Chapter 10

Approximately what percentage of the removed electrons are "trapped" in the conduction band?

50%

Which of the following statements is true concerning direct radiography (DR) systems?

Have detectors that directly capture and read out an electronic image signal

The highest spatial frequency that a digital detector can record is the

Nyquist frequency

DICOM is a standard format for digital medical images, therefore ______ allows the acquisition, display & storage of digital images.

PACS

Because digital systems are more sensitive to low-energy radiation, how can scatter radiation be effectively controlled?

Pre-exposure collimation & use of a grid

Which of the following is the correct sequence for extracting & processing the image w/the PSP plate?

Scanned by laser light, converted to electronic signal, sampling of signal, signal sent to ADC

Electronically sending radiologic images over a distance is

Teleradiology

Which of the following is true concerning direct capture DR imaging?

The DR direct-capture method does not use a scintillator, the DR direct-capture method uses a photoconductor & TFT array, the DR direct-capture method avoids the loss of resolution caused by indirect-capture methods

Which of the following statements is false concerning complimentary metal oxide semiconductors (CMOSs)

They have light sensitivity and resolution that is equal to or better that CCDs

Which of the following statements is true concerning computed radiography (CR) systems?

Use storage phosphors to temporarily store energy representing the image signal and require that the storage phosphor undergoes a process to extract the latent image.

Put the following sequence of events in this indirect capture system in order

X-rays are absorbed by the scintillator & converted to light, the light energy is then transmitted to the CCD, the CCD converts the energy to an electronic signal & Electronic signal is sent to the computer work station for processing & display

The histogram is

a graphic representation of a data set

DQE

a measure of how well the signal-to-noise ratio (SNR) is preserved in an image

The type of phosphor found in the PSP plate for computed radiography is

barium fluorohalide

The role of mAs in digital imaging includes

being the controlling factor of density, determining the quantity of radiation & patient dose, selecting optimum mAs to provide sufficient quanta to expose the receptor and avoid excessive noise

The scintillator for the indirect capture DR system that utilizes a CCD is

cesium iodide

Part of a DR system with indirect capture, the light-sensitive device that is commonly found in digital cameras is the

charge-coupled device (CCD)

The two methods for indirect capture in DR include

charge-coupled devices scintillator and TFT array

the part of a PSP plate that reduces and carries away static electricity is the

conductive layer

The values of interest (VOI)

determine what section of the histogram data set should be included in the displayed image

The value that indicates exposure to the IR w/a DR imaging system is the

dose-area product (DAP)

This part of the reader moves the PSP plate through the reader

drive mechanism

In PSP or CR imaging systems, this represents the exposure level to the PSP plate

exposure indicator

The useful imaging area of the digital receptor is the

field of view (FOV)

Sampling pitch is

how digital detectors sample the x-ray exposure

For PSP or CR imaging system, the exposure index is based on

how much exposure leaves the x-ray tube

Which of the following digital image receptors does not use a network of TFTs?

indirect capture with CCD

The trapped electrons in the conduction band of the PSP form the

latent image

The ability of a detector to resolve small structures is the

limiting spatial resolution (LSR)

The primary factor influencing contrast w/digital imaging is the

lookup table (LUT)

When the PSP plate is exposed to the laser of the reader, the energy is released and converted to a digital signal, becoming a

manifest image

The ideal expression of digital detector image resolution is the

modulation transfer function (MTF)

Primary workstation displays are used for

official image interpretation

Where is the PSP plate located?

on the inside of the cassette

The part of the reader that consists of a laser, optical filters, light-collecting, optics, and beam-shaping devices that is designed to project and guide a precisely controlled laser beam back and forth across the plate as the plate moves through the scan area is the

optical system

Part of the direct-capture DR system, the __________ absorbs x-rays and produces an electric signal

photoconductor

Amorphous selenium is used as the

photoconductor for direct capture DR imaging

The part of a reader that senses the light released from the PSP plate is the

photodector

Amorphous silicon is used as the

photodetector for indirect capture DR imaging

At the time of processing, the energy of the trapped electrons is released by exposure to a laser in a process called

photostimulable luminescence

When processing the PSP plate, the analog signal is digitized and divided into a matrix of squares. Each square is a

picture element (pixel)

This part of the plate reflects light released during the reading phase toward the photodetector

reflective layer

Digital imaging pre-processing includes

rescaling, histogram analysis

The rate at which a data sample is acquired from the detector is the

sampling frequency

A material that absorbs x-ray energy and emits visible light in response is a

scintillator

The part of a PSP plate that includes columnar crystals, resembling needles on end, is the

structured phosphor layer

The part of a PSP plate that gives some rigidity to the plate is the

support layer

Histogram analysis compares the histogram w/pre-established histograms specific to

the anatomic part being imaged

Digital imaging quality control focuses on

the display monitors and the viewing environment

If the DQE is too high

the image will be very noisy/grainy

One half of the Nyquist frequency is equal to

the spatial resolution of a digital system

In an indirect capture DR system, the electronic components that is configured in a network of detector elements is the

thin film transistor (TFT)

The placement of several CCD detectors close together to form a larger detector is called

tiling

The part of a PSP plate that includes a random distribution of crystals is the

turbid phosphor layer

Which of the following describes the extra step, and is therefore a limitation, of indirect-capture methods?

x-rays are converted to light & then to electrons

Which of the following imaging systems uses a cassette, a photostimulable phosphor plate, a plate reader, and a computer workstation?

Computed radiography

During image acquisition, the computer analyzes the histogram using

algorithms

Post-processing functions

allow changes to be made in the appearance of the digital image, are done through computer software operations, & include window width & window level adjustments

Europium serves as

an activator for the phosphor

Following the detection of the light released from the phosphor layer, the amplified signal is sent to the _____________ to convert it to a digital electronic signal for the display computer

analog-to-digital converter (ADC)