Unit 4 (Chapter 6 & 7)
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Who developed the first fluoroscope and when?
List the components of the Image Intensifier.
- Input screen
- Electrostatic lenses
- Output screen
- Evacuated glass envelope
What requires dual-field and triple-field intensifiers?
State the formula for brightness gain.
Brightness Gain = Minification Gain X Flux Gain (BG=MG X FG)
State the formula for minification gain.
MG = [Diameter of the input screen]2 / [Diameter of the output screen]2
State the forumla for flux gain.
FG = Number of light photons at the output screen / Number of light photons at the input screen
State the formula for conversion factor.
CF = Luminance of the ouput screen / Exposure rate at the input screen
With an optical image distributor, 10% of the light goes to the _______________ and 90% to the ________________.
- video camera
- photospot film camera
If using a dual field intensifer (25cm/17cm), which would produce a higher does to the patient?
17 cm mode (which is the magnification mode)
State the formula for dose increase.
Dose = (full field diameter2)/ (magnification mode2)
The spatial resolution image intensifier ____________ with a smaller input diameter mode.
__________________ is the ratio of the image brightness at the periphery to that at the center of the output screen.
An _____________ in mA can reduce noise.
To reduce dose, the ZnCdS input phosphor used in the early image intensifier tube was replaced with ______ which has a __________ DQE than ZnCdS.
- CsI (cesium iodide)
_______________ is the continued emission of light from the screen when the radiation beam has been turned off.
_____________ refers to the loss of brightness on the periphery of the image.
______________ and _______________ are two kinds of artifacts produced from the convex input screen of the Image Intensifier and the close vicinity of an electromagnetic field with the II.
- Pincushion distortion
- S distortion
The CCD camera has a _________ dynamic range than the pick-up tube's.
The generator used with digital fluoroscopy is a _________________ generator.
True or False: A flat-panel digital fluoroscopy system contains an image intensifier.
List some advantages of the flat-panel digital fluoroscopy system.
- high low-contrast resolution
- high DQE across all dose levels
- high dynamic range
- no pincushion distortion or veiling glare
- grids can be removed
- rectangularly shaped
- more compact
List the three digital post-processing capabilities of digital fluoroscopy.
- Grayscale-Image manipulation
- Last image hold
- Temporal frame averaging
What is a post-processing operation that is used to enhance image sharpening?
What is produced when the pre-contrast image referred to as a mask image is first obtained and post-contrast images are then digitally subracted from the mask image?
What is defined as images that are recorded based on subtraction of energies slightly above and slightly below the K-absorption edge of the contrast material used for the examination?
What are the limitations of Screen Film Mammography?
- limited dynamic range of film
- brighness and contrast are fixed once the film is developed
- the film serves 3 roles...acquisition, display, and storage
How is DQE expressed?
DQE = SNR2out / SNR2in
If the DQE for an imaging system were perfect, it would be represented as _____.
The DQE for SFM is ______ than DM. The SFM would be ______ DQE.
A ____ bit ADC would allow for excellent digitazation and display of images with excellent grayscale resolution.
The ____________________ uses data received from the ADC to produce the digital mammographic image.
Digital Image Processing
Two types of display technologies for DM are ___________ and ___________.
- Caathode ray tube (CRT)
- Liquid crystal display (LCD)
The four purposes for PACS in DM are to improve:
- management effeciency
- communicaion of images
List the seven specific image-processing algorithms for DM.
- manual intensity windowing (MIW)
- histogram-based intensity windowing (HIW)
- mixture-model intensity windowing (HMIW)
- contrast- limited adaptive histogram equalizaion (CLAHE)
- unsharp masking
- peripheral equalization
- Trex processing
What is a type of computer software that allows for additional information to be supplied to the radiologist to enhance diagnosis?
Computer-aided Detection and Diagnosis (CAD)
True or False: CAD is thought of as a "second opinion" in DM.
What is a technique that uses the principles of conventional tomography to produce tomographic images that are intended to enhance the conspicuity of lesions by blurring out structures above and below the layer of interest?
When was the first image intensifier used in fluoroscopy?
What is a dynamic image?
an image in motion
What is the major advantage of the image intensifier?
to decrease dose to the patient
What is another name for dynamic imaging?
real time imaging
What refers to an images intensifier coupled to a video camera that converts the image from the output screen of the image intensifier into a video signal?
What are the major components of conventional fluoroscopy?
- x-ray tube
- spot film device
- image intensifier tube
- optical image distributor
- photo spot camera
- video camera
- TV monitor
What type of images are recorded by the spot film device?
single static images
What happens to mA when switching from fluoro to shooting a spot film?
it increases significantly (from about 1-3 mA to 200-400 mA)
What is the spot film stored in until a stationary image is ready to be taken?
lead incased section
What type of film moves out to be exposed at the film plane and continues to move through until exposure was complete?
photospot film (very similar to a 35 mm camera)
What are the 4 types of monitors?
In fluoroscopy, what helps to reduce dose to the patient and decrease blurring from moving objects?
pulsed fluoroscopy (as short as 3-10 ms/image)
Pulsed fluoroscopy requires a grid-controlled x-ray tube which can reduce the dose as much as _____ compared to non-pulsed fluoroscopy.
What are the technical factors for dynamic fluoroscopy?
1-3 mA and 65-120 kVp
List the parts of the image intensifer to show its function.
- input screen (CsI phosphor: converts x-ray to light)
- photocathode layer (SbCs3 : converts light to electrons)
- electrostatic lenses (takes image from cathode (-) to anode (+) side)
- output screen (ZnCdS: converts electrons back to light)
How much energy helps accelerate the electrons in the II to move them to the anode side?
