Test 5 - Chpt 15 & 16 Flashcards
Who invented the first commercial fluoroscope and when
Thomas Edison
1896
When was the image intensifier introduced and what did it do
1950s
- brightened image and made indirect viewing possible
What uses low mA compared to the mA used in radiographic mode (50-1200mA)
Image intensified fluoroscopy uses (0.5-5mA)
Why is low mA used for fluoroscopy?
Allows for increased exposure time
How is the continuous beam activated in fluoroscopy?
Uses a deadman’s switch
- releasing pressure applied terminates radiation exposure
The input phosphor faces the patient, absorbs the ______ and emits ______ in response
Remnant beam
Light
Emitted light exposes the photocathode which emits _______ in proportion to the __________
Electrons
Light intensity
(T/F) fewer light photons are needed to result in one emitted electron
False
Many light photons
Emitted electrons are accelerated to the output phosphor by the accelerating _____ and focused on the output phosphor by the _______________
Anode
Electrostatic focusing lenses
High energy electrons result in many what being emitted from the output phosphor, which results in what
Light photons
Increased image brightness
Expression of the ability of an image intensifier tube to increase the brightness of the image
Brightness gain
Or
Conversion factor
Brightness gain used to be found by multiplying what
Flux gain x minification gain
What maintains the overall appearance of the intensified image (contrast and brightness)
Automatic brightness control (ABC)
What automatically adjusts the kVp, mA, or both
ABC
ABC operates by monitoring what two things? (Image intensifier and output phosphor)
-Current though the image intensifier
- output phosphor intensity and adjusting the exposure factors if value falls below preset levels
(T/F) ABC can be slow to respond to changes in patient tissue thickness and density as it is moved
True
What results in increasing voltage to the electrostatic focusing lenses? What happens to the electron stream and the focal point?
Magnification mode
- the increase tightens the electron stream diameter
- focal point is shifted father from the output phosphor
What improves the ability to see small structures in fluoroscopy?
What is the con of using it?
What is it improving?
Magnification mode
Increases patient dose (not in digital tho)
Improves spatial resolution
Why does magnification mode increase patient dose?
fewer electrons are incident on the output phosphor, so the output intensity decreases, Need to increase the number of photons reaching the input phosphor
What is the misrepresentation of the true size or shape of an object
Image distortion
Unequal magnification of an image creates a ________ and loss of ______ around the ________
- Pincushion appearance / vignetting
- Brightness
- Periphery
Image noise results when what is present to create the image?
Insufficient information
Too few X-rays exposing the input phosphor results in what?
Image noise
When not enough X-rays expose the input phosphor, what results with the light production?
Not enough light is produced
- decreases the number of electrons released by the photocathode
When decreased number of electrons is released by the photocathode what results with the output phosphor?
Fewer electrons interact with the output phosphor
Solution to fixing image noise in image intensification
Increasing mA
Two television cameras commonly used with image intensified viewing systems
Camera tube
Charge coupled device (CCD)
Early versions of digital fluoroscopy added what two things between the camera tube and monitor
Analog to digital converter (ADC)
Computer
In digital fluoro, replacing the camera tube with what along with the ADC improved digital fluoro?
With a charged coupled device (CCD)
CCD does what with light, noise, and spatial distortion?
More light sensitive
Exhibits less noise
No spatial distortion
Charge coupled device (CCD) does what to spatial resolution, radiation, and patient dose?
Higher spatial resolution
Less radiation
Reducing patient dose
In digital fluoro, what is used in place of an image intensifier?
Flat-panel detector
What is used for an indirect capture and direct capture detector
Indirect - Cesium iodide amorphous silicon (common)
Direct - Amorphous selenium
What is more lighter, more compact, and produces a digital signal directly, flat (panel detector or an image intensifier)
Flat-panel detector
When Bucky is built in and can’t be removed?
When the Bucky is able to be removed and handled by the tech
Direct capture
Indirect capture
Advantages of using flat panel detectors in place of an image intensifier
- Reduced size (tower/bulk/weight)
- replace spot filming and devices
- don’t degrade with age
- less artifacts
What has better contrast resolution, higher detective quantum efficiency (DQE), wider dynamic range
(Flat panel or image intensifier)
Flat panel detector
(T/F) image intensifier presents a rectangular field providing more information
False
Flat panel detector
Detective quantum efficiency (DQE) does what to patient dose
Decrease
(T/F) selecting kVp is the same as for general radiography
True
Collimation of the fluoroscopic beam does what to the field size exposing the patient?
