CT chapter 4

which CT scanner is based on fan-beam geometry and complete rotation of the x-ray tube and detectors

3rd generation

in which scanner is the apex of the fan-beam located outside the detector?

4th generation

which generation is classified as a high-speed scanner

5th

scanner that uses an electron gun to shoot electrons towaex a target ring is the

5th generation

Which generation of scanner, also called dual-source CT scanners, consists of two x-ray tubes and two sets of detectors?

6th

T/F first generation scanners were first to use fan-beam geometry

False 2nd generation

T/F: multirow CT detectors fall into two categories, namely, matrix array detectors and pixel array detectors

False matrix array detectors and adaptive array detectors

T/F: Gas-ionization CT detectors convert x-ray photons into electrical signals with no light conversion process in-between

True

which of the following refers to size, shape, motion, and path traced by x-ray beam as it scans the patient

beam geometry

filtration

beam hardening

What style of filter is common in CT filtration because it compensates for the difference in beam path length through the axial plane of the object such that a more uniform fluence can be delivered to the detector?

bowtie filter

the following crystals have been used in scintillation CT detectors except calcium tungstate NaI crystals calcium flouride bismuth germanate

calcium tungstate

compared with conventional CT scanners, slip-rings offer all of the following advantages except: facilitates continuous rotation of the x-ray tube capacity for interrupted acquisition protocols. minimal interscan delays elimination of start-stop process removal of wraparound process

capacity for interrupted acquisition protocols.

View in CT is

collection of rays from one translation across the object

The slice thickness in CT is determined by the :

collimator width

slip-ring design

continuous gantry rotation

which of the following refers to a method by which the patient is systematically scanned by the x-ray tube and detectors to collect enough information for image reconstruction?

data acquisition

detector electronics

data acquisition system

what detector innovation allows for acquisition for both low and high energies for every exposure in CT imaging

dual-layer detector

the ratio of the largest signal to the smallest measured by a CT detector is the:

dynamic range

refers to the ability of the CT detector to capture, absorb, and convert x-ray photons into electrical energy

efficiency

T/F Anistrophic is a term used to describe detector channels that are equal in size

false

T/F contactless slip-ring design uses a conductive wire as its sliding contact

false

T/F gas-ionization detector are prone to afterglow problems

false

T/F high-frequency generators use a low-frequency inverted circuit to convert low-voltage current from the main power supply to high-voltage current required by the CT x-ray tube

false

T/F streaking artifacts are the result of too many samples being measured by the detectors

false

T/F gas-ionization chambers where first introduced in second-generation scanners

false 3rd gen

T/F: 6th generation scanners are referred to as the cine CT scanner because of its high-speed acquisition for imaging the heart and circulation

false 5th generation

T/F: Straton x-ray tube was designed by Toshiba

false siemens

T/F: overall goal of the electron-beam CT (EBCT) scanner is to produce low-resolution images of moving organs that are free of artifacts caused by motion

false high-resolution

4th generation ct scanners are characterized by

fan-beam geometry and complete rotation of x-ray tube around a stationary ring of detectors

Scintillation

flashes of light

which x-ray generator is used in modern ct scanners

high-frequency

All of the following are radiation beams produced by an x-ray tube designed for CT except: polyenergetic polychromatic heterogenous homogeneous

homogeneous beam

What category of multirow detector array utilizes an isotropic design

matrix array detectors

total number of data samples per scn or per slice in CT

number of data samples per view times the number of views

In one type of 4th generation CT scanner, the tilting action of the detector ring is referred to as:

nutating

Collimation plays a role in:

patient dose ensures constant beam width at the detectors reduces scatter radiation

semiconductor

photodiode

the data acquisition system performs each of the following except:

powers the rotating components of the gantry Feedback: The DAS is located between the detectors and the computer, and it performs three major functions: (1) it measures the transmitted radiation beam, (2) it encodes these measurements into binary data, and (3) it transmits the binary data to the computer.

what design of collimation is influenced by size of the focal spot

prepatient collimation

Ct detectors generate a signal that represents the attenuation as the ray moves across the slice. This signal is called:

profile

The main purpose of a filter used in CT is to:

protect the patient

speed with which CT detector can detect an x-ray event and recover to detect another event

response time

which x-ray tube is most likely used in spiral/helical CT scanners

rotating anode with a rhenium tungsten disk

a single ray in computer tomography is

single straight line path of x-ray beam

method does not affect sampling information

slice thickness

collimation

slick thickness

electromechanical devices made up of rings and brushes to transmit electrical energy across a rotating interface

slip-rings

which scanner is based on slip-ring technology

spiral/ helical scanner

which scanner allows for continuous rotation of the x-ray tube while the patient moves simultaneously through the gantry aperture

spiral/helical scanner

which scanner results in a volume of the patient being scanned during single breath-hold (rather than a single slice of tissue)?

spiral/helical scanner

Which detector characteristic refers to the steadiness of the detector response

stability

T/F Adaptive section collimation is a design to overcome overscanning, an issue of exposing the patient outside the imaged range which occurs for spiral CT with multirow detectors at the start and the end of the scan.

true

T/F afterglow refers to the persistence of the image even after the radiation has been turned off

true

T/F optoelectronics refer to the used of lens and light diodes to facilitate data transmission

true

T/F: 7th generation scanners use flat-panel digital area detectors

true

T/F: photodiodes are now used in CT scintillation detectors

true

T/F: scintillation detectors convert x-ray photons to light and subsequently to electrical signals

true

T/F: the high-voltage generator of slip-ring scanners are located in the gantry

true

t/f configuration of the dual-row detector system results in faster volume coverage compared with single-row CT systems

true

which of the following is commonly used in gas-ionization CT detectors

xenon

ionization detector

xenon gas

What provides double sampling by obtaining two overlapping slices for each detector row per 360-degree rotation

z-flying focal spot technique