Interactions of Ionizing Radiation with Matter - 2024-2025

INTERACTIONS OF IONIZING RADIATION WITH MATTER Lecturer Pr. Malika ÇAOUI Nucl...

INTERACTIONS OF IONIZING RADIATION WITH MATTER Lecturer Pr. Malika ÇAOUI Nuclear Medicine Semester : 1 Academic Year : 2024-2025 Module BIOPHYSICS Module Element IONIZING RADIATIONS www.um6ss.ma  Interest of the course IR can only be detected and characterized through their interactions with matter They give up all or part of their energy to the environment they cross. Results : Changes within the matter by effects produced that are can be observed (Detection, Radiobiological Effects, Medical Applications, Radiation Protection...) 2  Plan Charged particles: Interactions of charged particles with matter Interactions of heavy charged particles with matter and path Light charged particle interactions with matter and path The photons: Law of attenuation of a beam of photons by the material: Attenuation coefficient Half-attenuation thickness Interactions of photons with matter Photoelectric effect Compton effect Pair production 3 Electromagnetic spectrum An Introduction to the Electromagnetic Spectrum – Blushield USA 4  Ionizing radiations There are two main categories of Ionizing Radiations (IR): Direct ionizing radiation: Light charged particles : β-, β+ electrons; μ +; μ-... Heavy charged particles (charged) : α, p, fragment of fissions, heavy ions... Indirectly ionizing radiation: Photons or Electromagnetic waves (EM) : wavelength  < 100 nm: RX et R Neutrons : n ; Neutrinos :  ; …. (UVC:  = 0,1µm with E = 12,4eV) Non ionizing Radiations : waves :  > 100 nm: - Radio waves - Infra red - Visible Light - Microwave - Ultra-violet (Most of UV) 5  CP Interactions Characteristics ⁃ These interactions directly ionize matter and they must occur. ⁃ 2 types of Charged Particles : heavy and light particles. ⁃ During these interactions, the energy transferred from the incident particle to the matter, depends on: ⁃ The type of the particle : nature – mass – energy (velocity) ⁃ The nature of the material it interacts with : composition, density (Z : atomic number) ⁃ In biology, most interactions happen with water +++ 6  Heavy Particles (HP) ⁃ Frequent interactions happen between alpha particles and electrons +++ : ⁃ Results : Lost Energy : by atoms Ionization and Excitation in the crossed material ⁃ 𝜶 Mass is much larger >> electron mass : ⁃ 𝜶 transfers little energy to the electrons (less affected by many low energy transfers) - it continues in straight line without losing much energy: then 𝜶 ‘s trajectory slightly modified The energy lost by different interactions is expressed by : LTE; DLI; and the Bragg curve - L.T.E. : The Linear Transfer of Energy (L): Transferred Energy by HCP to material each unit lengh TLE = dE/dx: KeV/m in water - In MeV/cm in air ⁃ L.D.I: Linear Density of Ionization : Number of Ion Pairs created /unit length : L∞ = W. LDI (W: Necessary Energy to cause 1 ionization (in biology: W= 33eV) 7  Interactions des RI avec la Matière Pic de Bragg des protons Pic de Bragg représentant la diffusion de la dose en fonction de la profondeur dans les tissus Bragg Curve: The study of DLI variation along trajectory - Bragg peak : represents dose diffusion as a function of tissue depth At the end, the kinetic energy of the particle decrease  and become ionizing so DLI  Pr J.F. HERON -http://www.oncoprof.net 8  Applications Applications in radiotherapy: ⁃ By selecting the kinetic energy of the particles, the depth of the Bragg peak can be adjusted to a tumor. ⁃ Thus, we can better protect the surrounding healthy tissues Applications in radiation protection: ⁃  Particles : large mass and charge (2p : +), so have an extremely limited ability to penetrate matter. ⁃  has a shorter range in matter: Ex:  = 5.3 MeV of TLE: 130 KeV / 𝝁m (high deposit of energy) ⁃  : stopped by a few cm of air, a sheet of paper, or by the surface layer of the skin. ⁃ Consequences:  particle outside the body does not present a great danger : no risk in external exposure ⁃ However, when  substances are, accidently, taken into the body (by inhalation them in or by ingesting