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45 Cards in this Set
- Front
- Back
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Is the specificity/ sensisitivity better with planar or SPECT imaging?
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SPECT
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What is the most common type of ECT rotation?
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Transverse (rotational)
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Name 2 types of ECT cameras?
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Transverse (rotational) and Fixed ring (longitudinal)
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Three types of transverse (rotational) ECT cameras?
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circular
ellipitical body contour |
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An imaginary line from camera head to AOR is the?
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Axis of rotation
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Distance from the camera head to AOR?
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Radius of rotation
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3 types of data reconstruction?
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Simple back projection
filtered back projection interative reconstruciton |
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How do you increase quality and signal to noise ration?
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Filtering frequencies
(top peak is noise, lower pt of peak is bkg) we only want middle frequencies |
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Name two types of filters
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Low pass
High Pass |
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Filters less frequencies?
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High pass
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FIlters more frequencies?
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Low pass( less noise)
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2 characterisitcs of filters
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Cut off frequency
order |
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Star artifact is commonly seen in what kind of data reconstruction? How is it removed?
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Simple back projection, removed with filtered back projection
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Name the 5 types of filters
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Parzen, Bartless, Hamming, Butterworth, RAMP
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Which type of filter allows more noise and gives highest resolution?
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RAMP
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Which type of filter give a good resolution and smoothness balance? Especially good for SPECT?
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Butterworth
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WHich filter is the smoothest?
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Parzen
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High cutoff frequency gives a (smoother or sharper image)?
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Sharper
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Order (b.w 1-5) varies the ?
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SLOPE (averages smoothness and sharpness)
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All SPECT images are initially created in the ? (coronal, transaxial, horizontal)
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Transaxial
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Imaging that visualizes the metabolic activity of the body is called?
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PET (kinetic imaging)
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Qualitative and quantitative information differs how?
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Qualitative- physical appearance
Quantitative- accummulated activity |
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Scintillation crystals in PET coincidence
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BGo, BaF, CsF, NaI
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Does the scanner rotate in PET?
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No, it's fixed
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Why is the energy spectrum broad in actual spectrum vs. a spike in theoretical?
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incomplete absorption, less light intensity (its brighter at center), improper voltage amplification, etc.
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Formula for energy resolution?
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Er=FWHM/E
or full width half max divided by peak gamma energy |
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What is the maximum limit of energy resolution?
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10-15%
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Higher the energy, the ? the energy resolution?
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lower
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Spectrum is the number of times a ? occurs per time
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Pulse
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Name the part of the gamma spectrum
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photopeak, backscatter, leak x-ray, iodine escape, compton scatter, coincidence peak, body scatter
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what is the photopeak?
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main peak energy of the gamma photon, ex, Tc99m=140kev
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Backscatter is seen at ? of peak?
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1/3
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What is seen at 77kev?
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Lead x-ray peak
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Where is the iodine escape peak seen? What is it from?
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28kev less than peak, it's form interaction of photons with iodine in NaI crystal
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What is the majority of activity seen below the peak in a gamma spectrum?
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Compton scatter
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2 gamma photons that reach the image at the same time combine the total of their energies. This is known as?
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Coincidence (or Sum) peak
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How can body scatter be removed?
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decreasing the window and increasing the resolution collimator
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Another name for resolving time is?
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Dead time
temporal resolution |
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Dead time depends on avalanche dissipation in what kind of detector?
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Gas filled
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How long is the dead time in a gas filled detector?
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50-300usec
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How long is the dead time in a scintillation detector?
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2-5 usec
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In a scintillation detector what does the dead time depend on?
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electronics and counting mechanisms
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What is the radiation detection limit in a gas filled detector?
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100mR/hr
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R1+R2-R1,2/2(R1 X R2)
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Formula for True count rate
R1=source 1 R2=source 2 R1,2= sum of 1 &2 |
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Count rate needs to be always the same RN and converted to what?
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usec
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