CT chapter 2 quiz

True

Collimators control the slice thickness by narrowing or widening the x-ray beam. True False

False

Detectors restrict the x-ray beam to a specific area, reducing scatter radiation. True False

True

High-frequency generators are currently used in CT. True False

False

If the patient's weight exceeds the specified limits, scanning is not possible. True False

gantry Gantries vary in size and aperture and house many of the components used to produce and detect x-rays.

The _________ is the ring-shaped part of the CT scanner.

incrementation Incrementation is also known as feed, step, or index.

The process of moving the table by a specified measure is most commonly called ________.

detector array The detector array contains detector elements which are situated in an arc or a ring. Each measures the intensity of transmitted x-ray radiation along a beam projected from the x-ray source to that particular detector element. Reference detectors that help to calibrate data and reduce artifact are included in the array.

The term __________ is used to describe the entire collection of detectors included in a CT system.

True

True or False? A microphone is a component of the gantry. True False

The fan beam The scan field of view determines the size of the fan beam and the fan beam determines the number of detector elements that collect data.

What determines the number of detector elements? The gantry The slip rings The fan beam The cooling system

The quantity of x-ray photons In CT, the x-ray beam passes through the patient's body and is recorded by detectors. Then the computer creates the CT image. The number of x-ray photons that pass through the body determine the shades of gray on the image.

What determines the shades of gray on a CT image? Air-filled structures The quantity of x-ray photons The thickness of the CT slice The scanning protocol

Slip rings Slip rings use a brush-like apparatus to provide continuous electrical power and electronic communication across a rotating surface, permitting the gantry frame to rotate continuously.

What do current systems use to rotate the gantry frame? Slip rings Collimators Recoiling system cables Detectors

It limits the amount of x-ray emerging to thin ribbons. The source collimator affects patient dose and determines how the dose is distributed across the slice thickness.

What does the source collimator do? It limits the amount of x-ray emerging to thin ribbons. It captures transmitted photons and changes them to electronic signals. It ionizes Xenon gas. It cools the imaging components.

A tube arc greater than 360°. Fourth-generation systems often use overscans to address motion artifacts.

What is an overscan? The occurrence of ring artifacts. A tube arc greater than 360°. A thin x-ray beam passed linearly over the patient. Streaking on the CT image.

feed The process of moving the table by a specified measure is most commonly called incrementation, but is also referred to as feed, step, or index.

What is another name for incrementation? overscan repositioning feed detection

Scintillation detectors Solid-state detectors are also called scintillation detectors because they use a crystal that fluoresces when struck by an x-ray photon.

What is another name for solid-state detectors? Detector bank Apertures Scintillation detectors Detector array

70 cm - 90 cm Gantries vary in total size and in the diameter the aperture. The range of aperture size is typically 70 to 90 cm.

What is the range of aperture size for a gantry? 90 cm - 100 cm 70 cm - 80 cm 70 cm - 90 cm 60 cm - 70 cm

kW The power capacity of the generator is measured in kilowatts (kW).

What is the unit of measure for the power capacity of the generator? kW HU MHU KHU

The data-acquisition system The data-acquisition system (DAS), is positioned in the gantry near the detectors.

What measures the number of photons that strikes the detector, converts the information to a digital signal, and sends the signal to the computer? An Xenon gas detector array High-frequency generators A solid-state detector array The data-acquisition system

First-generation In the first generation of scanners a thin x-ray beam passed linearly over the patient, and a single detector followed on the opposite side of the patient. The tube and detector were then rotated slightly, and the process was repeated until a 180 arc was covered.

Which generation of scanners used a thin x-ray beam passed linearly over the patient with a single detector following on the opposite side of the patient? First-generation Third-generation Fourth-generation Second-generation

Fourth-generation A fourth-generation scanner design uses a detector array that is fixed in a 360 circle within the gantry. The tube rotates within the gantry.

Which generation of scanners uses a detector array that is fixed in a 360° circle within the gantry? Third-generation Fourth-generation First-generation Second-generation

It reduces overscan. Filtering the x-ray beam also improves the quality of the image.

Which is a benefit of filtering the x-ray beam? It increases the intensity of the beam. It reduces overscan. It reduces scatter radiation. It decreases the time of CT imaging.

Xenon gas must be kept under pressure in an aluminum casing. Compared with the solid-state variety, xenon gas detectors are significantly less expensive to produce, somewhat easier to calibrate, and highly stable.

Which is a disadvantage of using Xenon gas detectors? They are highly unstable. They are more difficult to calibrate than the solid state variety. Xenon gas must be kept under pressure in an aluminum casing. They are the most expensive type of detector to produce.

High photon absorption High photon absorption is a characteristic of a solid-state crystal detector. A Xenon gas detector has moderate photon absorption.

Which is not a characteristic of a pressurized Xenon gas detector? Low-density material High stability High photon absorption No afterglow

Camera All CT scanners consist of a scanning gantry, an x-ray generator, a computer system, an operator's console, and a physician's viewing console. Many CT systems still include a laser printer for transferring images to film.

Which is not a component of a CT scanner? Computer system Scanning gantry Camera Operator's console

Low scatter suppression The optimal characteristics of a detector are 1) high detector efficiency; 2) low, or no, afterglow; 3) high scatter suppression; and 4) high stability.

Which is not a desired characteristic of a detector? Low scatter suppression Low afterglow High stability High efficiency

Data dispersal The CT process can be broken down into three segments: data acquisition, image reconstruction, and image display.

Which is not a segment of the CT process? Image reconstruction Data acquisition Data dispersal Image display

+35° The degree of tilt is usually 15 to 30.

Which is not a usual degree of tilt for a CT gantry? +35° -5° +15° -25°

Amplifier Detector elements, circuit board, photodiode, and scintillator crystal comprise a solid-state detector array. An amplifier is part of a Xenon gas detector array.

Which is not part of the structure of a solid-state detector array? Amplifier Scintillator crystal Photodiode Circuit board

tungsten Tungsten produces a higher-intensity x-ray beam because the intensity of x-ray production is approximately proportional to the atomic number of the target material.

________ is often used for the anode target material because it produces a higher-intensity x-ray beam.

slip rings Slip rings make helical scan modes possible.

________ permit the gantry frame to rotate continuously.