CT Registry Review (MIC)

In order for an x-ray photon to be measured it must:

1. enter the detector chamber

2. be absorbed by the detector material

3. be converted to a measurable event

1,2,3

Which system component converts the projection attenuation data into the proper digital form for the array processor?

analog-to-digital converter

Which of the following is NOT a function of a PACS system?

a. reconstruction of the image from the raw data

b. long term data storage

c. digital distribution of images

d. image display for the radiologist

reconstruction of the image from raw data

Which of the following is not part of the CT tube?

a. tungsten target

b. collimator

c. rotating anode

d. filament

collimator

Which of the following is FALSE regarding CT systems?

1. they are limited to nonoblique transverse scanning

2. they cannot generate a straight coronal or sagittal image

3. hey have no moving parts

1,2,3

Xrays are used in CT because:

a. they are easily produced by the high frequency generator

b. they are less harmful than the heating effects of microwave radiation

c. they penetrate the body according to specific attenuation characteristics of each tissue

d. the FDA imposes no limit on the dose to the patient

C

Most of the commands from the technologists are received by the:

operators console

Xrays are produced whenever fast moving electrons collide with any form of matter because:

The electron loses kinetic energy which is converted into the emission of an x-ray photon

The mA determines the:

quantity of x-ray photons

Which of the following is a component NOT normally located in the gantry of a modern CT system?

array processor

Tube interscan delay time refers to:

the time between the end of one scan and the start of the next scan during which the tube will cool

Increased _______ will increase the likelihood that a given x-ray will penetrate a material

1. kV

2. mA

3. exposure time

1

Which of the following are NOT commonly used on today's commercially available CT scanners?

1. xenon detectors

2. fourth-generation technology

3. continous rotation technology

1,2

Which of the following statements is FALSE regarding occurrences after an x-ray photon penetrates the detector aperture?

1. the photon can pass through the detector unmeasured

2. the photon is converted completely into a electron

3. the measured signal in enhanced by an amplifier

2

Scatter radiation is caused by:

deflections from the original trajectory of an x-ray photon through the patient

What control does the operator have over the x-rays in a CT exam?

the energy level and the quantity of x-rays can be selected

Which of the following is the standard that's used to achieve compatibility for image transfer between various imaging modalities, viewing stations, and printers in a hospital?

DICOM

The enormous heat that builds up in the CT tube is caused by what?

Collision of the electron beam with the tungsten target on the tube anode

_________________ made helical imaging possible

Continuous rotation scanners

The patient table:

a. may move continuously during the scan

b. can never be positioned automatically by software due to safety precautions

c. remains stationary through the exam once it is initially positioned

d. only moves after each slice is completed

A

The main purpose of the detector is to:

capture x-ray photons and convert them to a measurable signal

The cathode filament:

helps determine the size of the focal spot

Which of the statements in TRUE:

1. kV is the voltage potential between the tube cathode and anode while mA ultimately controls the filament temp of the cathode filament

2. kV controls the energy level of the x-ray photons and mA controls the number of x-ray photons emitted from the tube

3. although kV and the mA affect the operation of the CT x-ray tube, the two parameters have no bearing on the image quality

1,2

The number of electrons that flow from the cathode to the anode is controlled by the:

mA

Which of the following is TRUE regarding solid state detectors:

1. x-ray photons cause the detectors to generate a flash of light

2. they are the detector type used on most CT scanners

3. they can be used in both third-generation and fourth-generation CT systems

1,2,3

The slip ring on continous rotation CT scanners:

1. prevent the high voltage cable from winding up

2. allows the exam to commence more rapidly

3. eliminates the need for the reversal of gantry frame rotation

1,2,3

CT is commonly referred to as all of the following except:

1. computerized axial tomography

2. digital subtraction angiography

3. CAT-scan

4. computed tomography

2

Which of the following CT scanner designs does NOT use an x-ray tube?

