Chapter 25 & 18 of Bushong/ASRT Article (Fluoroscopy & photometric quantities)
Time required by the eye for recognition of an image (integration time) is _____ second
0.2
The lead thickness for the Bucky slot cover of the fluoro table must be at least: _______ mm Pb equivalent
0.25
The lead thickness used for the protective curtain in fluoro must be at least: ______ mm Pb equivalent
0.25
Lead glasses should have a minimum _______ mm Pb equivalent.
0.35 mm lead
Gonad shielding should be _________ lead (Pb) equivalent for the patient
0.50
Radiation doses to the lens of less than ___ Gy may be sufficient to cause cataracts.
1
The target assembly (serves as an anode) is located in the vidicon camera tube and has 3 layers starting from the outer most layer: 1. 2. 3.
1.) The window (thin part of the glass envelope) 2.) The signal plate (metal or graphite coating on the inside of the window) 3.) The target (photoconductive layer made of antimony trisulfide applied to the inside of the signal plate.
A primary barrier in which the x-ray beam can point to the wall during a particular exam should be 7ft tall and contain ________ inch lead.
1/16 (1.6 mm)
1 foot-candle (fc) = _________ lux (lx)
10.8
A 1024 x 1024 image matrix is described as a __________-line system for digital fluoroscopy.
1000
Fluoro ESE is limited to?
100mGy/min Note: Federal law under normal operation, shall not exceed this.
Photospot cameras recored images at a rate of _____ images per second.
12
The image intensifier replaced the conventional fluorescent screen, which had to be viewed in a darkroom & then only after _____ minutes of dark adaption
15
The International Commission on Radiological Protection (ICRP) has established the annual limit for occupational exposure to the eye lens at _________ .
150 mSv or (15,000 mrem) note: Failure to use radiation protection equipment during high-dose fluoroscopy can result in doses of 10 to 50 mSv per hour - doses that are sufficiently high to cause lens opacities & cataracts over a period of several years.
The fluoroscopic image receptor must be ______ -mm lead equivalent and is the ______________ _______________ ___________, intercepting the useful x-ray beam.
2 primary protective barrier
The minimum required HVL for fluoroscopy is _________ mm aluminum equivalent at 80 kVp. But it is suggested that the HVL at 80 kVp should be increased to _____ mm aluminum equivalent to reduce patient dose.
2.3 mm 3.0 mm Note: 70 kVp & above = 2.5 mm according to the NCRP
The total filtration, which includes the tabletop, patient cradle or other material positioned between the x-ray tube and the tabletop, must be at least _______ mm aluminum equivalent.
2.5 note: However to reduce patient dose, recommendations suggest that the aluminum HVL should be 3.0 mm aluminum at 80 kVp.
Multifield Image Intensifier tubes come in various sizes, but perhaps the most popular is?
25/17/12 cm note: these refer to the diameter of the input phosphor.
Video monitoring uses a rate of _____ frames per second.
30 note: At a frame rate of 30 per second, each frame is 33 ms long.
According to the FDA, the minimum SSD (the distance between the x-ray tube & the patient) when using mobile fluoroscopic device (C-arm) must be no less than ______ cm.
30 cm (12 inches) note: You can place a 12" spacer on the tube side of the c-arm as a reminder to keep distance.
The entrance skin dose (ESD) for an adult averages _____ to _____ mGy/min during fluoroscopy.
30 to 50 note: This can easily result in a skin dose of 100 mGy for many fluoroscopic examinations...
To ensure that the operator is aware of the relative beam-on time during each examination, a cumulative timer produces an audible signal when fluoroscopic time exceeds?
5 minutes Note: Technologists should recored total fluoroscopy beam-on time for each patient exam.
The Image intensifier tube is about ______ cm long.
50 cm (20 inches)
The brightness gain of most intensifiers is ____________ to _______________, and it decreases with tube age and use.
