CT All

Which of the following CT numbers represents water? 0 +1000 -1000 +3000

0

Modern CT scanners are able to differentiate tissue with density differences of less than _____ %. 1.0 0.5 0.1 0.15

0.5

When performing a routine CT scan of the neck, which pitch would result in the highest patient dose? 0.7 1.0 1.2 1.7

0.7

When performing a routine CT scan of the neck, which pitch would result in the highest resolution? 0.7 1.0 1.2 1.7

0.7

For a spiral/helical head CT scan using a multi-detector configuration, the recommended pitch is: 1 to 1.2. 0.7 to 1.2. 0.7 to 1.0. 1 to 1.7.

0.7 to 1.0.

To assure quality images for postprocessed reformats of the ankle joint, a _____-mm scan thicknesses and _____-mm slice interval is appropriate. 0.75; 0.04 0.75; 0.4 7.5; 4 4; 4

0.75; 0.4

For a routine chest CT, the recommended pitch is: 0.5 to 0.8 0.8 to 1.0 0.8 to 1.35 0.5 to 1.35

0.8 to 1.35

As the display field of view (DFOV) decreases: (1) noise increases (2) spatial resolution increases (3) spatial resolution decreases. 1 and 2 1 and 3 2 and 3 1, 2 and 3

1 and 2

Which of the following are functions of the patient table? (1) contributes to patient safety (2) Enhances subject contrast (3) transports the patient through the gantry? 1 and 2 1 and 3 2 and 3 1, 2 and 3

1 and 3

Window level (WL) refers to: (1)the midpoint in a range of CT numbers (2) image contrast (3) image brightness. 1 and 2 1 and 3 2 and 3 1, 2 and 3

1 and 3

Coronal and sagittal reconstructions of the lumbar spine require a slice thickness of _____ mm. 10 5 3 1-2

1-2

For postprocessed 3-D images of a chest CT angiogram (CTA), which pitch would provide images with the highest quality? 1.0 1.2 1.35 1.7

1.0

Overlap occurs when the pitch is less than: 1.0. 1.5. Overlap is not related to pitch. .5.

1.0.

For optimum enhancement of blood vessels and organs on a routine abdomen/pelvis CT scan, the average adult patient should receive _____ mL of IV contrast. 50 to 100 100 to 150 150 to 175 200

100 to 150

The typical kilovolt peak (kVp) range used for CT scans is: 90-100. 100-120. 100-140. 120-160.

100-140

The trigger threshold for an abdomen/pelvis CTA is _____ HU. 0 to 50 50 to 75 75 to 100 125 to 150

125 to 150

A 16-slice helical/spiral scanner produces _____ images from a single slice of scan data. 64 16 8 32

16

Spatial resolution can be increased by using: (1) larger-size detectors (2) a smaller pixel size (3) thinner slice thicknesses. 1 and 2 1 and 3 2 and 3 1, 2 and 3

2 and 3

Volume acquisition scanners are based on: (1) slice-by-slice data acquisition (2) slip-ring technology (3)continuous rotation of the x-ray tube 1 and 2 1 and 3 2 and 3 1, 2 and 3

2 and 3

The recommended slice thickness for a routine CT scan of the neck is _____ mm. 1 1.5 to 2.5 2.5 to 3 5

2.5 to 3

For a CT scan of the neck, the recommended DFOV is _____ cm and the SFOV is _____ cm. 50; 22-25 50; 50 22-25; 50 22-25; 22-25

22-25; 50

For a head CT exam, a scan field of view (SFOV) of _____ and a display field of view (DFOV) of _____ are recommended. 10 cm; 25 cm 25 mm; 25 mm 25 cm; 25 cm 75 mm; 25 mm

25 cm; 25 cm

When scanning a head with IV contrast, a scan delay of _____ is recommended. 30 seconds to 1 minute 1 to 2 minutes 3 to 4 minutes 10 minutes

3 to 4 minutes

Patients taking metformin should stop taking the medication _____ hours after IV contrast media injection. 12 24 48 72

48

50 millisievert (mSv) is equal to: 15 rem. 5 rem. 50 Gy. 100 Gy.