1. first generation

2. PET/CT

3. electron beam CT

4. MDCT

3

__________ allows remote authorized individuals to connect to a server in a secure fashion using the routing infrastructure provided on a public network, such as the internet.

VPNs (virtual private networks)

Which technology do multi-row detector scanners employ?

third-generation

Which of the following statements is FALSE regarding the collection of CT data?

1. long scan times are more desirable because they average out motion artifacts

2. reconstruction process used to create the image occurs in the array processor

3. to collect the complete st of CT data, x-rays must be passed through the body at many different angles

4. the detectors measure the x-rays which completely penetrate the patient

1

On a single-row detector scanner, collimation:

1. controls the slice thickness

2. minimizes the x-ray dose to the patient

3. reduces the detection of scatter radiation

1,2,3

In a radiology department, a ________________ is a example of a "client" on the network:

a. CT scanner

b. viewing console in the physicians reading room

c. printer for diagnostic images

a,b,c

Which of the following is TRUE regarding multi-row detector for CT scanners?

1. size of the detector arrays along the z-direction may be different

2. the attenuation information from adjacent detector arrays may be added together to generate thicker slices

3. all of the detectors arrays may or may not be used

1,2,3

The CT x-ray tube rotates around the patient to:

1. keep the tube cool

2. generate projection views at different angles

3. minimize the x-ray dose administered to the patient

2

Collimation:

1. accomplished by electrically blocking x-rays

2. affects scan time

3. limits low every x-ray photons and passed high energy photons

4. is accomplished by physically blocking x-rays

4

Tungsten is used as the target material on the tubes anode because it has a _________ atomic number and a _________ melting point

1. low, high

2. high, low

3. low, low

4. high,high

4

CT images can be directly scanned in planes other than transverse by:

1. orienting the patient's body part so that it is not perpendicular to the x-ray beam

2. tilting the gantry

3. changing the angle that the x-ray beam leaves the tube

1,2

Which of the following does NOT affect the quantity of x-rays that completely penetrates the patient?

1. the distance that the x-ray photons must travel on their course through the body

2. the molecular composition of the tissues through which the x-ray photons pass

3. the type of detector material used

3

The operators console may include

1. monitor

2. keyboard

3. graphic input device

1,2,3

___________ is the mathematical process used by single-row detector scanner to reconstruct CT images from raw data

Filtered back projection

MDCT scanners capable of collecting 64 slices in a single rotation do NOT:

a. perform conventional CT scans

b. perform helical CT scans

c. use filtered back projection as their method of image reconstruction

d. perform localizer scans

C

The x-ray beam used in CT scanning is ___________ the patients tissues.

1. reflected off of

2. attenuated by

3. generated by

2

A retrospective reconstruction, in which the reconstruction field-of-view is varied, uses:

a. reconstructed image in the sagittal plane

b. CT raw data

c. more photons

d. CT image data

C

CTA images come from a _____ scan.

1. conventional, or serial

2. helical

3. localizer

2

The actual attenuation data measured by the detectors from all projections during a scan is contained in CT ___________ data

raw

Using _______ reconstruction filter would decrease the appearance of noise in a CT image.

1. no

2. a sharp

3. a smooth

3

A kernel is a:

a. component in the x-ray tube

b. post processing filter applied to image data

c. type of detector

d. filter applied to the CT raw data

D

Iterative reconstruction is:

a. type of image reconstruction method used in CT before multi-row detector scanners were available

b. complex cycle of correction calculations applied during image reconstruction in order to reduce noise in the image

c. second reconstruction process performed after initial reconstruction in which a set of modified parameters is used

d. typically performed on helical image data, to generate images in orientations other than those that can easily be directly acquired with CT

B

From which of the following can the most diagnostic multi-planar reconstructions be generated?

