Radiobiology 7م
Upcoming SlideShare
Loading in...5
×
 

Radiobiology 7م

on

  • 3,995 views

 

Statistics

Views

Total Views
3,995
Views on SlideShare
3,986
Embed Views
9

Actions

Likes
3
Downloads
283
Comments
0

1 Embed 9

http://www.slideshare.net 9

Accessibility

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment
  • Bremsstrahlung (means braking radiation) Incident Beta (or e-) changes direction due to radial acceleration. In accordance with classical theory, beta loses energy by EM radiation Produce spectrum of photon NRG (Max is same NRG as incident beta) The probability of Brem production increases with the energy of the Beta and the atomic number of the absorber (larger nucleus is bigger target with bigger sphere of influence)
  • Manufacturers of X-ray for diagnostic regulated by FDA Typically have 3 basic controls - kVp, time, & mA (discuss each) Amount of filtration required depends on kVp 30 kVp = 0.3 mm Al equiv 70 kVp = 1.5 mm 120 kVp = 3.2 mm
  • Almost a century ago in 1895, Roentgen discovered the first example of ionizing radiation, x-rays. The key to Roentgens discovery was a device called a Crooke’s tube, which was a glass envelope under high vacuum, with a wire element at one end forming the cathode, and a heavy copper target at the other end forming the anode. When a high voltage was applied to the electrodes, electrons formed at the cathode would be pulled towards the anode and strike the copper with very high energy. Roentgen discovered that very penetrating radiations were produced from the anode, which he called x-rays. X-ray production whenever electrons of high energy strike a heavy metal target, like tungsten or copper. When electrons hit this material, some of the electrons will approach the nucleus of the metal atoms where they are deflected because of there opposite charges (electrons are negative and the nucleus is positive, so the electrons are attracted to the nucleus). This deflection causes the energy of the electron to decrease, and this decrease in energy then results in forming an x-ray. Medical x-ray machines in hospitals use the same principle as the Crooke’s Tube to produce x-rays. The most common x-ray machines use tungsten as there cathode, and have very precise electronics so the amount and energy of the x-ray produced is optimum for making images of bones and tissues in the body.
  • Since we cannot see, smell or taste radiation, we are dependent on instruments to indicate the presence of ionizing radiation. The most common type of instrument is a gas filled radiation detector. This instrument works on the principle that as radiation passes through air or a specific gas, ionization of the molecules in the air occur. When a high voltage is placed between two areas of the gas filled space, the positive ions will be attracted to the negative side of the detector (the cathode) and the free electrons will travel to the positive side (the anode). These charges are collected by the anode and cathode which then form a very small current in the wires going to the detector. By placing a very sensitive current measuring device between the wires from the cathode and anode, the small current measured and displayed as a signal. The more radiation which enters the chamber, the more current displayed by the instrument. Many types of gas-filled detectors exist, but the two most common are the ion chamber used for measuring large amounts of radiation and the Geiger-Muller or GM detector used to measure very small amounts of radiation. Demonstration of Geiger-Muller Detector.
  • The second most common type of radiation detecting instrument is the scintillation detector. The basic principle behind this instrument is the use of a special material which glows or “scintillates” when radiation interacts with it. The most common type of material is a type of salt called sodium-iodide. The light produced from the scintillation process is reflected through a clear window where it interacts with device called a photomultiplier tube. The first part of the photomultiplier tube is made of another special material called a photocathode. The photocathode has the unique characteristic of producing electrons when light strikes its surface. These electrons are then pulled towards a series of plates called dynodes through the application of a positive high voltage. When electrons from the photocathode hit the first dynode, several electrons are produced for each initial electron hitting its surface. This “bunch” of electrons is then pulled towards the next dynode, where more electron “multiplication” occurs. The sequence continues until the last dynode is reached, where the electron pulse is now millions of times larger then it was at the beginning of the tube. At this point the electrons are collected by an anode at the end of the tube forming an electronic pulse. The pulse is then detected and displayed by a special instrument. Scintillation detectors are very sensitive radiation instruments and are used for special environmental surveys and as laboratory instruments. Demonstration of NaI detector
  • The incident fast moving electron is interacted upon by the nuclear fields from the atom or molecule. The electron is then slowed down and deflected. As it slows down it gives of bremsstrahlung radiation.
  • Ch 15 RHHB: Ionizing Radiation Bioeffects and Risks
  • Perform Example on Board: If the exposure rate at 2 feet = 1000 mR/hr What is the exposure rate at 10 feet How much distance from the source in # 1 should a barrier be placed so the exposure rate is 2 mR/hr?
  • multiply gamma constant in (mSv/hr)/MBq by 3.7 to get (mrem/hr)/uCi RHHB p.3-11 has 6CEN rule of thumb RHHB p. 6-7 to 6-14 has gamma constants
  • RHHB p. 6-15 RHHB p. 6-61
  • RHHB p. 52, Table 3.1(3-2 - 3-4) Beta rules of thumb Range in air 12 ft per MeV Ave beta NRG is 1/3 Max NRG at 1 cm Dose rate (rad/hr) = 300*mCi at 1 foot Dose rate (rad/hr) = 300*Ci
  • RHHB p. 409:(11-14 through 11-23) Good Work Practices for surveys, instrument use, hoods, use of sealed sources, use of unsealed sources, use of radioluminous materials
  • Ch 15 RHHB: Ionizing Radiation Bioeffects and Risks
  • Response check - check source, did it pass Selecting proper scale - ALWAYS work from lowest to highest scale. Response time - Slow versus Fast in high radiation area
  • NARM not in agreement but most AS regulate
  • Units roentgen (R) or Coulomb/kg (C/kg) 1 C/Kg = 3876 R Applies only to X or Gamma field in air Essentially a measure of the amount of ionization in air by X or gamma
  • Unit is rad (radiation absorbed dose) or gray 1 gray = 100 rad Applies to all types of radiation For X or gamma in human tissue 1 rad = 1 R
  • Unit is rem or sievert 1 Sv = 100 rem Applies only to living humans Puts all radiation on an equivalent risk basis An administrative concept not intended for acute doses
  • Units roentgen (R) or Coulomb/kg (C/kg) 1 C/Kg = 3876 R Applies only to X or Gamma field in air Essentially a measure of the amount of ionization in air by X or gamma
  • Unit is rad (radiation absorbed dose) or gray 1 gray = 100 rad Applies to all types of radiation For X or gamma in human tissue 1 rad = 1 R
  • Unit is rem or sievert 1 Sv = 100 rem Applies only to living humans Puts all radiation on an equivalent risk basis An administrative concept not intended for acute doses