them): the particles can continuously emit , cause damage to cells, tissues: danger by internal exposure 9  Light Particles : Electrons Frequency Interactions : Most of the electron interactions happen with other electrons of matter : The incident electron : ei meet an other electron from atom : If the Energy of ei transferred is : sufficient, the e is removed from its orbit and ejected from the atom : ionisation not sufficient, the e only moved from its internal orbit to peripheral orbit : excitation Trajectory of ei is a broken line Consequences → Radiobiology : Ionizations and excitations are at the origin of radiation - induced biological effects. The eI interacts with the electric and magnetic fields produced by the nucleus ++++ ⁃ e : deflected and accelerated, by nucleus field and loses its energy which is emitted as X-Rays : Bremsstrahlung = Braking XR ⁃ This process is used to produce RX in : Coolidge tube (Diagnostic Imaging) & Particle Accelerators (External Radiotherapy) 10  Electrons Interactions with matter eI M Orbital e moved to external orbit: EXCITATION L K Orbital e pulled: IONISATION eI Braking X-Ray : Bremsstrahlung eI interact with nucleus magnetic field 11 11  Electromagnetic Radiations X Photons : Electronic origin : Braking X or Bremsstrahlung : are produced when a high-energy electron is decelerated as it interacts with nucleus field. Characteristic X-rays : Are produced when an incident particle collides with an atom, removes and ejects an electron from atom. When this happens, electrons move to fill the vacancy in the orbit, releasing energy in the form of an X-ray  Photons : emitted by nucleus during process : Nuclear transition ( radioactive decay) : from an unstable nucleus by excess energy which emits a  to become stable Particle annihilation after 𝜷 + emission (radioactive decay ) caused by disintegration excess protons. Energy domain of photons :  dozaines KeV & MeV X ‘’ ‘’ eV & GeV: (Braking R) 12  Photons are Indirectly Ionizing Radiations Photons XR & R : (No Mass & No Charge) have different interactions with matter / charged particles. Photons are indirectly ionizing, atoms or molecules when they pass through matter. They interact randomly with the matter through a different process : - Photoelectric Effect that create, first, an electron which will ionize in the 2nd time, the matter. - Compton Effect Incident Energy is distributed in (Transmitted,Transferred or Diffused) energy - A Pair Production h e- Electron : Ec → Ionisation 13 Excitation  Photons Attenuation x Absorption (Photoelec Effect – Materialization) (cm-1): linear attenuation coefficient depends on: N0 Material nature (Z) Transmission: without absorption Incident photon energy Nx = N0 e- x Diffusion: (Compton Effect) Attenuation refers to the reduction in intensity of a photon beam as it crosses a material Copper Compact Copper Density of material : /ρ Importance of ρ (density: m/V): N(x) = N0 e-(µ/r).x /ρ : Mass attenuation coefficient 14 /ρ = cm-1/ g.cm-3 → /ρ = cm2. g-1 14  Photons Attenuation Photons attenuation by matter depends on their : - Energy - Density - Composition of the material When attenuation occurs : - Higher energy photons are typically less attenuated than lower energy photons, - Materials with high densities and atomic numbers tend to attenuate photons more strongly. - Attenuation of photons is an important concept in fields such as radiology 15  Thickness of half-attenuation : X1/2 N/2 N/4 N/8 2 2 2 it means that the material reduces N N/2 the intensity of the photon beam by 50%. N/4 N/8 N/16 1 X1/2 1 X1/2 - X1/2 : Thickness x of the material necessary to 1 X1/2 1 X1/2 attenuate by 50% the intensity of IR : N0 - NHAL = N0/2 = N0.e- µx1/2 N - → Ln2 =. X1/2. → X1/2 = ln2/ N/16 15 4 X1/2 Jean Baptiste.Fleutot – Cours de Radioprotection 16  N Thickness of half-attenuation : X1/2 N0 1x1/2 2x1/2 3x1/2 x N(0) N0/2 N0/4 N0/2 N0/8 N0/4 0 N0/8 1x1/2 2x1/2 3x1/2 x N NX = N0 e-µx Log N = µx + Log N0 16 17 X1/2 of Electric Generators of X-Rays kV X1/2 Pb X1/2 béton 50 0,07 mm 3,8 mm 100 0,26 mm 16,5 mm 150 0,30 mm 21,6 mm 300 1,48 mm 30,5 mm 17 Jean Baptiste.Fleutot – Cours de Radioprotection 18  Photoelectric Effect Photon : h = Ei Photoelectric effect: occurs on: An electron bound in its orbit L Photon h disappears after giving up its energy K e- Photoelectron Ek = Ei- EL Photon Ei used to: - Extract the e from its orbit - Communicate to this e a kinetic energy: Ek by becoming a photoelectron Conditions of this effect : - Ei > electron binding E - This phenomenon occurs more in e bound on K orbit +++ than L++; M+ 20 19  Photoelectric Effect Consequences: Electrons move to fill the vacancy in the orbit K, releasing energy in the form of an X-ray Fluorescence X-Ray (or characteristic ray is emitted) Auger electron Ionizations & excitations of matter Probability  of interaction by Photoelectric effect :  :  depends on E & Z of material:   with Z &  with E Photoelectric is dominant up to E = 0,5 MeV with Z  (heavy nucleus) 20  Compton Effect e- Ek e compton Photon h : E1 h diffused photon : E2 Compton effect occurs on a loosely bound electron on its orbit (external orbit) Electron Projected at : Incident Photon diffused at: - angle : 0 < < 90 - angle: 0 < < 180 - an e with Ek : Excitation + Ionization - E2 = h diffused photon 21 21 22  A pair Production: Materialization Photon h interacts with nucleus magnetic fields Mechanism is possible if the initial energy of the photon reaches a threshold of : h > 1,022 MeV Production of a Pair (e-, e+) - e h Photon h disappears h - 1,022 = Eke- + Eke+ Consequences: e+ e- lost its EK by excitation & ionization e+: Annihilation with e- of matter and 2  are emitted in opposite directions, each  = 0,511 MeV Probability of attenuation PP p : - increase slowly with photon Energy -  with Z ( p  Z2 ) 23  Productions of different effects Z  cm-1 =  + c + p 100 – / =  / + c / + p / 80 – Photoelectric Materialization 60 – Effect Compton Effect 40- 20- 0,01 O,1 1 10 100 E ( MeV) 24  DETECTION OF IONIZING RADIATION Lecturer Pr. Malika ÇAOUI Nuclear Medicine Semester : 1 Academic Year : 2024-2025 Module BIOPHYSICS Module Element IONIZING RADIATIONS www.um6ss.ma  Principle of detection None of our senses are sensitive to detecting the presence of IR Principle of the detection: the IRI interact within the detector and lose their energy by: → ionization → Electric signal product : Measurable → excitement Detectors: converts IR '' invisible '' into a measurable signal 26  Detectors Main types of detectors Global constitution of a detector General characteristics of detectors Detector Functions: Detect and Quantify Radioactivity Gas detectors Scintillation detectors Individual dosimetry: - Dosimeter film, - Stimulated luminescence dosimeters (TLD and OSL) - Active dosimeters: electronic for operational mode 27  Main Types of Detectors Ionisation → ddp→ Gas detectors Chimical Réactions → Dosimeter film Ionisation→ electrons scintillator Excitation semi-conductor Modifications of Luminescence electronic shells → Absorption Atomic Excitation Vibration → Calorimeters 28  Global Constitution of a detector ⁃ Captor: place of interaction IR - matter ⁃ Signal amplification system ⁃ Signal processing : Amplitude discriminator ⁃ Display system : provides measurement datas - Particle flow counter - Energy particles: spectrometer - Absorbed dose in matter : dosimeter 29  Global Characteristics of detectors Different parameters: - Detection efficiency - Time resolution - Intrinsic Spatial resolution - Energy resolution - Clean movement - Geometric characteristics 30  Characteristics of detectors Detection Efficiency : ⁃ It depends on nature and energy of IR radiation being detected, the detector material : thickness- composition IR Number Detected IR Number Detected D. E = ----------------------------------------- D. E = ----------------------------------------- IR Number emitted by source IR Number received by detector Extrinsic Efficiency Intrinsic Efficiency Time Resolution :T.R : ⁃ Smallest time interval between two detections. is the ability of a machine to detect fast-moving particles ⁃ It’s measured in nanosec or picosec. If T.R short → High Count Rate (C.R). Ex : Scintillators : C.R  (> 109 events/sec) The clean movement: ⁃ The C.R recorded without source * ⁃ Origin :Telluric & Cosmic IR - Radioactivity of the detector materials - Sound of the associated electronics 31  Characteristics of detectors (2) Intrinsic spatial resolution ++: ⁃ Ability to distinguish the smallest distance between two radiation sources that are close together, measured in mm, 𝝁𝒎 ⁃ High spatial resolution is necessary for accurate diagnosis in medical imaging, such as PET and SPECT. Energy Resolution +++: ⁃ Ability to separate two IR energy values close together : Characterizes the quality of the detector Geometric characteristics: ⁃ They define the shape of the detector, the importance of its : sensitive surface and directivity.. In summary ⁃ The performance of an IR detector : characterized by its spatial and time resolution, clean movement, detection efficiency ⁃ The specific values of these parameters will depend on the design and materials used in the detector. 32  Detector Energy Resolution % of CR Co 57 122 KeV Tc 99m: 140 KeV 100 - ( E : FWHM: Full Width at Half Max) Energy Resolution : R ≈ E/E0(%): E (Current Detectors (NaI) ≈ 5 - 10%: Tc99m (before 20%) 50 - R = 1%: Finer spectrometry with ex : Semiconductor Diffusion (Compt on) 2 energy values close: overalp Good energy resolution reflects a detector’s ability to separate distinctly 2 very similar energies. 40 80 120 E0 : 140 160 E (KeV) Peak of Photoelectric Effect : total Absorption 34 33  Detector Functions ⁃ Detect radioactivity: presence or absence of IR ⁃ Quantifying radioactivity by measure: source Activity ⁃ Provide an image of the radioactivity fixed by a structure: scintigraphic image 34  Detector functions Presence or absence of IR IR interact into detector Ex : An ionization chamber → generates a signal → indicates presence Energy deposit of IR but nothing about the danger irradiation potential: cps /sec (Bq) Quantifying the Radioactivity: Source activity : Activimeter → In nuclear medicine: Measure the dose activity of the Radiopharmaceutical Drug before its administration to the patient. Absorbed dose rate or absorbed dose: mGy / h (mSv / h), mGy or mSv) : - Rγ: Babyline - 𝛃 and α radiation: surface detectors in case of contamination 35  Gas ionization Detector Cathode As soon as there is Passage of IR: γ, X, β R + + + In the absence of radiation, e- e- e- whatever the potential difference applied  Anode e- e- Gas No electricity is detected + + + If presence of IR : Production of a large number :   Ions (+) → cathode e (-) → anode  Result : Electric Current (Charge Q collected ) → Signal Detected 36  Different regimes of gas detectors Charge Q Proportional Passage of IR Counter  Electric Current (Charge collected Q)  Detection Signal 1 2 3 4 5  Tension (V) 5 regions according to the tension V Ionization Chamber Geiger-Müller « Babyline » 37  Gas ionization Detector Zone 1: Recombination (V < 100V): Insufficient field strength Ionization Chamber : « Babyline » : RX & R Zone 2: Primary ionization (V > 200V) All electrons or ions collected Independent of V but dependent on E Zone 3: Proportionality (300 < V < 1000V) Proportional counter – Primary ionization accelerated → secondary ions Q = kq Surface detector  &  if contamination Zone 4: limited proportionality Zone 5: Geiger-Müller regime (V > 1100V) The counter GM: cannot Almost complete ionization of the gas: avalanche of ions discriminate IR according Counts a particle but does not quantify (counter) to their energy. it can only count them 38  Scintillations Detectors ⁃ The (invisible) photon that enters the scintillator, generates ionizations and excitations of the crystal molecules. ⁃ Desexcitation is accompanied by the emission of visible light which will be transformed into a measurable electrical signal. ⁃ Scintillation detector is composed of: - Scintillator: transparent crystal (in NaI: Sodium Iodine) - Photomultiplicators (PM) coupled to scintillator - Associated Electronics 39  Signal R Anode 1000 V 800 Dynode 600 HT 400 200 PM NaI CrystaI Scintillation Detector Collimator 40  Cristal scintillant The Scintillator Crystal is transparent:  Detects incident R Converts them into light