5 rem

For a routine abdomen/pelvis CT scan, the recommended SFOV is _____ cm. 25 50 65 75

50

For a routine chest CT scan, the recommended SFOV is _____ cm. 25 50 75 100

50

The National Council on Radiation Protection and Measurements (NCRP) recommends that the annual occupational dose for imaging professionals not exceed: 1 mSv 5 mSv 50 mSv 1 Sv

50 mSv

For a routine thoracic/lumbar CT scan of an adult patient, the recommended SFOV is _____ cm and the recommended DFOV is _____ cm. 50; 50 50; 12-20 25; 12-20 25; 25

50; 12-20

For a routine abdomen/pelvis CT scan, the slices thickness should be _____ mm and the slice interval should be _____ mm. 3; 5 5; 5 10; 5 5; 10

5; 5

What is the window level if the CT/Hounsfield range is 200 to 1000? 600 800 500 400

600

A CT scanner with 16 detector rows, each scanning 4 widths, is called a _____ -slice scanner. 4 8 16 64

64

Which of the following types of CT scanners are capable of effectively imaging a beating heart? 16-slice and 64-slice 16-slice and 128-slice 64-slice and 128-slice 16-slice, 64-slice and 128-slice

64-slice and 128-slice

Gating is a technique that can effectively reduce patient dose by as much as _____ %. 100 90 80 70

70

A CT tube anode angle of _____ degrees would result in the smallest effective focal spot size. 8 12 15 18

8

A standard window width (WW) of _____ is used to demonstrate brain tissue. 20-40 60-80 80-100 100-200

80-100

CT scanner x-ray tube voltages range from ______ to _____ kilovolts (kV). 60; 100 80; 120 80; 140 100; 160

80; 140

The trigger threshold for a pulmonary embolus CT exam is _____ Hounsfield units (HU). 0 to 50 50 to 90 90 to 100 100 to 200

90 to 100

The term "translation" is associated with _____ generation scanners. first second third A and B are correct.

A and B are correct

Beam-shaping filters are generally composed of: aluminum? copper. teflon. A and C are correct.

A and C are correct

Which of the following includes a sampler, quantizer and a coder? detector array DAC ADC DAS

ADC

Which of the following terms is associated with seventh generation spiral-helical technology? multisection scanner multidetector scanner multiple detector array scanner All choices are correct.

All Choices are correct

Which of the following sources of radiation were used in Hounsfield's first primitive CT scanner? x-ray americium radium radon

Americium

The z-axis refers to the ______ plane. coronal axial sagittal transverse

Axial

Spiral-helical CT scanning is based on: sequential data acquisition. slip-ring technology. volume data acquisition. B and C are correct.

B and C are correct

The scout (topogram) image for a CT of the head must include _____ through the vertex of the skull. C2 the external auditory meatus (EAM) C1 floor of the orbits

C1

Which of the following is considered a secondary protective radiation barrier? lead apron thyroid shield CT control room walls protective glasses

CT control room walls

Sampling occurs at the: CT detectors. prepatient collimators. analog-to-digital converter (ADC). digital-to-analog converter (DAC).

CT detectors

Which of the following quality control (QC) tests should be performed daily? CT number calibration and CT couch indexing CT number calibration and standard deviation of the CT number in water CT couch indexing and standard deviation of the CT number in water CT number calibration, CT couch indexing and standard deviation of the CT number in water

CT number calibration and standard deviation of the CT number in water

Which of the following tests determines the uniformity of CT numbers throughout the image? high-contrast resolution low-contrast resolution standard deviation of CT numbers in water CT number flatness

CT number flatness

Which of the following tests determines the ability of the patient table to return to its original position after the scan? CT table indexing CT table backlash localization device accuracy slice width

CT table backlash

The scan field of view (SFOV) is determined by the: pitch. prepatient collimators. postpatient collimators. CT technologist before the scan begins.

CT technologist before the scan begins

A CT gantry includes all of the following components except: collimators. detectors. central processing unit. bow tie filters.

