Chapter 8 Exam Flashcards
Which of the following describes the process of radiographic image formation?
a. Beam attenuation
b. Differential absorption
c. Dynamic imaging
d. Ionization
b. Differential absorption
X-rays can eject electrons from atoms. This is known as:
a. Beam attenuation
b. Differential absorption
c. Dynamic imaging
d. Ionization
d. Ionization
The x-ray interaction with anatomic tissue that is responsible for scattering is:
a. Ionization
b. Photoelectric
c. Compton
d. Absorption
c. Compton
Which of the following will increase beam attenuation?
a. Higher kilovoltage
b. Decreasing tissue density
c. Thicker anatomic part
d. Lower atomic number
c. Thicker anatomic part
Factors that decrease x-ray absorption include:
a. Increased tissue density
b. Increased x-ray beam quality
c. Increased tissue thickness
d. Increased atomic number
b. Increased x-ray beam quality
The range of exposure intensities an image receptor can accurately detect defines:
a. Pixel bit depth
b. Dynamic range
c. Ionization
d. Attenuation
b. Dynamic range
Digital image quality is improved with:
a. Larger pixel sizes
b. Smaller pixel bit depths
c. Increased tissue density
d. Larger matrix size
d. Larger matrix size
- Increasing the pixel bit depth will:
a. Decrease scattering
b. Increase contrast resolution
c. Decrease image quality
d. Increase pixel size
b. Increase contrast resolution
What type of imaging system uses an intensifying screen to convert x-rays to visible light?
a. Film-screen
b. Image intensifier
c. Digital
d. Flat-panel detector
a. Film-screen
Film-screen imaging has a wider dynamic range than digital imaging
a. True
b. False
b. False
Dynamic imaging of internal structures can be visualized with a/an:
a. Image intensifier
b. Flat panel detector
c. Film-screen
d. a and b
d. a and b
The process of differential absorption to form an image is the same for digital, film-screen, and fluoroscopy
a. True
b. False
a. True
What device receives the x-rays?
image receptor
What are the “steps” to producing an x-ray image? (after x-ray production)
- Image receptor can accurately detect a wide dynamic range of exposure intensities
- Anatomic areas of widely different attenuation such as soft tissues and bony structures can be more easily visualized because of the wider dynamic range
- Number of bits that determines the amount of precision in digitizing the analog signal and therefore the number of shades of gray that can be displayed in the image
- Determines the shades of gray displayed on the monitor
- Calculated as 2^n
bit depth
A combination of rows and columns, of small, usually square “picture elements” called pixels (how the digital image is displayed)
matrix
The range of exposure intensities an image receptor can accurately detect
wide dynamic range
For a given FOV, increasing the matrix size will _______ the pixel size and _______ image quality
decrease, increase
For a given FOV, decreasing the matrix size will _______ the pixel size and _______ image quality
increases, decrease
The amount of pixels in the image, size of the matrix
Pixel density
the difference between the x-ray photons that are absorbed photoelectrically and those that penetrate the body
Differential absorption
the reduction in the energy or number of photons in the primary x-ray beam.
- two processes occur: absorption and scattering
Attenuation
the removal of electrons from the inner shell and filling it with the outer shells. Is responsible for total absorption of the incoming x-ray photon.
- occur throughout the diagnostic range 20 kVp-120kVp
Photoelectric absorption (effect)
doesn’t provide useful information to the image, it diminishes the contrast (outer shell)
Compton scatter
What happens to PE and Compton as we increase kVp?
PE absorption decreases sharply
Compton scatter remains proportionally greater
What would a high Z# part look like on a good radiograph?
It would appear white
matter per unit volume (or the compactness of the atomic particles composing the anatomic part) also affects the amount of beam attenuation
Tissue density
Increasing density = ________ attenuation & absorption, ________ transmission
increases, decreases
Decreasing density = ________ transmission, ________ attenuation & absorption
increases, decreases
The atomic number of the anatomic part and its tissue density affect _____ _____ _________
x-ray beam attenuation
Bone attenuates x-ray beam more than _______
muscle
Muscle attenuates the x-ray beam more than ______
fat
Fat attenuates the x-ray beam more than _____
air
the thicker the atomic part, the more x-rays are needed to produce a radiographic image
Tissue thickness
Increasing thickness = _______ attenuation & absorption, _______ transmission
increases, decreases
Decreasing density = _______ transmission, _______ attenuation & absorption
increases, decreases
- incident photon interacts with an K or L shell electron, gives all of its energy to the ejected electron, photon is absorbed
- Ejected electron imparts atom with energy equal to excess binding energy
- The vacancy in K or L shell is filled by an electron from the next orbital shell (cascade effect)
- As electron drops to fill the void is sheds its excess energy as a secondary photon
photoelectric effect
- Photon ejects outer shell electron
- The ejected electron leaves atom with equal energy to the excess imparted by the photon
- The photon continues on an altered path, with less energy (longer wavelength) than before collision
compton effect
Comes from excess energy shed by electron dropping to fill void of inner orbital shell
secondary photon
half value layer (HVL)
For every 4-5 cm of tissue, the number of photons decreases by half
comes from scattered photons from the compton effect, diminishes contrast
Image fog
Unwanted exposure to the image receptor
When the attenuated x-ray beam leaves the patient, is composed of both transmitted and scattered radiation
Remnant radiation (exit)
the invisible image that exists on the exposed film before it is chemically processed
latent image
is the visible image on the exposed film after processing
Manifest image
dynamic imaging of internal structures can be visualized with a/an:
a. film-screen
b. projection image
c. spot film
d. fluoroscopy
d. fluoroscopy
total absorption of the incoming x-ray photon is the result of the photoelectric effect
a. true
b. false
a. true
which of the following will decrease beam attenuation?
a. increased tissue density
b. lower kilovoltage
c. higher z#
d. higher kilovoltage
d. higher kilovoltage
contrast resolution is the ability of the imaging system to represent 2 different structures with the same level of gray
a. true
b. false
b. false
the spatial resolution of a digital image is determined by the pixel size
a. true
b. false
a. true
