Digital Imaging Flashcards
Two Step process for image capture and readout;
uses imaging plate (IP)
Computed radiography (CR)
Combined image capture and readout; uses flat panel detectors
Direct radiography (DR)
Individual picture elements in CR
Pixel
Matrix size in CR
Field of view (collimation)
_____ pixel size = better image quality in CR
smaller
Demonstrates exposure range (S number)
Exposure index
Two step process for CR
image capture and image readout
In CR, the image receptor houses the:
imaging plate (IP)
Absorbs x-rays in CR
IP phosphor
Converts latent image into electric signal that can be digitized
CR reader
3 stages on a CR reader:
scanning, sampling, quantization
Laser scanning of the exposed IP converts the ____ into an ______.
released energy (visible light); electrical signal (voltage)
The photodetector collects, amplifies, and converts the _____ to an _____ proportional to the range of energies stored in the IP
visible light; electrical signal
How often the analog signal is reproduced in its digitized form on CR imaging
Sampling frequency
Distance between sampling points on CR imaging
Sampling pitch
Each pixel brightness value on CR image is assigned a numerical number:
quantization
number of grey shades on CR image (contrast resolution)
Pixel depth
Integrated into the flat-panel device in DR
Signal storage, signal readout, digitizing electronics
Top layer of flat panel detector
X-ray converter
second layer of flat panel detector
TFT tray
third layer of flat panel detector
glass substrate
Two types of conversion that flat panel detectors use
indirect/direct
radiation to visible light, light to electrical charge, electric signal sent to ADC for digitization
Indirect conversion
Made up of rows/columns of individual pixels
Matrix
number of bits; number of shades of gray
Pixel bit depth
Every pixel value of an image would demonstrate the photo’s:
Histogram
X-axis of an image’s histogram:
Pixel value
Y-axis of an image’s histogram:
Pixel count
Exposure histogram is compared to a:
reference histogram
An image formed by recording a continuous changing signal is known as
Analog
Which of the following measures the efficiency of a system to convert the x-ray input signal into a useful output image?
DQE
The useful signal is determined during which part of the imaging cycle?
Image sampling
In digital projection radiography, what process is used to normalize an image that has been taken with too great of an exposure?
Automatic rescaling
Which processing technique will amplify particular known frequencies in an image while suppressing others?
a. Edge enhancement
b. High-pass filtering
c. Masking
d. All of the above.
D
The active layer in a PSP plate is usually made of phosphors from what family group?
Barium fluorohalide
What device in the reader detects the light being released from the PSP plate during reading?
Photodetector
T/F: Dark line artifacts can be caused by too much kVp in an exposure.
True
What does a photoconductor do?
absorbs x-rays and produces electrical charges.
A charge-coupled device (CCD) does all of the following except:
a. Reduce the size of the projected light image
b. Transfer the image to a capacitor
c. Convert light into X-ray photons
d. Act as receptors via lenses or fiber optics
C
T/F: Digital systems are more sensitive to scatter radiation
True
What component of the CR reader converts light to an electric signal?
photodetector
When x-rays strike the PSP material, ____ is released
Light
T/F: The LUT is unique for each anatomic part
True
Europium serves as:
An activator for the phosphor
Two methods for indirect capture DR include:
Charged couple device
TFT arrays + scintillator
DR converts x-rays into:
Electrons
The scintillator for the indirect capture DR system using CCD that is made of
Cesium iodide
T/F: After the digital data leaves the ADC, the process of image formation is very different for the 3 types of DR systems
False
The ability of phosphors to emit visible light when exposed to x-rays
Fluorescence
PSP stands for:
Photostimulable Phosphor
Intensifying screens are used to:
Decrease patient exposure
The type of image receptor (IR) that uses a photostimulable phosphor to acquire the latent image is ________________.
Computed radiography
What is used to extract the latent image from an imaging plate (IP)?
Laser beam
T/F: Digital imaging systems have a wide dynamic range.
True
T/F: A 16-bit digital system would have a narrow dynamic range compared to a 12-bit system.
False
What provides an indication of patient radiation risk during a radiographic procedure?
DAP and KAP
Digital detectors that require a two-stage process to acquire and digitize the latent image include
A. flat-panel detectors indirect conversion.
B. CCD.
C. CMOS.
D. all the above.
D
The exposure latitude of digital projection radiography responds in a _______ manner.
Linear
Which radiographic image capture method uses an x-ray absorber material coupled to a thin film transistor or a charge-coupled device (CCD) to form the digital radiographic image?
FPD
