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Imaging Questions
Image Questions for Radiographic Technology
| Question | Answer |
|---|---|
| Causes of Film Fog | contaminated developer, out-dated film, safelight fog, scatter radiation fog, base-plus-fog (manufacturer) |
| Spatial Resolution | Ability of the monitor to display fine details (in digital imaging systems) |
| Noise | Any graininess in the image |
| Voxel | Stands for volume element and it corresponds to the 3-dimensional volume of tissue that is represented by each pixel (digital imaging) |
| How is the electron beam in a television camera tube produced? | Thermionic Emission (just like in an x-ray tube) |
| Input Phosphor | Converts the x-ray image leaving the patient into a visible light image |
| Input Phosphor Material | cesium iodide screen |
| Electrostatic Lenses | Takes the electron image from the photocathode and maintains that image as it accelerates the electrons and focuses them on a smaller output phosphor (condensing) |
| R.A.I.D. | Redundant Array of Independent Disks is a way of storing the same data in different places (thus, redundant) on multiple hard disks |
| Amorphous | Noncrystalline state of an otherwise crystalline material |
| How fast can dynamic flat-panel detectors, used in digital fluoroscopy, capture and display an image? | 30-50 ms |
| What is the technical name of a CR imaging plate? | Photostimulable phosphor plate |
| How would dirt in the light guide of a CR reader appear on a digital image? | As white lines. - The dirt will absorb the light creating a constant loss of information. |
| Europium | Part of a photostimulable phosphor plate. It is mixed with barium fluorohalide and releases and captures electrons to create the photostimulable luminescence |
| Bit | Comes from binary digit. In machine language, a bit is either 0 or 1. 0 means the current is off. 1 means the current is on. |
| Byte | 8 bits make up a byte |
| DICOM | Digital Imaging and Communications in Medicine. Universal standard that allows various devices to work together within a network no matter the manufacturer |
| Pixel | Stands for picture element. It is each cell of an image matrix |
| Matrix Size | The number of the columns and rows |
| Field of View | Area that information is displayed within |
| What comprises spatial resolution? | Field of view and matrix size |
| Window Level | Controls image density in digital imaging systems. When the level is increased, density is increased. |
| Window Depth | Controls contrast in a digital imaging system by adding or subtracting the number of grays in an image. |
| CCD | Charged-Coupled Device. It is an array of detector elements that converts light into a proportional number of electrons |
| Algorithm | Step-by-step process that a computer uses to solve a problem, create an image, or store & retrieve information |
| Dynamic Range | Shades of gray that can be represented. The human eye can detect approx 32 shades of gray. Computer can reproduce about 1000 shades of gray. |
| In digital subtraction, which image is usually used for the mask? | The image right before the contrast appears |
| Amorphous Silicon | Releases electrons when struck by light photons with indirect digital radiography |
| Amorphous Selenium | Releases electrons when struck by x-rays with direct radiography |
| Analog Computer | Handles data composed of continuously changing electrical currents |
| Digital Computer | Handles data composed of definite quantities of current (current on vs. current off) |
| Digitization | Reduces the quantity and quality of the remaining information |
| Program | Operating instructions for the computer that provides specific instructions for calculations and the subsequent steps to be followed |
| Data | Collected facts |
| Software | Type of programs written for specific purposes |
| Hardware | Computer equipment |
| Binary Code | The code that computers operate off of. A 2 symbol alphabet is used. Off=0. On=1 |
| CPU | Central Processing Unit. Heart of the computer. Directs information to and from various components that make up the computer system |
| Bus | System of conductors that connects the various components of a computer system |
| Read Memory | Extracts information without changing it |
| Write Memory | Replaces or deletes old memory with new information |
| ROM | Read Only Memory. Contains basic operating instructions that are rarely changed. ROM is always maintained even when the computer is off. |
| RAM | Random Access Memory. Temporary storage of programming & operating instructions. Constantly being changed. RAM is erased each time the computer shuts off |
| Peripherals | Devices that allow input or output of information to and from the CPU |
| Hard Disk / Hard Drive | Memory storage device used for storing large amounts of information |
| Cursor | Visual Marker |
| Mouse | Specialized sliding control unit |
| Output Devices | CRT (monitor), Printer: Provides a means of retrieving information from the computer |
| Input Devices | device which allows one to input information into computer (mouse, keyboard, etc) |
| Array Processor | Specialized computer that functions as a peripheral; Performs all the functions at the same time and at a very high speed |
| Scanning | Type of detector used to acquire information by scanning the area |
| Array | Type of detector used to acquire information from a whole area at once (as in CT) |
| Matrix | Series of square boxes that forms the image |
| Pixel | Picture element; Individual box |
| Voxel | Volume element; Depth |
| Fourier Transformation | Transforms extremely complex information into separate but simpler functions that can be recorded |
| Convolution | Changing pixel values by mathematical formula. Sometimes called a mask, which can be reconstructed and displayed |
| Deconvolution | Process of returning the pixel values to their original level by a reverse process |
| Mask | Set of mathematical operations is placed over each pixel, then changing the pixel value |
| Frequency | Raw data before Fourier Transformation converts it to a digital image |