5000 to 30,000 note: As an image intensifier ages, patient dose increases as a consequence of maintaining image brightness.
Standard broadcast & closed circuit televisions are called ________ line systems while special purpose systems have 875 or 1024 lines/frame which equals better spatial resolution (important in digital fluoroscopy).
525 note: A 525-line TV system provides a spatial resolution of approximately 1 lp/mm.
The _______ feature keeps the overall image brightness at a constant level.
ABC (Automatic Brightness Control)
Should the X-ray tube be positioned closer to the patient or further away from the patient during fluoroscopy?
As further away as possible! Note: Increasing the distance of the X-ray tube from the patient means that the dose to the patient's skin will decrease according to the inverse square law
This allows the Radiologist to select image brightness levels that are maintained automatically by varying the kVp, the mA, or both. This feature of the fluoroscope is called?
Automatic brightness control (ABC) note: function is to maintain a consistent overall appearance of the image by automatically adjusting the kVp and/or mAs
Magnification mode results in: 1. 2. 3.
Better spatial resolution Better Contrast resolution Higher patient radiation dose
Photopic: Is ________ light vision with the ________of your eyes and is best at _______nm.
Bright cones 555
Newer fluoroscopy systems have digital imaging equipment such as a _______________________ or a ______________________.
CCD (charged-coupled device) video flat-panel detector
middle layer of the eye, which is interlaced with many blood vessels called the?
Choroid note: also called the, "Tunica vasculosa" or "uvea"
The ______________ ___________ is the proper quantity for expressing image intensification.
Conversion factor note: Brightness gain is now defined as the ration of illumination intensity at the the output phosphor, (cd/m2) to the radiation intensity incident on the input phosphor, (mGy/s).
_______________ law is important when describing the luminous intensity of a digital display device like a monitor. Luminous intensity falls off rapidly as one views a digital device at larger angles from perpendicular.
Cosine law note: Luminous intensity decreases in proportion to the inverse square of the distance from the source. "this is the famous inverse square law"
The __________ always is measured from the surface closest to the x-ray source.
ESE (Entrance Skin Exposure) Example: If the operator moves the c-arm to obtain a lateral image with the IR on the patient's left side, the ESE is measured from the surface closest to the x-ray source.
Television camera tubes & CCDs are coupled to an image intensifier tube in two ways: 1.) 2.)
Fiberoptics (simplest method) Lens system
_______________________ delivers the highest occupational radiation doses experienced by radiologic imaging personnel.
Fluoroscopy
The ratio of the number of light photons at the output phosphor to the number of x-rays at the input phosphor is the?
Flux gain note: Flux gain = # of output light photons/# of input x-ray photons.
The _________________ converts the incident x-rays into a miniature visible light image, amplifying image brightness by about 10,000.
Image-Intensifier
The _________ ________________ converts the x-ray energy into visible light
Input phosphor
X-rays incident on the glass envelope of the image-intensifier tube first interact with the _________ ______________.
Input phosphor
Is there a well-established, "safe" level of ionizing radiation for the eyes? Yes or No?
NO!
The _________ ________________ is the site where accelerated electrons interact & produce light.
Output phosphor
__________________ is electron emission that follows light stimulation.
Photoemission note: The term is similar to thermionic emission.
The _______________ ____________ is similar to a movie camera except that it exposes only one frame when activated. receives its images from the II tube and requires less patient dose.
Photospot camera
________________ ____________ require less patient exposure than cassette-loaded spot films. They expose only one frame at a time when activated.
Photospot cameras
Back in the early days Radiologists had to undergo dark adaption which is when they sit in a dark room before the procedure to allow their eyes to adjust. This activates the _________ of the eyes found on the retina of the eye. This type of sight is known as ____________ vision. Often Radiologist used red tinted glasses to help their eyes adjust.
Rods scotopic
What radiologic positioning method is used for abnormalities of the optic foramen?
