CT Exam 1 retake

On a conventional CT scan on an MDCT scanner that acquires the data from sixteen contiguous 1 mm slices in one rotation in order to have the next group of slices be contiguous at the end of the rotation the table should move ___________ mm

16 mm

Which of the following cross sectional orientations of an abdomen can be directly scanned in CT? 1. sagittal 2. coronal 3. transverse

3 only

Which of the following is a result of reducing the reconstruction FOV? 1. reduction in the ability to resolve small objects 2. decreased appearance of image noise 3. anatomical structures appear larger on the display monitor

3 only

Which of the following processes utilizes the raw data? 1. 3D surface rendering 2. multiplanar reconstruction 3. retrospective reconstruction

3 only

How many shades of gray can be found in 1 pixel of a digital image?

1

Which of the following might improve our ability to visualize a tiny lung nodule? 1. decrease the acquired slice thickness 2. decrease the reconstructed slice thickness 3. decrease the reconstruction interval

1 & 3

The slip ring on a CT scanner: 1. prevents the high voltage cable from winding up 2. advances the patient table 3. alleviates the needs for reversal of the rotating assembly to which the tube is attached

1 and 3

Which of the following is FALSE regarding the cathode and anode in a CT x-ray tube? 1. x-rays travel from the cathode to the anode 2. electrons travel from the anode to the cathode 3. the cathode rotates to keep cool

1 and 3

Which of the following is true regarding the final slice thickness of an image reconstructed from a helical scan? 1. on a single-row detector scanner, the thickness is equal to the beam collimation 2. on a multi-row detector scanner, the thickness is equal to the beam collimation 3. on a single row detector scanner, the thickness can be varied retrospectively

1 only

Collimators: 1 reduce scatter radiation 2. restrict the path of the x-ray beam 3. minimize the x-ray dose to the patient

1, 2 and 3

In order for an x-ray photon to be measured it must: 1. produce a measurable event 2. collide with a detector atom 3. enter the detector

1, 2 and 3

On a MDCT scanner, which of the following may be TRUE when acquiring thicker slices compared to thinner slices? 1. attenuation information from adjacent detector arrays is added together 2. the x-ray beam is collimated to a greater thickness 3. the same anatomical regions is scanned in less time

1, 2 and 3

Which of the following affects the slice thickness on a single- row detector scanner? 1. cathode filament 2. focal spot 3. collimation

1, 2 and 3

Which of the following is a factor in determining the attenuation of an x-ray beam? 1. the energy of the x-ray photons 2. the atomic number of the atoms in the tissue penetrated by the beam 3. the density of electrons of the atoms in the tissues penetrated by the beam

1, 2 and 3

NOT considering patient motion, and with all other factors equal, which of the following CT scanning methods generates the best image quality, free from artifacts, demonstrating the greatest detail? a. conventional scan b. localizer scan c. helical scan

a conventional scan

The CT number of water is: a. 0 b. -100 c. -1000 d. +100

a. 0

Which of the following is a result of increasing pitch? a. cover the anatomy faster without increasing the slice thickness b. decrease image contrast c. increased number of rotations necessary to cover the anatomy d. increased dose to the patient

a. cover the anatomy faster without increasing the slice thickness

Which of the following is a characteristic of CT but NOT of conventional radiography? a. cross-sectional slices b. differentiation of tissues is dependent upon x-ray attenuation c. magnetization and radio waves are used d. no ionizing radiation is used

a. cross-sectional slices

The _____ provides the electric potential difference to the CT x-ray tube a. high voltage generator b. array processor c. host computer

a. high voltage generator

Tungsten is used as the target material in a CT tube because it has a ____atomic weight and a _____ melting point a. high, high b. high, low c. low, high d. low, low

a. high, high

The anode in a CT x-ray tube rotates to: a. prevent the tungsten target from melting b. acquires angled slices c. collect data at different positions around the patient d. reduce scatter

a. prevent the tungsten target from melting

The CT x-ray tube: a. produces the beam of x-rays b. shields the patient from the x-rays c. measures the x-ray information coming from the patient d. moves the patient table during the scan

a. produces the beam of x-rays

If we want to accentuate the bony detail on a case of ankle trauma, ______ reconstruction filter would be the best choice a. a smooth b. a sharp c. a multiplanar d. no

b. a sharp

A CT artifact is: a. a parameter used to control the brightness b. an anomaly in the CT image c. used to time the injection of contrast media d. always a reason to call for repair of the CT scanner

b. an anomaly in the CT image

Attenuation data collected from the projections during a helical scan: a. is planar b. does not correspond to any one slice plane c. is the data required for multiplanar reconstruction d. is used in making the localizer image

