-
Bone density scanning also called:
Dual Energy X-ray Absorptiometery (DEXA)
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Dexa is today's standard for measuring:
Bone minderal density (BMD); or bone loss
-
Dexa is most often performed on
Lumbar Spine and hips
-
Dexa is most often used to diagnose:
osteoporosis
-
Dexa can also assess an individuals risk for:
fractures
-
Risk of fracture affected by:
Age, weight, history or prior fracture, family history of osteoporotic disease, and lifestyle
-
Bone mineral denisity is calculated by finding the difference between:
peak energy absorbed by soft tissue and by bone
-
Dexa score that shows the amount of bone you have as compared to a young adult of the same gender with peak bone mass.
T Score
-
Normal T Score
A score above -1
-
T score classifying osteopenia (low bone mass)
A score between -1 and -2.5
-
T Score identifying osteoporosis
Score below -2.5
-
T Score is used to estimate risk of
developing a fracture
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The Dexa number that reflects the amount of bone you have compared with other people in your age group of the same size and gender.
Z Score
-
A DXA test cannot predict who will experience a fracture but can provide indications of
relative risk
-
Osteoporosis involves a gradual loss of:
Calcium
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X-ray imaging of a selected plan of the obdy by a method that elimiates the outline of structures in other planes.
Tomography
-
Principal advantage of tomography:
Improved contrast resolution
-
Principal disadvantage of tomography:
Increased patient dose
-
X-ray tube attached mechanically to the image receptor; the tube moves in one direction while the bucky moves in the opposite direction.
Linear Tomography
-
Imaginary point about which the x-ray tube and image receptor moves
Fulcrum
-
What determines the object plane in Tomography?
The fulcrum
-
Anatomical structures lying within what plane are imaged clearly in tomography?
The object plane
-
The farther from the object plane an anatomical structure is, the more
blurred the image will be
-
Section thickness in tomography is determined by:
Tomographic angle
-
A large angle in tomography results in
A thin section
-
Long flexible fine spring used to introduce and position an intravascular angiographic catheter:
Guidewire
-
Hollow flexible tube for insertion into a body cavity, duct, or vessel to allow passage of fluids or distend a passageway.
Catheter
-
Common uses of catheter angiography:
To examine blood vessels in the brain, kidneys, pelvis, legs, lungs, heart, neck and abdomen
-
X-ray tube and IR move around the head
Panoramic tomography
-
Images of structures above and below the object plane become more blurred as tomographic angle
increases
-
The thickness of tissue to be imaged is called the ____ ____ and is controlled by ____ ____.
tomographic section/tomographic angle
-
If the tomographic angle is less than 10 degrees, the section thickness will be ____. This is called _____.
large/Zonography
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Primary function of fluoroscope:
To provide real-time dynamic images of anatomic structures; to view motion and function
-
What is used for the examination of moving internal structures and fluids?
Fluoroscope
-
Who invented the fluoroscope? When?
Thomas Edison; 1896
-
Original Fluoroscope:
Zinc Cadmium Sulfide backed by leaded glass
-
Permanent fixed image taken during fluoroscopy; a small static image on a small format image receptor:
Spot Film
-
Fluoroscopic visualization of vessels:
Angiography
-
What is Automatic Brightness Control (ABC)?
The image brightness selected by the radiologist is maintained automatically by varying the kVp, mAs, or both.
-
Radiographs are visualized under illumination levels of:
100-1000 lux
-
LUX=
Lumen per square meter
-
How many rods and cones are there in the eye per cubic mm of retina?
