ITNM 110 - Week 1 Tutorial Fall 2024 PDF

Image Source: https://www.verywellhealth.com/spect-scan-4173223 ITNM 110 – Week 1: Tutorial Fall 2024 T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN” Week 1: Tutorial Overview Introduction to Detection of Radiation Instrumentation of Gas Filled Dete...

Image Source: https://www.verywellhealth.com/spect-scan-4173223 ITNM 110 – Week 1: Tutorial Fall 2024 T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN” Week 1: Tutorial Overview Introduction to Detection of Radiation Instrumentation of Gas Filled Detectors End of Session Wrap-Up T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN” Introduction to Detecting Radiation T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  The Electromagnetic Spectrum Ionizing Radiation: Radiation with the ability to knock electrons out of orbit, disrupting the electron/proton balance potentially resulting in cellular damage. Types of ionizing radiation: alpha, beta, gamma, neutron radiation and x-rays. Dose: the amount of energy absorbed by tissue from ionizing radiation. Units: Sieverts (Sv) Ref: https://nuclearsafety.gc.ca/eng/resources/fact-sheets/natural-background-radiation.cfm T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  Natural Radiation Sources Naturally occurring within the body; Polonium-210, carbon-14 and potassium-40 Foods (containing potassium-40) Red meat, white potatoes, carrots, bananas, lima beans, brazil nuts In Canada natural background is 1.8- 2mSv compared to average of 2.5mSv worldwide. This value poses no danger. Ref: (CNSC, 2013) https://nuclearsafety.gc.ca/eng/pdfs/Fact_Sheets/Fact-Sheet-Background-Radiation-eng.pdf T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN” What are some factors that impact natural background radiation levels? Image Ref: https://www.cnsc-ccsn.gc.ca/eng/resources/videos/player/index.cfm?videoid=radiation_health T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  Canadian Nuclear Association: Radiation Ref: https://cna.ca/wp-content/uploads/2019/08/2020-Factbook-EN-digital.pdf T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  Sources of Radiation Exposure CNSC Radiation Dose Limits Five-year dose Annual Dose Effective Dose (mSv) Effective Dose (mSv) Nuclear Energy 100 50 Worker General Public -- 1 Note: Annual Canadian Average of natural background is 1.8mSv Ref: http://gazette.gc.ca/rp-pr/p1/2019/2019-06-15/html/reg4-eng.html Ref: https://www.nuclearsafety.gc.ca/eng/pdfs/Fact_Sheets/Fact-Sheet-Understanding-Radiation-eng.pdf T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  Ionizing Radiation Refers to any radiation capable of displacing electrons from atoms, thereby producing ions. What type of emitter is 99mTechentium? Image created by Napy1kenobi - Own work based on: Strahlenarten.png and Strahlenarten en.png T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN” Radiation: Basic Principle for Detection It is this electron that is released from the matter that the radiation interacts with that we used to detect/measure for the presence of radiation. There are multiple ways radiation can interact with different atoms (matter). T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  Detection of Radiation Basic Principle of detection: Radiation carries energy and when this energy interacts with a detection medium it deposits all or some of its energy into that material. Classification of detector: Depends on the type of medium and the ability if the medium to translate all or some of the energy of the radiation event into a signal. Application of the detector: The ability to convert the signal will determine what type of monitoring the detector is best suited for. Images Source: https://www.ene100.jp/map_6_en T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  Introduction to Handheld Radiation Detectors There are three main categories of detectors for measuring radiation: 1) Gas Filled Detectors (GFDs) Consists of a volume of gas between two electrodes 2) Scintillation Detectors Interaction of ionizing radiation produces UV and/or visible light 3) Semiconductors Pure crystals wit trace amounts of impurities so that they behave as diodes. Images Source: https://www.ene100.jp/map_6_en T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  GFDs: Theory of Operation Gas-filled detectors function by measuring the ionization that radiation produces as it passes through a gas. When radiation interacts with atoms/molecules it results in ionization and the production of ion pair(s) in the gas. The ion pair consists of a free electron (e-) and the remaining ionized atom/molecule which is now positive in charge. Silva, M. Ionizing Radiation Detectors © 2015 InTech T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  Gas-Filled Detectors (GFDs) The three types of gas-filled detectors that are commonly used in Nuclear Medicine are; i. Ionization Chambers ii. Proportional Counters iii. Geiger-Müeller (GM) Counters All