Central Processing Unit

Beam-shaping filters are designed to: remove higher-energy photons from the beam. change the spatial distribution of the beam. decrease subject contrast. restrict the path of photons coming from the x-ray tube.

Change the spatial distribution of the beam

The process related to the first computed tomography scanner was called: computer-assisted tomography. reconstructive tomography. Hounsfield tomography. computerized transverse axial scanning.

Computerized transverse axial scanning.

Which of the following x-ray beam geometries is used by modern, multidetector CT scanners? pencil beam cone beam fan beam pinpoint beam

Cone beam

Fourth generation scanners employed detectors that were: curved/nonrotating. linear/rotating. curved/rotating. linear/nonrotating.

Curved/nonrotating

Which of the following most closely approximates the actual radiation dose to a specific patient for a specific exam? dose length product (DLP) multiple scan average dose (MSAD) CTDI

DLP

As pitch increases, patient dose: increases. decreases. is unaffected.

Decreases

As postpatient collimation decreases, slice thickness: decreases. increases. remains the same

Decreases

As pitch increases, the z-gap _____ and image quality _____ . increases; decreases decreases; increases increases; increases decreases; is unaffected

Decreases, increases

To view a CT image on a LCD monitor, data must be undergo: digital-to-analog conversion. analog-to-digital conversion. digitization. quantization.

Digital-to-Analog conversion

All spiral-helical scanners incorporate copper brushes as a component of the slip-ring design. True False

False

One advantage of reformatting is that image detail is increased. True False

False

To achieve optimum detail and the thinnest slice possible, modern spiral-helical CT scanner x-ray tubes contain only one filament/focal spot. True False

False

Virtual reality (VR) and volume rendering imaging techniques are identical. True

False

Compared with conventional (axial) CT scanning, spiral-helical CT has: longer interscan delays. faster imaging times. increased misregistration artifacts. B and C are correct

Faster imaging times

Which generation of CT scanners is associated with the term "EBCT" and the use of an electron beam gun? seventh sixth fifth fourth

Fifth

Which of the following types of scanners used water bags? first generation only first and second generation first, second and third generation Water bags have never been used with CT scanning.

First Generation Only

Which operation forms the basis for CT reconstruction? filtered-back projection Lambert-Beer Law convolution Fourier transform

Fourier transform

First generation scanners were only capable of imaging the: head/brain. extremities. chest, abdomen and pelvis. A and B are correct.

Head/Brain

Spiral-helical scanners incorporate _____ slip rings. high-voltage low-voltage high- and low-voltage No choice is correct.

High and low voltage

Generators are often times located within the gantry. These types of generators are typically: full wave/three-phase. medium frequency. high frequency. multiwave/two-phase.

High frequency

The window width (WW) determines the: image density. image contrast. voxel depth. voxel width.

Image contrast

In multidetector CT scanning, which of the following determines slice thickness? prepatient collimators postpatient collimators image reconstruction parameters detector type

Image reconstruction parameters

When the x, y and z planes (length, width and height) are equal, the volume data set is: isotropic. linear. anisotropic. rectangle-shaped.

Isotropic

The typical modern CT scanner generator converts: low-voltage AC to high-voltage DC. low-voltage DC to high-voltage DC. high-voltage DC to low-voltage DC. low-voltage DC to high-voltage AC.

Low voltage AC to high voltage DC

Scintillation detectors are associated with _____ patient dose and _____ image noise. lower; reduced higher; reduced lower; increased higher; increased

Lower; Reduced

First generation CT scanners used _____ beam scanning. cone pencil fan pinpoint

Pencil

Which of the following is the most effective type of CT detector? scintillation xenon gas linear array photodiode

Scintillation

The CT dose index (CTDI) is most accurate when applied to: single-slice scanners. multislice scanners. helical/spiral scanners.

Single-slice scanner

All power to the gantry of a spiral-helical CT scanner is conveyed via: high-tension cables. rotating wire brushes. photon flux. slip rings.