The Rhese position
Support pads should be designed to minimize attenuation. __________ foam pads may be acceptable for fluoroscopy.
Thin note: Thick gel pads have been associated with excessive attenuation.
Does use of cassette-loaded spot films increase patient radiation dose? True or false?
True note: produce high quality images
Cassette-Loaded Spot Films have a higher spatial resolution then photospot camera? True or false?
True note: spatial resolution for cassette-loaded spot film is 8 lp/mm verses photospot at 5 lp/mm.
Fluoroscopic television operates at a frame rate of: a. 30 frames per second b. 60 frames per second c. 2621⁄2 frames per second d. 525 frames per second e. 1024 frames per second
a. 30 frames per second
Horizontal television resolution is limited principally by which of the following? a. Bandpass b. Field rate c. Frame rate d. Lines per frame e. Modulation
a. Bandpass note: the higher the bandpass the better the horizontal resolution.
What is the most important component of a television monitor? a. Cathode ray tube b. Charge-coupled device c. Coupling device d. Electromagnetic coils e. Television camera tube
a. Cathode ray tube note: It is the "heart" of the television monitor. Also called a television picture tube & similar to a television camera tube but much larger & with an anode assembly that consists of a fluorescent screen & graphite lining.
What is the photoemissive component of image- intensified fluoroscopy? a. Cesium iodide b. Electrons from light c. Minification d. Synchronized e. Vidicon
a. Cesium iodide
Which of the following structures is most sensitive to color? a. Cone b. Fovea centralis c. Rod d. Cornea e. Iris
a. Cone note: cones permit color vision
Which of the following is the component of the image intensifier responsible for focusing the electron beam? a. Electrostatic lens b. Glass envelope c. Input phosphor d. Output phosphor e. Photocathode
a. Electrostatic lens (focusing) note: located along the length of the image-intensifier tube. maintains proper electron travel from cathode to anode & the electron path must be reduced to the smaller output phosphor. (electron optics).
Image-intensifier brightness gain increases with increasing: a. Flux gain b. kVp c. mA d. Output phosphor size e. Radiation exposure
a. Flux gain
The minification gain of an image intensifier increases with increasing: a. Input phosphor size b. kVp c. mA d. Output phosphor size e. Tube voltage
a. Input phosphor size
An image that displays vignetting: a. Is dim around the periphery b. Isdiminthecenter c. Has higher contrast resolution d. Has higher spatial resolution e. Shows the barrel stay artifac
a. Is dim around the periphery note: a reduction in brightness at the periphery of the image.
What is the function of the iris? a. To control the light level b. To distinguish colors c. To focus the light onto the retina d. To protect the eye e. To sense visible-light photons
a. To control the light level
Scotopic vision is associated with: a. dim vision b. cone vision c. day vision d. black & white vision
a. dim vision note: Rods of the retina are primarily used for dim vision "night vision"
A loss of image brightness or intensity around the periphery of the image is called? a. vignetting b. lag c. veiling glare d. pincushion distortion e. S distortion
a. vignetting
Fluoroscopy normally requires a tube current of: a. 0.1 to 1.0 mA b. 1 to 5mA c. 5 to 10mA d. 10 to 100 mA e. 10 to 1000 mA
b. 1 to 5mA note: compared to radiography tube current, which is measured in hundreds of mA
The ability of an image intensifier to enhance image illumination is called: a. Automatic brightness b. Brightness gain c. Flux gain d. Illumination gain e. Minification gain
b. Brightness gain
In an optical coupling arrangement, which is nearest the television camera? a. Beam splitter b. Camera lens c. Deflection coil d. Mirror e. Objective lens
b. Camera lens
The luminance of a mammography view box must be uniform and at least 3000 nit. What is a nit? a. Candela per foot squared b. Candela per meter squared c. Lumen per foot squared d. Lumen per meter squared e. Lumen per steradian
b. Candela per meter squared (Candela/m2)
The luminance of a digital display device is measured in: a. Candelas b. Candelas per meter squared c. Foot-candles d. Lumens e. Luxes
b. Candelas per meter squared (candelas/m2) note: or expressed in "nit"
If an image intensifier is described as a 25⁄12 tube, 25⁄12 refers to which of the following? a. Area of the input phosphor in square inches b. Diameter of the input phosphor in centimeters c. Diameter of the output phosphor in centimeters d. Radius of the input phosphor in inches e. Radius of the output phosphor in centimeters
b. Diameter of the input phosphor in centimeters
Compared with a radiographic examination, the primary purpose of a fluoroscopic examination is to visualize: a. Cross-sectional images b. Dynamic images c. Longitudinal images d. Static images e. Transverse images
b. Dynamic images note: Dynamic studies are examinations that show the motion of circulation or the motion of internal structures. Provides real-time dynamic viewing of anatomic structures.
