Bennett Test 3-7,8,11,12,28
Terms
undefined, object
copy deck
- Accuracy of exposure index determination and image appearance depends on...
- reader calibration
- Vendor must use ___________ to calibrate reader to target exposure index, otherwise image will be too dark or light
- dosimeter
- range of exposures (signal width) over which a detector can acquire image data
- dynamic range
- the range of values over which a system can respond (contrast resolution)
- dynamic range
- What has a larger dynamic range, F/S or CR/DR?
- CR/DR
- Digital detectors have a _____________ exposure response
- linear
- Typical digital systems respond to exposures as low as ____ and as high as ______
- 100 microRoentgens; 100 milliRoentgens
- ________ is about 2 days background exposure. Background exposure is about ________ each day
- 100 microRoentgens; 60-80 microRoentgens
- Dynamic range _______ exposure latitude
- IS NOT
- Dynamic range of F/S is about __________
- 1000
- The human eye has a dynamic range of __________
- 32 shades of gray (5-bit; 2^5)
- The exit beam can have a dynamic range of _________ shades of gray
- 1024 (2^10; 10-bit)
- Digital systems are characterized by their....
- dynamic range
- 8-bit has a dynamic range of...and intensity level of...
- 2^8, or 256 shades of gray (intensity level of 0-255)
- MRI and CT have a ____ dynamic range
- 12 bit
- Digital radiography has a ____ dynamic range
- 14-bit
- Mammo has a ____ dynamic range
- 16-bit
- Histogram analysis uses shape of image signal distribution to determine:
-
-Relevant info in exposure field
-Exposure index - software function that maps the grayscale to the values of interest (VOI) in the histogram to achieve specific display levels
- automatic rescaling
- When does automatic rescaling occur?
- When exposure is greater or less than the optimal amount to produce a diagnostic image
- Automatic rescaling produces images with uniform ___________ over a ____________, regardless of ______________
- brightness and contrast; wide exposure range; amount of exposure
- Automatic rescaling uses ______________ to correct exposure errors
- histogram shape recognition
- Problems occur with automatic rescaling when too little exposure is used (leads to....) and when too much exposure is used (leads to....)
- noisy image (quantum mottle); loss of contrast and loss of distinct edges due to extra scatter
- Alignment of structure/beam (exposure field) with IR is more critical in ___ than in ____
- CR/DR; F/S
- Inappropriate beam configuration can lead to...
- histogram analysis errors
- Small fields (less than ____ of plate) should be centered
- 1/3
- Multiple fields are common with ___, allowed with ____ under certain rules, and not possible with ___
- F/S; CR; DR
- In CR, multiple images may be put on 1 plate as long as they are...
- symmetric (same size; same relative area)
- For CR, vendor probably recommends ___ image per plate and _____ collimation
- 1; no
- Proper __________ ensures the data collected is relevant
- centering
- Proper ________ removes irrelevant data from the image
- collimation
- In what is scatter control more important, F/S or CR/DR?
- CR/DR
-
Grids are generally indicated for any exam where remnant beam scatter is greater than ____ of total beam.
Chest > __ cm
Other structures > _____ cm -
50%
26
10-12 - Grid use carries risk of _______ and/or ________
- grid cutoff; moire effect (aliasing artifact)
- When does moire effect occur?
-
Because of grids or computer error.
Occurs when alignment of grid to laser scan direction is incorrect (laser parallel to grid lines) OR when spatial frequency is greater than Nyquist frequency and sampling occurs less than twice per cycle (when sampling frequency is close to grid frequency) - Moire with cassetteless flat panel detector occurs when exposure times are...
- greater than 10 msec
- To reduce risk of moire
-
avoid grid frequency near Nyquist
change sampling frequency
larger files
- Preprocessing is controlled by...
- software and technologist
- In preprocessing, you select __________, __________, and _______
- projection; orientation; speed class
- graphical representation of intensities recorded on imaging plate
- histogram
- process of determining what values to include in the histogram
- histogram analysis
- Exposure data recognition (histogram analysis) processes only...
- the optimal density exposure range
- If system fails to find collimation edges, images may be...
- too bright or too dark
- when laser traverses plate and causes light emission
- image sampling
- investigating or evaluating a segment of the image
- image sampling
- Low energy (kVp) gives a _______ histogram; high energy (kVp) gives a _______ histogram
- narrower; wider
- Histograms are different for ________________ and remain fairly constant from patient to patient
- specific anatomic regions
- when sampling a signal, the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect
- Nyquist theorem
- the highest spatial frequency that can be recorded by a detector
- Nyquist frequency
- 1/2 the number of pixels per mm
- Nyquist frequency
- Nyquist frequency is determined by...