Slip rings

In multislice CT scanners, detector systems with equal-size detector elements are called _____ arrays. linear curved adaptive symmetric

Symmetric

With respect to detectors, the term "dynamic range" refers to: detector consistency. how efficiently the detectors gather the photons coming from the patient. the accuracy of response to low- and high-energy radiation. No choice is correct.

The accuracy of response to low and high energy radiation

Partial volume averaging can be improved by using: smaller pixel sizes. a smaller SFOV. thinner slice thicknesses. a larger DFOV.

Thinner slice Thicknesses

Which generation of CT scanners was the first to use a curved array of rotating detectors? second third fourth fifth

Third

Nutating refers to the process of: tilting the detector ring. tilting the x-ray tube. tilting the gantry. translation.

Tilting the detector ring

A log amplifier calculates the amount of attenuation that occurs during data acquisition. True False

True

Absorption efficiency refers to how efficiently x-ray photons are captured by the detectors. True False

True

Image reconstruction occurs only after a scan is completed. True False

True

Radiopaque nonionic contrast agents are considered safe for pregnant patients. True False

True

Modern CT scanners have x-ray tubes designed to withstand large amounts of heat. The anode on these tubes includes a target made of: molybdenum. copper. rhodium. tungsten.

Tungsten

CT scanner x-ray tubes incorporate rotating anodes composed of: tungsten, copper and molybdenum. molybdenum, tungsten and rhodium. tungsten, molybdenum and rhenium. rhenium, tungsten and rhodium.

Tungsten, molybdenum, and rhenium

Which of the following is associated with a 3-D representation of tissue volume? matrix pixel voxel sampling

Voxel

Which of the following would most likely be associated with a CT scan of the lung? WW 80; WL 40 WW 1600; WL 300 WW 80; WL -400 WW 1500; WL - 400

WW 1500; WL - 400

Which window width (WW)/window level (WL) would be appropriate to display the lungs and air-filled spaces on a routine chest CT scan? WW 400; WL 40 WW 1500; WL -600 WW 1500; WL 600 WW 40; WL -600

WW 1500; WL -600

The recommended bone algorithm WW/WL for a routine thoracic/lumbar spine CT is: WW 2000; WL 200. WW 2000; WL 100. WW 200; WL 2000. WW 400; WL 50.

WW 2000; WL 200.

For a routine abdomen/pelvis CT, the recommended WW/WL is: WW 40-60; WL350-400. WW 1500; WL 600. WW 600; WL 1500. WW 350-400; WL 40-60.

WW 350-400; WL 40-60.

In sixth generation CT scanners, which of the following elements rotate around the patient? the x-ray tube detectors x-ray tube and detectors No choices are correct.

X-ray tube and detectors

The mathematical unit that describes shades of gray on a CT image is called: a voxel unit. the window level. the window width. a Hounsfield unit.

a Hounsfield unit

Second generation scanning employed: a pencil beam/a single detector. a fan beam/multi-detectors. more indexing (compared with first generation scanners) B and C are correct.

a fan beam/multi detectors

Compared with traditional single-slice axial scanners, helical/spiral scanners acquire images at _____ rate. a slower the same a faster

a faster

Auto milliamperage is generally used during the acquisition of: a standard convolution algorithm. a topogram a region-of-interest. interative data.

a topogram

Which of the following medications may be used to prevent nephrotoxicity? metformin acetylcysteine glucophage diphenhydramine

acetylcysteine

Filtered backprojection is most closely associated with: aliasing artifacts. ring artifacts. artifact-free images. misregistration.

artifact-free images.

Backprojection is associated with: helical/spiral scanning. pitch. increased image sharpness. artifacts.

artifacts.

What is the linearity phantom used to test? spatial resolution assignment of CT numbers to known linear attenuation coefficients contrast resolution temporal resolution

assignment of CT numbers to known linear attenuation coefficients

What does the Fourier transform calculate? projection data attenuation-to-detector time patient dose convolution

attenuation-to-detector time

Linear attenuation coefficients are directly related to: attenuation. axial scanners only. patient dose. helical/spiral scanners only

attenuation.

