Unit 1 (Overview and Processing Concepts)
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What is another name for Digital Imaging?
What allows the attenuated beam to be recieved by either CR or DR digital detector rather than an x-ray film cassette?
What changes the information to an electronic form?
Analog to digital convertor (ADC)
What changes digital image data to the displayed image?
Digital to analog convertor (DAC)
Name some image storage devices:
- magnetic tapes
- laser-optic discs
- RAID (redundant array of independent discs)
What is the standard that allows software's to communicate with each other?
DICOM (Digital Imaging and Communications in Medicine)
What is another name for the characteristic curve?
the H & D curve (views ranges of density offered)
What are three of film-screen radiography?
- it cannot show tissue differences in tissue contrast less than 10%
- if inappropriate technique is used repeat exposure is necessary to correct it
- requires manual archival and retrieval (of film)
Name the seven major components of a digital radiographic imaging system:
- Data Acquisition
- Computer Data Processing
- Image Display
- Post Processing
- Image Storage
- Image and Data Communications
- Image and Information Management
What refers to the collection of x-rays transmitted through the patient, which takes place at a detector?
Where does the ADC send the digital data?
to the CPU (central processing unit) for processing
The computer uses special software to create or build up digital images using what type of system?
a binary number system
Binary system operates on discrete values of:
"0" or "1"
Describe the relationship amounts between digits, bits and bytes (in the binary system):
- one digit makes a bit
- eight bits make a byte
After the image is displayed via monitor, what can alter the input image in order to enhance diagnosis?
Name 5 post processing enhancements:
- Image noise reduction
- Enhance image sharpness
- Change image contrast
- Stitch several images together
- Gray scale mapping
Name some systems of Image and data Communications (5):
- LANs (Local Area Network, ex. co-lin)
- WANs (Wide Area Network, ex. internet)
- PACs (Picture and Archiving Communication System)
- RIS (Radiology Information System)
- HIS (Hospital Information System)
HIS - medical records; integrated with PACs using DICOM and HL-7
What is used to reduce storage space and decrease the image transmittion time?
Name the two types of image compression and their differences:
- Lossless Compression - reversible; no loss of info
- Lossy Compression - irreversible; loss of info
Which information management systems are textual and which are for images?
- textual - RIS and HIS
- images - PACS
What is a model for ensuring that the standards for communication (DICOM and HL-7) work effectively to facilitate integragion?
- Integrating the Health Care Enterprise
- originated in 1998 by RSNA (Radiologic Society of North America) and HIMSS (Healthcare Information Management Systems Society)
What is the technical framework of "Integrating the Health Care Enterprise" based on (3)?
- Data Model
- An Actor
- An Integration Profile
Who introduced CR?
- Fuji Medical Systems, in 1983
- (also Agfa, Kodak, Konica, and Cannon)
What is the IP plate coated with?
Barium-fluoro-halide (a photostimulable phosphor)
Review the basic steps to the production of a CR image:
- 1. IP plate x-rayed, electrons move to higher energy level as the "latent image"
- 2. IP plate fed into Image Reading Device (IRD) to a laser beam, exciting electrons to release energy in form of light
- 3. The light is collected by a photomultiplier tube (PMT) which transfers light to electrical energy that is sent through ADC to produce digital data
- 4. Digital processor processes digital data to produce image viewable on monitor
- 5. Very intense light scans IP to erase residual latent image
- 6. IP to be reused
What are two categories of flat-panel detectors?
- indirect conversion (includes light)
- direct conversion (does not include light)
List the flow of conversion for both indirect and direct conversions:
- x-ray --> light --> electrical signal --> image
- x-rays --> electrical signal --> image
What absorbs x-ray photons, converts them to light photons, and channels them to photodiode array?
Cesium Iodide Scintillator
What does a direct-conversion detector use to convert x-ray photons into an electric charge?
amorphous selenium, a photoconductor
What does an indirect-conversion detector use to convert x-rays into an electrical charge?
amorphous silicon photodiode arrays or CCDs
What is a software that is used in digital mammography which allows for enhancement of microcalcifications and malignant lesions and can also function as a "second reader"?
Computer Aided Diagnosis (CAD)
Two names for using software to get rid of high or low energy ranges:
- Dual energy subtraction
- Contrast enhancement
What aspect of Digital Fluoroscopy increases the photons energy while significantly decreasing dose to the patient?
What type of digital fluoroscopy can increase detail, can even color-code different vessels based on their frequencies?
Digital Subtraction Angiography (DSA)
What standard is concerned primarily with textual information from the HIS and RIS?
What are the three intentions of QA/QC policies?
- ensure that the ALARA principle is upheld
- produce optimum image quality for diagnosis
- reduce the costs of radiology operations
What is the application of information of information technology to medical imaging?
medical imaging informatics
The information shared with the computer is which image?
the input image
Once the computer processes the digital image, it can be called the:
output image or manifest image
When and by whom did digital processing begin and for what purpose?