of the different types of gas-filled detectors operate on the similar principle but differ in the amount of voltage applied across the volume of gas within the detector. This is shown in the gas amplification curve and it determines the type of GFD T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN” Types of Gas Filled Handheld detectors at the Michener Ionization Proportional Geiger Müller Chamber Counter Detector Meter T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  GFDs: Theory of Operation Gas-filled detectors function by measuring the ionization that radiation produces as it passes through a gas. Image Ref: http://www.geocities.ws/muldoon432/gamma_rays_and_x.htm T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  GFDs: Theory of Operation Each ion pair requires a set amount of radiation energy, so the number of electrons created is able to represent an amount of radioactivity. In air, the average energy needed to produce an ion is 34eV. Question: If 1MeV radiation be completely absorbed in the detector, how many ion pairs will be produced? Step 1) Convert: 1MeV = 1,000,000eV Step 2) Cross multiply: 1,000,000eV = 34eV Χ ion pairs 1 ion pair Χ = 1,000,000 /34 Χ = 29411 ion pairs ≅ 3 x 104 T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  GFDs: Theory of Operation An external electrical field is applied to prevent the recombination of the ion pair. Resulting in the positive and negative ions drifting in opposite directions. This electrical current on the electrodes is measured externally at the meter. cathode anode Copyright © 2014 by Jones and Bartlett Learning, LLC an Ascend Learning Company T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  Q: Cathode or Anode … What direction will the ion pair move? Positive ion(s) move toward the _______________. Negative ion(s)/electrons move toward the _____________. Image Source: https://www.ene100.jp/map_6_en T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  GFDs: Components Consists two electrodes (anode and cathode) with an electric potential, separated by a non-conducting gas (i.e. air, argon, xenon, krypton etc.) Anode is positively charged Cathode is negatively charged External power source/battery keeps the anode and cathode charged The meter measures the flow of electricity that occurs as a result of neutralization that occurs when the electrons reach the anode (positive). https://www.slideshare.net/AmaraUsman/gas-filled-detectors T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN” Q: In the simplest terms then for nuclear medicine … the current between the electrodes is a measurement of what on a handheld detector? cathode anode Copyright © 2014 by Jones and Bartlett Learning, LLC an Ascend Learning Company T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  The Six Regions of the Gas Amplification Curve How dose amplifying the voltage generate this curve? Image Source: https://www.nuclear-power.net/nuclear-engineering/radiation-detection/gaseous-ionization-detector/proportional-counter-proportional-detector/gas-amplification-factor-gas-amplification-curve/ T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  Primary and Secondary Ionization Primary Ionization: The effects of ionization produced directly by the incident particle. Secondary ionization: Occurs as a result of the electric field being strong enough to cause the electrons of the primary ionization to acquire enough kinetic energy between collisions to produce a new electron- ion pair creating an electron avalanche (aka Townsend Avalanche). This multiplication of electrons is called gas amplification; T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  Break Time (10mins) T H E M I C H E N E R I N S T I T U T E  I: Recombination Region The electric field is not large enough to accelerate electrons and ions. Result: the electrons and ions recombine soon after they are produced, and only a small fraction of the produced electrons/ions reach their respective electrodes. vi v iv Would this be a iii useful region for ii i trying to measure radiation? T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  II: Ionization Region (saturation region) Sufficient voltage applied to stop recombination = primary ionizations are occurring and most of the ions are reaching the electrodes. No ion pair recombination since at saturation voltage This begins at 50-300V depending on chamber design. Recombination Region No gas amplification in this region, so the curve is flat Type of detector used; vi Ion chamber survey meter v Dose calibrator iv iii ii i T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN” Ionization Chamber: Dose Calibrator Image Source: https://www.wikiwand.com/en/Ionization_chamber T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  Dose Calibrator: Design The Dipper holds either; A syringe (in the upper ring) A vial/non-syringe (lower dipper/cup) The dipper sits inside the lucite well insert which lines and protect