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36 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Which of the following radionuclides is not a positron emitter?
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82Rb
15O 18F 14C 68Ga |
14C
- 14C decays by beta emission....all other choices listed decay by positron emission, some also by electron capture |
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Which of the following has the shortest half life
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82Rb = 75 seconds
13N = 9 min 15O = 21 min F18 = 110 min |
82Rb = 75 seconds
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When FDG is transported across most cell membranes:
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- it diffuses back out of the cell in about 3 hours
- it is trapped in the cell - it is not further metabolized - b & c - a & c |
b & c
- 18F is a glucose analog, and is therefore, useful for metabolic imaging of the brain. Since it does not diffuse back out of the cell after localization, no further metabolism takes place. |
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When a neutron deficient nucleus emits a positron:
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- atomic mass number decreases by 1
- atomic mass number increases by 1 - atomic number increases by 1 - atomic mass number is unchanged |
- atomic mass number is unchanged
- The atomic mass number = # of particles in the nucleus. Because the proton is "converted" to a neutron, the number of protons decreases by one and the number of neutrons is inceased by one so the net effect is no change to the atomic mass number. The atomic number, which is the number of protons in the nucleus, decreases by one |
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Which of the following will not affect the distribution of 18FDG on a PET Image?
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- intense physical activity the day before scanning
- serum insulin levels - serum glucose levels - bladder catheterization - all of the above effect distribution |
all of the above effect distribution
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Normal 18 FDG distribution would show the least activity in the
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brain
bone bladder myocardiun |
bone
18 FDG will accumulate in the brain, urinary tract and myocardium. Bone Activity can be seen with 18F not 18FDG |
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All positorm emitting isotopes are produced in a cyclotorn
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true
false Many positron emitters are cyclotron produced, but not all. 82Rb is eluted from generators containing 82Sr |
false
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18 FDG-PET is not an important tool for:
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-re-staging of colorectal cancer
- monitoring the response to treatment of non-Hodgkin's lymphoma - detecting Helicobacter pylori - imaging metastases in breast cancer |
- detecting Helicobacter pylori is accomplished using a radioactive carbon breath test
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Which of the following is true regarding 18FDG?
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-it is taken up by a disease free myocardium
-its distribution to the brain is related only to blood flow - it is a potassium analog - it has a half life of 60 minutes |
it is taken up by a disease free myocardium
- The normal distribution of 18 FDG in the brain is related to both blood flow and metabolic rate, with gray matter showing the greatest uptake. It is a glucose analog, has a half life of 109 or 110 minutes and is taken up by normal myocardium |
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FDG-PET images show a map of the _________ distribution in the body
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oxygen
insulin glucose potassium |
glucose
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What length of time should a lactating female who undergoes 18FDG-PET scanning wait before resuming breast feeding?
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4 hours
24 hours one week breastfeeding should be stopped |
24 hours
18FDG physical half life 109 min biologic half life = 6 hours effective half life = 1.4 hours. Most places recommended 24 hours or even as little as 6 hours |
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Because of the relatively high energy of the photon detected in PET imaging......attenuation correction does not need to be performed
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true
false |
false
- Attenuation correction is necessary to correct for tissue interactions that the annihilation photons have undergone. This can be acchomplished by using a transmission scan from either a sealed source or a CT.) which measures attenuation through all lines of response |
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Question 13
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page 151
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What part of a PET scanner quality control regimen is necessary for the computation of attenuation factors?
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- concidence timing collection
- normalization correction - PMT gain adjustment - blank scan |
blank scan
- A blank scan is performed using a transmission source in an empty field of view. This is used to monitor system stability, and is also needed along with the transmission scan to perform attenuation correction. |
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Which of the following describes random coincidence?
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the simultaneous detection of photons originating from different positrons
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True Coincidence = simultaneous detection of annihilation photons originating from a single positron
Scattered Coincidence = simultaneous detection of annhilation photons after one of the photons has undergone Compton Scattering Because the direction will have chnaged for the photon undergoing scatter, this photon will be assigned to an incorrect line of response and this will increase noise. Random Coincidence = simultaneous detection of photons orignating from the different positrons. This must be corrected for in order to obtain quantitative data |
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Scintillation crystals for PET scanners are not made of
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sodium iodide Na(I)
lutetium oxyorthosilicate LSO bismuth germinate BGO lead sulfate b and d |
lead sulfate
Scintillation detectors capable of detecting positron emission include Na(I) LSO and BGO |
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PET images are reconstructed using
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coincidence detection = refers to the process by which photons are accepted or rejected a originating from an single annihilation event.