photons 41  PM: Conversion light signal into electric signal Photocathode converts light photons into electrons Dynodes multiply electrons Anode collects the electrons and transforms them into an electrical pulse 42  Associated Electronics Spectrometer ou discriminator Device that sorts the pulses leaving the TPMs according to their energy Keeps the photons absorbed by photoelectric peak (total absorption: E. detected ≈ E emitted): → Good quality image Reject the scattered photons produced by Compton effect which deteriorates the image quality (E. detected < E. emission ) 43  Main types of scintillation detectors Gamma-camera : simple or coupled to X-Ray (CT : Computer Tomography or scanner) or MRI (magnetic resonance imaging): ⁃ SPECT: Simple Photon Emission Tomography (SPECT) : detects one Photon , usually, emitted by the Tc99m tracer after administration to the patient ⁃ SPECT - CT: Excellent fusion image provided by CT (morphological image) and SPECT (functional image). ⁃ PET : Positon Emission Tomography : the machine detects simultaneous detection in coincidence of 2 photons  of 511 keV, emitted at 180° from each other and resulting from ß+ annihilation, from patient body who have received ß+ tracer. ⁃ PETSCAN (= PET-CT) or PET- MRI 44 SPECT single head 45 SPECT-CT: (Scanner + Gamma Camera double head) SPECT double head Courtesy of Dr. Ph. Declerck, Ir. J. Walravens – St-Janskliniek, Nuclear medicine – , Be 46 PET- CT (Scanner + PET) PET - CT 47  Individual dosimetry Passive dosimeters with delayed reading of the dose received: ⁃ Dosimeter film (photographic) ⁃ Stimulated luminescence detectors ⁃ Thermoluminescent dosimeter (TLD) ⁃ Optical Stimulus Luminescence Dosimeter (OSL) Active dosimeters with a direct reading of the dose received ⁃ Ionization chamber: ambient dosimeter ⁃ Semiconductor Detectors: Operational Individual Dosimetry 48  Individual dosimetry Passive delayed reading dosimeter Dosimeter film Stimulated luminescence dosimeters (TLD - OSL) Direct reading operational dosimeter 49  Dosimeter film photographic : Principle RI ➔ Silver Bromide  Metallic Silver: measurement of the optical density → responsible for the darkening of the film → received dose. Dosimeter: Estimates a dose of external exposure Monitors cumulative doses (but not instantaneous doses) It must be developed, result known late: a posteriori Low sensitivity (Simpler and older dosimeter) 50  Stimulated luminescence dosimeters Principle: Dosimeter TLD Absorbed IR → crystal structure defects → Heating → Crystalline structure repair → is recovering → Light emission: thermoluminescence phenomenon proportional to the dose received. → Advantages: TLD OSL Dosimeter TLD : Measures the equivalent doses of the ends exposed to IR: Better sensitivity than photographic films, Easy dosimeter reading Dosimeter OSL : "Optically stimulated luminescence » : non-destructive reading; Wide measuring range from 0.01 mSv to 10 Sv; Better sensitivity to all energies / film and TLD 51  Active dosimeters - Electronic dosimeters, giving real-time information - Displays the integrated dose and dose rate - Information read by remote transmission with integrated alarms → monitor of an area or a team continuously - Dose history - Better risk management - Better prevention of accidental irradiations 52  EXPOSURES - DOSIMETRY Lecturer Pr. Malika ÇAOUI Nuclear Medicine Semester : 1 Academic Year : 2024-2025 Module BIOPHYSICS Module Element IONIZING RADIATIONS www.um6ss.ma  Plan Radiation in life Natural and artificial sources of radiations Natural and artificial exposure Exposure modes External exposure Internal exposure : External contamination & Internal contamination Means of protection IR Penetration Penetration abilities of different types of IR Dosimetry : Dosimetric quantities Absorbed Dose Equivalent dose Effective dose 54  Course Objectives - Distinguish the different modes of exposure and contamination - Describe the course of the different IRs in the matter. - Explain the choice of appropriate material to protect against IR. - Define dosimetry quantities and interpret their respective meanings - Illustrate the factors