For upper GI exams during fluoro, the radiologic technologist should stand: a. In the exam room next to the Radiologist b. In the exam room behind the Radiologist or in the control room c. In the control room only d. At the head of the Patient e. At the feet of the patient
b. In the exam room behind the Radiologist or in the control room
Photoelectric emission: a. Is the emission of electrons from a heated wire b. Is the emission of electrons from an illuminated surface c. Is the emission of photons d. Occurs at the input phosphor of an image-intensifier tube e. Occurs at the output phosphor of an image- intensifier tube
b. Is the emission of electrons from an illuminated surface note: The photocathode emits electrons when illuminated by the input phosphor.
Automatic brightness stabilization (ABS) is designed to compensate for changes in which of the following? a. Examination time b. Patient composition c. Patient dose d. Patient positioning e. Technique selection
b. Patient composition
Where are rods & cones located in the eye? a. Iris b. Retina c. Fovea centralis d. Pupil e. Cornea
b. Retina
The photocathode converts: a. Electrons into visible light b. Visible light into electrons c. Visible light into x-rays d. X-rays into electrons e. X-rays into visible light
b. Visible light into electrons
Fluoroscopic image recording: Which recording system has the highest patient dose? a. photospot b. cinefluorography c. video tape d. cassette-loaded spot film e. DR recording systems
b. cinefluorography note: video tape has the lowest pt dose.
Photopic vision is associated with: a. night vision b. cone vision c. dim light d. black & white vision e. rod vision
b. cone vision note: cones of the retina are primarily used for day light vision
This artifact degrades the resolution of the final image and is caused by luminescence after x-ray stimulation. (property of vidicon tubes whereby the image is blurred when the fluoro carriage is moved rapidly over the patient). a. vignetting b. lag c. veiling glare d. pincushion distortion e. S distortion
b. lag Note: not caused by the II tube...
In digital fluoroscopy, spatial resolution is determined by both the?: a. bit depth, matrix size b. matrix size, size of the II tube c. size of the II tube, bit depth d. pixel size, bit depth
b. matrix size, size of the II tube note: spatial resolution is determined by both the image matrix & the size of the image intensifier. Also the smaller the pixel & the larger the matrix size, the better the image resolution. spatial resolution is limited by pixel size.
The ____________ is expressed in frequency (Hz) & describes the number of times per second that the electron beam can be modulated.
bandpass
The fluoroscopy operator's single best way to limit dose is to restrict the _________ - ____ ___________
beam-on time note: Beam-on time is a key factor in patient & staff dose.
