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Digital
Digital radiography and PACS key terms
| Term | Definition |
|---|---|
| Algorithms | highly complex math formulas used during digital processing of the image to construct the image. |
| Binary Code | machine language of 1s & 0s |
| Bit | single unit of data |
| Byte | made up of 8 bits and the amount of memory needed to store one alphanumeric character |
| Motherboard | largest circuitry board inside the computer. It contains CPU, BUS, BIOS, CMOS, memory, and ports |
| CPU | brains of the computer, small chips in the motherboard that manipulate data sent from a program |
| Hard drive | main repository or storage for programs and documents on the computer |
| Contrast resolution | ability of a digital system to display changes in gray scale value, primary affected by algorithms |
| Pixel | basic picture element on a display |
| Matrix | a rectangular or square table of numbers that represent the pixel intensity to be displayed on the monitor. |
| Bit depth | the number of bits stored per pixel; the shades of gray available for each pixel |
| Voxel | volume element; individual pixel with the associated volume of tissue based on the slice of thickness |
| resolution | a number of pixels contained on a display |
| Image plate/photostimulable phosphor plate | rigid sheet of several layers designed to record and enhance transmission of image from an x-ray beam |
| Computed radiography | the digital acquisition modality that uses storage phosphor plate to produce projection images. |
| CR reader (Image plate reader) | reads and digitizes the image using a laser |
| Direct digital radiography | 1 step cassette less imaging process system where x-rays are directly converted to electric signals using photo conductor like TFT made of amorphous selenium. |
| Indirect digital radiography | 2 steps process where x-ray photons are converted to light in the scintillation layers which contained either gadolinium oxysulphide (Gd2O2S) or cesium iodide (CsI) and then the light photons are converted to an electric signal though photo-detector. |
| CCD | charged-coupled device- a photosensitive integrated circuit that stores and display the data for an image; coupling devices that acts as cameras |
| TFT | thin-film transistor; a photo detector that converts light into electrical charges. |
| Exposure index number | calculated how much radiation was absorbed; the amount of light given off or electric signal by x-ray photons received, converted and calculated. |
| Edge enhancement | high-pass filtering or masking; occurs when fewer pixels in the neighborhood are included in the signal average. amplify particular known frequencies in an image while suppressing others. |
| Digital radiography | cassette less systems that use an x-ray absorb material coupled to a flat-panel detector or CCD to form an image |
| Sensitivity "S" number | one of the exposure index number used by Fuji, Phillips and konica Minolta, the numeric value of exposure received by the receptors in the digital systems. |
| DICOM | Digital imaging and Communications in Medicine. A format or device that allows virtually all electronic components to talk to each other. |
| WAN | Wide area network- network that spans a large area, city, state, nation continent or world |
| LAN | local area network, small area network with cables or wireless access points so that computers can share information and devices on the same network. |
| PACS | Picture Archiving and Communications Systems- a networked group of computers, servers and archives that can be used to manage digital images. |
| HL-7 | Health level 7, standard protocol used for medical data system |
| EMR | electronic medical records, a digital version of paper charts in the medical office. |
| Smoothing | low-pass filtering, averaging surrounding pixel to remove high frequency noise, reduction of noise and contrast |
| SNR | signal to noise ratio, the amount of total signal vs the amount of noise present in any digital image. mAs increased as SNR increased; higher signal, lower noise |
| CNR | contrast to noise ratio, a measure used to image quality |
| Detector element | AKA DEL, pixel-sized piece of information |
| Spatial frequency | spatial resolution- the amount of detail or sharpness in a digital image. Ability to image small objects that have high subject contrast. |
| post processing manipulation | any image manipulation done after x-ray is taken |
| contrast enhancement | post processing that alters pixel values to improve contrast |
| Shuttering | used to blacken out the white collimation borders in a digital image and eliminating veil glare |
| Noise | any type of signal interference in a digital image |
| brightness | level of intensity of a digital image on a display monitor |
| dynamic range | range of densities, the ability of an imaging system to respond to varying level of exposure |
| receptor contrast | the fixed characteristic of receptor. |
| exposure latitude | the amount of error that can be committed and still in the capture of a quality image. |
| Subject contrast | the magnitude of the signal difference in the remnant beam |
| window width | control the ratio of black and white; contrast |
| window level | control how light or dark the image, brightness and densities |
| Moire pattern | occurs when the grid lines and the scanning laser are parallel, produce a wavy artifact |
| DQE | detective quantum efficiency, measurement of how efficiently a system converts an x-ray input signal into useful output image |
| Saturation | extreme overexposure will create "black holes" in low density tissue areas on the image. increase of mAs at least 4 times more than the necessary. |
| automatic rescalling | occurs when exposure is greater or less than the optimal amount to produce diagnostic image, fix exposure errors |
| stitching | software that combine multiple images together |
| annotation | preset terms or manual text input that can be overlay the image during post processing |
| histogram | a graphic representation of all of the digitally recorded signals of a digital x-ray exposure. |
| Nyguist theory or theorem | need at least twice the number of pixel or the highest frequency to form or reproduced an image |
| digital imaging | any imaging acquisition process that produces an electronic image that can be viewed, manipulated on a computer |
| look-up table | a table that maps that image gray scale into some visible output intensity on a monitor or printed film; processing software based on algorithms specific to density |
| analog | refers to a device or system that captures or measures a continuously changing signal, recorded or used in its original form |
| pixel bit depth | the number of bits within a pixel |
| FOV | field of view; x-ray field, the amount of body part or patient included in the image. |
| air kerma | kinetic energy released per unit mass (joules) absorbed in unit of air, expressed as j/kg or gray (Gy) |
| K ind | Indicated equivalent air kerma- the measurement of the radiation that was incident on the IR for that particular exposure. the amount of exposure on the IR, read pixel values. |
| DI | deviation index- the difference between the actual exposure (K ind) and the target exposure (K tgt) |
| image manager | contains the master database of everything that is in the archive. Controls all DICOM processes. |
| RAID | redundant array of independent (inexpensive) disk-short term storage |
| Quality assurance | a plan for the systemic observation and assessment of the different aspect of a project, service, or facility to make certain that standards of quality are being met. focus on people |
| Quality control | a comprehensive set of activities designed to monitor and maintain system that produce a product. focus on equipment |
| Photometer | device to measure the luminance of a monitor |
| SMPTE pattern | Society of Motion Pictures and Television Engineers test pattern-used to determine if the monitor is playing any distortion over the display |
| CQI-contionous quality improvement | tends to focus on the process rather than on the people or the service. total quality management that includes maintenance of equipment, image acquisition and processing standards. |
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Momomuff
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