Radiobiology 7م Radiobiology 7م Presentation Transcript

  • Prof.Dr.Tarek Elnimr L 7 Presented to the Biology Departments in Faculty of Sciences on February 15 , 2009
    • Bremsstrahlung Radiation
    Energy is lost by the incoming charged particle through a radiative mechanism Beta Particle - Bremsstrahlung Photon + + Nucleus
    • X-Ray Machine Components
    High Voltage Power Supply Tungsten Filament Target Glass Envelope Tube Housing Cathode Anode Current View slide
    • X-Ray Machine Basics
    • kVp - how penetrating the X-rays are
      • Mammography - 20 - 30 kVp
      • Dental - 70 - 90 kVp
      • Chest - 110 - 120 kVp
    • mA - how much radiation is produced
    • Time - how long the machine is on
    • Combination of the above determines exposure
    View slide
  • X-Ray Production Electron X-Ray Target Nucleus Tungsten Cathode (-) Anode (+) X-Rays
  • Radiation Detection Gas Filled Detectors Air or Other Gas Incident Ionizing Radiation Electrical Current Measuring Device + - Cathode - Anode + + + + - - - + - Voltage Source
  • Radiation Detection Scintillation Detectors Incident Ionizing Radiation Sodium-Iodide Crystal Photocathode Optical Window - Pulse Measuring Device Light Photon Photomultiplier Tube Dynode Anode
  • Bremsstrahlung Radiation Incident Electron (E 1 ) X-ray Photons Energy = (E 1 - E 2 ) Deflected Electron (E 2 ) (E 1 > E 2 )
  • X-ray Tube
  • Target
    • made of high atomic number material with good thermal properties, typically tungsten (W)
    • approx. 1%
    • of energy forms
    • x-rays, rest as
    • heat
    • anode rotates
    • to increase heat
    • loading capacity
  • Production of X-rays
    • 2 types of interaction of e - with target
    • Bremsstrahlung (braking radiation)
      • e - passes close to the nucleus (+ ive charged) of the target material
      • electrostatic interaction causes the e - to bend form its path
      • energy given off as x-rays
    • Gamma Interactions
    • Gamma interactions differ from charged particle Interactions
    • Interactions called "cataclysmic" - infrequent but when they occur lot of energy transferred
    • Three possibilities:
      • May pass through - no interaction
      • May interact, lose energy & change direction (Compton effect)
      • May transfer all its energy & disappear (photoelectric effect)
    • Compton Effect
    An incident photon interacts with an orbital electron to produce a recoil electron and a scattered photon of energy less than the incident photon Before interaction After interaction - - - Incoming photon Collides with electron - - - - Electron is ejected from atom - Scattered Photon
    • Interaction of Radiation
    • with Matter
    • Radiation deposits small amounts of energy, or "heat" in matter
      • alters atoms
    • changes molecules
      • damage cells & DNA
      • similar effects may occur from chemicals
      • Much of the resulting damage is from the production of ion pairs
  • Radiation Protection Concepts
    • Time
    • Distance
    • Shielding
    • Risk/Benefit
    ALARA
  • Shielding
  • Radiation Protection Basics
    • Time: minimize the time that you are in contact with radioactive material to reduce exposure
    • Distance: keep your distance. If you double the distance the exposure rate drops by factor of 4
    • Shielding:
      • Lead, water, or concrete for gamma & X-ray
      • Thick plastic (lucite) for betas
    • Protective clothing: protects against contamination only - keeps radioactive material off skin and clothes
  • Time
    • Accumulated time from external radiation exposure is directly proportional to the amount of time spent in the area
  • Distance
    • The radiation field is inversely proportional to the square of the distance from the source
  • Shielding
    • The amount of shielding required depends on the type of radiation, the activity present and the dose rate acceptable outside the shielding material
      • < 2.5 uSv/hr
  • Required Personal Protective Equipment (PPE)
  • Personnel Monitoring
  • Workplace Monitoring
  • Safe Work Habits