The ability of the image intensifier to increase the illumination level of the image is called its?
brightness gain. note: Brightness gain = Minification gain X Flux gain
Which of the following is the input phosphor of image intensifiers? a. Cadmium tungstate b. Calcium tungstate c. Cesium iodide d. Sodium iodide e. Zinc cadmium sulfide
c. Cesium iodide
The rods are used principally for which of the following? a. Bright vision b. Color perception c. Dim vision d. Focusing e. Visual acuity
c. Dim vision
What unit is used to describe illuminance, the intensity of light incident on a surface? a. Candela b. Candela per meter squared c. Foot-candle d. Lumen e. Nit
c. Foot-candle (fc) note: The metric equivalent is 1 lumen/m2 which is a lux (lx)
Which of the following applies to the output phosphor? a. Electrons emitted b. Light absorbed c. Light emitted d. X-rays absorbed e. X-rays emitted
c. Light emitted
Which is a critical component in optically coupling an image intensifier with a photospot camera? a. Electrostatic lens b. Face plate c. Objective lens d. Signal plate e. Subjective lens
c. Objective lens
The fovea centralis is: a. Essential to focusing b. Next to the lens c. Part of the retina d. The blind spot e. The disclike structure
c. Part of the retina
In a 10/7/5 image intensifier: a. Contrast resolution is best in the 10 mode. b. Spatial resolution is best in the 10 mode. c. The field of view is largest in the 10 mode. d. There are three different input phosphors. e. There are three different output phosphors
c. The field of view is largest in the 10 mode.
Fluoroscopic image recording: Which recording system has the highest resolution? a. DR recording systems b. video tape c. cassette-loaded spot film d. cinefluorography e. photospot
c. cassette-loaded spot film Note: video tape has the lowest resolution
The major source of occupational radiation exposure is scatter radiation from the: a. Surgeon/physician b. x-ray tube c. patient d. Image receptor e. Table
c. patient
In most fluoroscopy procedures, the lead apron should be placed: a. on the side of the patient away from the operator b. on top of the patient c. underneath the patient d. only if needed
c. underneath the patient note: most fluoroscopy equipment has the x-ray tube under the exam table.
All processes that contribute to image scatter, except the x-ray scatter process. Processes include optical scatter in the input phosphor, electron scatter within the tube & optical scatter in the output optics. Results in reduced contrast between objects of different opacities. This artifact is known as? a. vignetting b. lag c. veiling glare d. pincushion distortion e. S distortion
c. veiling glare
The patient tables designed for fluoroscopy units must be able to support large patients and also cause minimal x-ray attenuation. Tables are primarily constructed of?
carbon fiber composite material.
Antimony trisulfide is photoconductive because, when illuminated, it ____; when dark, it behaves as an ____and no signal is produced
conducts (electrons) insulator note: The target of a television camera tube conducts electrons creating a video signal only when illuminated.
visual acuity is controlled by the __________ of the eye which increases the ability to detect fine detail.
cones note: not the rods!
Both precise & synchronous electron beams are directed by external coils. The difference between the electron beam of the television camera tube & the electron beam of the television picture tube is that the television camera tube has a ____________ electron beam & the television picture tube has a _____________ electron beam.
constant modulated
The _________ _____ modulates the intensity of the electron beam, which is attached to the electron gun in the television picture tube.
control grid
Light first passes through this, a transparent protective covering of the eye called?
cornea
Vertical television resolution is limited principally by which of the following? a. Bandpass b. Field rate c. Frame rate d. Lines per frame e. Modulation
d. Lines per frame
Compared with radiography, the x-ray technique required for fluoroscopy calls for which of the following? a. Higher kVp b. Higher mA c. Lower kVp d. Lower mA e. Shorter exposure
d. Lower mA note: no more than 5 mA (1 to 5 mA)
Visual acuity is the ability to do which of the following? a. Control the amount of light entering the eye b. Detect differences in brightness c. Distinguish colors d. Perceive fine detail e. Vary depth of field
d. Perceive fine detail note: Cones perceive small objects much better than rods.
What is the component of the television monitor in which the video signal is transformed into an image? a. Electron beam b. Electron gun c. Electrostatic grid d. Phosphor screen e. Target assembly
d. Phosphor screen
What is the principal disadvantage of coupling the television camera to the image intensifier with the use of fiber optics? a. Cassette-loaded spot film cannot be used. b. Fragility is increased. c. Image noise is increased. d. Photospot camera cannot be used. e. Spatial resolution is reduced.
d. Photospot camera cannot be used.
