Question 1

The CT system's ability to freeze any motion of a scanned object is termed:&#10;A) detector quantum efficiency.&#10;B) temporal resolution.&#10;C) reconstruction algorithm.&#10;D) spatial resolution.

Accepted Answer

Temporal resolution refers to the system's ability to freeze any motion of a scanned object. Detector quantum efficiency is a measure of the detector's ability to convert incoming x-rays into a measurable signal. Reconstruction algorithm refers to the mathematical process of producing an image from the raw CT data. Spatial resolution is the ability of the system to resolve small objects or details within an image.

Question 2

Contrast is adjusted by windowing,changing window width and window level.Window width determines the:&#10;A) number of gray levels displayed.&#10;B) midpoint of the gray range.&#10;C) size of the field of view.&#10;D) slice thickness.

Accepted Answer

number of gray levels displayed.

Question 3

Oral contrast for CT should be mixed so it is:&#10;A) the same as for general diagnostic examinations.&#10;B) more concentrated than for general examinations.&#10;C) less concentrated than for general examinations.&#10;D) contrast media is not necessary.

Accepted Answer

Oral contrast for CT should be less concentrated than for general examinations as it allows for better visualization of the bowel without causing artifact or obscuring lesions.

Question 4

Which two factors affect image quality in CT? (Select all that apply.)&#10;A) Spatial resolution&#10;B) Contrast media&#10;C) Noise&#10;D) Aperture size

Accepted Answer

Spatial resolution and noise are two important factors that affect image quality in CT. Spatial resolution refers to the ability of the imaging system to distinguish between two closely spaced objects, while noise is the presence of unwanted variations in image intensity. Contrast media and aperture size may also have an impact on image quality, but they are not as significant as spatial resolution and noise.

Question 5

Contrast is adjusted by windowing,changing window width and window level.Window level determines the:&#10;A) number of gray levels displayed.&#10;B) midpoint of the gray range.&#10;C) size of the field of view.&#10;D) slice thickness.

Accepted Answer

Window level determines the midpoint of the gray range displayed.

Question 6

CT detectors are most commonly _____ detectors.&#10;A) ionization (xenon gas)&#10;B) scintillation (solid state)&#10;C) thermoluminescent&#10;D) phosphorescent

Accepted Answer

CT detectors are typically scintillation detectors, which use solid state materials such as cadmium tungstate or cesium iodide to convert incoming X-rays into visible light. This light is then converted into an electrical signal, which is processed and used to create the CT image. While other types of detectors have been used in CT, such as ionization detectors, scintillation detectors are the most common.

Question 7

Which generation of CT scanners uses a dual-energy source (two x-ray tubes)?&#10;A) Third generation&#10;B) Fourth generation&#10;C) Fifth generation&#10;D) Sixth generation

Accepted Answer

The answer of Which generation of CT scanners uses a...

Question 8

CT is able to differentiate between tissues with similar densities compared with conventional radiography because of:&#10;A) digital magnification.&#10;B) the use of a computer for data processing.&#10;C) improved contrast resolution.&#10;D) axial slices.

Accepted Answer

The answer of CT is able to differentiate between tissues...

Question 9

The most significant geometric factor that contributes to spatial resolution is:&#10;A) detector aperture width.&#10;B) FOV.&#10;C) slice thickness.&#10;D) x-ray beam energy.

Accepted Answer

The detector aperture width, or the size of the collimator, directly affects spatial resolution by controlling the amount of scattered radiation and limiting the size of the x-ray beam. A smaller aperture width results in a higher spatial resolution. FOV, slice thickness, and x-ray beam energy can also affect spatial resolution to some degree, but not to the same extent as the detector aperture width.

Question 10

The measured x-ray transmission values are called:&#10;A) raw data.&#10;B) pixels.&#10;C) voxels.&#10;D) Hounsfield units.

Accepted Answer

The answer of The measured x-ray transmission values are called:&#10;A)...

Question 11

The reference material for CT is _____ and is related to the _____ of the tissue.&#10;A) water; field of view&#10;B) water; linear attenuation coefficient&#10;C) muscle; gray level&#10;D) bone; mass attenuation

Accepted Answer

The answer of The reference material for CT is _____...

Question 12

The most common reporting method of dose reporting on the present scanners is:&#10;A) multiple scan average dose (MSAD).&#10;B) computed tomography dose index (CTDI).&#10;C) dose-length product (DLP).&#10;D) computed tomography dose index volume (CTDIvol).

Accepted Answer

The answer of The most common reporting method of dose...

Question 13

An array of numbers arranged in a grid of rows and columns is called a:&#10;A) pixel.&#10;B) voxel.&#10;C) matrix.&#10;D) scan profile.

Accepted Answer

The answer of An array of numbers arranged in a...

Question 14

Dose in CT is considered to be:&#10;A) independent of size.&#10;B) size dependent.&#10;C) related to the CT numbers.&#10;D) similar to a chest examination.

Accepted Answer

The answer of Dose in CT is considered to be:&#10;A)...

Deck 25: Computed Tomography