  • Proper Lab Bench Set Up
    • A proper lab bench including:
    • survey meter
    • whole body shield
    • spill trays
    • waste container
    • labeling
    • etc.,
  • Use of high activity sealed sources to examine structural components such as beams or pipes
    • Radiological Hazards
    • Total Effective Dose
    • Equivalent, (TEDE)
    • Used to combine internal and external doses
    • Puts all dose on the same risk base comparison, whether from external or internal sources.
    • TEDE = CEDE + DDE
    • All units are in rems or Sieverts (Sv)
    • All regulatory dose limits are based on controlling the TEDE
    • External Radiation
    • Inverse Square Law
    • Radiation levels decrease as the inverse square of the distance (i.e. move back by a factor of two, radiation levels drop to one fourth)
    • Applies to point sources (distance greater than 5 times the maximum source dimension)
    where I = Intensity (exposure rate) at position 1 and 2 and R = distance from source for position 1 and 2 Position 1 Position 2 (mrem/hr) (mrem/hr) Source 2 2 2 2 1 1 R I R I  R 1 R 2 I 2 I 1
    • Gamma Ray Constant
    • Gamma Ray Constant to determine exposure rate
      •  (mSv/hr)/MBq at 1 meter
      • Hint: multiply (mSv/hr)/MBq by 3.7
      • to get (mrem/hr)/uCi
    • Exposure Rate Calculation, X (mrem/hr) at one meter:
      • X = 
      • Where, A = Activity (  Ci)
        •  Gamma Ray Constant(mSv/hr)/Mbq
        • 3.7 is the conversion factor
  • Sample Calculation
    • 5 Curie Cs-137 Source
    • Calculate Exposure Rate at 1 meter
    •  = 1.032 E-4 mSv/hr/MBq @ 1 meter
    • X = 1.032 E-4 * 3.7 * 5 Ci * 1000 mCi/Ci * 1000 uCi/mCi
    • X = 1909 mrem/hour
    • X = 1.91 rem/hour
    • Gamma Ray Shielding
    • Effectiveness increases with thickness, d (cm)
    • Variation with material, (1/cm)
      • attenuation coefficients µ
      • High Z material more effective
        • Water - Iron - Lead
        • good - better - best
    • Shielding Beta Emitters
    • Low energy betas (H-3, C-14, S-35) need no shielding for typical quantities at Clarkson
    • Higher energy beta emitters (P-32) should be shielded
    • Beta shielding must be low Z material (Lucite, Plexiglas, etc.)
    • High Z materials, like lead, can actually generate radiation in the form of Bremsstrahlung X-rays
    • Bremsstrahlung from 1 Ci of P-32 solution in glass bottle is ~1 mR/hr at 1 meter
    • Contamination and
    • Internal Hazards
    • Units of Measure
      • activity/area (dpm/100 square cm)
    • Fixed vs Removable
    • Internal Hazards and Entry Routes
      • Ingestion
      • Inhalation - Re-suspension
      • Skin absorption
      • Wound Entry
    • Protective Clothing
    • Can be a very effective means of preventing skin, eyes, & clothing from becoming contaminated
    • Gloves (may want double layer)
    • Lab Coat
    • Eyewear to prevent splashes and provide shielding for high energy beta emitters
    • Closed toe footwear
    • It is much easier to remove contaminated clothing than to decontaminate your skin!
    • Contamination Control
    • Watch out where you put your “hot” hands during an experiment
    • Monitor yourself and your work area frequently for radioactivity (gloves, hands, feet, etc.)
    • Use most sensitive scale on meter (X0.1 or X1)
    • Have meter out and handy
    • Make sure to wash your hands frequently and after finishing an experiment
      • Don’t bring radioactive material to lunch or to your home!
    • Monitor your work area before and after an experiment
    • Avoid Ingesting
    • Radioactive Material
    • Don’t bring hands or objects near your mouth during an experiment
    • Eating, drinking, smoking, applying cosmetics are strictly prohibited in radioisotope use areas
    • Never mouth pipette
    • Never store personal food items in refrigerators or freezers used for radioactive material or other hazardous material storage
    • Avoid Inhaling
    • Radioactive Material
    • Make sure you have proper ventilation for your experiments