Which of the following properties is associated with rods but not with cones? a. Color detection b. Contrast perception c. Ray focusing d. Scotopic vision e. Visual acuity
d. Scotopic vision
With a multifocus image intensifier in the magnification mode: a. Contrast resolution is reduced. b. Noise is increased. c. Patient dose is reduced. d. Spatial resolution is improved. e. Field of view is increased
d. Spatial resolution is improved.
Which of the following is photoconductive? a. Electron gun b. Electrostatic grid c. Signal plate d. Target e. Window
d. Target note: "A photoconductive layer of antimony trisulfide is applied to the inside of the signal plate. This layer, called the target, is swept by the electron beam. Antimony trisulfide is photoconductive because, when illuminated, it conducts electrons; when dark, it behaves as an insulator." (412 Bushong)
In general, during fluoroscopy as compared with radiography: a. A smaller focal spot is used. b. Patient dose is lower. c. Spatial resolution is better. d. The mA is lower. e. The SID is longer.
d. The mA is lower.
The electron beam in a television camera tube is produced by which of the following means? a. Electroemission b. Photoconduction c. Photoemission d. Thermionic emission e. Thermoluminescence
d. Thermionic emission
The cones are: a. Essentially color blind b. Located in the iris c. Located on the periphery of the retina d. Used for photopic vision e. Very sensitive to light
d. Used for photopic vision
When an image intensifier receives x-rays at the input phosphor, what is emitted at the output phosphor? a. Electrons b. Infrared light c. Ultraviolet light d. Visible light e. X-rays
d. Visible light note: The output phosphor is the site where accelerated electrons interact & produce light.
To increase the contrast of an image using fluoroscopy, you would need to? a. increase mA b. decrease kVp & increase mA c. control monitor adjustments d. control monitor adjustments & kVp
d. control monitor adjustments & kVp
With digital radiography, the cosine law applies to: a. grayscale imaging b. image inversion c. inverse square law d. off-axis viewing e. reduced spatial resolution
d. off-axis viewing note: "looking at a display from an angle"
This artifact occurs because the input screen is curved & the output screen is planar, resulting in more accurately focused central electrons & peripheral electrons that tend to flare out from their course. causes unequal magnification & a curving or warping, of the image in the periphery. a. vignetting b. lag c. veiling glare d. pincushion distortion e. S distortion
d. pincushion distortion
Scotopic: Is ________ light vision with the ______ of your eyes and is best at _______ nm.
dim rods 505
In fluoroscopy, _________ is considerably higher than radiography.
dose note: Dose is higher because the x-ray beam exposes the patient continuously for a much longer time.
Usually 3 to 5 magnification modes are available, and _________ typically increases with greater magnification.
dose note: when using magnification, the dose increases by the square of the ratio of the image intensifier diameter.
Place the following in proper sequence for image-intensified fluoroscopy: 1. Electric signal to light 2. Electrons to light 3. Light to electric signal 4. Light to electrons 5. X-ray to light a. 1, 2, 3, 4, 5 b. 2,3,4,5,1 c. 3,5,2,1,4 d. 5, 3, 1, 4, 2 e. 5,4,2,3,1
e. 5,4,2,3,1 note: x-ray to light, light to electrons, electrons to light, light to electric signal, electric signal to light.