More than 100,000
-
Cones are concentrated at the ___ ____ and are used for ____ vision.
fovea centralis/photopic
-
Rods are concentrated at the ____ of the retina and are used for ____ vision.
periphery/scotopic
-
Threshold for rod vision:
2 lux
-
Threshold for cone vision:
100 lux
-
Ability to perceive fine detail:
Visual Acuity
-
Detecting differences in brightness:
Contrast Perception
-
Developed to replace conventional fluorescent screen:
Image intensifier
-
An image intensifier raises illumination into the:
Cone vision region
-
Complex electronic device that receives the image forming x-ray beam and converts it into a visible light image of high intensity:
Image intensifier tube
-
X-rays that exit the patient and are incident on the image intensifier tube interact first with the:
Input phosphor
-
The input phosphor is composed of:
Cesium Iodide
-
When x-rays interact with the input phosphor, their energy is converted to:
visible light
-
What is bonded directly to the input phosphor with a thin transparent adhesive?
The photocathode
-
The photocathode responds to light from the input phosphor by emission of:
Electrons
-
The emission of electrons by the photocathode is called:
photoemission
-
The number of electrons emitted by the photoemission of the photocathode is _____ to the intensity of the incident image forming x-ray beam.
Proportional
-
Circular plate with a hole through which electrons pass to theh output phosphor.
Anode
-
What is the potential difference maintained across the tube between the photocathode and anode?
25,000 V
-
Site where electrons interact and produce light:
Output phosphor
-
The output phosphor is composed of:
Zinc Cadmium Sulfide
-
What are located along the length of the image intensifier tube to ensure that the electrons are reduced to the small output phosphor?
Electrostatic focusing lenses
-
What is the flux gain?
The ratio of the number of light photons at the output phosphor to the number of x-ray photons at the input phosphor
-
Each photoelectron that arrives at the output phosphor produces how many times the light photons as were necessary to create it?
50-70 times
-
What is the minification gain?
The ratio of the square of the diameter of the input phosphor to the ratio of the square of the diameter of the output phosphor
-
What is the Brightness gain?
The minification gain x the flux gain; the ablility of the image intensifier to increase ilumination level of the image
-
Brightness gain of most image intensifiers:
5,000-30,000
-
The conversion factor of most image intensifiers is:
50-300
-
Conversion factor
Output illumination/input exposure rate
-
What reduces the contrast of an image with internal scatter radiation?
Veiling glare
-
What uses a smaller diameter to result in a magnified image in direct proportion to the ratio of diameters?
Multifield Image intensification
-
In magnified mode, the minification gain is____.
reduced
-
In magnified mode ____ photoelectrons incident on the output phosphor
fewer
-
In magnified mode, the image is _____.
dimmer
-
Magnification mode results in ____ patient dose.
higher
-
What effect does magnified mode in fluoroscopy have on spatial and contrast resolution.
Improves
-
Reduction in brightness at the periphery of the image:
Vignetting
-
In television fluoroscopy, the output phosphor is coupled:
directly to the camera tube
-
Television camera tube used most often in television fluoroscopy:
Vidicon
-
The input surface of the vidicion is the same size as:
the output phosphor
-
The vidicion converts light from the output phosphor into an:
electrical signal
-
Electromagnetic coils in the television camera are used to:
properly steer the electron beam within the tube
-
Two methods commonly used to couple the television camera tube to the image intensifier:
- 1. Bundle of Fiber Optics
- 2. Lens coupling
-
Power supply of 60Hz results in ___ television fields per second, and ____ frames per second. Each frame is ___
60, 30, 33ms
-
Describe interlace
An active trace in field 2 lies between two active traces in field 1. This forms a frame.
-
When the electron beam blanks and turns off to return to the left side of the screen, this is called:
Horizontal retrace
-
How many new cases of breast cancer are there yearly?
210,000
-
How many breast cancer patients are cured with early diagnosis?
80%
-
Ratio of benefit to risk in mammography:
1000:1
-
What tissue is most sensitive to cancer by radiation?
Glandular
-
What percentage of breast tissue is ductal?
80%
-
Incidence of breast cancer is highest in what part of the breast?
Upper outer quadrant
-
A baseline mammogram is usually obtained before age:
40
-
Optical densisty is highest with what kind of breast tissue?