    • When using volatile materials such as Iodine-125 and some Sulfur-35 compounds, be sure to use a fume hood that has been inspected and certified for proper airflow
    • DACs & ALIs
    • DAC: Derived Air Concentration, an airborne concentration of of radioactive material which if inhaled for 2000 hrs per year will result in 5 rem CEDE or 50 rem CDE.
      • Units are uCi/cc
      • Each DAC-hour gives 2.5 mrem of dose.
    • ALI: Annual Limit on Intake, A quantity of radioactive material, which if inhaled or ingested, would result in the applicable annual dose limit.
      • 1 ALI = 5 rem (CEDE) or 50 rem (CDE)
    • ALI and DAC Values listed for each nuclide in NHRCR (He-P 4090)
    • External vs Internal Dose
    • TEDE: Total Effective Dose Equivalent
      • TEDE = DDE + CEDE
      • Total Dose = External Dose + Internal Dose
    • 1 rem internal (CEDE) same as 1 rem external (DDE)
    • Internal dose is protracted over several years but calculated over 50 years and assigned in the year of intake
    • Radiation Detection
    • Use of Survey Instruments
    • Check Physical Condition
    • Cables, Connections, Damage
    • Check for Current Calibration (License Requirement)
    • Battery Check
    • Zero Check
    • Response check prior to use
    • Select Proper Scale
    • Response Time (Fast or Slow?)
    • Audio (On or Off)
    • U. S. Nuclear Regulatory Commission
      • Regulates the nuclear industry pursuant to the Atomic Energy Act
      • Regulatory guides published to describe methods for complying with regulations
    • Agreement States
      • Some states have entered into an agreement with the NRC to regulate by-product material (and small quantities of source and special nuclear material)
      • Currently, 30 states are agreement states including New York
    Regulatory Agencies
  • Ordering & Receipt of Radioactive Materials
    • Only RSO is authorized to order radioactive material
    • Use the Radionuclide Purchase Request Form
    • Complete form and fax to RSO at 268-7118
    • Be sure to state any special ordering instructions (preferred delivery date, fresh batch, etc.)
    • Packages are received by RSO, checked for contamination, logged in, and delivered to the lab on the same day as receipt
  • Posting & Labeling Notices
    • Labels
      • All containers (unless exempt) must be labeled
      • With “Caution – Radioactive Material”
      • Should include radionuclide, quantity, date,
      • initials, radiation levels, etc.
    • Posting
      • New York Notice to Employees form
      • Caution Radioactive Materials or X-Rays
    • Employee Rights
    • and Responsibilities
    • Right to report any radiation protection problem to state without repercussions
    • Responsibility to comply with the Radiation Protection Program and the RSO's instructions pertaining to radiation protection
    • Right to request inspection
      • in writing
      • grounds for notice
      • signed
    • Responsibility to cooperate with NY State inspectors during inspections and RSO during internal lab audits
    • Security
    • Licensed RAM must be secured against unauthorized removal at all times
    • Must maintain constant surveillance for any radioactive material outside a restricted area
    • Lock labs containing radioactive material if last one out - even if it’s “just for a minute”
    • Challenge all unknown individuals with “May I help you?”
    • OK to ask for ID
    • Report to supervisor if suspicious
    • Annual Dose from
    • Background Radiation
    Total US average dose equivalent = 360 mrem/year Total exposure Man-made sources Radon Internal 11% Cosmic 8% Terrestrial 6% Man-Made 18% 55.0% Medical X-Rays Nuclear Medicine 4% Consumer Products 3% Other 1% 11
    • Exposure, X
    • A measure of the ionization produced by
    • X or Gamma Radiation in air
    • Unit of exposure is the Roentgen
    X = Q (charge) M (mass of air)
    • Absorbed Dose, D
    • Absorbed Dose (or Radiation Dose) is equivalent to the energy absorbed from any type of radiation per unit mass of the absorber
    • Unit of Absorbed Dose is the rad