Dose modulation is most closely related to which of the following terms? automatic mA and convolution convolution and automatic exposure control automatic mA, convolution and automatic exposure control automatic mA and automatic exposure control

automatic mA and automatic exposure control

A topogram image for a routine abdomen CT should include the _____ to the _____ . jugular notch; pubic symphysis jugular notch; iliac crests axilla; iliac crests xiphoid tip; iliac crests

axilla; iliac crests

Tube arcing appears as a: ring artifact. streak artifact. band of increased noise across the image. cone-beam artifact.

band of increased noise across the image.

The data acquisition system (DAS) is located: between the detectors and the analog-to-digital converter (ADC). between the detectors and the digital-to-analog converter (DAC). in the gantry. between the detectors and the computer.

between the detectors and the computer.

CT fluoroscopy is especially useful for: biopsies. vessel tracking. xenon studies. VR colonography.

biopsies.

Which of the following types of beam geometry results in increased scatter? pencil beam cone beam fan beam parallel beam

cone beam

Modern multislice CT scanners use _____ geometry. fan-beam parallel-beam pencil-thin beam cone-beam

cone-beam

Which of the following is a filtering technique in which the reformatted raw data are copied to create what looks like the original raw data set? sectional reformatting mulitplanar reconstruction convolution kernel

convolution

What is the effect of increased image noise? increased contrast resolution decreased contrast resolution improved image quality A and C are correct.

decreased contrast resolution

When manipulating an image using the zoom tool, the resolution: increases. stays the same. decreases.

decreases.

Which of the following medications most likely would be used to treat urticaria (hives)? metformin dopamine naloxone diphenhydramine

diphenhydramine

A digital-to-analog converter is needed to: transform the electric signal to light. change the remnant beam to an electric signal. encode transmitted radiation into binary data. display data on a LCD monitor

display data on a LCD monitor

Which of the following is not a common contrast injection reaction? pain at the injection site metallic taste flushed feeling in the pelvis dyspnea

dyspnea

Which of the following workstation applications would most likely be used by cardiologists? ejection fraction and calcium scoring ejection fraction, calcium scoring and stereotaxis calcium scoring and stereotaxis ejection fraction and stereotaxis

ejection fraction and calcium scoring

Which of the following medications may be used to treat bradycardia? epinephrine naloxone soluMedrol diphenhydramine

epinephrine

Which of the following terms is most closely associated with image reconstruction immediately following a scan? multiplanar postprocessing longitudinal interpolation filtered backprojection interleaved sampling

filtered backprojection

Which of the following terms refers to the automatic removal of artifacts that occur in anatomy of various densities? filtered backprojection interleaved sampling z-axis filtering backprojection

filtered backprojection

In a _____ CT scanner, the x-ray tube rotates continuously around the patient as the patient travels through the gantry. third-generation high-speed helical/spiral axial

helical/spiral

The Lambert-Beer Law is most closely associated with a _____ beam. polychromatic homogeneous heterogeneous fanned

homogeneous

If extravasation occurs, contrast can be dissipated by reducing its viscosity. This can be accomplished by applying a: hot pack. cold pack. sterile bandage.

hot pack.

The term "misregistration" refers to: convolution. backprojection reconstruction. incorrect image reconstruction. noise.

incorrect image reconstruction.

Increased pitch results in: increased spatial resolution. increased image contrast. increased partial volume averaging. ring artifacts.

increased partial volume averaging.

Images acquired in ciné mode require overlapping thin data sets. This results in _____ spatial resolution and _____ patient dose. increased; decreased decreased; increased decreased; decreased increased; increased

increased; increased

In helical/spiral scanning, overlapping results in _____ patient dose and _____ spatial resolution. increased; decreased decreased; decreased increased; increased decreased; increased

increased; increased

For CT scanning, as mAs increases, patient dose _____ and image noise _____ . decreases; decreases increases; increases increases; decreases decreases; increases

increases; decreases

Image noise can be reduced by: increasing mAs. decreasing slice thickness. decreasing pixel size. B and C are correct.

increasing mAs.

