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What is the approximate number of known radionuclides?
What is the approximate number of known radionuclides?
What happens to the atomic number of a nucleus when an additional neutron is forced into it?
What happens to the atomic number of a nucleus when an additional neutron is forced into it?
What type of particles are accelerated in a cyclotron?
What type of particles are accelerated in a cyclotron?
What happens to the mass number of a nucleus when a proton is forced into it?
What happens to the mass number of a nucleus when a proton is forced into it?
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What is a characteristic of radionuclides produced in a cyclotron?
What is a characteristic of radionuclides produced in a cyclotron?
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What is the reason why radionuclides produced in a cyclotron can only be used reasonably close to the cyclotron?
What is the reason why radionuclides produced in a cyclotron can only be used reasonably close to the cyclotron?
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What is the reaction that occurs in a nuclear reactor?
What is the reaction that occurs in a nuclear reactor?
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What is the product of the reaction 18O +p?
What is the product of the reaction 18O +p?
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What is the result of a positron (β+) decay in a radionuclide?
What is the result of a positron (β+) decay in a radionuclide?
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What happens when a nucleus undergoes K-electron capture?
What happens when a nucleus undergoes K-electron capture?
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What is emitted when an electron from an outer shell fills the created vacancy in the K-shell?
What is emitted when an electron from an outer shell fills the created vacancy in the K-shell?
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What is the energy of the gamma rays emitted by Iodine-131 (131I)?
What is the energy of the gamma rays emitted by Iodine-131 (131I)?
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What is the difference between gamma rays and X-rays?
What is the difference between gamma rays and X-rays?
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What happens when a positron comes to the end of its range?
What happens when a positron comes to the end of its range?
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What is the characteristic of the gamma rays emitted by a given radionuclide?
What is the characteristic of the gamma rays emitted by a given radionuclide?
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What is the mode of decay of Iodine-123 (123I)?
What is the mode of decay of Iodine-123 (123I)?
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What happens to the atomic number of a radionuclide during β- decay?
What happens to the atomic number of a radionuclide during β- decay?
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What is the term for the nucleus that remains in an excited state for a variable length of time?
What is the term for the nucleus that remains in an excited state for a variable length of time?
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What is the energy of the gamma ray emitted during the decay of 99mTc to 99Tc?
What is the energy of the gamma ray emitted during the decay of 99mTc to 99Tc?
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What is the half-life of 99Tc?
What is the half-life of 99Tc?
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What is the process by which a radionuclide with a neutron deficit loses energy and becomes stable?
What is the process by which a radionuclide with a neutron deficit loses energy and becomes stable?
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What is the term for nuclei having different energy states and half-lives, but otherwise indistinguishable as regards mass number, atomic number, and other properties?
What is the term for nuclei having different energy states and half-lives, but otherwise indistinguishable as regards mass number, atomic number, and other properties?
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What is the daughter nuclide produced during the decay of 99mTc?
What is the daughter nuclide produced during the decay of 99mTc?
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What is the term for the emission of a positive electron from the nucleus with high energy?
What is the term for the emission of a positive electron from the nucleus with high energy?
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What is the energy equivalent to the mass of an electron according to Einstein's formula?
What is the energy equivalent to the mass of an electron according to Einstein's formula?
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What is the result of the annihilation of a positive and negative electron?
What is the result of the annihilation of a positive and negative electron?
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Why is it impossible to predict which unstable nucleus in a sample will disintegrate next?
Why is it impossible to predict which unstable nucleus in a sample will disintegrate next?
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What is the quantity of radioactivity measured by?
What is the quantity of radioactivity measured by?
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What is the unit of measurement for the activity of a radioactive sample?
What is the unit of measurement for the activity of a radioactive sample?
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What is the rate of disintegration of a radioactive sample?
What is the rate of disintegration of a radioactive sample?
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What is the purpose of positron emitters in medical imaging?
What is the purpose of positron emitters in medical imaging?
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What is the characteristic of radioactive decay that makes it possible to predict the fraction of nuclei that will disintegrate?
What is the characteristic of radioactive decay that makes it possible to predict the fraction of nuclei that will disintegrate?
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What is the unit of measurement used for most radionuclide administrations in medical gamma imaging?
What is the unit of measurement used for most radionuclide administrations in medical gamma imaging?
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What is the relationship between the count rate and the activity of a radioactive sample?
What is the relationship between the count rate and the activity of a radioactive sample?
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What is the fundamental law of radioactive decay?
What is the fundamental law of radioactive decay?
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What is the unit of measurement used for radionuclide generators?
What is the unit of measurement used for radionuclide generators?
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What happens to the activity of a radioactive sample over time?
What happens to the activity of a radioactive sample over time?
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What is the relationship between the count rate and the number of radioactive atoms in a sample?
What is the relationship between the count rate and the number of radioactive atoms in a sample?
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What is the conversion rate from curie to megabecquerels?
What is the conversion rate from curie to megabecquerels?
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What happens to the gamma rays when they enter a detector?
What happens to the gamma rays when they enter a detector?
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Study Notes
Production of Radionuclides
- Over 2700 known radionuclides exist.
- Medical imaging radionuclides are artificially produced using nuclear reactors or cyclotrons.
Methods of Production
- Neutron Addition: In nuclear reactors, stable nuclei capture additional neutrons, resulting in neutron excess (e.g., 98Mo + n → 99Mo).
- Proton Addition: Cyclotrons accelerate protons that force an additional proton into a stable nucleus, creating a neutron deficit (e.g., 18O + p → 18F + n).
Characteristics of Radionuclides
- Radionuclides produced in cyclotrons typically have short half-lives, ranging from less than a minute to a few hours, limiting their use to proximity to the cyclotron.
- Radionuclides with a neutron deficit can undergo positron decay or K-electron capture, converting into more stable forms (e.g., Fluorine-18 (18F) transforms into Oxygen-18 (18O)).
Decay Processes
- Positron Emission: Positive beta particles (positrons) annihilate upon encountering negative electrons, neutralizing without changing mass number but increasing atomic number.
- K-Electron Capture: Nuclei capture an electron which may increase neutron count relative to protons, emitting X-rays when an outer-shell electron fills the vacancy.
Gamma Rays
- Emission involves gamma rays that possess specific energies unique to each radionuclide (e.g., Iodine-131 emits 364 keV gamma rays).
- Gamma rays share properties with X-rays.
Isomeric Transitions
- Some radionuclides, such as 99Mo, emit beta particles and may remain in an excited state before emitting gamma rays (99mTc).
- 99mTc decays to stable 99Tc, emitting a gamma ray at 140 keV.
Radioactive Decay
- Radioactive decay is a random process, making it impossible to predict individual nucleus disintegration while allowing for statistical predictions about sample fractions.
- Activity measures the disintegration rate of radioactive samples, not the number of remaining atoms.
Measurement of Activity
- Activity is measured in Becquerels (Bq), with 1 Bq equivalent to 1 disintegration per second.
- Common units in medical contexts include megabecquerels (MBq) and gigabecquerels (GBq).
- Counts measured by detectors may not reflect true activity due to detection inefficiencies, but there is a proportionality between count rate and activity.
Exponential Decay Law
- The activity of radioactive samples decreases by equal fractions over equal time intervals, known as the exponential law; activity never fully reaches zero.
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Description
Learn about the production of radionuclides, including the ways they are artificially produced for medical imaging. Discover how neutron excess occurs in a nuclear reactor.