the inside of the dose calibrator T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  Ionization Survey Meter Design features Operates in ionization region; low sensitivity, high range Measures using current mode Some have the option of a mylar window to be opened to detect other particles Measures in µSv/hr to inform you of the intensity of and risk associated with a radiation field Uses Patient monitoring Measuring high levels of known radiation Not good for contamination surveys T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN” The Penetrating Power of the Four Types of Radiation Image Ref: http://www.nandalalsarkar.com T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  Ionization Detection Region Image Ref: https://www.radiation-dosimetry.org/what-is-proportional-counter-proportional-detector-definition/ T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  III: Proportional Region At a higher voltage secondary ionizations occur, which produce a cascade of electrons called Townsend avalanches. This multiplication is linear; the collected charge is proportional to the number of ion pairs created by the incident radiation. Measured pulse amplitude (or height) is proportional to incident particle energy vi Type of detector used; v Proportional counter/detector iv » Berthold LB 122 iii ii i T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  III: Proportional Region vi v iv For proportional iii counters, is gas amplification a ii i desirable effect for radiation detection? T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  Proportional Counting Region Image Ref: https://www.radiation-dosimetry.org/wp-content/uploads/2019/12/Gaseous-Ionization-Detectors-Regions-min.png T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  Proportional Detector/Counters Summary Basic Operation Operates in proportional region; high sensitivity, high range Measures using pulse mode Detection mode is selectable (alpha, beta or gamma) The entrance window is aluminized plastic, which shields from the ambient light. Uses Patient monitoring Contamination & survey monitoring T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  Creation of Discrete Avalanches in a Proportional Counter A strong signal, the amplification factor can reach about 105 Image Source: https://www.nuclear-power.net/wp-content/uploads/2019/02/Geiger-Mueller-Region-avalanches-in-G-M-tube.jpg T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  IV: Limited Proportional The gas amplification factor does not continue to increase proportionally to the voltage. Result: Additional ionizations and nonlinear effects causes, that there is no proportionality of the output signal to the deposited energy at a given applied voltage. vi v iv Would this be a iii useful region for ii i trying to measure radiation? T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  V: Geiger-Mueller Region The voltage and thereby the electric field are so strong that secondary avalanches can occur. Result: Intense gas amplification occurring. The moving electrons raise other gas molecules to excited states via kinetic collisions, from which they deexcite by emission of ultraviolet light. UV light interact via photoelectric effect producing more free electrons Type of detector used; – Geiger-Mueller detector T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  Geiger-Müller Survey Meter Summary Basic operation Geiger discharge of tertiary electrons for each photon interacting Very sensitive, can detect individual photons Pulse mode operation Dead time with high-activity sources Uses Patient monitoring Contamination & survey monitoring Image ref: Mettler, F & Guiberteau, M. Essentials of Nuclear Medicine and Molecular Imaging 7th edition. 2018. T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  Spread of Avalanches in a Geiger-Muller Tube A strong signal, the amplification factor can reach about 1010 Image Source: https://www.nuclear-power.net/wp-content/uploads/2019/02/Geiger-Mueller-Region-avalanches-in-G-M-tube.jpg T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  VI: Continuous Discharge Region At a higher voltage, triggered breakdowns start to occur and a continuous unquenchable discharge occurs. Result: Even in the absence of radiation, there is a spontaneous and ‘continuous’ ionizations of gas molecules that stops only when the voltage is lowered. vi i.e. the visible ionization seen in a neon sign v iv iii ii i http://www.signageqld.com.au/wp2/wp-content/uploads/2012/04/neon-lighting.jpg T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN”  PAT 4: Assignment #1 (2.5%) Format: 5 short answer questions | Total marks: /20marks Due: Friday, September 13th 2024 by 11:59 pm. (End of Week 2) T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN” Reminder: Pre-lab #1 Due: Monday September 9th 2024 by 11:59pm T H E M I C H E N E R I N S T I T U T E MICHENER “WE MAKE HEALTHCARE HAPPEN” T H E M I C H E N E R I N S T I T U T E