Dense
-
Low kVp is used in mammography to minimize____, maximize ____, and enhance ____.
Compton scatter/ Photoelectric effect/ differential absorption
-
What kVp is effective in mammography?
23-28
-
What type of target/filter combination is best for thick, dense breasts?
Rh/Rh
-
What type of target/filter combination is best with thin, fatty breasts?
Mo/Mo
-
In mammography, effective focal spot is obtained with an anode angle of ____ and a tube tilt of ____.
23 degrees/ 6 degrees
-
The cathode is positioned toward the chest wall during mammography to make use of the:
anode heel effect
-
Focal spot blur in mammography results in reduced:
spatial resolution
-
SID of most mammography imaging systems: 60-80 cm
-
Inherent filtration of mammography imaging systems:
.1 mm Al equivalent
-
Total beam filtration of mammography imaging system should never be less than:
.5 mm Al equivalent
-
The use of a filter of the same element as the target in mammography is done to allow ____ to expose the breast while limiting high and low ____.
Characteristin/Bremmstrahlung
-
Compression of breast reduces:
Motion blur, scatter, tissue superimposition, focal-spot blur, absorption blur, and patient dose.
-
Most mammography systems have a moving grid of:
4:1 or 5:1
-
-
Why are phototimers for mammography positioned after the IR?
to reduce OID and improve spatial resolution
-
Two types of AEC for mammography:
1. Ionization chamber 2. Solid State Detector
-
Magnification mammography requires a focal spot size no larger than:
.1 mm
-
When used with AEC, screen-film mammography must have a
low absorbing back cover
-
Quality assurance deals with:
people
-
Quality Control deals with:
Instrumentation and equipment
-
QA is principally the responsibility of:
the radiologist
-
QC is principally the responsibility of:
the medical physicist
-
The ten step monitoring and evaluation process resolves
identified patient care problems
-
Pertaining to whether the patient's ultimate disease or condition agree with the radiologist's diagnosis.
Outcome analysis
-
Three steps of an acceptable QC program:
Acceptance testing, monitoring and maintenance
-
In private officies, clinics and hospitals, the QC program is established and overseen by:
a medical physicist
-
The most important protection characteristic of a radiographic imaging system:
filtration
-
Collimation misalignment must not exceed
2% of the SID
-
Distance must be acurate within
2% of the SID
-
Centering must be accurate within
1% of the SID
-
Spatial resolution is determined principally by:
focal spot size
-
Focal spot size must be measured when:
new equipment or replacement tube are installed
-
Filtration should be evaluated annually or any time after
a change has occured in the tube or housing
-
3 tools used to measure focal spot size
slit camera, pinhole camera, star pattern
-
What is the standard tool for measuring focal spot size?
slit camera
-
The star pattern is only useful for measuring focal spot sizes greater than
.3 mm
-
Specification of focal spot size depends on
geometry of the tube and focusing of the electron beam
-
An acceptable alternative to focal spot size measurement:
Line pair test tool
-
kVp calibration should be evaluated annually or when
high voltage generator components have changed
-
Measured kVp should be within
10% of the indicated kVp
-
For times above 10ms, exposure timer accuracy must be within
5% of indicated time
-
For times 10 ms or less, exposure timer accuracy should be within
20%
-
AEC is evaluated by exposing an image receptor through:
varying thickness of aluminum or acryllic
-
The accuracy of the exposure timer should be assessed annually or more frequently if repairs have been made to:
the operating console or high voltage generator
-
Assessing the function of the backup timer can be done by inserting a
lead filter
-
If the phototimer fails, the backup timer should terminate the exposure at
600 mAs or 6 seconds
-
The ability of a radiographic unit to produce a constant radiation output for various combinations of mA and time:
Exposure linearity
-
Exposure linearity must be within:
10% for adjacent mA stations
-
Exposure linearity is determined by a:
precision radiation dosimeter