Tube arcing occurs: inside the x-ray tube and outside the x-ray tube inside the x-ray tube and because of fluctuations in line voltage outside the x-ray tube and because of fluctuations in line voltage inside the x-ray tube, outside the x-ray tube and because of fluctuations in line voltage

inside the x-ray tube and outside the x-ray tube

Which of the following is not an example of a kernel? standard convolution algorithm smoothing filter edge enhancement filter interative algorithm

interative algorithm

The ability of the CT scanner to calculate image data from multiple, overlapping acquisition data sets is called _____ sampling. interpretive and interlaced interpretive, interleaved and interlaced interpretive and interleaved interleaved and interlaced

interleaved and interlaced

What does longitudinal interpolation with z-axis filtering calculate? filtered backprojection scan time pitch interslice distance

interslice distance

As the display field of view increases, the resulting radiation dose to the patient: decreases increases is not affected.

is not affected.

When a spiral-helical CT scanner takes a scout image, the x-ray tube: rotates around the patient. is stationary. can take a frontal and lateral projection at the same time.

is stationary

Which of the following terms refers to the center of the scan field? z axis target epicenter isocenter

isocenter

Which of the following terms is also referred to as a convolution algorithm? ring artifact iterative algorithm interpolation kernel

kernel

Compared to barium used for regular fluoroscopy procedures, the barium used for CT procedures is: less dense. more dense. of the same density.

less dense

A pitch of _____ results in the highest dose to the patient. 1 2 less than 1 Pitch does not affect patient dose.

less than 1

Which of the following processes is associated with reconstructing volumetric acquired data to make the data look like individual slices? backprojection linear interpolation pitch filtering

linear interpolation

Which of the following tests uses a solid plastic phantom with two holes drilled into it at 90 degrees angles to form an "X"? low-contrast resolution localization device accuracy CT numbers calibration high-contrast resolution

localization device accuracy

Which of the following is not a postprocessing technique? volume rendering image smoothing longitudinal interpolation maximum intensity projection (MIP)

longitudinal interpolation

A smoothing filter is applied to scans that display very: high contrast. high brightness. low contrast. low brightness

low contrast.

Compared with volume acquisition, axial acquisition results in: lower partial volume averaging. increased noise. thinner slices. better high-contrast resolution.

lower partial volume averaging.

Which type of postprocessing technique would most likely be used for CT virtual colonography exams? volume rendering MIP minIP shaded surface rendering

minIP

Modern CT scanners rely on _____ to process acquired data. microcomputers minicomputers mainframe computers supercomputers

minicomputer

Ghosting refers to _____ artifacts. motion cupping ring static

motion

Cone-beam artifacts only appear in _____ scanners. first generation second generation third generation multislice

multislice

Which of the following medications reverses the effects of narcotics? atropine sulfate diphenhydramine dopamine naloxone

naloxone

Xenon studies are most closely associated with: radiation oncology treatment planning. virtual reality (VR) colonography. neurology studies. cardiology studies.

neurology studies

Which of the following medications most likely would be used to treat chest pain caused by angina? nitroglycerin soluMedrol dopamine naloxone

nitroglycerin

For a routine CT scan of the neck, the gantry should: be angled perpendicular to the OML. not be angled. be angled to coincide with the OML. be angled to coincide with the MML.

not be angled.

Which of the following devices is the most accurate monitor used to measure occupational radiation exposure? film badge thermoluminescent dosimeter optically stimulated luminescent dosimeter Geiger counter

optically stimulated luminescent dosimeter

When scanning the head/brain, which radiographic baseline should be oriented parallel to the axial scan plane? mentomeatal line (MML) infraorbitomeatal line (IOML) orbitomeatal line (OML) acanthiomeatal line (AML)

orbitomeatal line (OML)

To assure fast scan times and immediate data processing, CT computers depend on: multitasking. distributed processing. multiprocessing. parallel processing.

parallel processing.

