87 Questions
What is the primary reason alpha or beta particles are not used in imaging?
They have a short range in tissue
What is the ideal energy range for gamma rays in imaging?
50-300 keV
Why is it desirable for a radionuclide to emit monoenergetic gamma rays?
To eliminate scattered radiation
What is a desirable property of a radionuclide for imaging?
Easy attachment to pharmaceuticals
Why is it desirable for a radionuclide to be readily available at the hospital site?
To facilitate timely imaging procedures
What is a desirable property of a radiopharmaceutical?
Localization in the target tissue
What is high specific activity characterized by?
High activity per unit volume
What should a radionuclide ideally decay to?
A stable daughter
What is the result of forcing an additional neutron into a stable nucleus?
A neutron excess
What is the purpose of a medical minicyclotron?
To produce short-lived radionuclides at or near the hospital site
What is the result of forcing an additional proton into a stable nucleus, knocking out a neutron?
A neutron deficit
What is the change in the atomic number of a nucleus when an additional neutron is forced into it?
It remains unchanged
What is the half-life range of radionuclides produced in a cyclotron?
From less than a minute to a couple of hours
What is the target material in a cyclotron?
Any stable nucleus
What is the result of the reaction 98Mo + n → 99Mo?
A neutron excess
How many known radionuclides are there?
Over 2700
What type of decay is represented in the graph of the number of nuclei present as a function of time?
Exponential decay
What is the physical half-life of a radionuclide unaffected by?
None of the above
What is the range of physical half-lives for radionuclides?
From fractions of a second to millennia
What is a pharmaceutical that has been labelled with a radionuclide referred to as?
Radiopharmaceutical
What is the purpose of the metabolic properties of a radiopharmaceutical in medical imaging?
To concentrate the radionuclide in the tissues or organ of interest
What is the term for the half-life of a radionuclide when it is used in medical imaging?
Effective half-life
What is the purpose of the physical half-life of a radionuclide in medical imaging?
To determine the shelf life of the radiopharmaceutical
Why is a radionuclide with a half-life of less than a minute useless in medical imaging?
It decays too quickly
What is the primary criteria for a radiopharmaceutical to be effective?
To have low toxicity
What is the purpose of using a generator in radiopharmaceuticals?
To reduce the decay during transport and storage
What percentage of radionuclide imaging uses Technetium-99m (99mTc)?
90%
What is the half-life of Technetium-99m (99mTc)?
6 hours
What is the energy of the gamma emission of Technetium-99m (99mTc)?
141 keV
What is the purpose of the exchange column of alumina beads in the Technetium generator?
To absorb the parent 99Mo
What is the half-life of the parent 99Mo in the Technetium generator?
67 hours
Why is it possible to administer a reasonably large activity of Technetium-99m (99mTc)?
Due to its short half-life and pure gamma emission
What happens to the daughter and parent in a technetium generator?
They decay together with the halflife of the parent
What is the purpose of eluting the technetium-99m generator?
To wash off the technetium-99m as sodium pertechnetate
What happens to the activity of technetium-99m in the column after 24 hours?
It grows again to a new maximum value
How often can the technetium-99m generator be eluted?
Daily, but the strength of successive eluents diminishes
What is the typical lifespan of a technetium-99m generator?
A week
What is sodium pertechnetate-99mTc used for?
Imaging of the tissues
What is the purpose of the pressure system in the technetium generator?
To elute the technetium-99m
What is the halflife of technetium-99m in the column?
6 hours
What is left behind on the column after elution?
The molybdenum-99
Why is the technetium-99m generator replaced after a week?
The activity of the technetium-99m decreases significantly
What is the primary advantage of 123I over 131I for imaging?
Cyclotron production
What is the primary use of Xenon-133 in medical imaging?
Lung ventilation imaging
What is the half-life of Krypton-81m, a radionuclide used in pulmonary ventilation studies?
7.13 seconds
Which of the following radionuclides is used in brachytherapy seeds?
125I
What is the method of production for Xenon-133?
Nuclear reactor
What is the purpose of administering potassium perchlorate in radionuclide imaging?
To block the thyroid from taking up iodine
What is the radionuclide labelled compound used for cerebral blood flow imaging?