filtered back projection k space filling = MRI reconstruction method block detection = refers to the division of scintillators into seperate channels using material that will not conduct light |
filtered back projection
Reconstruction of PET images can be performed using filtered back projection or iterative reconstruction schemes. |
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Following an annihilation reaction, two 511 keV photons are emitted in opposite directions. If one the photons is deflected in the body
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- only the unscattered photon will contribute to the image
- the deflected photon may be detected outside the LOR - the LOR may contain an angle - none of the above `` |
the deflected photon may be detected outside the LOR
- only the unscattered photon will contribute to the image is not correct because an unpaired photon will not contribute to the image. - the LOR may contain an angle = lines of responses are lines and NOT ANGLES The deflected photon can be detected in a position that changes the assignment of the LOR |
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question 19 & 20
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page 153
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Chewing gum between injection of 18FDG and PET scanning will have no affect on the resulting images
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true
false |
false
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Why is it important to know of an patient has inflammatory condition before performing an 18 FDG-PET scan?
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some inflammatory conditions cause areas of increased uptake of FDG
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Patient Preparation for an 18 FDG uptake- PET scan of the whole body includes
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- NPO after midnight the evening before imaging
- fasting state of at least 4 hours prior to the exam - avoiding intense physical activity the day before the exam - b and c only |
- b and c only
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18 FDG is useful for imaging tumors because
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-it is a glucose analog
-there is an elevated rate of glycolysis in tumors - it becomes trapped in tumor cells - all of the above |
all of the above
18 FDG is taken up by tumors according to their glycolytic rate, at which is often higher than that of normal tissues, and once localized in tumor cells, it remains there |
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What dose and route of adm. is the best choice when performing a whole body PET scan with 18 FDG and a dedicated PET scanner
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10 mCi IV
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Fill in the blank....high blood glucose levels may _________ 18FDG uptake in tumors
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decrease
increase |
decrease
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Relative to another 82Rb and 82 Sr are
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isobars
isotopes isotones |
isobars = are atoms of different elements; they have different number of neutrons, but have the same mass number
Isotopes = are members of the same element that have differing numbers of neutrons. Isotones = have the same number of neutrons |
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What determines the lower limit of spatial resolution in the PET imaging?
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timing window
detector type poistron range Compton Scatter |
positron range = is the distance that the positron travels after leaving the nucleus before undergoing annihilation with an electron. This means that the line of response is assigned a slight distance away from the actual site of positron emission.
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Parenteral nutrition should be discontinued for several hours prior to 18 FDG Imaging
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true
false |
true
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A patient presents a whole body imaging to assess response to chemotherapy for prostate cancer. The scan should begin
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cranially
caudally |
caudally
if the bladder is emptied prior to scanning ans the scan is begun caudally.....the bladder will be least full when the pelvis is imaged |
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Two inrealted annihilation photons are detected within the window and judged to be in coincidence. This is
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true coincidence
random coincidence scatter coincidence none of the above |
random coincidence = is when 2 annihilation photons from different annhiliations are judged to be true.
**You should know these by heart....do further reading and keep going over |
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Noncolinearity refers to
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annihilation photons that are not emitted at exactly 180 degrees to one another due to particle momentum
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The angle difference from 180 degres is typically +- 0.25% and negatively affects spaital resolution........ the effect is increased with increasing diameter
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On a 18FDG PET scan of the whole body.....muscle uptake can be decreased by
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-adm. diazepam before injection of 18FDG
-maintaining the patient in the supine position during uptake - minimizing chewing, talking, and swallowing during uptake all of the above |
all of the above
diazepam = premeditating the patient with this or any other anxiolytic drug will help reduce muscle uptake |
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Dedicated PET scanners are
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electronic collimation = the photons are rejected on the basis of non-coincidence
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Benefits of delayed imaging for whole body 18 FDG PET include
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-tumor uptake will increase over time
-bowel and urinary activity may change -activity resulting from infection will increase - all of the above |
bowel and urinary activity may chnage, aiding diagnosis
Delayed imaging is often crucial to diagnosis because uptake not related to malignancy may show a relative decrease in activity and changes in bowel and urinary tract activity may allow better visualization of the pelvis |
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Standard uptake values are useful for
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- differential diagnosis of tumor
- assessing tumor size changes - assessing response to treatment - all of the above - none of the above |
assessing tumor response to treatment
Tissue concentration of tracer / injected dose x calibration factor The calibration factor used is calculated using body weight. This measurement is applied to pre and post treatment may show response to therapy.; |
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A patient presents for PET scanning with 18 FDG for suspected tumor of the left axilia...... what is the best injection site?
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right antecubital vein
left antecubital vein foot either a or c |
either a or c
The injection site should be contra-lateral to the area in question or in the foot |
