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Digital Imaging
Abbreviations and Terminology
Question | Answer |
---|---|
ADC | Analog to Digital Converter |
CPU | Central Processing Unit |
CR | Computed Radiography |
DICOM | Digital Imaging and Communications in Medicine |
DR | Direct Radiography Direct Digital Radiography |
IP | Imaging Plate |
PACS | Picture Archiving Communication System |
PMT | Photomultiplier Tube |
ROM | Read Only Memory |
RAM | Random Access Memory |
RF | Radio Frequency |
HL7 | Health Level 7 - standard protocol used for medical data systems |
EMR | Electronic Medical Record |
CCD | Charge Coupled Device |
PRIEF | Partition Recognition of Irradiated Exposed Fields |
EDR | Exposure Data Recognition |
ACR | American College of Radiology |
bit | single unit of data, binary digit, an 8 bit ADC encodes 256 values |
bus | system of controls that connects various components of computer system |
byte | made up of 8 bits and is the memory needed to store one alphanumeric character |
dynamic range | the shades of gray that can be represented |
edge enhancement | increases in contrast due to high-pass filtering; also known as sharpening |
lattitude | the range of exposures that will produce densities within the diagnostic range; the range between the minimum and maximum exposures that will produce and acceptable range of densities for diagnostic purposes |
matrix | the layout of rows and columns of pixels |
noise | random background information /quantum mottle /grainy appearance |
pixel | the picture element box of a digital image |
program data | operating instructions |
resolution | the ability to distinguish 2 adjacent details as being separate and distant from each other |
quantum mottle | graininess caused by a lack of sufficient incoming data to process an image also known as quantum noise |
voxel | three-dimensional volume correlating to each pixel |
partitioned pattern recognition | recogntion of divided exposure patterns |
exposure field recognition | Fiji system's method of locating the raw data |
histogram | graphic representation of pixels and signal intensities present in an image; generated by dividing a scanned area into pixels and determining the signal intensity for each pixel; can be calculated for specific anatomy and procedures |
look-up-table | reference histogram of the luminance values cerived during image acquisition |
image stitching | process of "sewing" together multiple images to form one continous image |
direct aquisition | the direct conversion of x-ray energy to electrical signals without the light-conversion step |
indirect acquisition | 2 step process in which x-ray photons are converted to light and then the light photons are converted to an electrical signal |
data clipping | clinically irrelevant data is not included in image display |
flat panel detector | descriptive term used for the plates used in both direct and indirect digital systems |
flat field detector | detector that consists of a photo-conductor which holds a charge on its surface that can be read out by a thin-film transistor |
HIS | Hospital Information System |
RIS | Radiology Information System |
RAID | redundant array of independent disks |
JPEG | The Joint Photographic Experts Group |
DAS | direct attached storage |
soft copy | computer image |
hard copy | printed image |
jukebox | storage system that houses removable media and robotics to deliver the digital media |
compression | a mathematical reduction of the size of a piece of data to reduce the amount of time needed to transmit the data or the amount of space needed to store it. |
lossless | Reduces the size of a piece of data so the process can be mathematically reversed perfectly. There is no loss of information. |
lossy | There will be loss of image information that can never be completely reversed. |
redundancy | able to store and retrive digital images multiple ways |
reliability | able to move images back and forth without interuption |
shuttering | used to blacken out the white collimation borders in a digital image, effectively eliminating glare |
cropping | post processing elimination of some of the areas within the digital image where the exposed area of the patient part was exposed with radiation. Violation of ALARA and ASRT Code of Ethics. |
Nyquist theorem | when sampling a signal such as the conversion from an analog to a digital image, the sampling freguency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect |
bandwidth | the frequency response from the incoming signal |
band-pass filtering | amplifies or deletes all but the selected range or band of frequencies |
characteristic curve | a radiographic relationship between the amount of exposure and the resultant density on the image; also known as the Hurter and Driffield curve (H&D curve); also called the D log E curve |
DQE | detective quantum efficiency ; measurement of how efficiently a system converts x-ray input signal into a useful output image |
EI | exposure index |
S number | sensitivity; how you know the exposure factors were set properly |