Question 1

All of the following are methods of 3D reconstruction techniques in CT except:&#10;A) volume rendering.&#10;B) maximum intensity projection.&#10;C) shaded surface display.&#10;D) pixel-voxel reregistration.

Accepted Answer

Pixel-voxel reregistration is not a method of 3D reconstruction in CT. Volume rendering, maximum intensity projection, and shaded surface display are all commonly used 3D reconstruction techniques in CT imaging.

Question 2

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

A matrix is a grid of numbers arranged in rows and columns, commonly used in mathematics and computer programming. A pixel is the smallest unit of a digital image, a voxel is a three-dimensional pixel used in medical imaging, and a scan profile is not a term commonly used in this context.

Question 3

Factors that affect image quality in CT consist of:&#10;1)spatial resolution.&#10;2)noise.&#10;3)contrast media.&#10;A) 1 and 2&#10;B) 1 and 3&#10;C) 2 and 3&#10;D) 1, 2, and 3

Accepted Answer

Spatial resolution and noise are intrinsic factors affecting image quality in CT. Contrast media is not an intrinsic factor but an external agent used to enhance image quality.

Question 4

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 most commonly solid-state scintillation detectors. These detectors use a material, often cesium iodide, that produces light when exposed to x-rays. The light is then detected by a photodiode or photomultiplier tube and converted into an electrical signal. This technology is preferred over ionization detectors because it produces less electronic noise and has a higher signal-to-noise ratio, resulting in better image quality. Thermoluminescent and phosphorescent detectors are not commonly used in CT imaging.

Question 5

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 6

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

Dose in CT is size dependent, as it varies based on the size and thickness of the patient's body part being imaged. CT scanners use a higher dose of radiation than other medical imaging techniques, so it is important to optimize the dose to minimize risk while still obtaining diagnostic images. CT dose can be adjusted based on the size and weight of the patient, as well as the type of exam being performed. CT numbers are used to generate the images and do not directly relate to dose. The comparison to a chest examination is not relevant to the question of dose.

Question 7

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 8

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

The answer of Contrast is adjusted by windowing, changing window...

Question 9

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

Dose-length product (DLP) is the most common reporting method on current scanners. It represents the product of the CTDIvol and the scan length. It takes into account both the radiation intensity and the length of the scan, making it a more accurate representation of the total radiation exposure the patient receives during the scan. The other options listed are also important measures in evaluating radiation dose, but DLP is the most commonly used reporting method.

Question 10

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, while window width controls the range of grays displayed. The other options are not related to windowing or adjusting contrast.

Question 11

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

The answer of The CT system's ability to freeze any...

Question 12

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 answer of The most significant geometric factor that contributes...

Question 13

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 14

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

The answer of Oral contrast for CT should be mixed...

Question 15

The advantages of multislice helical CT (MSHCT) include:
1)multiphase studies.
2)isotropic viewing.
3)longer anatomic coverage.

A) 1 and 2
B) 1 and 3
C) 2 and 3
D) 1, 2, and 3

Accepted Answer

The answer of The advantages of multislice helical CT (MSHCT)...

Question 16

Fourth-generation CT scanners use the following configuration:&#10;A) translate tube and rotating detectors.&#10;B) rotating tube and detectors.&#10;C) only rotating detectors.&#10;D) only rotating tube.

Accepted Answer

The answer of Fourth-generation CT scanners use the following configuration:&#10;A)...

Deck 29: Computed Tomography