- several decades ago
- NASA (National Aeronautics and Space Administration) space program
- to manipulate images sent back by the Ranger spacecraft
Who helped to conceptualize images as a subset of all objects and when?
What is included in Subsets of the image (4)?
- visible images
- invisible images
- optical images
- mathematical images
Describe the two Mathematical Image types we covered:
- continuous function - analog; fluxuates; wave-like
- discrete function - digital; 1 or 0; on or off; very precise; better resolution
How is an analog image obtained?
by having a light source that scans from left to right in front of the object and photomultiplier tube recieve the varying levels of density
Quite simply, a digital image is a numerical representation of:
What are the two image domains that represent images in radiology?
- spatial location domain
- spatial frequency domain
Which domain is involved as a numerical image arranged in a manner that the location of each number in the image can be identified using X-Y coordinate system?
Spatial location domain
Which domain is involved as the number of times a signal changes direction in a given length?
Spatial frequency domain
Small structures produce ______ frequencies and large objects produce ______ frequencies.
In Spatial Location Domain, each ______ has a specific numerical value?
When the numerical value of a pixel in Spatial Location Domain is higher, what type of tissue is usually represented?
muscle, tissue (higher = more information)
When the numerical value of a pixel in Spatial Location Domain is lower, what type of tissue is usually represented?
bone (lower = less information)
In Spatial Frequency Domain, higher frequency better represents:
"the small" (higher resolution)
In Spatial Frequency Domain, lower frequency better represents:
"the large" (lower resolution)
What allows for radiography digital processing to change spatial location domain to spatial frequency domain?
The Fourier Transform
What allows for radiography digital processing to change spatial frequency domain to spatial location domain?
The Inverse Fourier Transform
The radiologist would probably prefer to view in the ______ ________ domain.
Physicists and engineers would prefer to view in the ________ ________ domain.
Five fundamental classes of operations of digital imaging include :
- image enhancement
- image restoration
- image analysis
- image compression
- image synthesis
What are some of the ways Image Enhancement is achieved (5)?
- contrast inhancement
- edge enhancement
- spatial and frequency filtering
- image combining
- noise reduction
What two classes of operations are used to isolate and highlight objects of interest?
- image restoration
- image analysis
What is the newest addition to image compression and its advantages?
- wavelet (special waveforms)
- no loss in either spatial or frequency information; able to store more with less memory space
What creates images from other images or non-image data, or "interperlating"?
What are the characteristics or fundamental parameters used to describe digital imaging?
- matrix (2D)
- Pixels (2D)
- Voxels (3D)
- Bit Depth (3D)
- Appearance of Digital Images
In radiology, we refer to a matrix as the:
Field of View (FoV)
The formula to calculate the size of the image is:
The formula to calculate the sice of the pixel is:
Pixel size = FOV/Matrix Size
If the discrete value number of a pixel is higher, the brightness will ___________.
Pixels in a digital image represent the information contained in a volume of tissue in the patient...this volume of tissue is:
voxel (volume of element); the z axis
The number of bits per pixel is the:
What calculates the total number of shades available in bit depth?
2 to the power of bits available
Three steps to digitizing an image:
this process will change the algorithmic values to make the image brighter/less bright as needed
Name three general processing operations of Gray-Scale Processing:
- Image Subtraction
- Temporal Averaging
Name three general processing operations of Local Processing Operations:
- Spatial Filtering
- Edge Enhancement
Name four terms to describe gray-level mapping:
- contrast stretching/enhancement
- histogram modifications/stretching
- LUT (Look up Table)
________ histograms offer low contrast, while ______ histograms offer high contrast.
What is a graph of the number of pixels in the entire image or part of the image having the same gray levels?
histogram (petrometer in analog)
Name some aspects of Windowing:
- Window level changes the brightness/density
- Window width changes the contrast
What allows brightness and contrast to be changed when values are out of the norm?
- Look Up Table (LUT)
- restricts the range (takes away sections of white-white and dark-dark)
What changes the variation of adjacent pixel density values (by at least greater than 10% difference)?
- Look up Table (LUT)
- the higher the number, the lower the brightness
Where is the output pixel value obtained?
from a small area around the corresponding input pixel
When finding the output pixel value, the average is computed using a group of pixel called a ________________.
__________ post processing is also known is spatial frequency processing.**
Which does not occur in gray scale processing?
C. Temporal averaging
D. Image Subtraction
(this multiple choice question has been scrambled)
High-Pass Filtering is used to ____________ in spatial frequency.
- Sharpen (by suppressing lower frequencies)
- A.K.A. Edge Enhancement Sharpening
Low-Pass Filtering is used to _________ in spatial frequency.
Smooth (by suppressing higher frequencies)
What is produced from the Low-Pass filtering process subtracted from the original image?
- Unsharp (blurred) Masking
- changes a blurred image to a shart image
What implies that ALL of the pixels in the entire input image are used to change the value of a pixel in the output image?
Global Processing Operations
What allows for the position of orientation of the pixels within the image to be changed in order to enhance dignosis?
Geometric Operations result in:
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