Random Flashcards
Molybdenum breakthrough allowed by NRC
May not exceed 0.15 microCi of Mo-99 per 1 mCi of Tc-99m
Minimum peak pixel count in LV myocardium on a planar technetium-99m SPECT projection?
200 counts/pixel (anterior projection)
Minimum peak pixel count in LV myocardium on a planar thallium-201 SPECT projection?
100 counts/pixel
Compared to adenosine, its receiving regadenoson are more likely to have what?
headaches
Prone imaging improves SPECT MPI accuracy because it allows recognition of what?
Diaphragmatic attenuation
Nitrates-enhanced technetium-99m sestamibi test in evaluating hibernating myocardium compared to thallium rest-distribution
higher NPV and higher PPV
11C-heptagluconate is a tracer of:
myocardial fatty acid utilization
11C-hydroxyephedrine is a tracer of:
depict sympathetic innervation of the myocardium
FDG is a tracer of:
myocardial glucose metabolism
11C-acetate is a tracer of:
myocardial oxidative substrate metabolism;
can also be use to assess myocardial perfusion given high first-pass myocardial extraction fraction; images obtained early following tracer injection can be used to measure regional tissue blood flow.
Organ receiving highest radiation dose in a rubidium-82 PET perfusion study?
Kidneys, than heart
Minimum number of acquisition projections or stops recommended for SPECT acquisition over 180 degrees using technetium-99m and thallium-201?
technetium-99m: 60-64
thallium has lower resolution, so 32 projections
well counter
most sensitive and practical for measuring the swipes that are to test packages delivered to a nuclear lab.
solid scintillation counter and is very sensitive to low levels of radioactivity
dose calibrator
used routinely to measure radiotracer doses prior to being injected into the patient
ionization chamber
a gas-filled enclosure between two conducting electrodes that can be used to measure gases, liquids, or solid
Geiger counters
used to detect ionizing radiation (usually beta particles, gamma rays, some can detect alpha particles)
an inert gas-filled tube (usually helium, neon, or argon with halogens added) briefly conducts electricity when a particle or photon of radiation makes the gas conductive.
In-vitro labeling of RBCs
ultratag
1-3 ml heparinized blood added to vial containing stannous citrate and incubated at room temperature for 5 minutes. During incubation period, the stannous ion diffuses the RBC membrane after which sodium hypochlorite along with acid citrate dextrose is added to the reaction vial, followed by the addition of 30-40 mCi of sodium pertechnetate-technetium-99m and incubated for another 20 minutes. extracellular stannous ion is oxidized by the sodium hypochlorite. The pertechnetate-technetium-99m diffuses the RBC membrane and is reduced inter cellularly by the stannous ions. Reduced pertechnetate-technetium-99m doesn’t diffuse out of the RBC.
Typical labeling efficiency is >97%.
mSV of SPECT MPI vs Rb82 or NH3 based PET MPI
SPECT MPI (technetium): 12-16 mSV
Pet Rb82: 3.7 mSV
PET NH3: 2.3 mSV
Annualized event rate for patients with non-ischemic PET perfusion studies and calcium scores between 400-999:
5%
Radioactive signs
not required where radioactive materials are handled for <8 hrs and are under constant observation, and in rooms where sealed sources are stored and the exposure doesn’t exceed 5 mrem/hr at 1 m
White I limits
surface < 0.5 mR/h
at 1m <1
Yellow II
Surface >0.5, <50 mR/h
at 1 m, >1, <10
Yellow III
Surface >50, <200 mR/h
Breast feeding after exercise stress Tl-201
stop for 2 weeks after test
PET - Attenuation correction, what rotating rod sources/rings used to acquire a transmission scan for attenuation correction
Germanium-68 (Ge-68/Gallium-68)
or
Cesium-137
Calculation of effective half-life (Te)
1/Te = 1/Tp + 1/Tb
Caution: Very high radiation area sign should be posted in area where radiation exceed
> 500 rads/hr at 1 m
Fluorine-18 half life
110 minutes
Technetium-99m half life
6 hours
thallium-201 half life
3.04 days or 73 hours
Cobalt-57 half life
271.7 days
NRC annual body radiation exposure limit for a radiation is:
whole body dose 5 rem/year
specific organ limits: 15 rem for eyes, 50 rems for extremities
Rubidium-82 is made in:
Carbon-11 is made in:
Fluorine-18 is made in:
Nitrogen-13 is made in:
Rubidium is made in generator (eluted from a strontium-82/rubidium-82 generator)
The rest are from cyclotrons
Danger: Radiation area
Unrestricted area of a nuclear imaging facility.
If <2 mrem/hr, do not require posting
Transportation index is a measure of:
exposure measurement at 1 m from the surface of the package
NRC max. exposure for a pregnant occupational worker is:
500 mrem for entire pregnancy (declared pregnant worker)
Technetium-99m tracers artifacts:
liver and GI activity –> scatter, scaling, or normalizing problems
Ramp filter artifacts associated with filtered back projection during reconstruction
Extraction fraction across coronary bed - Technetium-99m agents vs Tl-201
lower in Technetium-99m
Technetium-99m vs thallium
higher photo energy resulting in less tissue attenuation
administration of nitrates prior to the resting injection mages of technetium-99m MPI helps:
improves readers’ ability to detect viable myocardium in severely hypo-refused segments (similar to thallium)
Regadenoson half life
initial IV phases of 2 minutes, then a longer intermediate phase of 30 minutes, and a third phase of 2 hours
CKD and normal SPECT annual cardiac death rate
2.7%
No CKD and normal SPECT annual cardiac death rate
0.8%
CKD and scar annual death rate
5.7%
CKD and ischemia annual death rate
11%
DTS annual CV mortality:
high =5
=5% annual CV mortality
>=5 is 0.5% annual CV mortality
Nitrogen-13 ammonia
in some pos, there may be a decrease in nitrogen-13 ammonia uptake in the inferolateral region of the ventricle
FDG PET trapping mechanism
Once FGD is transported across the cell membrane via GLUT transport proteins (GLUT-1 and LGUT-3 for macrophages), it is phosphorylated by the enzyme hexokinase to FDG-6-phosphate; addition of the phosphate moiety to the molecule largely traps the FDG within the cells, as FDG-6-phospate is a poor substrate for further glycoltytic or glycogen synthetic pathways
13NH3 activity in cell
13NH3 passively crosses the myocyte cell membrane, once within the cytosol of the cell it is metabolically trapped as glutamine via the glutamine synthase reaction
FDG highest dose organ
urinary bladder
Radiation hormesis
a protective effect of exposure to low amounts of ionizing radiation
Rubidium-82 highest dose organ
kidneys
Adenosine’s common adverse event
Second degree AVB (4.1%) > hypotension (1.8%) > bradycardia (0.2%) > third degree AVB (0.8%)
Agents that can be used for detection of a recent ACS
I-123 BMIPP (fatty acid analog that is not taken up in areas of infarction due to cell damage)
Technetium-99m Myoscint (antibody directed to myosin that is exposed following acute damage and detects damage earlier than technetium-99m pyrophosphate)
Technetium-99m pyrophosphate is retained in areas of healing infraction that has been used for detection of infarcts that are 3-7 days old