1. stacked transverse images from helical scan

2. stacked transverse images from conventional, serial scan

3. stacked localizer images

1

A pixel is a:

single 2D picture element within the image plane

In a ______, the highest pixel values from a stack of CTA images are projected along many "rays"

MIP

If an image matrix has 360 rows and 360 columns, how many pixels are there in the image?

a. 21,600

b.129,600

c. 259,200

d.379,800

B

Important clinical benefits of iterative reconstruction include:

1. ability to reduce radiation dose without compromising image quality

2. no longer needing to perform multi-planar reconstructions

3. reduction in noise seen in the image

1,3

Which statement is FALSE regarding 3D SSD?

a. helical image data is well suited for 3D SSD because there is minimal misregistration or gaps

b. the volume data, form which the 3D SSD is generated, is created by combing transverse, sagittal, and coronal recons.

c. the tissue surface may be selected by using a threshold vaule equal to the tissue's CT number

d. patient motion during the scan is detrimental to the quality of the 3D images

B

What is 3D SSD?

3D (Shaded surface display) Reconstructed images of the surfaces of anatomical structures

A helical scan performed on a 64 slice MDCT scanner is reconstructed with:

Cone beam recons

A CT manufacturer has a scanner in which the focal spot of the x-ray beam can move to two, slightly separated, distinct locations. What benefit does the dual focal spot provide compared to an identical scanner possessing a single focal spot?

The number of projections is doubled

A __________ scan uses only a single projection

Localizer

What does convolutin do to the image quality when it is added to the back projection reconstruction process?

a. normalizes the attenuation coefficients to ensure tissues are displayed with correct CT numbers

b. increases the number of projection thereby reducing streaking artifacts.

c. improves contrast resolution by reducing scatter radiation

d. enhances important characteristics of attenuation profiles thus reducing streak and star artifact

D

The ______moves during a helical scan on a third generation scanner

1. x-ray tube

2. patient table

3. detector elements

1,2,3

Which of the following is a reconstruction technique applied to the raw data after the primary reconstruction has already been accomplished?

Retrospective recontruction

A smooth, or low pass, reconstruction filter is typically NOT selected for a(n) _____ exam.

a. pituitary

b. kidneys

c. liver

d. IAC (internal auditory canals)

D

Which is NOT an advantage of a helical study compared to a conventional serial CT study?

1. minimal anatomical misregistration sometimes caused by inconsistent breath-holding

2. shorter total exam time

3. can retrospectively reconstruct a slice at any arbitrary position

4. offers the best image quality for a brain exam

4

An increase in ___________ does NOT occur in the resulting images when applying a sharp, or high-pass reconstruction filter during the image reconstruction of CT raw data.

1. contrast resolution

2. edge enhancement

3. appearance of noise

1

Which of the following utilizes convolution?

1. 3D SSD

2. Fourier tranform

3. filtered back projection

3

_____________ yields an image that appears 3D but also shows anatomical details above and below 3D surfaces

VR (volume rendering)

Which type of storage media may hold CT image data?

1. internal hard disk

2. CD

3. re-writable optical disk

1,2,3

____________ may have to be edited from the data set to get a diagnostic MIP of a CTA exam

Bones

In which technique are tissues other than the surface of a structure excluded by setting a threshold value and eliminating pixels above or below that threshold?

3D shaded surface display

Which statement is TRUE:

1. amplified electrical signal obtained from detectors must be digitized

2. digital CT images are numerical representations of cross-sectional anatomy

3. digital signals may be formed by sampling analog signals at discrete time intervals

1,2,3

Muti-planar reconstructions are performed on which of the following:

a. image data

b. raw data

c. attenuation profiles

A

____________ allows helical data to be converted into planar raw data

Interpolation

Which of the following may occur during the interscan delay of a conventional or serial CT scan, performed on a continuous rotation scanner?

a. table position is incremented

b. tube continues to rotate in same direction as during scan

c. tube assembly makes a 360 degree rotation

a,b,c

On a third generation single row detector scanner, if there are 750 detectors and there are 900 projections in a full rotation, how many samples of attenuation data are collected for the raw data of a single slice if the scan call for an overscan of 400 degree rotation.

