabolism: – "Radioactive Indicators in the Study of Phosphorous Metabolism in Rats"

(Chievitz and Hevesy 1935).Fi t i t l th t bi l i l t i t i d i– First experimental prove that biological systems exist in a dynamic equilibrium

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NeutronsNeutronsNeutrons in matter undergo several physical processes:

To each process corresponds a cross section:

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Cross sectionCross section

The cross section is strongly dependent on the energy (1/v behavior)

Slow neutrons are more effective to produce artificial isotopes !

Note : 1 barn = 10-24 cm2 (which corresponds to the physical cross section of a heavy nucleus)section of a heavy nucleus)

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Slow neutronsSlow neutronsA neutron of kinetic energy E encountering a nucleus of atomic number A looses: 2EA

(A +1)2

For hydrogen, this gives E/2

How many collisions are needed to reach thermal energies (i e 1/40How many collisions are needed to reach thermal energies (i.e. 1/40 eV = 0.025 eV) ?

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Macroscopic cross sectionsMacroscopic cross sections

To calculate the attenuation of a neutron flux a macroscopic approach can be used

I(x) = I e−Nσ t xI(x) = I0e t

where

N is the atom density

σt is the total cross section

Usually, (Nσt)-1 = λ

For fast neutrons, λ is about 10 cm for concrete, 5 cm for polyethylene (PE)

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Neutron dose calculationsNeutron dose calculations

To perform precise calculations (ex. for shielding) complex Monte Carlo codes are used (MCNPX, FLUKA, etc.)

One has to keep in mind that the dose is given by neutrons and gammas (especially 2.2 MeV gammas from neutron capture in g ( p y g phydrogen) !

Neutrons behave veryNeutrons behave very differently in different

materials !

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One exercise in radiation protectionOne exercise in radiation protection

A generator 68Ge-68Ga is installed in a laboratoryThe maximum activity that can be eluted is 1 GBq of 68Ga Which dose rate is received by an operator using a 5 cm Pb shielding?

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GermaniumGermanium--68 and Gallium68 and Gallium--6868The material of the generator is produced with an accelerator via the reaction:

The generator is a sealed (and shielded !) source of radiation producing negligible dose rate in the environment. The only increase of dose rate is produced be the elution of Gallium (opened liquid source). ( p q )

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The decay schemeThe decay scheme

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The law comes first… The law comes first…

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… and we can use it for solving our exercise!

Dose rate calculationDose rate calculation

• Which quantity do we need to calculate?

• H*(10)

H = Ah

t T

H (10)

H = A ⋅r2 ⋅ t ⋅T

where

A is the activityy

r is the distance

t is the time

T is the transmission coefficient

… and h is a parameter – characteristic of the isotope – which has been calculated

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pand is given by the law!

The parameter h The parameter h

H = 0.149 (mSv/h) / GBq at 1 m distance( ) q

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The transmission coefficient T The transmission coefficient T

We have mostly 511 keV from positron annihilation

661.7 keV gammas from 137-Cs can be used to estimate T

T= 4 x 10-3

For a precise estimation one can use the NIST data base :NIST data base :

T 6 10 3T= 6 x 10-3

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www.nist.gov

Dose rate calculationDose rate calculation

• We can now calculate H*(10) from

hH = A ⋅

hr2 ⋅ t ⋅T

∂H∂t

= A ⋅hr2 ⋅T = 1GBq ⋅ 0.149

mSvh ⋅GBq

⋅6 ⋅10−3 = 0.9μSvh

• Further questions:

q

• Is this value acceptable? (Natural background about 0.2 uSv/h)

• Do we need measurements during operations?

• Do we need an authorization?

• Can we operate the generator in a “normal” or in a “special” laboratory?

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End of part IEnd of part I

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