linking the dose to the risk 55  Radiation Sources Radiation sources are now an integral part of life. Many sources of radiation exist all around us. ⁃ Natural sources : Radioactivity is primarily a natural process. Radiation has always been present all around us in many forms. ⁃ Our bodies have adapted to it. We find radioactivity in: ⁃ Cosmic radiation: in space ⁃ Terrestrial radiation : Floors and walls of our homes, schools, or offices. Food we eat and drink. ⁃ Internal radiation : from inside our bodies, from radioactive: Potassium-40 (K*40) and Carbon-14 ⁃ Artificial sources from our technologies ⁃ Medical sources: Radiation has many uses in medicine: X-Rays, Nuc Med, Radiotherapy, ⁃ Industrial sources: Nuclear gauges used in the building of roads ⁃ Nuclear fuel cycle: Nuclear power plants (NPPs) use uranium to produce a chain reaction to product electricity ⁃ Atmospheric testing: of atomic weapons from end 2d World War → 1980 released radio mater 56  Sources of IR exist all around us and are an integral part of life. Radioactivity: a natural process all around us in many forms. Our bodies have adapted to this natural source 57 Canadian Nuclear Safety Commission – Dec 2012  Natural Sources of IR Many natural radioisotopes formed from solar system : interaction of cosmic rays with molecules in the atmosphere. Exposure to cosmic radiation: in space ⁃ Natural radioisotopes: formed in the solar system by the interaction of cosmic IR with atmospheric molecules. ⁃ Some IR will penetrate the earth’s atmosphere and become absorbed by humans : results in natural radiation exposure. Exposure to terrestrial radiation : ⁃ The earth's crust is a major source of natural radioactivity: U, K, thorium: release of small quantities. ⁃ They are constantly present in our natural environment: soil, rocks, homes, schools, offices... food, water... ⁃ Exposure to natural radioactivity can therefore occur both indoors and outdoors. 58  Internal Natural Sources of IR Exposure through inhalation radioactive gases : - Produced by radioactive minerals found in soil and bedrock (Radon from uranium decay – Thoron thorium decay,) - Released into the air : But sometimes trapped and accumulate inside buildings and are inhaled by occupants Exposure through ingestion - Trace amounts of radioactive minerals are naturally found in the contents of food and drinking water. - Once ingested, these minerals result in internal exposure to natural radiation: K40 and C14 (natural) - K40 content of certain foods : per 500g : Ex: Red meat : 56 Bq - Potato : 63 - Carrot : 63 - Banana: 65- Bean : 86 59  Natural Radioactive isotopes in Human Body Several radioactive isotopes also occur naturally in the human body Radioactive isotopes found in the human body (70 kg adult) 60 Canadian Nuclear Safety Commission – Dec 2012  Sectors using IR Different sectors use IR: ⁃ Medical sources +++: Radiation has many uses in medicine radiology, nuclear medicine, radiotherapy, surgery, cardiology… ⁃ Research field +++: Universities and Research Structures... ⁃ Civil industrial environment: ⁃ Nuclear fuel cycle: Nuclear power plants (NPPs) use uranium to product electricity in nuclear power plants ⁃ Industrial sources: Sources * (gauges) used in different sectors: civil engineering: buildings roads... ⁃ Military Field: Nuclear Weapons: o Atmospheric testing: of atomic weapons from end 2d World War → 1980 released radio mater o Fission "Bombs A": Hiroshima, Nagasaki (1945) o Fusion: - Thermonuclear bombs or "H Bombs” - Neutron bomb - Ballistic missiles surmounted by nuclear warhead 61 Exposure to human radiation https://radioactivity.eu.com/in_daily_life/natural_exposures 62  Exposure to IR The exposure of Man to IR may be either: - Total exposure = sum of exposures (internal + external) - The exhibition maybe: - Global: whole body (internal + external) - Partial: organization part (internal + external) - The different modes of irradiation: we distinguish: - External exposure - External contamination - Internal contamination 63  External exposure ⁃ Source *: outside and away from the body; only RI reaches the body ⁃ Protection: - Time: minimize time near the source * - Distance: increase as far as possible the distance between S * - Using screens: protecting yourself behind the screen if source* used or manipulated ⁃ An irradiated person doesn’t carry radioactive material ⁃ → He doesn’t irradiate or cannot be a danger to others or the environment. 