Hexamethyl propylene amine oxime (HMPAO)
What is the radionuclide labelled compound used for renal studies?
Dimercaptosuccinic acid (DMSA)
What is the purpose of using autologous red cells in radionuclide imaging?
For cardiac function studies
What is the radionuclide used for biliary studies?
Iminodiacetic acid (HIDA)
What is the half-life of Gallium-67 (67Ga) used in tumor detection?
67 h
What is the energy of the gamma rays emitted by Indium-111 (111In) used in labeling white blood cells and platelets?
171.3 keV and 245.4 keV
What is the common use of 18F, a positron emitter, in PET scans?
Brain and heart metabolism, as well as epilepsy and tumor detection
What is the half-life of Indium-113m (113mIn) used sometimes instead of Indium-111?
100 min
What is the energy of the gamma rays emitted by Indium-113m (113mIn)?
390 keV
What is a desirable property of a radionuclide for imaging in terms of gamma ray energy?
Energy between 50-300 keV
Why is it desirable for a radionuclide to have a high specific activity?
To increase the activity per unit volume
What is a desirable property of a radiopharmaceutical in terms of localisation?
To localise quickly in the target tissue
Why are alpha or beta particles not used in imaging?
They have a short range in tissue and deposit unnecessary dose in the patient
What is a desirable property of a radionuclide in terms of attachment to a pharmaceutical?
Firm attachment at room temperature with no effect on metabolism
What happens when an additional neutron is forced into a stable nucleus?
The mass number of the nucleus remains unchanged.
What type of accelerator is used to produce radionuclides with a neutron deficit?
Cyclotron
Why are medical minicyclotrons designed?
To produce short-lived radionuclides at or near the hospital site
What is a characteristic of radionuclides produced in a cyclotron?
Short half-life
Why is it necessary to have a cyclotron near the hospital site?
To use short-lived radionuclides reasonably close to the cyclotron
What is the characteristic of the physical half-life of a radionuclide?
It is a fixed characteristic of the radionuclide.
What is the purpose of a pharmaceutical labeled with a radionuclide in medical imaging?
To concentrate in the tissues or organ of interest.
What is the term for a pharmaceutical that has been labeled with a radionuclide?
Radiopharmaceutical.
What is the half-life range of radionuclides used in medical imaging?
From fractions of a second to millennia.
Which radionuclide is used in pulmonary ventilation studies?
Krypton-81m.
What is the primary advantage of using a generator in radiopharmaceuticals?
It reduces the decay during transport and storage
What is the energy of the gamma emission of Technetium-99m (99mTc)?
141 keV
Why is Technetium-99m (99mTc) used in 90% of radionuclide imaging?
It fulfils most of the desirable criteria for a radiopharmaceutical
What is the purpose of the exchange column of alumina beads in the Technetium generator?
To absorb the parent 99Mo
What is the half-life of the parent 99Mo in the Technetium generator?
67 hours
What is the effective half-life (teff) dependent on?
Both the physical half-life (tphys) and biological half-life (tbiol)
Why is a radionuclide with a physical half-life of a few hours desirable for imaging?
Because it matches the time from preparation to injection
What happens to the radioactivity in specific tissue, organ, or whole body when a radiopharmaceutical is administered to a patient?
It decreases because of radioactive decay and metabolic turnover and excretion
What is the formula for the effective half-life (teff)?
1/teff = 1/tbiol + 1/tphys
What is the biological half-life (tbiol)?
The time it takes for the radiopharmaceutical to be eliminated from the body
What is the physical half-life (tphys)?
The time it takes for the radioactivity to decay physically
What is the effective half-life (teff) compared to the biological and physical half-lives?
Shorter than both
What determines the effective half-life (teff) in a patient?
Both the radiopharmaceutical used and the organ involved
Why is a physical half-life of a few hours desirable for imaging?
Because it matches the time from preparation to injection
What happens to the radiopharmaceutical when it is administered to a patient?
It is gradually eliminated from the tissue, organ, and whole body
This lecture covers the production of radionuclides in nuclear medicine, including the process of adding neutrons to stable nuclei to create neutron excess. The lecture explains how radionuclides are produced artificially in a nuclear reactor.
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