Which of the following structures is responsible for the vision of dim objects? a. Cornea b. Fovea centralis c. Iris d. Pupil e. Rod
e. Rod note: rods allow black-&-white vision
When an external electromagnetic source acts on the electrons traveling within the II. Results in spatial warping of the image along an S-shaped axis. This artifact is? a. vignetting b. lag c. veiling glare d. pincushion distortion e. S distortion
e. S distortion
What is normally the weakest imaging link in television fluoroscopy? a. Image-intensifier tube b. Optical coupling device c. Spot-film device d. Television camera e. Television monitor
e. Television monitor
When a multifocus image intensifier is operated in the magnification mode: a. A larger area of input phosphor is used. b. Contrast resolution is reduced. c. Patient dose is lower. d. Spatial resolution is reduced. e. The electron focal point is closer to the input phosphor.
e. The electron focal point is closer to the input phosphor. Example: When switching to the 17cm mode, the voltage is increased on the electrostatic focusing lenses. This causes the electron focal point to move farther from the output phosphor & closer to the input phosphor.
One television frame is equivalent to which of the following? a. 17 ms b. 2621⁄2 lines c. 1024 lines d. One television field e. Two television fields
e. Two television fields (interlaced television fields)
What is the camera tube most used in television fluoroscopy? a. Cesium iodide b. Electrons from light c. Minification d. Synchronized e. Vidicon
e. Vidicon
What is the television camera tube component of image-intensified fluoroscopy? a. Cesium iodide b. Electrons from light c. Minification d. Synchronized e. Vidicon
e. Vidicon
Which of the following is the output phosphor of image intensifiers? a. Cadmium tungstate b. Calcium tungstate c. Cesium iodide d. Sodium iodide e. Zinc cadmium sulfide
e. Zinc cadmium sulfide
Photometry is the science of the: a. anatomy of human vision b. measurement of photographic images c. quantity of light d. reflection & refraction of light e. measurement of the response of the human eye to light
e. measurement of the response of the human eye to light
The electron beam is focused onto the output fluorescent screen by the ______________ _______. The electrons interact with the output phosphor & produce?
external coils (Focusing & Deflection coils) burst of light
Mobile fluoroscopy units are equipped with high-dose fluoroscopy controls. The control to activate high dose mode is in the foot pedal or remote marked with an _______ & ________. This mode is also referred to as "__________" mode.
eye & + sign boost
The fluoroscopic x-ray beam can be stopped by the ________ _________. This is referred to as "the dead man type," terminate the exposure if pressure is released. Additionally, some fluoroscopic units have _____________ _________________ mode that emits the x-ray beam in short bursts rather than in a steady stream. (breaks in exposure much like a strobe light).
foot pedal/switch pulsed fluoroscopy (reduces Pt dose only if set at low frame rates).
Cones are concentrated at the center of the retina in an area called the ________ ____________.
fovea centralis
The cones are concentrated at the center of the retina in an area called the ________ ____________. No rods are found here.
fovea centralis note: Rods on the other hand are most numerous on the periphery of the retina.
In Photospot camera uses 70 & 105 mm spot film sizes: Large film format results in better ____________ quality but ______________ patient dose.
image increased note: Even with larger 105 mm spot films, however, the patient dose is only approximately half that used with cassette-loaded spot films.
During fluoro, the _______________ should be placed as close as possible to the patient when using under table x-ray tube. Doing this will: 1. reduce __________________ 2. improve ______________ ____________ 3. reduce ____________ _______
image intensifier 1. magnification 2. image quality 3. patient dose
Digital Fluoroscopy pixel size is calculated _________________ divided by ________________.
image intensifier size divided by matrix size
Because exposure to the image intensifier must be maintained, the mA ____________ as distance between the x-ray tube and the image intensifier _______________.
increases increases Note: The maximum distance between the x-ray tube & patient, and minimum distance between the patient & image intensifier, should be used. SSD must be at least 38 cm (15 inches) on stationary fluoroscopes.
The increase in dose is approximately equal to the ratio of the area of the _________ ______________ used.
input phosphor. ex: 25/12 squared = 4.4 dose
A video frame is formed from a raster pattern of two ______________ video fields.
interlaced
The ________ is between the cornea and lens of the eye and controls the amount of light that is admitted to the eye.
iris
A useful technique for reducing fluoroscopy time is called ________________. During surgery or interventional procedures, this allows the surgeon or radiologist to view the last image without making another exposure.
last-image hold.