64  Measures against External Exposure Multiply the distance to the source by 2, divide the dose received by 4 H1 et H2 : Equivalente doses d1 et d2 : respective distances H1/ H2 = (d2 / d1)2 → D : a rule that obeys the inverse square law of distance. « Radiation protection in medical sector » Emmanuelle Martin- PSRM 65  External contamination Source* is in contact with the skin protection: - Confinement of the sources - Clothing protection for people Irradiated person is a contaminant for: - Him/herself - the entourage around - the environment 66  Internal contamination - Source* is incorporated in the body - Protection: - Containment of sources, - Cutaneous and respiratory protection, - Rules of food hygiene and construction (building). - Creation of new lesions, related to the continuous presence in the body of the source *: - after removal of the victim to the S * contamination, - and even after external decontamination. 67  Exposure Modes NOTIONS DE RADIOBIOLOGIE ET DE RADIOPATHOLOGIE-INSTN-2009   EXTERNAL X,  n IRRADIATION   EXTERNAL CONTAMINATION X,  n INTERNAL X,  n  CONTAMINATION  Outer layer skin Epidermis Internal Organism Basal layer Different Paths of IR 68  Means of Radiation Protection TIME – DISTANCE External Exposure SCREEN Person doen’t radiate External Contamination Containment S* Sealed source Sujet irradiated : contaminates External Protection Internal Contamination External Protection Continuous Lesions - Isolation S* Hygiene External Décontamination 69  The Paths of IR in matter It‘s directly related to the deposit by the RI of energy per unit length of material Air Water, tissus IonizationDegrees Penetration power - Stop  10 cm Some µm Strongly ionizing paper  1m 1mm Moderately ionizing Plexiglas or aluminium X,  > 10 ou 100 m 10aine cm Faiblement ionisants lead 70  Penetration abilities of different types of IR Each radiation source differs in its ability to penetrate various materials, such as paper, skin, lead and water. Les RI « Dossiers Pédagogiques » 71  Dosimetry Définition : Dosimetry is the tool that serves to measure doses due to IR, using methods determined in accordance with radiation protection concepts and criteria. - Absorbed Dose - Equivalent dose - Efficace dose 72  Absorbed Dose: D +++ ⁃ D = dE/dm : J. kg-1 = Gray : Gy – ⁃ 1 J.kg-1 = 1Gy ⁃ A dose of 1 Gy is a very high dose. In practice, submultiples of the gray are used (mGy or mGy) ⁃ Absorbed doses : variables applications: - 0,2 mGy : Dental radiology - 1 mGy : Chest X-Ray - +++kGy: Food ionization - 2 Gy : Radiotherapy : the doses imparted within tumors range up to 50 Gy ⁃ A 1Gy Dose from  will not produce the same biological effects as a 1Gy D from  source! ⁃ So the need to introduce another parameter! 73  Equivalent Dose: H +++ ⁃ To take into account the harmfulness of ≠ IR, we apply à D: WR : HT = WR. DTR ; WR : weighting factor ⁃ HT : Equivalent Dose to the irradiated T organ is not measured, it is calculated. - HT compares doses delivered by different IR. - Unit HT : Sievert (Sv); 1Sv = 100 Rems (old unit) ⁃ DTR: Average absorbed Dose in tissue or organ T due to IR (Gy). ⁃ WR : Weighting Factor, applies to the average dose received by the irradiated tissue or organ. - So WR depend on on the type and energy of the IR. - But WR is independent of the nature of the irradiated tissue or organ 74  Weighting Factor WR WR : is relative to IR nature WR = 1 : RX - R - é (all energies) WR = 5 : protons ; neutrons < 10 keV ; WR = 10 : neutrons : 10 - 100 keV; WR = 20 :  , ou neutrons : 100 KeV to 2 MeV Ex : In internal contamination : 1 Gy D, (Dose in the body): H = 1 (D) x 1 (WR) = 1 Sv if element* incorporated is : K40 (, ) → WR = 1 H = 1 (D) x 20 (WR)= 20 Sv ‘’ ‘’: ‘’ : Thorium232 ()→ WR = 20 75  Weighting Factor WR H T =  (DT , R  wR ) R 76  Examples A person undergoes