Decreases
What allows for virtual collimation without exposing the patient
Last image hold (LIH)
What averages multiple frames together and what does it do to spatial resolution, patient dose, and image noise
Frame averaging
- decreases
- decreases
- decreases
(T/F) the option to include the grid in fluoro is a control setting
True
(T/F) modern fluoro units allow for the selection and interchangeability of added filtration thickness or material
True
Automatic exposure rate control (AERC) automatically adjusts what to maintain exposure to the flat panel detector
Adjusts tube current, voltage, filtration, and pulse width
Electronic magnification is the selection of what and it does what to patient dose?
Of a smaller field of view (FOV)
- no change to pt. Dose
What rapidly turns the X-ray beam on and off during a fluoro operation, and it’s effect on pt. dose?
Pulsed fluoroscopy
- decreases dose
Dose rate settings provide a control of what at the flat panel detector
Radiation dose
G/cm^2
What specifies the intensity of X-rays at a given point in air at a known distance from the focal spot or source of X-rays
Air KERMA
Kinetic energy released in matter
Air KERMA is measured in what
Gray
What are other dose displays that provide indicators of patient radiation risk and should be monitored in the patient’s record?
DAP and KAP
Specialized equipment is used in imaging to do what two things?
- improve visualization
- provide important information about anatomic tissue
interventional fluoroscopy uses what technology, and _____ ______ imaging such as cardiac imaging
bi-plane technology, rapid sequence (60 frames/ sec)
what is digital subtraction?
when you can switch the whites into blacks on the image, and the opposite
what is road mapping? What does it help with?
overlaying images as contrast moves
- navigating catheters or wires through veins
Mobile X-ray units are categorized by the design of what and the types
generator
- direct power, battery power, capacitor-discharge, high-frequency
What is typically used in the OR, and what capabilities does it have?
C-arm, fluoroscopic capabilities
When using a C-arm what should be put close to the patient (above the patient) and why?
image intensifier
- lowers dose to the patient and everyone around
when using fluoroscopy, pay particular attention to the distance between ____ and _____, and the total ________.
- patient and x-ray tube
- total fluoroscopy time
What is used for feet, ankles, hands, and other small anatomy
mini c-arm
What is a portable CT scanner, that also can provide both static and dynamic ranges along with 2D and 3D?
O-arm
designed to image curved surfaces, like the mandible
panoramic x-ray
- most dentistry
evaluates patients’ bone mineral density and mass for evidence of osteoporosis
bone densitometry
the most common procedure with bone densitometry
dual-energy x-ray absorptiometry
for bone densitometry, the lower spine and hips are scanned with two ______ x-ray energies to _______ bone from soft tissue
-different
-isolate
what uses low kVp to image breast tissue having low subject contrast?
mammography
(24-34 kVp)
breast is composed of soft tissues that attenuate the x-ray beam _____
similarly
(T/F) mammographic X-ray tube is constructed of a different target material to produce more X-ray photons in the desired kVp range. What is the material commonly used?
True
- Molybdenum, rhodium, tungsten
what grid is best for mammography
lower-ration grid with lower frequency
the AEC for mammography must be more what and provide exposures to the IR
accurate in terms of reproducibility
in mammography, why is compression used? (tissue, scatter, structures)
- makes tissue thickness and optical density more uniform
- reduces scatter
- places structures closer to the IR
when using magnification in mammography, what happens to patient dose, and why is it used?
increases dose
- used to visualize small structures
Edison’s first fluoroscope was made with what type of screen that interacted with which beam?
calcium tungsten screen
interacted with the remnant beam
when was the image intensifier introduced into the fluoroscopic system?
1950s
the image intensifier did what two things?
-brightened the image
-allowed for indirect viewing of the image
brief summary of what the image intensifier does
converts the remnant beam to light, then to electrons, then back to light, which increases the light intensity
the 5 basic parts of the image intensifier
input phosphor, photocathode, electrostatic focusing lenses, accelerating anode, output phosphor
what can be attached to the fluoroscopic unit to create permanent radiographic images?
spot film of cine (movie film)
what is the input phosphor made of and where is it located in the tube?
cesium iodide, bonded to the curved surface of the intensifier tube
the cesium iodide that a part of the input phosphor does what?
absorbs the remnant x-ray photon energy and emits light in response
what is the photocathode made of and what do these materials do?
cesium and antimony compounds
- they emit electrons in response to light stimulus in a process called photoemission
the photocathode is bonded to what?
directy to the input phosphor using a thin adhesive layer
why are the input phosphor and the photocathode layers curved?
so that all of the electrons emitted from the photocathode travel the same distance to the output phosphor
what are the negatively charged plates placed along the length of the image intensifier tube?
electrostatic focusing lenses
what do the negatively charged plates (electrostatic focusing lenses) do?
repel the electron stream, focusing it toward the small output phosphor
what sets the electron stream in motion at a constant velocity?
where is it placed?
accelerating anode
- located at the neck of the image intensifier near the output phosphor
the accelerating anode maintains a constant potential of approx. what kV?
