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54 Cards in this Set

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Changes a time domain signal into a frequency domain signal

Fourier Transform



Measure of the total absorption of x-rays along a straight line is referred to as:

ray sum

Basic problem in CT is the calculate:

ms for tissues form a large set of projection data

Horizontal ray sums for the pixels shown below are:




> 2 3 0 1 5 2 >

13

Back-projection technique results in:

-classical star pattern in the image


-image blur


-poor image quality and, therefore, a diagnosis cannot be made



CT scanners now use the:

filtered back-projection algorithm

Image date are obtained:

after back-projection

The first operation to which raw data are subjected is referred to as:

convolution

Belongs to class of analytic algorithms for CT:

Filtered back-projection

purpose of Ct imaging system is to:

1. Convert x-rays into digital data.


2. Detect and measure the radiation transmitted through the patient.


3. Produce, shape, and filter the x-ray beam.

Houses the x-ray tube and detectors:

Gantry



Components of the imaging system:

1. x-ray tube


2. collimator


3. detectors

Generator used in modern CT scanner:

High-frequency

Computer and image-processing systems of a CT scanner system consist of all of the following:

1. software


2. hardware


3. processing architecture

A hard copy (film image) is produced by a:

laser imager (printer)

On the control consule what controls picture contrast?

window controls (WW-window width)

CT software refers to all of the following:

1. UNIX


2. Operating systems


3. Applications software

Modular design concept is intended to:

Simplify upgrading of scanners

A hardware option for CT scanners is:

independent workstation.

The CT gantry houses all of the following except:




-the couch


-the gantry


-the xray tube


-the CPU





The CPU

Imaging system components are located in the:

Scan room

Purpose of the imaging system is to perform all of the following except:




-produce x-rays


-store images for retrieval


-collect attenuation data


-collimate the x-ray beam

Store images for retrieval

Digital image processing technique used to


modify images through a filter function

Convolution

Where images are stored in a filmless imaging department

PACS

Method of image compression that results in no loss of information during the compression process:

Lossless

Describes the beam that diverges from the x-ray tube to the outer edges of the detectors

Cone beam

Set of ray sums is:

projection

Removes the classical star pattern of the back-projection algorithm:

Filtered back projection

Result of preprocessing of the signals from the CT detectors is called:

Raw data

Refers to a defined set of instructions for solving a problem

Algorithm

First operation to which raw data is subjected to is:

Convolution

Opening in the gantry in which the patient is


positioned during scanning is:

Aperature

Mathematical technique used to estimate the value of a function form known values on either side of the function:

Interpolation

concept of modular design in CT scanner


development is intended to:

Simplify upgrading of the scanner

Gray-level mapping is also referred to as all of the following except:




-Contrast stretching


-Windowing


-Image enhancement


-Histogram modification

Image enhancement

In CT, windowing is an example of:

gray-level mapping (control control)

In CT, the window width (WW) is the:

Range of CT numbers

The window level (WL) in CT is defined as the:

Middle of the range of CT numbers

The contrast of the CT image is controlled by:

Window Width (WW)

The brightness of the image can be altered by the:

Window Level (WL)

When the Window Level (WL) changes from -100 to +400, the picture changes from:

white to black

The software program that generates sagittal and coronal images from the transaxial dataset is referred to as:

Multidectector CT

Which of the following is NOT an example of a basic visualization tool?




-image magnification


-statistics


-CT histogram


-3D imaging

3D imaging

The following are example of advanced


visualization software tools except:




-3D imaging


-CTA


-split imaging


-virtual reality imaging

split imaging

Determines image quality:

-spatial and contrast resolution


-noise


-artifacts


-radiation dose

The unit for spatial resolution of a CT scanner is:

line pairs per cm=




lp/cm

The capability of the CT scanner to discriminate small differences in tissue contrast is:

contrast resolution

Spatial resolution of the FBP algorithms is affected by all of the following except:




-detector cell width


-size of the focal spot


-slice thickness


-photon flux



photon flux

Slice thickness can be measured by:

Shallow-angled slice ramp

the pixel size in CT is equal to:

FOV/ divided by/ matrix size



CT number fluctuation from pixel to pixel in the image for a scan of water phantom is referred to as:

noise

To reduce noise (standard deviation) by a factor of 2, the dose must be increased by a factor of:

4

Which of the following produces a streak


artifact:




1. aliasing


2. metal objects


3. motion of the patient



all

Ring artifacts in CT arise from:

One of more bad detector cells