Chapter 15 Exam Flashcards
- Which of the following is composed of cesium iodide?
a. Conventional fluoroscopic screen
b. Intensifier input phosphor
c. Intensifier output phosphor
d. Intensifier photocathode
b. Intensifier input phosphor
- Which of the following are negatively charges electrodes plated on the inner surface of the glass envelope of the image intensifier?
a. Photocathode
b. Electrostatic focusing lenses
c. Input phosphor
d. Output phosphor
b. Electrostatic focusing lenses
- Which of the following emits electrons in response to light stimulus?
a. Conventional fluoroscopic screen
b. Intensified input phosphor
c. Intensified output phosphor
d. Intensified photocathode
d. Intensified photocathode
- What part of the image intensifier will attract the electrons and increase their kinetic energy?
a. Input phosphor
b. Output phosphor
c. Electrostatic focusing lenses
d. Accelerating anode
d. Accelerating anode
- Which of the following will occur if voltage to the electrostatic focusing lenses is increased?
a. Inversion of the image
b. Reversal of the image
c. Minification of the image
d. Magnification of the image
d. Magnification of the image
- What portion of the TV camera tube will conduct only when illuminated?
a. Electron gun
b. Target layer
c. Signal plate
d. Face plate
b. Target layer
- A signal is received by the monitor from which part of the TV camera tube?
a. Electron gun
b. Target
c. Signal plate
d. Face plate
c. Signal plate
- Which display monitor design used nematic liquid crystals?
a. LCD
b. Plasma
c. Television (CRT)
d. These gases are not used in monitors
a. LCD
- Which of the following is within the spatial resolution range of a flat-panel detector?
a. 1.0 Lp/mm
b. 2.0 Lp/mm
c. 3.0 Lp/mm
d. 4.0 Lp/mm
c. 3.0 Lp/mm
- The maximum air kerma rate for fluoroscopy is:
a. 2 R/min
b. 6 R/min
c. 10 R/min
d. 14 R/min
c. 10 R/min
- The ratio of the number of light photons at the output phosphor to the number at the input phosphor equals:
a. Brightness gain
b. Flux gain
c. Minification gain
d. Magnification gain
b. Flux gain
- What fluoroscopic operation is defined as the number of exposures per second?
a. Frame averaging
b. Pulse width
c. Pulse rate
d. Dose rates
c. Pulse rate
- The ability to adjust the collimator without exposing the patient to additional radiation is known as:
a. Frame averaging
b. Air kerma
c. Virtual collimation
d. Electrostatic focusing lens
c. Virtual collimation
- What fluoroscopic feature defines the exposure length of time during pulsed fluoroscopy?
a. Dose rates
b. Pulse width
c. Pulse rate
d. Flux gain
b. Pulse width
- Which fluoroscopic feature will minimize patient radiation exposure?
a. Frame averaging
b. Last image hold
c. Fluoro loop save
d. All of the above
d. All of the above
Operational QC testing of fluoro unit
The radiographer may be responsible for the operational inspection of the equipment
Fluoro documentation patients’ record
Fluoro machine keeps track of everything
refers to the length of each pulse
Pulse width
refers to how many pulses occur per second of operation (how many exposures occur per second
Pulse rate
Reduces patient dose and image noise by averaging multiple frames together, however, spatial resolution decreased
Frame averaging
When operating the image intensifier in magnification mode, the voltage to the electrostatic focusing lenses is ________
This increases the ability to see _____ ______, but ________ the radiation dose to the patient.
increased, small structures, increases
Digital magnification and radiation dose
Flat panel detector FOV and dynamic range
- Dynamic versions of these detectors must respond in rapid sequences to create a dynamic image.
- Have wider dynamic range, current dynamic versions are capable of up to 60 frames per second
- Present a rectangular field providing more info
The area of each pixel that is sensitive to x-ray detection materials
How much of each dexel can see x-rays (80%)
Fill factor
Advantages of a flat panel detector
- Reduce tower size, bulk, weight
- Replace spot filming
- Do not degrade with age, more durable
- Have better contrast resolution, higher DQE, wider dynamic range, rectangular field, post processing options
- Do not exhibit most image artifacts
what is indirect-capture detector made of?
cesium iodide amorphous silicon
optical lens system
is a series of optical lenses that focus the image from the output phosphor on the camera tube
What does the flat panel detector replace?
Image intensifier
- A light-sensitive semiconducting device that generates an electrical charge when stimulated by light and stores this charge in a capacitor. The charge is proportional to the light intensity and is stored in rows of pixels.
- More light-sensitive and exhibits less noise and no spatial distortion
CCD and CCD capacitor
A loss of brightness around the periphery of the image
Vignetting
When operated in the magnification mode, the voltage to the electrostatic focusing lenses is ________.
This _______ tightens the diameter of the electron stream, and the focal point is shifted farther from the output phosphor so that only those electrons from the center area of the input phosphor interact with the output phosphor, giving the appearance of magnification
increased, increase
Magnification _______ spatial resolution
increases
Magnification _______ voltage to the electrostatic focusing lenses
increases
A function of the fluoro unit that maintains the overall appearance of the intensified image by automatically adjusting the kilovoltage peak (kVp), milliamperage (mA), or both
Automatic Brightness Control (ABC)
Conversion factor measurement
An expression of the luminance at the output phosphor divided by the input exposure rate
Output phosphor illumination (cd/m^2) / input exposure rate (mR/s)
An expression of the ability of an image intensifier tube to convert x-ray energy into light energy and increase the brightness of the image in the process
Brightness gain
The reduction in the size of the output phosphor image compared with that of the input phosphor image also increases the light intensities
Minification gain
Accelerating the electrons increase the light intensities at the output phosphor
Flux gain
Not lenses but are negatively charged plates along the length of the image intensifier tube. They repel the electron stream, focusing it toward the small output phosphor
Electrostatic lenses
Changes light rays into electrons
Photocathode
Located at the neck of the image intensifier near the output phosphor. Maintains a constant potential of approximately 25 kV
Accelerating anode
made of silver-activated zinc cadmium sulfide and is much smaller than the input phosphor. Located at the opposite end of the image intensifier, just beyond the accelerating anode
Output phosphor
faces the patient, absorbs the remnant beam, and emits light in response
Input phosphor
Luminance of original fluoroscopy units
It wasn’t bright so the operator had to be in a dark room while wearing adaption goggles with red lenses
monitors that offer superior resolution and brightness over television monitors, made up of several layers
LCD (liquid crystal display)
respond is rapid sequences to create a dynamic image, capable of up to 60 frames per second
dynamic imaging
a process using a radiographic cassette to obtain an image, or uses a photo-spot camera
static imaging
what is the magnification formula?
MF = full size input phosphor / selected input phosphor
