Digital Imaging Flashcards
A Digital Image is made up of what?
Matrix- Rows and Columns
Pixel- The little boxes within
(Digital Image Characteristics)
- Stored as digital date
- Must be processed by a computer for viewing on a display monitor
Latent Image
What are two types of digital radiographic systems?
- Computed Radiography (CR)
* Direct Radiography (DR)
________ resolution refers to the smallest object that can be detected in an image?
Spatial
Picture archival and communication system; consists of digital acquisition, display workstations and storage devices interconnected through a network
PACS
Digital imaging and communications in medicine; standards that allow imaging modalities and and PACS to communicate the same “language”
DICOM
A network that connects computers locally across short distances, for example within a building or complex
LAN
A computer network that extends over a larger area, which can include global coverage
WAN
Hospital information system; hold patients full medical information from hospital billing to inpatient ordering
HIS
Radiology information system; holds all radiology specific date, including patient scheduling
RIS
Failure of an imaging system to record densities usually caused by lack of x–ray photons
Quantum Mottle/Noise
FOV
Filed of View
What happens if you increase the number of pixels when you print an image
It improves spatial resolution, however it increases computer processing time, network transmission time and digital store space.
(Digital Image Characteristics)
Digital Image- can be manipulated by computer
- Alter brightness
- Change Contrast
(Matrix- rows and columns, Pixels- picture element)
FOV- Field View
Dimensions of an anatomic area
Digital quality improved with larger matrix size
What is directly related to FOV?
Pixel Size
Ex; increasing the field of view for the SAME MATRIX will increase the size of the pixel- decrease spatial resolution
What is Inversely related to matrix size?
Pixel Size
Ex; increasing the matrix size for the SAME Field of View will decrease the size of the pixel- this will increase spatial resolution
The pixel spacing or distance measured from the center of a pixel to an adjacent pixel
Pixel Pitch
A greater number of pixels per unit area
Pixel Density
What are two types of digital image receptors?
Computed radiography (CR) Direct Radiography (DR)
- Combines image capture & image readout process
- Images are available almost instantly after exposure
- DR receptors are more fragile & expensive than CR IRs
Direct Radiography
Pixels
- Increasing pixel density and decreasing pixel pitch increases spatial resolution
- Decreasing pixel density and increasing pixel pitch decreases spatial resolution
Computed Radiography Image Receptors (CR IRs)
- Portable or fixed in a table
* Includes a cassette that houses the imaging plate
What are the two step process for image acquisition in Computed Radiography Image
1) Image Capture in the imaging plate
2) Image readout
(longer delay between image capture and image readout)
Digital Image vs. Computer Image
- The detector system is usually dedicated to a single room and can be permanently mounted
- Flat panel detectors are also mobile IRs and can be removed from Bucky and used on table top
- After exposure digital image is available within milliseconds on viewing monitor
- Flat panel system are highly dose efficient and provide quicker access to images
- The spatial resolution of flat panel receptors is general superior to that of CR
A digital composite of the varying x-ray intensities exiting the patient
Image Matrix
What happens to an x-ray when the intensities are converted to numeric data?
The digital image can be electronically processed, manipulated, transported or stored.
Computer software operations available to you that allow manual manipulation of the displayed image
Post-processing
Sets the midpoint of the range of brightness visible in the image
Window level
A control that adjusts the radiographic contrast-
Window width
(Narrow) increases the image contrast
(Wide) decreases the image brightness
An image-processing technique commonly used to asses the raw data prior to image display
Histogram Analysis
True of False: Does digital IRs have a much wider dynamic range than film screen detectors?
True- small degree of under or overexposure is okay
True of False: Too low or too high exposure techniques guarantee a quality digital image?
False: It is NOT guaranteed
Represents the number of digital pixel values versus the relative prevalence of those values in the latent image
Histogram
- amount of exposure is on the x-axis
- the incidence of pixels is on the y-axis
