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The advantages of large format spot film cameras, such as 100 mm and 105 mm, over smaller format cameras, such as 70 mm and 90 mm, include
improved image quality
A significant advantage of spot film cameras is
the big reduction in patient dose that their use permits
However, as the film format increases (from 70 mm to 100 mm), so do
image quality, patient dose, and heat production
Patient dose, however
is so much smaller than the dose with conventional spot film cassettes that it is almost insignificant given the small improvement in image quality afforded by cassette spot films.
What is essential to high-quality mammographic examinations?
1. Small focal spot x-ray tube
2. High radiographic contrast
3. Use of a compression device
Which of the following is (are) tested as part of a quality assurance (QA) program?
1. Beam alignment
means that repeated exposures at a given technique must provide consistent intensity
means that a given mAs, using different mA stations with appropriate exposure time adjustments, will provide consistent intensity.
The brightness level of the fluoroscopic image is dependent on
3. patient thickness.
Because the projected focal spot is greatest at the cathode end of the x-ray tube,
geometric blur is also greatest at the corresponding part (cathode end) of the radiograph
TV camera tubes used in image intensification, such as the Plumbicon and Vidicon, function to
transfer the output phosphor image to the TV monitor
Image intensification is a process that
converts the dim fluoroscopic image into a much brighter image, much like normal daylight
As x-ray photons emerge from the patient and enter the image intensifier, they
first encounter the input phosphor, which is generally composed of cesium iodide phosphors.
At the input phosphor, x-ray photons are converted to
light photons, which in turn strike the photocathode.
is a photoemissive metal (usually antimony and cesium compounds); when struck by light, it emits electrons in proportion to the intensity of the light striking it
The electrons are then directed to the
output phosphor via the electrostatic focusing lenses, speeded up in the neck of the tube by the accelerating anode, and directed to the output phosphor for further amplification.
From the output phosphor, the image is
taken by the TV camera, most often a Plumbicon or Vidicon tube, and transferred to the TV monitor
The effective energy of the x-ray beam is increased by increasing the
1. added filtration.
To maintain image clarity, the path of electron flow from photocathode to output phosphor is controlled by
controls/selects the amount of voltage sent to the primary winding of the high-voltage transformer and operates on the principle of self-induction.
The instrument that is frequently used in quality control programs to measure varying degrees of x-ray exposure is the
device used in quality control programs; it is used to give a precise exposure to a film emulsion
Several types of exposure timers may be found on x-ray equipment. Which of the following types of timers functions to accurately duplicate radiographic densities?
The important advantage of the phototimer
it can accurately duplicate radiographic densities. It is therefore very useful for providing accurate comparison in follow-up examinations, and for decreasing patient dose by decreasing the number of "retakes" required because of improper exposure.
As the CR laser scanner recognizes various tissue densities, it constructs a graphic representation of pixel value distribultion called a
the radiographer has selected a processing algorithm by
selecting the anatomical part and particular projection on the computer
The CR unit matches that information with a particular
Lookup Table (LUT)—a characteristic curve that best matches the anatomical part being imaged
histogram analysis and use of the appropriate LUT together function to
produce predictable image quality in CR.
Change is affected in
average exposure level and exposure's latitude; these changes will be reflected in the images informational numbers ("S number," "Exposure Index," etc).
Other factors affecting histogram appearance and, therefore, these informational numbers, include
selection of the correct processing algorithm (eg, chest vs femur vs cervical spine), changes in scatter, SID, OID, and collimation. In short, anything that affects scatter and/or dose
Three-phase current is obtained from
three individual alternating currents superimposed on, but out of step with, one another by 120°
All of the following statements regarding three-phase current are true
1. Three-phase equipment produces more x-rays per mAs.
2. Three-phase produces higher-average-energy x-rays than single-phase.
3. The three-phase waveform has less ripple than the single-phase.
A focal spot size of 0.3 mm or smaller is essential for which of the following procedures?
A fractional focal spot of 0.3 mm or smaller is essential for
reproducing fine detail without focal spot blurring in magnification radiography
As the object image is magnified, so will be
the associated blur unless the fractional focal spot is used
The image intensifier's input phosphor differs from the output phosphor in that the input phosphor
is much larger than the output phosphor
The image intensifier's input phosphor is
six to nine times larger than the output phosphor. It receives the remnant radiation emerging from the patient and converts it into a fluorescent light image.
the fluorescent light image strikes the
photocathode and is converted to an electron image, which is focused by the electrostatic lenses to the small output phosphor
To eject a K shell electron from a tungsten atom, the incoming electron must have an energy of at least
The biggest advantage of coupling the image intensifier to the TV camera or CCD via a lens coupling device is its
ability to accommodate cine and/or spot films
The image intensifier can be coupled to the TV camera via
a fiber optic bundle or via a lens coupling device
The big advantage of the objective lens is
that it allows the use of auxiliary imaging devices such as a cine camera or spot film camera
Which of the following x-ray circuit devices operate(s) on the principle of mutual induction?
1. High-voltage transformer
2. Filament transformer
two coils are in close proximity, and a current is supplied to one of the coils. As the magnetic field associated with every electric current expands and "grows up" around the first coil, it interacts with and "cuts" the turns of the second coil. This interaction, motion between magnetic field and coil (conductor), induces an emf in the second coil. This is mutual induction, the production of a current in a neighboring circuit.
Transformers such as the high-voltage transformer and the filament (step-down) transformer operate on
The line focus principle refers to the fact that
the actual focal spot is larger than the effective focal spot
The effective focal spot is the
foreshortened size of the focus as it is projected down toward the image receptor
What are the advantages of photospot camera imaging over cassette spot imaging during fluoroscopy?
1. Lower patient dose
2. Less interruption of the fluoroscopic examination
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