Radiopharmaceuticals, Radiation, & Radiographic Contrast Agents Flashcards
1
Q
Element
A
- The smallest amount of a substance that exhibits the properties of that substance
- Grouped by the # of protons in each atom, and are arranged in the Periodic Table
2
Q
Radioactivity
A
- The process by which the nucleus of an unstable atom loses energy by emitting ionizing radiation
- Radioactive elements have nuclear imbalance (# protons/neutrons)
3
Q
Nuclide
A
- Term used to describe any atom by referencing the nucleus mass and energy
- # on top is mass
- # on bottom is atomic
- mass # = protons + neutrons
4
Q
Isotope
A
- Term used to describe elements with the same nucleus and the same # of protons but varying numbers of neutrons
5
Q
Radioactive Transformation
A
- Process by which a radioactive unstable element transforms to a less unstable or more stable element
6
Q
Curie (Ci) - unit of measure
A
- 3.7 x 10^10 nuclear transformations per second or disintegrations per second (dps)
7
Q
Becquerel (Bq) - unit of measure
A
- 1 Becquerel is equivalent to 1 disintegration per second
- 1 mCi = 37 MBq = 3.7x10^7 Bq
8
Q
Radioactive Half-life (T1/2)
A
- The time required for a radionuclide to decay to 50% of its original radioactivity
- Or, the time required for 50% of the radioactive atoms to decay
9
Q
Decay Constant
A
- Each radionuclide has a characteristic Decay Constant (λ)
- (λ) = ln2 / T1/2
- Large decay constant = small half-life = radionuclide decays rapidly
- Small decay constant = big-half life = radionuclide decays slowly
10
Q
Activity and Decay Constant
A
- Relationship between activity (A) and decay constant (λ) is:
A = λN / (3.7 x 10^10)
11
Q
Decay Equation
A
- Used to predict the radioactivity at any time once one knows the original radioactivity
- Nt = (N0)e^-λt
- Nt = # of un-decayed atoms at time (t)
- N0 = original # of un-decayed atoms at time = 0
12
Q
Radiation Decay Types
A
- Alpha particles, beta particles and gamma rays are emitted from the nuclei of the radioactive atoms
- X rays are generated as electrons from higher orbitals fall down into lower orbitals
13
Q
Alpha particles
A
- Helium nucleus = 2 neutrons + 2 protons; charge of +2
- Emitted from nuclei of radioactive atoms
- Transfer energy in very short distances (50-90 um in tissue)
- Shielded by paper or layer of skin
- Primary damage from internal exposure to tissues (bone, kidney, liver, lung, spleen)
14
Q
Beta Particles
A
- Small, electrically charged particle w/a negative charge (negatron, electron) or a positive charge (positron)
- Ejected from nuclei of radioactive atoms
- Emitted with kinetic energy
- Shielded by low-density materials, such as plastic or wood (penetration 0.2-1.3 cm)
- Can cause tissue damage - skin burns
15
Q
Gamma Photons
A
- Electromagnetic photons or radiation
- Emitted from nuclei of radioactive atoms
- Emitted w/kinetic energies related to radioactive source
- Highly penetrating
- High-density shielding required: Lead, Tungsten, Concrete
- External radiation hazards
16
Q
X Rays
A
- Overlap w/gamma-rays in wavelength
- Electromagnetic photons or radiation
- Produced from orbital electrons of radioactive atoms
- Emitted w/various energies & wavelengths
- Highly penetrating
- High-density shielding required: Lead, Tungsten, Concrete
- External radiation hazards
17
Q
Auger Electrons
A
- Small electrically charged particle w/a negative charge
- Ejected from orbital electrons of radioactive atoms
- Relatively lower kinetic energies than B-particles
18
Q
Radiation
A
Particles or waves of energy emitted from unstable atoms
19
Q
Radioactive Contamination
A
Radioactive material usually in any undesired location
20
Q
Radiation Dose
A
- The amount of radiation absorbed by body tissue
- Typically, it is measured in rad (radiation absorbed dose)
- 1 rad = 100 ergs energy / 1g of tissue
- 1 Gray (gy) = 100 rad
- Gy is the international unit of absorbed dose
21
Q
Effect of Ionizing Radiation on Living Cells
A
1) Injured cells repair themselves
2) Cells die and are replaced
3) Cells incorrectly repair themselves resulting in a biophysical change (i.e. cancer)
- Exposure to ionizing radiation can cause damage to DNA and ultimately increases lifetime risk of developing cancer
22
Q
Tissue Sensitivity
A
- Radiosensitivity is the relative susceptibility of cells to radiation damage