Light is passed through the _______ of the eye where it is focused on the retina.
lens
A television camera tube or CCD converts the _________ signal from the output phosphor to an _____________ signal.
light electronic
The Radiologist must actuate a control that positions the cassette in the x-ray beam & changes the operation of the x-ray tube from a _______ fluoroscopic mA to a ________ radiographic mA. When a cassette spot-film exposure is desired.
low high
The basic unit of photometry is the _____________.
lumen note: it is scaled to the maximum photopic eye response at 555 nm.
Multifield image intensifiers produce different __________________ of the image.
magnification note: Use of the smaller dimension of a multifield II tube always results in a magnified image, with a magnification factor in direct proportion to the ratio of the diameters.
When a monitor is viewed straight on, the luminous intensity is __________.
maximum note: when a monitor is viewed from an angle, the contrast and the luminous intensity are reduced.
The ____________________ _________ tells you how much the image is miniaturized.
minification gain note: Minification gain = (di/do) squared or mg = input phosphor diameter2/output phosphor diameter2
____________________ is a change in a quantity or signal in response to another quantity or signal & is widely used in medical imaging.
modulation
Although the x-ray tube may be operated at less than ___ mA during continuous fluoroscopy, the patient dose is considerably higher than plain radiographic exams because the x-ray beam exposes the patient constantly & for a longer time. Therefore, operators are trained to depress the what?
on-and-off foot switch note: this reduces patient exposure while providing a quality image.
Spot film is masked by a series of loaded diaphragms that allow several image formats: - Entire film exposed at one time is called: - Only half of the film exposed at a time, 2 images is called:
one-on-one mode two-on-one mode note: four-on-one & six-on-one modes are also available with images becoming smaller.
The spot film is positioned between the ____________ and the _____________________.
patient image-intensifier note: cassette-loaded spot film is used with image-intensified fluoroscopes.
One of the benefits of pulsed fluoroscopy is the ability to reduce?
patient dose -especially when the pulse rate is reduced
In the magnified mode the minification gain is reduced (diameter of the output & input phosphors) = dimmer image. To maintain the brightness, the mA is increased by the ABC , which increases?
patient radiation dose!
When a surface, usually metallic, absorbs electromagnetic radiation at a sufficiently high frequency (light), the surface then emits electrons, a process called?
photoemission Note: "The photocathode of the II tube absorbs light & emits electrons" or "photoelectrons".
The movement of both electron beams (television camera tube & television picture tube) produces a ___________ ____________ on the screen of a television picture tube.
raster pattern note: remember that the same electron beam pattern occurs in the television camera tube as well.
The structures in the eye that are responsible for the sensation of vision are called _______ & ________.
rods & cones note: when light arrives at the retina, it is detected by the rods & the cones.
___________ focal spots are used for fluoroscopy to minimize geometric blur.
small
________________ devices use film-screen cassettes to acquire radiographic images.
spot-film
The best viewing of a digital display device is ______________ _____.
straight on
The weakest link in the imaging chain is the?
television monitoring system Note: has lower spatial resolution then the II tube. (lp/mm)
The production of scatter radiation is directly related to patient ______________.
thickness note: increased thickness leads to increased scatter production.
The video signal (from signal plate) is amplified & is transmitted by cable to the television monitor, where it is transformed back into a ___________ ___________.
visible image (electric signal to light)
The image-intensifier tube is a complex electronic device that receives the image-forming x-ray beam & converts it into a ____________ _________ image of high intensity.
visible-light note: Tube components are contained within a glass or metal envelope which maintains a vacuum.
When using mobile fluoroscopy equipment, the exposure from scatter radiation is greater on the ________________ side of the c-arm than on the ____________________ side.
x-ray tube image receptor note: When the c-arm is oriented vertically, the x-ray source should be positioned below the table with the IR above the patient if possible.