    • 1 rad = 100 ergs/g = 0.01 joules/Kg
    • In SI notation, 1 gray = 100 rads
    • Dose Equivalent, H
    • One unit of dose equivalent is that amount of any type of radiation which, when absorbed in a biological system, results in the same biological effect as one unit of low LET radiation
    • The product of the absorbed dose, D , and the Quality Factor , Q
    H = D Q
    • Units of Dose Equivalent
    • Human dose measured in rem or millirem
    • 1000 mrem = 1 rem
    • 1 rem poses equal risk for any ionizing radiation
      • internal or external
      • alpha, beta, gamma, x-ray, or neutron
    • In SI units 1 sievert (Sv) = 100 rem
    • External radiation exposure measured by dosimetry
    • Internal radiation exposure measured using bioassay sample analysis
    • Quality Factors for Different Radiations
    Quality Factor X and Gamma Rays Electrons and Muons Neutrons < 10 kev >10kev to 100 Kev > 100 kev to 2 Mev >2 Mev Protons > 30 Mev Alpha Particles 1 1 5 10 20 10 10 20
    • Annual Dose from
    • Background Electromagnetic Radiation
    Total Egyp average dose equivalent = 360 mrem/year Total exposure Man-made sources Radon Internal 11% Cosmic 8% Terrestrial 6% Man-Made 18% 55.0% Medical X-Rays Nuclear Medicine 4% Consumer Products 3% Other 1% 11
    • Annual Dose from
    • Background Radiation
    Total US average dose equivalent = 360 mrem/year Total exposure Man-made sources Radon Internal 11% Cosmic 8% Terrestrial 6% Man-Made 18% 55.0% Medical X-Rays Nuclear Medicine 4% Consumer Products 3% Other 1% 11
    • Exposure, X
    • A measure of the ionization produced by
    • X or Gamma Radiation in air
    • Unit of exposure is the Roentgen
    X = Q (charge) M (mass of air)
    • Absorbed Dose, D
    • Absorbed Dose (or Radiation Dose) is equivalent to the energy absorbed from any type of radiation per unit mass of the absorber
    • Unit of Absorbed Dose is the rad
    • 1 rad = 100 ergs/g = 0.01 joules/Kg
    • In SI notation, 1 gray = 100 rads
    • Dose Equivalent, H
    • One unit of dose equivalent is that amount of any type of radiation which, when absorbed in a biological system, results in the same biological effect as one unit of low LET radiation
    • The product of the absorbed dose, D , and the Quality Factor , Q
    H = D Q
    • Units of Dose Equivalent
    • Human dose measured in rem or millirem
    • 1000 mrem = 1 rem
    • 1 rem poses equal risk for any ionizing radiation
      • internal or external
      • alpha, beta, gamma, x-ray, or neutron
    • In SI units 1 sievert (Sv) = 100 rem
    • External radiation exposure measured by dosimetry
    • Internal radiation exposure measured using bioassay sample analysis
    • Quality Factors for Different Radiations
    Quality Factor X and Gamma Rays Electrons and Muons Neutrons < 10 kev >10kev to 100 Kev > 100 kev to 2 Mev >2 Mev Protons > 30 Mev Alpha Particles 1 1 5 10 20 10 10 20
  • N(t 0 ), A (t 0 ) are the initial number of radionuclides and initial activity, respectively. The half life t 1/2 of a radionuclide is the time by which the number of radionuclides has reduced to 50%. This shows a direct correlation between half life and decay constant for each radionuclide. The lifetime r of a nucleus is defined by: Quite often the expression “lifetime” can be found for radionuclides. This means that after a period corresponding to the “lifetime”  of a radioactive nucleus the initial abundance has decreased to 36.8% of its initial value, of a nucleus can be found!
  •  
  •  
  • Unit for exposure E is the Roentgen [R] which is defined by the ionization between EM-radiation and air. 1 Roentgen is the amount of EM-radiation which produces in 1 gram of air 2.58  10 -7 C at normal temperature (22°C) and pressure (760 Torr) conditions. Dosimetry Units Due to the interaction between radiation and material ionization occurs in the radiated material! (Energy transfer from the high energetic radiation photons or particles to atomic electrons.) The ionization can be used as measure for the amount of exposure which the material had to radiation. 1 R = 2.58  10 -4 C/kg