- pixel pitch
- Nyquist is __________ by slow scan movement
- reduced
- Nyquist frequency predicts ___________ in CR
-
maximum spatial resolution
For example, if pixel density is 10 pixels/mm, max spatial resolution (Nyquist frequency) is 5 lp/mm - table of the luminance values derived during image acquisition
- lookup table
- image mapping function in which all pixels are changed to a new gray value
- lookup table
- _____ is used as a reference to evaluate the raw info and correct the luminance values
- LUT
- LUTs are only used in...
- digital imaging
- LUTs are assignments that are specific to each...
- anatomic part
- LUTs are used to assign ______________ to ___________
- colors (gray values; brightness values); histogram values
- LUT will have a more vertical slope for ________ window width, and more horizontal slope for ________ window width
- narrow; wide
- __________ can be increased or decreased by changing slope of LUT graph
- Contrast
- _________ can be increased or decreased by moving the line of the LUT slope up or down the y-axis
- Brightness (density)
- range of exposures that can be used and still result in the capture of a diagnostic quality image
- exposure latitude
-
In CR, if exposure is more than ____ too low, mottle is seen.
In CR, if exposure is more than _____ too high, contrast loss is evident - 50%; 200%
- a measure of how well the image can accurately image an object
- MTF
- the ability of the system to accurately represent the imaged object
- MTF
- the ability of a system to record available spatial frequencies
- MTF
- a measure of the ability of the imaging system to preserve signal contrast as a function of spatial resolution
- MTF
- ratio of image to object as a function of spatial frequency
- MTF
- mathematical procedure for determining resolution
- MTF
- ____ is a way to quantify the contribution of each system component to the efficiency of the entire system (to total resolution)
- MTF
- The closer the MTF is to ______, the better the resolution
- 1 (100%)
- At low spatial frequencies, does mammography or radiography have a higher MTF?
- Radiography, since radiography uses 2 screens
- MTF is controlled by...
- spatial resolution
- High-contrast can image ____ objects, while low-contrast can image ______ objects
- small; large
- DR has higher MTF at _____ spatial frequencies due to...
- lower; large dynamic range and higher DQE
- The _____ the pixel, the smoother the image appearance
- smaller
- The ______ the area of pixel values averaged, the smoother the transition of brightness levels
- larger
- What is the result of smoothing (low-pass filtering)?
- reduced noise and contrast
- When is smoothing (low-pass filtering) useful?
- For visualizing small structures such as fine bone tissues
- The _______ the area of pixels averaged, the more the contrast and edges are enhanced
- smaller
- Edge enhancement occurs when ______ pixels in the neighborhood are included in the signal average
- fewer
- when some signal values are suppressed while others are strengthened (this enhances contrast and edge)
- high-pass filtering
- High-pass filtering can aid in visualizing....
- large structures like organ edges, but it can be noisy
- suppressing signal (suppressing frequencies of lesser importance)
- masking
- Masking can result in...
- loss of small details
- The most common image processing parameters are those for....
- brightness (window) and contrast (level)
- ___________ allows us to visualize a portion of the dynamic range
- windowing
- What controls # of shades of gray to display?
- window width
- What determines the value that will be the darkest on the image (where to set value for black)?
- window level
- What removes excess light from image that would result in veil glare?
- Shuttering/black border/background removal
- ____________ allows images to be sent to more than 1 computer or destination
- manual send
- function that allows retrieval of archived images from PACS
- archive query
- grid of cells in rows and columns
- image matrix
- the number in each cell in the image matrix represents the ___________ at that location
- brightness (intensity)
- What determines matrix size?
- The smallest matrix size (ex. imaging equipment/IR, computer, and monitor)
- the ability of an imaging system to resolve and render on the image a small high-contrast object
- spatial resolution
- What is human eye spatial resolution?
- 200 micrometers
- Spatial frequency refers to the....
- line pair
- Low spatial frequency are _____ to image; high spatial frequency are ______ to image
- easy; hard
- High spatial frequency-->Spatial resolution is _______
- better
- What determines spatial resolution in CR?
- sampling frequency
- What determines spatial resolution in DR?
- DEL spacing (pixel size)
- What determines spatial resolution in F/S?
- FS size
- If field of view remains the same, spatial resolution increases as matrix size __________
- increases
- Minimum matrix size for radiography is...
-
2048x2048
(so cells of IR, computer, and monitor must each have a minimum of 2048x2048 cells) - the ability of the system to distinguish between many shades of gray from black to white
- contrast resolution
- contrast resolution is described as...
- grayscale; dynamic range
- If dynamic range is 2, the 2 shades of gray are...
- black and white (100% contrast)
- What controls contrast resolution in CR/DR systems?
- Dynamic range and SNR
- As dynamic range _______, contrast resolution gets better
- increases
- What has better contrast resolution, CR/DR or F/S?
- CR/DR
- electric response to exit beam that represents anatomy
- signal
- electric response to anything other than subject
- noise
- Is it possible to have a noise-free system?
- No, all systems have some inherent noise
- As mAs increases, SNR... and contrast resolution...
- increases; increases
- What determines image detail (spatial resolution)?