b. does not correspond to any one slice plane

The stationary metal contacts through which electrical signals are transferred to and from the rotating slip ring are knownas the: a. detectors b. electrical brushes c. CT x-ray tube d. power supply

b. electrical brushes

The cathode filament: a. emits x-rays in response to being bombarded by fast-moving electrons b. emits electrons which travel to the anode target c. emits electrons which are attenuated by the patient's tissues d. lights up the tube so it can be serviced by an engineer

b. emits electrons which travel to the anode target

The main purpose of the detector is to: a: amplify the measured signal b. generate a measurable signal from captured x-ray photons c. limit the x-ray dose to the patient d. collimate the x-ray beam before it enters the patients body

b. generate a measurable signal from captured x-ray photons

Which of the following will increase the number of x-ray photons produced by the Ct x-ray tube? a. decreased kV b. increased mA c. decreased mA d. increased kV`

b. increased mA

Which of the following will result in displaying a wider range of CT numbers as shades of gray on the CT images? a. increasing the window level b. increasing the window width c. decreasing the window width d. decreasing the window level

b. increasing the window width

Which of the following is NOT a characteristic of a localizer image? a. it allows the operator to position slices for a helical scan b. it is a cross-sectional image c. it may be obtained in a lateral orientation d. it has lower resolution than a conventional CT image

b. it is a cross-sectional image

A pixel is a: a. bright artifact on an image b. single 2D picture element within a digital image c. row of 2D picture elements within a digital image

b. single 2D picture element within a digital image

What control does the operator have over the x-ray in the CT exam? a. the temperature and color of the x-ray can be tuned b. the energy level and the quantity of x-rays can be selected c. the volume and tone of the x-ray can be adjusted d. the phase and frequency of the x-ray can be adjusted

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

Which of the following statements is true? a. the density of a structure has nothing to do with how it attenuates an x-ray beam b. a dense structure will attenuate an x-ray beam less than a structure which is not dense c. a dense structure will attenuate an x-ray beam more than a structure which is not dense d. a structure with a low atomic number will attenuate an x-ray beam more than a structure with a high atomic number

c. a dense structure will attenuate an x-ray beam more than a structure which is not dense

Beam hardening refers to the increase in: a. number of low energy photons reaching the detectors b. number of electrons striking the anode c. average energy of the photons that reach the detector d. number of photons reaching the detectors

c. average energy of the photons that reach the detector

Which of the following is NOT on the inside of the CT x-ray tube? a. filament b. rotating anode c. collimator d. tungsten target

c. collimator

Which of the following will make the image appear darker so that bony structures can be evaluated? a. decrease the window width b. increase the window width c. increase the window level d. decrease the window level

c. increase the window level

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. increased mAs

Which of the following will yield the lowest patient dose (assuming all other parameters are the same)? a. mA = 100 1 sec rotation b. mA = 200 1 sec rotation c. mA = 100 0.5 sec rotation d. mA = 200 0.5 sec rotation

c. mA = 100 0.5 sec rotation

The material in the CT x-ray tube which is bombarded with electrons which gives off x-ray photons is known as the: a. detector b. electrical brushes c. target d. power supply

c. target

CT images which are not strictly transverse can be directly acquired by: a. turning the x-ray tube b. shielding the patient c. tilting the gantry d. collimating the x-ray beam

c. tilting the gantry

A tube voltage of ________ kV will produce x-ray photons that penetrate tissue the most easily. a. 70 b. 90 c. 100 d. 120

d. 120

A detector array: a. is stationary in all scanner designs commercially available today b. was first seen on first generation CT scanners c. rotates around the patient in all scanner designs d. allows for much faster data collection than using a single detector

d. allows for much faster data collection than using a single detector

The ADC: a. reconstructs the CT images b. controls the movement of the patient table c.provides the high voltage for the CT x-ray tube d. digitizes the attenuation information

d. digitizes the attenuation information

Though which component are most of the commands from the technologist entered? a. ADC b. amplifier c. array processor d. operators console

d. operators console

continuously, without stopping and incrementally stopping at discrete positions are typical movements of the ______ through the gantry. a. DAC b. CT tube c. detector array d. patient table

d. patient table

The attenuation information measured by the detectors is called the: a. CT image b. back projection c. filtered data d. raw data

d. raw data

Which of the following events is responsible for changing the raw data into image data? a. attenuation b. reconversion c. ionization d. reconstruction

d. reconstruction

A first generation scanner: a. produced an image in less than 5 seconds b. used multiple detectors c. used a curved array of detectors d. used a pencil beam of x-rays

d. used a pencil beam of x-rays