-
Method of assessing exposure linearity:
Hold exposure time constant and vary the mA
-
Two methods to evaluate exposure reproducibility:
1. Make a series of at least 3 exposures with the same technical factors while changing between exposures. 2. Select technique factors and hold constant for 10 exposures
-
Sequential radiation exposures should be reproducible within:
5%
-
Screen cleaning should not occur less often than
every other month
-
Screen-film contact is evaluated:
semi-annually
-
Protective apparel should be radiographed/fluoroscoped
annually
-
Viewbox illumination is analyzed annually with a:
photometer
-
Filters used to determine adequacy of ABS:
aluminum, copper, lucite, and lead
-
As the active area of the input phosphor is increased, patient dose is:
reduced
-
Fluoroscopic ABC should be evaluated:
annually
-
For conventional tomography, patient exposure should be measured for:
the most common procedures
-
Most frequent tomographic procedures:
TMJ, C-spine, T-spine, Chest, IVP, Nephrotomogram
-
In conventional tomography, section uniformity is evaluated by imaging:
a hole in a lead sheet
-
A 90 second film processor can handle
500 films per hour
-
90 second film processor requirements:
Water 87 degrees, developer temperature 95 degrees, high concentration chemistry, 22 second developer immersion
-
In most facilities, processor cleaning is done
weekly
-
Processor monitoring should be done at least
once per day
-
3 types of maintenance programs for QC
Scheduled maintenance, preventative maintenance, non-scheduled maintenance
-
Average ESE during fluoroscopy:
3-5R/minute
-
Skin dose during fluoro
10 rads
-
Skin dose during interventional procedures
100 rads
-
ESE for fluoroscopy should not exceed:
10R/min
-
ESE for interventional studies should not exceed
20R/min
-
Proper exposure of cassette spot film depends on:
kVp, mAs, and sensitivity characteristics of screen-film combination
-
ESE for cassette spot film:
200 mR
-
Input exposure rate to the image intensifier tube should be in the range of:
10-40 microR/s
-
In tomography, agreement between the indicated section level and the measure level should be within
5 mm
-
Incrementing from one tomographic section to the next, section level should be within
2mm
-
QC team for mammo
Radiologist, Mammographer, and Medical Physicist
-
Daily QC the responsibility of:
mammographer
-
How many specific tasks does the QC mammographer have and what is the total annual time required for mammographic QC?
12, 160 hours
-
Daily mammo. QC tasks:
Darkroom cleaning, processor monitoring
-
What kind of thermometer should never be used to check developer temperature in the processor?
mercury
-
Which end of the sensitometeric strip should be fed into the feed tray first?
Least exposed, emulsion side down
-
OD closest to 1.2 but not less than 1.2
Mid density/speed index
-
Difference between OD of 2.2 and OD closest to but not less than. 5
Density difference/contrast index
-
Average OD from unexposed area of the strips:
Base + Fog
-
MD and DD allowed to vary within:
.10
-
Base plus fog allowed to vary within
.03
-
Weekly mammography QC tasks:
Viewbox, screen cleaning, phantom images
-
Technique used for imaging mammographic phantom should be the same as used clinically for:
4.5cm compressed breast, 50% glandular, 50% adipose
-
Time or mAs values for mammographic phantom images should be within
15%
-
For mammographic phantom images, background OD should be ___ with a range of ____
1.4, .2
-
For mammographic phantom images, DD should be ___ with a range of ___
.4, .05
-
Monthly mammographic QC tasks:
Visual checklist
-
Quarterly mammo QC tasks:
Repeat analysis, analysis of fixer retention, conferense w/radiologist
-
Quarterly repeat analysis valid if patient volume results in at least:
250 exams
-
Analysis of fixer retention in film is used as an indicator of:
archival quality
-
They hypo estimator should not result in more than
.05g/m2
-
Semi-annual mammographic QC tasks:
Screen/film contact, compression, darkroom fog
-
Safelight or fluorescent light fog should not exceed
.05
-
Background of the phantom image should be:
1.4-1.6
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