- System MTF
- What reduces contrast resolution?
- Noise
- plot of minimum visual size as a function of contrast
- contrast-detail curve
- Left side of contrast-detail curve is related to...and is limited by...
- high-contrast objects; MTF of imaging system
- Right side of contrast-detail curve is related to...and is limited by...
- low-contrast objects; noise (SNR)
- Lower curve in contrast-detail curve represents _______ contrast resolution
- better (since tissue with lower subject contrast can be imaged)
- With proper use of digital systems, patient dose can be reduced by...
- 20-50%
- Why should patient dose be less with digital imaging than F/S imaging?
- Because of higher DQE and linear IR response
- Low mAs and high kVp is preferred, but at lower techniques noise ____ and SNR _____
- inc; dec
- indicates the potential "speed class" or dose level required to acquire an optimal image
- DQE
- a measure of the efficiency with which the SNR of the incident exposure is preserved in an image
- DQE
- ____ is a measure of x-ray absorption efficiency
- DQE
- What has highest DQE? CR, DR, F/S
- DR has highest, then CR, then F/S
- PACS consists of...
- image acquisition, display workstations, and archive servers
- The software that makes PACS usable across many networks is...
- DICOM
- What allows images acquired in any modality to be viewed at any display?
- DICOM
- medical image on display monitor
- softcopy
- What is the most interactive component of a PACS system?
- display workstation
- What has replaced viewboxes?
- display workstations
- How many monitors are used for diagnostic workstations?
- 2 generally (to compare)
- What is the most important piece of the workstation?
- Monitor
- What are the 2 ways a digital image is displayed?
- As digital image composed of shades of gray, and as histogram
- Cross-sectional imaging is read on __K monitor. CR and DR on __K monitor. Mammo on __K monitor
- 1; 2; 5
- Physician review station is __K. Technologist QC station is __K
- 1; 1
- how a process is done, step-by-step; throughput
- workflow
- computers that act as file room of PACS
- archive servers
- What are used as the central hub for images sent to PACS and images viewed by doctors?
- archive servers
- the hardware and software infrastructure of a computer system
- system architecture
- Common system architectures with PACS:
-
-Client/server-based
-Distributed (stand-alone)
-Web-based - In what PACS system architecture are images sent directly to the archive server after acquisition and are centrally located, but application software is locally loaded?
- Client/server-based
- What is client in client/server-based system, and what is server?
- Display workstation. Archive server
- What is PACS workflow where acquisition modalities send the images to a designated reading station and possibly review stations, so each workstation "archives" and PACS archives?
- Distributed (stand-alone) systems
- system architecture in which images AND application software for client display are held centrally
- web-based system
- how images will be displayed on a monitor
- hanging protocols
- What type of imaging uses cine function most often?
- Cross-sectional imaging, such as CT or MRI, which has lots of images to scroll through in a stack
- Radiation safety, PPE, linearity, reproducibility are part of __ activities
- QC
- Most QC activities are part of an overall...
- QA program
- 3 major categories of QC test
-
-acceptance testing
-routine maintenance
-error maintenance - CQI focuses on...
- the processes of QC/QA programs, not on individual performance
- Quality is both _____________ -centered
- people and product
- a plan for systematic observation and assessment of the different aspects of a project, service, or facility to ensure that standards of quality are being met
- quality assurance
- a comprehensive set of activities designed to monitor and maintain systems that produce a product
- quality control
- Why are members more likely to participate in CQI?
- Because it focuses on processes, not individual performance or mistakes
- ACR recommends use of ____________ test pattern
- society of motion pictures and television engineers (SMPTE)
- AAPM recommends use of ________ test pattern
- TG18 (comprehensive)
- ACR recommends QC tests be performed _____, and AAPM has a _____ rigorous schedule
- monthly; more
- AAPM recommends that tests be done for acceptance ______ by a trained _______
- annually; physicist
- Routine QC tests are performed by...
- trained technologists or physicists
- What is the weakest link in the digital imaging chain?
- Monitor
- What do you use to measure luminance response?
- TG18-LN test pattern and photometer
- All readings on TG18-UN test pattern should be within __% of each other
- 30
- What is tested using TG18-CT pattern?
- angular response
- Speed in QC refers to processing speed of _____ and ____________ rate
- workstation; retrieval/transfer
- What is used to reduce size of image files to increase speed of network transfer of images?
- Compression
- To test compression recall...
- save several images of TG18-QC test pattern with different compression ratios (no compression, lossless compression-2:1 ratio, lossy compression-variable ratios)
- Who primarily recognizes undiagnostic images?
- Radiologist
- Who does system training for PACS?
- PACS administrator or superusers
- QC standards for image acquisition, processing, and equipment maintenance contribute to...
- TQM
- QC standards are covered by...
- ACR recommendations and AAPM report #3
- Who is the first line in preventing, recognizing, and reporting QC issues?
- Techs