25 kV
what is the output phosphor made of and what does it do?
made of silver-activated zinc cadmium sulfide
-absorbs electrons and emits light in response
the light emitted from the input phosphor is proportional to the percentage of what?
x-ray absorption
(T/F) the ratio of light to electron emission is one-to-one
false
-takes many light photons to result in the emission of one electron
accelerating the electrons increases the light intensities at the output phosphor is called?
flux gain
the reduction in the size of the output phosphor image compared with that of the input image also increases light intensities is called
minification gain
how does minification gain make the image appear brighter?
because the same number of electrons is being concentrated on a smaller surface area
(T/F) the ability of the image intensifier to increase brightness deteriorated with the age of the tube which means more radiation is necessary to produce the same level of output brightness
true
a light-sensitive semiconducting device that generates an electrical charge when stimulated by light and stores that charge in a capacitor?
charge-coupled device (CCD)
the charge from the CCD is proportional to what and is stored in rows of what?
- the light intensity
- in rows of pixels
to digitize the CCD, the _______ between each pixel (row gates), are charged in ______ moving the signal down the _____, where it’s transferred into the _____
electrodes
sequence
row
capacitors
what is read out by the charge in each pixel?
what is read out by an electronic beam?
CCD
vidicon
for the television monitor, the control grid forms the electrons into a beam that is controlled by the what and directed to the what?
focusing and deflecting coils
-fluorescent screen
static imaging process in which standard radiographic cassette is used to obtain an image
cassette spot film,
static imaging system that is used with an optical lens system incorporating a beam-splitting mirror
film / photospot camera
when the photospot camera spot-film exposure switch is pressed, the beam-splitting mirror is moved into place, which does what?
diverts some of the beam toward the photospot camera and exposes the film
(T/F) the number of bits that the signal is divided into determines the contrast resolution (number of gray shades) for ADC
true
what material makes the flat-panel detector possible?
amorphous silicon (photodetector)
what are electronic components layered into glass substrate that include the readout, charge collector, and light-sensitive elements?
TFT array
with flat-panel, the x-ray energy is absorbed by the _____ and converted into ____ energy, which is then absorbed by the photodetectors and converted to ______ charges, which are then captured and transmitted by the ________ to the monitor for display
scintillator
light
electric
TFT array
what is used to minimize noise and amplify the signal from the active matric in flat-panel
ASIC - application-specific integrated circuits
ASIC does what for noise, readout speed, and allows for what?
minimize
maximize
- allows for switching from low dose to high does inputs (static imaging)
(T/F) flat-panel detectors also exhibit pincushion (vignetting) and S distortion artifacts
false
flat-panel detector mA range
50-1200
defines the exposure length of time during pulsed fluoro
pulse width
ability to adjust the collimator without exposing the patient to additional radiation
virtual collimation
digital subtraction techniques increase the visibility of vasculature by creating what 3 images?
precontrast, post-contrast, subtracted image
what is the mask image that will be subtracted from the post-contrast image?
precontrast image
the pre-contrast image results in an image with just the what?
contrast-filled vasculature
(T/F) mobile units that are plugged into the wall may experience fluctuations in voltage, which affects the radiation output
true
which x-ray generator needs to be plugged into the wall during operation?
capacitor discharge and high-frequency
what primarily indicates fracture risk?
what may signify the need to evaluate the patient for secondary causes of osteoporosis?
T score
Z score
aka 3D mammography
digital breast tomosynthesis (DBT)
movement of the X-ray tube and IR in opposing directions to create images in a focal plane by blurring the anatomy located above and below the pane of interest
linear tomography
(T/F) with linear tomography, the greater the amount of blurring above and below the more visible the area of interest
true
what is directly related to the tomographic angle, and what is inversely related?
direct - amount of blur created
inverse - thickness of the section
what is the fulcrum/pivot point and how can it be changed?
a fixed point that lines in the plane of interest
- the height of the fulcrum can be changed by moving the patient up/down (fixed) or the pivot point up/down (adjustable)
what lies at the level of the fulcrum, and why are structures sharper?
focal/object plane
- objects above and below are blurred
thickness or width of the focal plane is referred to as?
It’s determined by what and what is the relationship?
sections
- tomographic angle, inversely related
the smaller the tomographic angle the greater the ________?
the thickness of the focal plane
to achieve maximum blurring during tomography, the AOI should be _______ to the direction of movement
perpendicular
to achieve the required blurring during tomography what must be increased?
exposure time
