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20 Cards in this Set
- Front
- Back
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Which of the following may reduce the out-of-field artifact?
a. increasing the scan field-of-view b. reducing the reconstruction field-of-view c. reducing the slice thickness d. increasing the matrix |
a. increasing the scan field-of-view
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A cone beam artifact may look like stars:
a. at the center of the image b. coming from structures around the edge of the image c. coming from cone-shaped structures d. from all structures with high CT numbers |
b. coming from structures around the edge of the image
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Which of the following affects beam hardening?
1. the types of tissues the beam passes through 2. the thickness of the tissues traversed by the beam 3. the energies of the photons in the beam. a. 1 only b. 2 only c. 3 only d. 1, 2 & 3 |
d. 1, 2 & 3
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A CT artifact is:
a. a parameter used to control the brightness of the image b. always a reason to call for repair of the CT scanner c. used to time the injection of contrast media d. an anomaly in the CT image |
d. an anomaly in the CT image
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Which of the following would display the greatest amount of partial volume artifact?
a. a 10mm slice from a 20 slice study b. a 5mm slice from a 40 slice study c. a 5mm slice from a 20 slice study d. a, b and c would experience the same amount of partial volume artifact |
a. a 10mm slice from a 20 slice study
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Which of the following is a result of reducing the slice thickness to reduce partial volume effects?
1. increased appearance of noise 2. increased spatial resolution 3. decreased anatomical coverage with the same number of slices a. 1 only b. 2 only c. 3 only d. 1, 2 & 3 |
d. 1, 2 & 3
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Which of the following is a possible manifestation of beam hardening?
1. CT number inaccuracies 2. streaks in the image 3. cupping artifact a. 1 only b. 2 only c. 3 only d. 1,2 & 3 |
d. 1,2 & 3
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Which of the following would result if the filter at the aperture of the x-ray tube removed even more low energy x-ray photons?
a. beam hardening artifact would decrease b. partial volume artifact would increase c. beam hardening artifact would increase d. partial volume artifact would decrease |
a. beam hardening artifact would decrease
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What is the cause for the cupping artifact?
a. the central tissues are not penetrated by the x-ray beam b. the tissues of the body attenuate low eenergy photons c. the mean energy of the photons that comprise the x-ray beam is lowered d.the interface between tissues with different densities causes the high energy photons to be absorbed |
b. the tissues of the body attenuate low eenergy photons
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Which of the following would make noise in the image appear less noticeable?
1. increased window widths 2. increased mAs 3. increased slice thickness a. 1 only b. 2 only c. 3 only d. 1, 2 & 3 |
d. 1, 2 & 3
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Which of the following may be the cause of two parallel lines seen on a localizer image?
a. two faulty detector elements b. cone beam artifact c. tube arcing d. a problem with the reconstruction algorithm |
a. two faulty detector elements
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How would we expect metal to affect the appearance of a localizer image?
a. the CT numbers of the tissues in the image will be misrepresented b. the metal object will be represented by high CT numbers and there will be no streaks c. the entire image will appear blurry d. streaks will emanate from the metal object in the image. |
b. the metal object will be represented by high CT numbers and there will be no streaks
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Why must we choose a scan field-of-view which is larger than the anatomy to be scanned?
1. to achieve the highest spatial resolution 2. to minimize partial volume artifacts 3. to avoid out-of-field artifacts a. 1 only b. 2 only c. 3 only d. 1, 2 & 3 |
c. 3 only
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Which of the following may be the cause of a metal artifact?
1. earrings 2. a zipper 3. dental fillings a. 1 only b. 2 only c. 3 only d. 1,2 & 3 |
d. 1,2 & 3
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Beam hardening refers to:
1. the increase in the number of photons reaching the detectors 2 . the increase in the number of low energy photons reaching the detectors 3. the increase in the average energy of the photons that reach the detectors a. 1 only b. 2 only c. 3 only d. 1 & 3 |
c. 3 only
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Which of the following might increase the possibility of motion artifacts occurring?
a. explaining the procedure to the patient b. using a helical scanning technique to acquire the necessary slices in a single breath-hold (assuming the patient can refrain from breathing for the required time) c. using no straps or pads so that the patient feels comfortable and unrestricted d. immobilizing the patient |
c. using no straps or pads so that the patient feels comfortable and unrestricted
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What is the cause of cone beam artifacts?
a. faulty detector elements b. the use of a standard filtered back projection reconstruction when the x-ray beam is more than 20 mm thick c. hardening of the x-ray on multi-row detector scanners d. inefficient x-ray tubes used on multi-row detector |
b. the use of a standard filtered back projection reconstruction when the x-ray beam is more than 20 mm thick
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Which of the following would reduce the partial volume effect?
a. increased reconstruction field-of-view b. increased mAs c. decreased matrix d. decreased slice thickness |
d. decreased slice thickness
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Which of the following would increase the severity of the edge gradient effect?
1. a scanner with a small detector aperture 2. a scanner with a low data sampling rate 3. using thin slices a. 1 only b. 2 only c. 3 only d. 1, 2 & 3 |
b. 2 only
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Which of the following affects the severity of metal artifacts?
1. the quantity, composition and shape of the metal 2. the slice thickness 3. the number of data sampling points a. 1 only b. 2 only c. 3 only d. 1, 2 & 3 |
d. 1, 2 & 3
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