Which is smaller: the output screen or the input screen?
the output screen (image is intensified and flipped)
The output screen is ____ the size of the input screen.
Brightness gain ranges from:
The brightness gain concept has been replaced with the ____________________ which measures light gain at the output screen.
What is the unit of measurement for luminance or light brightness?
Candela/square meter (Cd/m2)
Conversion factor gain ranges from:
What is the glass envelope enclosed in that provides mechanical support and shielding?
a metal housing
What is the purpose of the optical image distributer?
to split the light received from the output screen
Name sizes for dual-field and triple-field intensifiers and give their exposure rates.
- dual-field: 25cm (30 micro R/sec)
- 17cm (60 micro R/sec)
- triple-field: 25cm (30 micro R/sec)
- 17cm (60 micro R/sec)
- 12cm (120 micro R/sec)
What are the typical contrast ratio values?
- 10:1 to 30:1
- 15:1 to 35:1
What are the five types of image intensifier artifacts?
- image lag
- veiling glare
- pincushion distortion
- S distortion
What characteristic of the II causes pincushioning and S distortion?
the shape is convex
What artifact results when light is scattered in the image intensifier?
Why does the radiologist view images on a TV monitor instead of an output screen?
the image is too small and bright to be seen clearly for proper viewing and interpretation
For first generation video cameras that used television tubes, what was needed when it came to image lag and SNR?
What is the SNR for conventional fluoroscopy? digital fluoroscopy?
- conventional 200:1
- digital 1000:1
in analog to digital conversion, digitizing the analog signal requires dividing it into a number of bits referred to as:
The __________ the bit, the more accurate the ADC.
Digital fluoroscopy uses a ____________ for receiving dynamic digital data from the ADC and processing it quickly for display and storage.
List the key components of the Flat-Panel Detector (Digital):
- x-ray tube
- dynamic FPD host computer
- television display monitor
What are the two types of dynamic FPDs?
- CsI a-Si TFT indirect digital detector
- a-Se TFT direct digital detector
- (detector dimensions) 31x31, 35x35, 30x40, 41x41, 43x43
- (matrix sizes) 1024x1024, 2304x2304, 2048x2048
a process that allows for four pixels in one while equipment is being used for fluoro rather than radiography:
binning (improves resolution)
What are some significant differences between FPDs for digital radiopraphy and dynamic real-time fluoroscopy:
electronics must use high frame rates (15 to 30 fps) and fast data transfer rates (30-50 msec)
The purpose of _______________ is to change the contrast and brightness to improve diagnostic quality.
process that displays the last frame continuously when the beam has been suspended; repeats itself once the beam is turned on again:
Last frame hold/Last image hold
Does temporal frame averaging increase or decrease noise?
Name the items involved with screen-film mammography:
- x-ray source
- screen-film cassette
- chemical processor
Name two advantages and three disadvantages of screen-film mammography:
- advantage: high image contrast
- advantage: high spatial resolution (15-20 lp/mm)
- disadvantage: limited dynamic range
- disadvantage: can't adjust brightness/contrast w/o repeats
- disadvantage: inability to acquire, display and store like digital
What are the dynamic ranges of screen-film mammography vs. digital mammography?
What is another name for digital tomosynthesis for mammography?
what are the four types of digital detectors in mammography?
- flat-panel detector
- charged couple device
- flat-panel amorphous selenium
- CR DM system
Detectors must be capable of providing at least ____________ of spatial resolution to improve lesion detectability, in mammography.
Detectors must cover an image area of at least _________ to capture the entire breast.
24cm X 30cm
Detectors must have pixels spaces about _________ apart in mammography.
25 micrometers (.025 mm)
What is a fundamental requirement when it comes to the matrix size for mammography?
at least 9600x12000 (large detector)
What are two more things required for mammography besides high spatial resolution, large image area, pixel spacing, and matrix size?
What must happen to the digital information from the computer before the mammography image can be displayed on a monitor?
the digital information must be converted back to an analog signal
DM computer display monitors should be in rooms with an ambient light of:
less than 5 lux2
Name 3 major components of a flat-panel scintillator/amorphous silicon system:
- scintillator (CsI, activated by thallium)
- photodiodes (light to electrical signal)
- TFT (a matrix of photodiodes)
advantages to the compact design of a charge-coupled device DM system:
- costs less
- excellent scatter rejection
- no grid needed (decrease pt dose)
What would need to happen because of the narrow scan by the charge-coupled device DM?
longer compression times to complete the study of the whole breast
Name disadvantages of CR DM:
- loss of spatial resolution
- have to print images
- noise associated with low collection of efficiency of emitted light
- difficulty correcting flat field corrections
name advantages of CR DM:
- small detector element size
- plates can be used in any mammography unit
- multiple plate sizes
- low cost
Name some point-processing operations in DM:
- grayscale processing:
- windowing (contrast & brightness)
- image subtraction
- temporal averaging (less noise)
Name some local processing operations in DM:
- spatial filtering
- edge enhancement
name some global operations in DM:
- the Fourier Transform (numerical values given to pixels)
- (processing algorithms)
Name some processing operations used to enhance and extract lesions within breast tissue:
- filtering baser
- fourier analysis
- artificial neural networks
- wavelet transform
What are three steps of quantitation of image features in CAD (DM)?
- select size, contrast and shape of candidates
- uses image features that have been used for years due to accuracy
- finds unique features that can readily distinguish between a lesion and normal tissue
Data processing in CAD for DM uses techniques such as:
- rule-based methods
- discriminant analysis
- artificial neural networks
- decision tree method
name two CAD systems commercially available:
- R2 "image checker", R2 Technology, INC. Los Altos, CA
- CADx "Second Look," CADx Medical Systems, Quebec, Canada
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