- Factors increasing cell sensitivity to radiation: high division rate, high metabolic rate, undifferentiated, well-nourished
23
Q
Radiography
A
- The traditional image receptor is a cassette that contains a fluorescent screen and a piece of photographic film
- X-rays cause the screen to glow
- The light exposes the film
- Modern image receptors are now digital
24
Q
4 Tissue Densities
A
1) Bone
2) Soft tissue
3) Fat
4) Air
25
Q
X-ray Contrast Agents
A
- Contrast agents are used to highlight features that would normally not be seen
- Materials are used which are radio-opaque
- Administration may be oral, rectal, IV injection or retrograde into the bladder and ureters
- Barium-based agents are often used for GI studies
- Iodine-based agents are used in IV studies
- VERY VISCOUS (needs to be warmed up)
26
Q
Computed Tomography
A
- This array of data can be used to form “slices” in any orientation
- Advantage of CT is a large volume of the body can be sampled at one time
27
Q
Nuclear Medicine
A
- The radiopharmaceutical biodistribution is determined by the physiologic procceses occurring within the patient
- Images are acquired of the biodistribution
- Image physiology rather than anatomy
28
Q
Single Photon Emission Computed Tomography (SPECT)
A
- Nuclear medicine equivalent of CT
- Detectors rotate around the patient
- Typical acquisition time is 10-45 minutes
29
Q
Positron Emission Tomography (PET)
A
- The positron is the anti-particle of the electron
- When a positron and an electron meet, they undergo annihilation
- Each particle is entirely converted into energy, which takes the form of 2 photons moving in opposite directions
30
Q
Radiopharmaceutical
A
Chemical substance that contains radioactive atoms and is suitable for administration to humans for diagnosis or treatment of disease
31
Q
Ideal Properties of DIAGNOSTIC Isotopes
A
- Readily Available (7 days a week)
- Low production costs
- Short t1/2 (hours)
- Good physical properties: γ-rays for imaging
- No particulate emissions
- Allows for high specific activity labeling
- Reproducible chemistry
- Candidates: 99mTc, 111In, 18F, 68Ga
32
Q
Ideal Properties of THERAPEUTIC Isotopes
A
- Readily Available (7 days a week)
- Low production costs
- Physical T1/2 matched to biological application
- Good physical properties (alpha/beta/auger particles for therapy and gamma/x photons for imaging)
- Dose rate and range in tissue: LET = ∆E/∆X
- Allow high specific activity labeling
- Reproducible chemistry
- Candidates: 177Lu, 90Y, 131I, 188Re
33
Q
Properties that Influence Renal and Hepatic Excretion
A
- Molecular Weight
- – MW >10^5 = hepatic
- – MW <10^3 = renal; <68,000 glomerular filtration
- Lipophilicity (Octanol-Water Partition Coefficient)
- – Lipophilic (Octanol) = favors hepatic
- – Water Solubility = favors renal
- Charge
- – Hepatic = +/- or Neutral = All
- — Renal = Neutral or +1
34
Q
Optimum Dose of Radiopharmaceutical
A
- Allows acquisition of the desired info with the least amount of radiation dose or exposure to the patient
- Half-life
- Radiation type
- Energy
35
Q
Cyclotron Production of Radionuclides
A
- Charged particle accelerator
- 18O (p,n) 18F (PET Imaging)
- 111Cd (p,n) 111In (SPECT Imaging)
36
Q
18F-FDG
A
- 18F-FDG most widely used PET radiopharmaceutical
- (18F) Fluoro-2-deoxy-D-glucose
- 18F-FDG is made by nucleophilicsubstitution of 18F-for OH-group at 2
37
Q
18F-FDG Metabolism
A
- Like glucose,18F-FDG is transported into the cell
- 18F-FDG undergoes glycolysis (Phosphorylization)
- Further metabolism requires -OH group in the C-2 position
- 18F-FDG cannot undergoglycolysis. It hits a metabolic “dead end”and is retained in the cell
38
Q
18F-FDG PET Distribution
A
- Some tissues selectively use glycolytic metabolism
- Need higher metabolism than surrounding tissues (want high target:background)
- 18F-FDG is used to image:
–Cancer
–Infection
–Brain metabolism
–Myocardial Ischemia
–Trauma
39
Q
9 Domains Encompassing Nuclear Pharmacy Practice:
A
- Procurement and storage
- Radiopharmaceutical preparation
- Quality assurance
- Radiopharmaceutical dispense
- Radiopharmaceutical distribution
- Health and safety
- Provision of drug information and consultation
- Monitoring patient outcomes
- Research and development