| Noise | Background information that is detected but doesn't contribute to image quality. |
| How does noise effect contrast? | An increase in noise causes a decrease in contrast |
| S/N Ratio | Signal to Noise Ratio; How noise is measured |
| Window Level | Controls image density; Increase in window level increases density |
| Window Width | Controls image contrast and changes visibility of detail; Increasing window width will decrease image contrast |
| Resolution | Controlled by matrix size; When matrix size increases, resolution increases |
| Bandwidth | Frequency response of the incoming signal |
| Filtering | Extracts more diagnostic information |
| Masking | Applied to filtering process to indicate which frequency has been suppressed; Masking of high frequency produces low pass filtering and vice versa |
| Smoothing | Low pass filtering; Low radiation count used in areas like NM |
| Edge Enhancement | Increases image contrast; High pass filtering used in vascular studies; Also called sharpening |
| Digital Radiography | Uses image receptors coated with barium fluorohalide screens coated with europium |
| Digital Fluoroscopy | Used to angiographic subtraction procedures |
| Digital Subtraction Radiography | DSR - Combines digitization of the image with subtraction techniques |
| PACS | Picture Archiving and Communications System |
| Archiving | Storing of images on the computer's harddrive |
| Latent Image | Image stored in the screen phosphor upon exposure to radiation; Its released upon stimulation of light |
| 2 Types of Computers | Analog and Digital |
| What does digitization of analog information always reduce? | Quantity and quality of the remaining information |
| Digital to Analog Converters are sometimes used to? | 1) Transmit data faster 2) Convert data back for digital display or processing |
| 2 Types of Memory | RAM (random access memory) and ROM (read only memory) |
| Bus speed is critical because ... | It shows how fast the computer system can function. The higher the bus #, the faster the system. |
| What fields most need array processors? Why? | CT & MRI. Array processors are very useful when using large numbers of repetitive calculations |
| Region of Interest (ROI) | Used in CT and MRI to calculate the density of structures. Helpful to determine whether structure is solid or cystic in nature. |
| What type of image is the radiology image? | Analog: Image has to be digitized so it can be transmitted faster and stored in memory. |
| Digital Image | Image thats been converted into numerical values for transmission or processing |
| The greater the _____ size, the greater the resolution | Matrix Size |
| How is digital image quality measured? | Frequency, Contrast, and Noise |
| What is frequency measured? | Amount of contrast within an image. High contrast images have high frequency and vice versa. |
| Acquired Contrast | Measure of the difference between the data values. When subject contrast is high, the acquired data contrast will also be high. |
| What type of relationship exists between window level and density? | Direct - Increasing window level will increase density. |
| What type of relationship exists between window depth and contrast? | Inverse - Increasing window width will decrease contrast. |
| Monitor Resolution | Can be 525 or 1,050 lines |
| Slow Scanning | Increases resolution. Not used in real time digital fluoroscopy |
| Low Pass Filtering | Masking high frequencies. Amplifies or deletes everything but the low frequencies. |
| Band Pass Filtering | Amplifies or deletes all but a selected range or band of frequencies. Eliminates characteristic radiation. |
| High Pass Filtering | Amplifies or deletes all but the high frequencies. Increases contrast |
| Interrogation Time | Time it takes the tube to be switched on and reach present ma and KVP |
| Extinction Time | Time it takes to switch the tube off. (EX: Esophagram using 3 frame/sec... tube has to cut on and off rapidly) |
| Digital Fluoroscopy | Requires computer, 2 video monitors, complex operating console, 3-phase generator with interrogation and extinction time less than 5ms |
| Advantage of digital fluoroscopy? | Image Subtraction |
| Array Processor Speed for DF? | 30 images per second |
| DF X-ray Tube Operation | Operates in pulses at 100-300 range to avoid quantum mottle |
| DF Image Intensifier | High resolution using a low lag plumbicon tube as image receptor |
| Temporal Subtraction | Basic subtraction image obtained (scout), then is subtracted from the late images (those with contrast). Used in fluoroscopic angiography |
| Time Interval Difference Subtraction (TID) | Permits visualization of the difference between 2 phases of vascular injection (arterial phase and venous phase). It eliminates motion. |
| Matched Filtering | Uses the sum of several images obtained when contrast is at its maximum. Then mask is subtracted from the images with maximum contrast |
| Recursive Filtering | Combines several injected images to form a subtraction |
| Dual Energy Subtraction | use 2 different x-ray beams alternating to provide a subtraction image resulting from differences in photoelectric interactions |
| Hybrid Subtraction | Combination of energy subtraction with one of the temporal subtraction techniques. Adv is it reduces patient motion |
| Pixel Shifting | Used in digital subtraction. Computer shifts pixel values. Used to overcome patient motion. |
| Computed Radiography (CR) | Uses a film cassette. Acts like a screen and receives information |
| CR Image Receptors | Screen contains a layer of europium-doped barium fluorohalide crystals (the photostimulable phosphor) |
| Image Plate Conversion - CR | Image plate reader converts latent image (analog) on the imaging plate to a digital image |
| Advantages of CR | Patient dose is decreased and digital contrast and latitude are superior. Results in fewer repeats. Can control brightness, contrast, and density. |
| Archiving | Storage of images on computer. It reduces film storage problems. Misfilings don't occur. Easy access to images. |
Created by:
team_edwards