715,000

The _______________ determines the intensity of the laser beam in a laser camera

1. intensifying grid

2. pixel values in the image data

3. magnifying power of the lens

2

The pencil thin section of the x-ray fan beam that strikes a single detector is called a :

a. line

b. projection

c. view

d. ray

D

3D shaded surface displays are performed on CT:

1. image data

2. raw data

3. attenuation profiles

1

Which of the following is TRUE regarding the slice thickness of an image reconstructed from a helical scan

a. on a multi-row detector scanner the thickness is equal to the beam collimation

b. on a single-row detector scanner, the thickness is equal to the beam collimation

c. on a multi-row detector scanner the thickness is always equal to the detector size

B

MIP images:

a. are most frequently used for visualizing air filled spaces

b. can NOT be run in a cine loop

c. are most accurate when a large volume of interest is selected

d. do NOT demonstrate detail beneath the brightest pixel

D

Which of the following determinants of CT image quality is responsible for how grainy or speckled a CT image appears

Noise

An increase in ________ will result in hardening of an x-ray beam

1. tissue density

2. tissue thickness

3. kVp

1,2,3

Which of the following are possible results of partial voluming

1. decreased sharpness

2. misleading CT numbers

3. improvement in resolution

1,2

Which of the following is FALSE about the spatial resolution of an image

a. resolution is dependent on matrix size

b. resolution is dependent on reconstruction OB

c. resolution is dependent on scanned FOV

3

Which of the following is NOT directly proportional to mAs

1. the mean energy of the x-ray photon leaving the tube

2. number of x-ray photons leaving the tube

3. x-ray tube heating

4. dose to patient

1

Which of the following has the highest patient dose assuming all other parameters are the same

1. mA=200, rotation time=2 seconds

2. mA=200, rotation time=1 second

3. mA= 150, rotation time= 3 seconds

4. mA=400, rotation time=1 second

3

What will result in a increased voxel size?

increased slice thickness

What is the conversion equation from CT number to Hounsfield unit?

CT number= Hounsfield unit

If the radiologist requires 2 mm thick contiguous slices through the pituitary, and 2.4 cm of coverage, ___ slices are necessary?

a. 8

b. 10

c. 12

d. 13

C

CT number ____________ would appear black if a window width of 400 and a window level of -100 are used.

Below -300

If a reconstruction FOV of 32 cm and a 512x512 matrix are used, the pixel size is ________mm.

0.625 x 0.625

Which of the following is a reason to increase pitch?

a. greater volume of anatomy can be covered in a given time

b. given volume of anatomy can be covered faster

c. radiation dose to the patient can be increased

a,b

Which of these would be used to better visualize low contrast resolution:

1. decreased mAs

2. sharp reconstruction filter

3. narrow window width

3

Increasing ___________ results in lowering the patient dose

1. pitch

2. mAs

3. table increment

1,3

If a thin slice is used, which of the following would help reduce the apparent image noise?

a. reduced reconstruction field of view

b. increased matrix

c. increased mAs

d. increased kVp

C

A set of images is reconstructed with a 150 mm reconstruction FOV. Keeping all other parameters constant, a second set of images is reconstructed with a 300 mm reconstruction FOV, and then magnified so that the anatomical structures in the first and second set appear the same size. Which of the following statements is FALSE?

1. the resolution of the second set of image is better then the first set

2. the apparent noise in the second set of images is more pronounced than the first set

3. the patient dose of the first set of images is higher than the second set

1,2,3

The ___________determines how penetrating the x-ray beam will be

kVp

The smallest object that can be resolved if a reconstruction FOV of 24 cm and a 512 x 512 matrix are used is ____________mm.

.47

Which of the following parameters affects the contrast of a CT image?

kVp

Which of the following values for pitch would stretch the x-ray helix the most?

a. 1.5

b. 1.0

c. .8

d. 05

A