irradiation in whole body by neutron, E = 50 keV (WR=10) Dn = 1 mGy → Hn = Dn. WR = 1 x 10 = 10 mSv If this person received in the same conditions a R Dose = 10 mGy The risk involved would be the same → H = D. WR = 10 x 1 = 10 mSv If he had received mixed irradiation n +  : D = 10 mGy & Dn = 1mGy → He would have received 11 mGy D. But he would have received Equivalent D: - H = H + Hn = D. WR + Dn.WRn= 20 mSv - H = H + Hn = (10 x 1) + (1 x 10) = 20 mSv NOTIONS DE RADIOBIOLOGIE ET DE RADIOPATHOLOGIE-INSTN-2009 77  Efficace Dose: E +++ ⁃ Equivalent dose to organ HT affected by WT by a factor becomes for the whole body: la dose efficace E. HT. WT = E ⁃ HT : Equivalente Dose to organ T in Sievert : Sv ⁃ E : Efficace Dose in Sv ⁃ WT : Tissue Weighting Factor, WT depends on tissue nature exposed organe, so on organ radiosensibility. ⁃ WT : indépendant on IR nature. (Distinguish : WR et WT!) : WR→ RI & WT → Exposed Tissue or organ. 78  Efficace Dose: E +++ Since the 1990 recommendations introduced in Publication 60, the ICRP has continued its work. A new publication incorporating new recommendations for WT is today effective A. Hammadi - INSTN -CEA (Paris – France)  Meaning of différent doses % surviving ₵ 100 One culture is irradiated by 3 sources * of ≠ doses : With  (239Pu) all ₵ die for D < 4 Gy 10 - : need reach 10 Gy to have the same effect : ₵ resist to increase absorbed Dose 1 - (3H)  (60 Co)  (239Pu) 0 0 4 8 12 D (Gy) 80 www.kaptitude.com© Aptitude – INSTN -CEA (Paris – France)  Absorbed Dose & Dose Flow A single dose received at one time is more harmful than the same dose received over a long period of time. The speed which a IR dose is delivered explains the results of the biological effects: notion of Flow which determines the intensity of irradiation. This dose rate linked to time: in Gy.s-1 or in Gy.h-1  D = D / dt 81  Applications: Dose splitting in radiotherapy In radiotherapy: Dose splitting allows: To administer a greater absorbed dose compared to a single dose, so better efficiency of the treatment. In effect, this splitting allows: The pathological tissue to mobilize in the cell cycle and be more receptive and sensitive to IR. The irradiated healthy tissue to have time to repair its radiation-induced lesions. 82  In summary : Dosimetry Absorbed Dose D : D = dE / dm ; D en Gy Dent: 0,2 mGy Chest ray: 1 mGy Radiothérapie : 2 to 50 Gy Equivalent Dose HT: HT = WR. DTR (Gy) ; HT en Sv ⁃ WR : depends on type & E : RI ➔ Harmfulness of IR ⁃ WR = 1 : RX - R - é ➔ WR = 20 :  ; n : 100 KeV - 2 MeV Effective Dose E : E = HT. WT ; E en Sv ⁃ WT : depends on nature of tissue or organ, ➔ Radiosensitivity of the organ - Gonads : O,08 - Bone marrow : 0,12 - Bladder : 0,05 - Thyroïd : 0,05 - Skin : 0,01 - Bone : 0,01 83  Factors relate dose to risk Generators E. Absorbed Harmfulness IR (WR) Human Impact (WT) RADIOACTIVITY ABSORBED DOSE EQUIVALENT DOSE EFFICTIVE DOSE Disintegrations /s D (J/kg) H (D. WR) E (H. WT) Becquerel (Bq) Gray (Gy) Sievert (Sv) Sievert (Sv) 1 dis/s (1 J/kg) (Gy.WR) (Gy.WR.WT) Curie (Ci) OLD UNIT: Rad OLD UNIT: Rem 3,7.1010dis/s 1 Gy = 100 Rad 1 Sv = 100 Rem NOTIONS DE RADIOBIOLOGIE ET DE RADIOPATHOLOGIE-INSTN- JB Fleutot 84  Some References h ttp://www-pub.iaea.org/books/ http://www-pub.iaea.org/books/ h ttp://www.irsn.fr/FR: http://www.irsn.fr/FR: Les collections d'ouvrages scientifiques de l'IRSN www.kaptitude.com© Kaptitude – INSTN -CEA (Paris – France) - 2013 i [email protected] Irène Buvat-Quantification en tomographie d’émission - Oct 2018 - CEA/Inserm/Univ Paris Sud /Orsay [email protected] www.cnebmn.jussieu.fr : Collège National des Enseignants de Biophysique et de Médecine Nucléaire + Les différents traceurs et leur production - Les détecteurs 𝛾 − 𝛽 - Irène Buvat - oct 2006 h ttp://www.guillemet.org/ http://www.guillemet.org/ h ttp://www-instn.cea.fr http://www-instn.cea.fr Radioactivité. com h ttp://www.iaea.org: http://www.iaea.org: détection des RI (F.N.Flakus) Notions de radiobiologie et de radiopathologie : cours de l’INSTN 2010 D.J. GAMBINI / R. GRANIER, décembre 2000. Manuel pratique de radioprotection. Editions Médicales Internationales. 85