Large array parallel processors are responsible for: executing several tasks sequentially. performing numerous tasks simultaneously. hardening the x-ray beam. assessing faulty detector arrays.

performing numerous tasks simultaneously

Which of the following would normally not be used to administer contrast with a power injector? power PICC line power port-a-cath perma-cath A and B are correct.

perma-cath

Interpolation is directly affected by: A and B are correct. pitch. filtered backprojection. focal spot size.

pitch.

When image data is acquired by a CT scanner, it goes through a process known as: convolution. photon flux. digitization. quantization.

quantization

Which of the following techniques would be used for a patient who has trouble holding his or her breath or has an irregular heart beat? half-scan algorithm prospective gating smoothing retrospective gating

retrospective gating

Which of the following artifacts is a result of faulty detector elements? ring artifacts aliasing artifacts streaking partial volume averaging

ring artifacts

How can partial volume averaging be reduced? scanning with thicker slices scanning with thinner slices using a half-scan algorithm B and C are correct.

scanning with thinner slices

Which of the following techniques reduces edge gradient artifacts? scanning with thinner slices decreasing data sampling rates scanning with thicker slices using detectors with large apertures

scanning with thinner slices

Which of the following detector types produces higher quality images? gas scintillation linear

scintillation

The detectors measure the transmitted x-ray beam. The beam that has been attenuated or changed after interacting with the tissues of the patient is called the _____ beam. secondary dominant incoming primary

secondary

Which of the following International System of Units (SI) measurements is associated with monitoring radiology staff? coulomb/kilogram (C/kg) becquerel (Bq) gray (Gy) sievert (Sv)

sievert (Sv)

Partial volume averaging occurs when: similar tissue types share the same voxel. cardiac studies are performed. metal objects are present within the patient or the patient's clothing. detector elements fail.

similar tissue types share the same voxel.

Filament size is directly related to: slice thickness and spatial resolution mA selected and spatial resolution slice thickness and mA selected slice thickness, mA selected and spatial resolution

slice thickness, mA selected and spatial resolution

Which of the following factors decreases contrast resolution? smaller field of view smaller matrix size smaller pixel size higher mAs

smaller pixel size

Edge gradient artifacts appear as a: streak. ring. band of noise across the image. white circles.

streak.

Which of the following conditions is an indication for a CT scan of the head without intravenous (IV) contrast? stroke aneurysm metastatic disease arteriovenous malformation

stroke

Which of the following image manipulation tools is most useful for viewing 3-D images? zoom swivel scroll pan

swivel

The half-scan algorithm technique is used to improve: temporal resolution. uniformity. linearity. spatial resolution.

temporal resolution.

Which of the following results in higher resolution? thick collimation thin collimation Collimation does not affect resolution.

thin collimation

Spatial resolution can be improved by using: thin slice thicknesses and a matrix with large pixel sizes thin slice thicknesses and small detector sizes a matrix with large pixel sizes and small detector sizes thin slice thicknesses, a matrix with large pixel sizes and small detector sizes

thin slice thicknesses and small detector sizes

Ring artifacts only appear in _____ scanners. first generation second generation third generation multislice

third generation

When performing a routine chest CT scan, the scanner should be zeroed with the laser light at the: jugular notch. xiphoid tip. EAM. top of the shoulders.

top of the shoulders.

Cupping artifacts are most closely related to which image quality? linearity contrast resolution uniformity temporal resolution

uniformity

A topogram for a CT scan of the neck must include the ______ to the _____ . vertex of the skull ; axilla vertex of the skull ; mid-chest OML; mandibular rami OML; axilla

vertex of the skull ; mid-chest

Which of the following postprocessing techniques is referred to as 4-D reconstruction? curved multiplanar reconstruction volume rendering shaded surface rendering edge enhancement

volume rendering

Which of the following techniques requires 100% of the data set for postprocessing? volume rendering minimum intensity projection (minIP) shaded surface rendering MIP

volume rendering

When using a gonadal shield for a CT exam, the shield should be: placed anteriorly (on top of the pelvis). placed posteriorly (underneath the pelvis). wrapped 360 degrees around the patient. It is not necessary to use gonadal shielding for CT scans.

wrapped 360 degrees around the patient.