  • When interacting with matter EM-radiation shows particle like behavior. The 'particles' are called photons. The energy of the photon and the frequency  (or wavelength  ) of the EM-radiation are determined by the Planck constant h: h=6.62 -34 J  s = 4.12  10 -21 MeV  s The photon energy for X-rays and  -rays is in the eV to MeV range.
  • X-rays originate either from characteristic deexcitation processes in the atoms (K  , K  transitions) (Characteristic X-rays). The photon energy corresponds to the difference in binding energy of the electrons in the excited levels to the K-level.
  • X-rays also originate from energy loss of high energy charged particles (e.g. electrons) due to interaction with the atomic nucleus ( bremsstrahlung )
  • The exposure rate ER (= ionization/time) can be related to the activity A of a source (in units mCi) via : F is the exposure constant in units [ (R  cm 2 ) / (h  mCi) ] , and d is the distance between source and material in units [cm]. The exposure constant is characteristical for the radiation source:
  • The absorbed dose D of radiation in any kind of material depends on the typical ionization energy of the particular material. The absorbed dose is defined in terms of the absorbed radiation energy per mass W 1P . It therefore clearly depends on the energy loss behavior of the various kinds of radiation. The unit for the absorbed dose is : 1 Gray = 1Gy = 1 J/kg = 10 4 erg/kg = 100 rad The average ionization energy for air is W 1P  34 eV/ion. With 1 eV = 1.6022  10 -19 J and the charge per ion is 1.6  10 -19 , this yields for the absorbed dose in air D for 1 R exposure of EM radiation: D = 1 R • 34 J/C = 2.58  10 -4 C/kg  34 J/C = 8.8  10 -3 J/kg = 8.8  10 -3 Gy = 0.88 rad
  • The average ionization energy depends critically on the material.
  • There is an empirical relation between the amount of ionization in air and the absorbed dose for a given photon energy and absorber (body tissue). The absorbed dose in rads per roentgen of exposure is known as the roentgen-to-rad conversion factor C C is approximately equal to one for soft body tissue in the energy range of diagnostic radiology. The increase for bone material is due to higher photoelectric absorption cross section for low energy photons.
  • Dose (rad) = Exposure (R) x R to Rad Conversion factor
  •  
  •  
  • Exposure, exposure rate and absorbed dose are independent of the nature of radiation. Biological damage depends mainly on the energy loss of the radiation to the body material. These energy losses differ considerably for the various kinds of radiation. To assess the biological effects of the different kind of radiations better, as new empirical unit the dose equivalent H is introduced: DOSE EQUIVALENT with the quality factor Q which depends strongly on the ionization power of the various kinds of radiation per path length. In first approximation Q  Z of radiation particles, Q(  , X,  )  1. As higher Q as higher the damage the radiation does!
  •  
  • EFFECTIVE DOSE The various body organs have different response to radiation. To determine the specific sensitivity to radiation exposure a tissue specific organ weighting factor w T has been established to assign a particular organ or tissue T a certain exposure risk. The given weighting factors in the table imply for example that an equivalent dose of 1 mSv to the lung entails the same probability of damaging effects as an equivalent dose to the liver of (0.12/0.05)  1 mSv = 2.4 mSv The sum of the products of the equivalent dose to the organ H T and the weighting factor w T for each organ irradiated is called the effective dose H  : Like H T , H  is expressed in units Sv or rem!.
  •  
  •  
  •  
  • or Natural Decay Law The rate of the decay process is determined by the activity A (number of decay processes per second) of the radioactive sample. The activity is proportional to the number of radioactive nuclei (radionuclide)  is the decay constant! Differential equation for N(t) can be solved
  •  
  • Thank You