P2 Flashcards
ideal for gamma cameras
Gamma emissions of suitable energy (100-200 keV)
for external detection of radioactive decay
Positron emission tomography (511 keV) and sufficient abundance (percent likelihood of emissions per decay)
most closely matches these desirable features for the gamma camera and fluorine-18 for PET.
Technetium-99m
Neutron bombardment of enriched uranium-235 results in
fission products
Bombardment of medium-atomic-weight nuclides with low-energy neutrons (neutron activation) in a nuclear reactor results in
neutron-rich radionuclides
Neutron-rich radionuclides (e.g., iodine-131, xenon-133, chromium-51, and molybdenum-99) generated through fission or neutron activation undergo
beta-minus decay
They have no clinical role in diagnostic nuclear medicine.
Naturally occurring radionuclides
commonly used clinically are artificially produced by nuclear fission or through the bombardment of stable materials by neutrons or charged particles.
Radionuclides
Charged particle bombardment (with protons, deuterons, alpha particles) to a wide variety of target materials in cyclotrons or other special accelerators produces proton-rich radionuclides that will undergo:
Positron decay
Electron capture
is produced by the fission of U-235.
Mo-99
Mo99 is produced by the fission of
U-235
• Mo-99 is produced by the fission of U-235. The product is often referred to as _____.
fission moly
is readily available from a generator used in ~80% of all nuclear medicine examinations
Technetium (99mTc)
• 99mTc has a gamma ray energy of _____ that is ideal for imaging and a half-life of 6 hours that is convenient.
140 keV
is produced directly from 99Mo using a saline eluant.
Pertechnetate
(99mTc04)
Pertechnetate (99mTc04) is produced
directly from ____ using a ___.
99Mo, saline eluant
99mTc decays by _____ where 88% of nuclear transformations result in emission of a 140 keV gamma ray
isomeric transition
The half-life of 99Mo is _____, which allows the generator to remain useful for approximately 1 week (*2.5 half-lives).
66 hours
A ____ generator is normally eluted daily over the course of a week and then replaced.
99mTc
The technetium generator is shielded with _____ and consists of an alumina column loaded with ___
lead, 99Mo
99Mo decays to 99mTc, and ____ is added to the generator when 99Tc is needed.
saline
Saline passes through the column to elute (wash off) the 99mTC in the form of ____
sodium pertechnetate
_____is not soluble in saline and remains in the column.
99Mo
The process of removing Tc-99m from the Mo- 99/Tc-99m generator is known as ____.
elution
- Most commonly used in regional radiopharmacies, come with a reservoir of normal saline (0.9%).
Wet systems
the 2.8-day half-life of Mo-99 allows generators to be used for ____
2 weeks
Elution volumes are in the range of ____
5to20ml
A brand new ____ has only 99Mo activity but no 99mTc activity.
99Mo/99mTc generator
-A typical generator initially starts with
37 GBq (1 Ci) of 99 Mo.
As ___ decays, 99mTe activity is produced.
99Mo
A 99Mo generator thus takes approximately ___ hours to reach equilibrium.
24
In equilibrium, the activity of 99mTc is ____ of the 99Mo activity.
90%
is the name given when the parent radionuclide is short lived.
Transient equilibrium
is the name given when the parent is long lived.
Secular equilibrium
are designed to mimic a natural physiologic process.
Radiopharmaceuticals
Radionuclides should have a ___ half-life to minimize the patient radiation dose.
short
Ideal gamma rays have energies between ___
100 and 300 keV
_____ should have minimal particulate radiations (e.g., beta particles) to minimize patient dose.
Radionuclides
In addition to containing radioactive atoms, ____ contain molecules that are designed to travel inside the body of the patient until they reach their target tissue or organ.
radiopharmaceuticals
as sodium iodide was the first
radiopharmaceutical of importance in clinical nuclear medicine.
I-131
Used for physiological studies of the thyroid gland for several years in the late 1940s.
I-131
Used to radiolabel radiopharmaceuticals for scintigraphy, including human serum albumin, MAA, hippuran, and meta-lodo-benzyl-guanidine (MIBG).
I-131
These radiopharmaceuticals
are no longer diagnostically used.
I-131 and I-123
has recently been approved to confirm or exclude the diagnosis of Parkinson disease.
1-123 ioflupane (DaTscan)
Has proved useful for clinical nuclear medicine
Indium 111
Its principal photon energies of 172 and 245 keV are favorable, and their abundance is high (>90%).
Indium 111
Half life of In-111
2.8 days
for detection of inflammation and infection the somatostatin receptor-binding peptide
In-111 oxine leukocytes
to detect neuroendocrine tumors.
In-111 pentetreotide (OctreoScan)
became available in the mid-1970s for myocardial scintigraphy.
TI-201
It behaves as a potassium analog, with high net clearance (~85%) in its passage through the myocardial capillary bed, which makes it an excellent marker of regional blood flow to viable myocardium.
TI-201
are used for pulmonary ventilation imaging.
Radioactive inert gases
is the most commonly used.
Xe-133
The ability of the gamma scintillation camera to discriminate scattered events from primary photons is suboptimal at this energy.
Thalium 201
is theoretically superior to Xe-133 because of its higher photon energies.
Xenon-127
Half life of Xe-127
36 days
- High principal gamma emission (190 keV)
- Short half-life (13 seconds), allowing for postperfusion imaging and multiple-view acquisition without concern for retained activity or radiation dose.
Krypton-81m
has the advantage of a longer half-life than
C-11, N-13, or 0-15 and has been used as a label for the glucose analog fluorodeoxyglucose (FDG).
F-18
has found wide-spread clinical application in whole-body tumor imaging and, to a lesser extent, imaging of the brain and heart.
F-18 FDG
The uptake of ____ is a marker of tumor metabolism and viability.
F-18 FDG
is available from a generator system with a relatively long-lived parent (strontium-82, T½ = 25 days)
Rubidium-82
Like thallium, it is a potassium analog and used for myocardial perfusion imaging.
Rubidium-82
Physical half-life of I-131
8 days
Physical half- life of I-123
13.2 hr
Physical half- life of Ga-67
78.3
Physical half-life of Tl-201
73.1 hr
Physical half-life of In-111
2.8 days
Physical half-life of Xe-133
5.2 days
Physical half-life of Xe-127
36 days
Physical half-life of Co-57
272 days
Half life of C-11
Production Method:
20 min
Cyclotron
Half-life of N-13
Production Method:
10
Cyclotron
Half life of O-15
Productuon Method:
2
Cyclotron
Half life of F-18
Production Method:
110
Cyclotron
Half-life of Ga-68
Production Method:
68
Generator (Ge-68)
Half-life of Rb-82
Production Method:
1.3
Generator (Sr-82)
Fraction of wanted vs. unwanted chemical in preparation
Chemical purity
Fraction of total radioactivity in desired chemical form
Radiochemical purity
Fraction of total radioactivity in the form of desired radionuclide
Radionuclide purity
Fraction of total pharmaceutical in desired physical form
Physical purity
Absence of microorganisms and pyrogens
Biological purity
