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114 Cards in this Set
- Front
- Back
Anatomic Alignment |
Since the amount of radiation required to produce a quality, diagnostic radiograph depends on the cell selected, careful positioning and central ray centering is required when using AEC techniques. |
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Spatial Resolution |
The ability of the system to record adjacent small structures, equipment related. |
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Pixel |
Picture element; smallest component of the matrix |
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Pixel pitch |
The pixel spacing or distance measured from the center of a pixel to the center of an adjacent pixel. |
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Pixel Size |
The measure of the pixel from end to end |
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Pixel Density |
Number of pixels per unit area (millimeter) |
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Matrix |
Combination of rows and columns of pixels that make up a digital image. |
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CNR |
As noise increases it is more difficult to visualize low contrast objects. |
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Affected Focal Spot Size is.... |
always bigger than the effective focal spot size bc more photons are hitting it. |
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The anode is made of... |
Tungsten |
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The anode base is made of... |
Copper, molybdenum, or graphite. |
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Induction motor operate the... |
Rotor that spins the anode. |
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Isotropically |
Produced with equal intensity in all directions. Fact: xray beams are isotropic. |
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Leakage Radiation |
Photons produced in the X-ray tube that are traveling in all directions other than toward the patient. (Emitted through the metal protective housing of the tube) Should not exceed 100mR/hr at 1 meter. |
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AEC relies on... |
Effective and accurate patient positioning and photo time cell selection. |
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AEC is NOT |
Intended to be a means of primary termination of exposure. PT safety device in case machine malfunctions. |
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Minimum Response Timer (MRT) |
The time is takes for a system to respond and send the signal to terminate the exposure. |
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Sampling Frequency |
The number of pixels sampled per millimeter as the laser scans each line of the imaging plate. |
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Aperture Diaphragm |
Simplest type of beam restricting device. Lead plate with hole cut in the middle that is smaller than the IR size. |
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Variable Aperture Collimators |
Beam restricting device that can be controlled by the radiographer. Utilizes a light-localization device to estimate the size and shape of the radiation field. |
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Cylinders and Cones |
Beam restricting devices that attach to the bottom of the collimator housing. Creates circular shaped collimation. |
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Collimation |
Most common type of beam restricting method. |
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Electrical energy supplied to the xray unit is? |
Alternating Current (AC) |
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Induction requires.. |
AC current |
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Transformers operate on the principle of? |
Electromagnetic induction and require AC current to operate. |
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Self Induction |
The changing magnetic field that is created by inducing an opposing voltage in a single coil of wire. |
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Mutual Induction |
Inducing a current through a secondary coil by varying the current through the primary coil. |
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Electromotive Force (EMF) |
Voltage |
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Increasing the sample frequency... |
Results in the laser moving a smaller distance and there is an increase in spatial resolution. |
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Shell Core |
Type of transformer. Most efficient and commonly used of the transformers. |
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Types of transformers: |
Air Core, Open Core, Closed Core, and Shell Core. |
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Autotransformer |
A single coil conductor material acts as both primary and secondary sides of the autotransformer. Purpose is to determine the amount of line voltage that will be sent to the step-up transformer. Operates on Self Induction. |
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What is the source for KVP? |
Autotransformer |
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Step-up Transformer aka (high voltage transformer) |
Separates xray circuitry into primary or low voltage and secondary or high voltage sections. Operates on mutual induction. Converts low voltage from the secondary side of the autotransformer into the high voltage or KV required to produce an xray in the tube. |
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Filament transformer (aka low voltage or step down transformer) |
Takes care of thermonic affect. Operates on mutual induction. |
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mA station |
Selected by the rad tech, determines the amount of current and voltage sent to the primary side of the filament transformer. (Varies the level of resistance) |
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Pre-reading KVP meter |
Read voltage, NOT KILOvoltage. |
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Mechanical Exposure timer |
No longer in use |
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Synchronous Exposure Timer |
Capable of exposure times in multiples of 60 |
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Nyquist Frequeny |
is the relationship between the sampling frequency and the spatial resolution. |
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Electronic Exposure Timer |
Complex, accurate up to 1 millisecond. (Most accurate) |
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mAs (exposure timer) |
Establishes the highest, safest mA at the shortest exposure time. |
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AEC exposure timer |
Utilizes an ionization chamber placed between the patient and the image receptor. |
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mA Selector |
Variable resistance |
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Focal Spot Selector |
Purpose is to select the size of the filament within a dual filament X-ray tube that will be used to produce a source of free electrons. (Can withstand heat) |
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In the U.S., electrical energy is supplied in 60-cycle alternating current. |
Each Cycle consists of 2 pulses of electric current, with the pulse going in the opposite directions. 1 cycle= 2 pulses= 2 alterations of electric current. |
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Rectifiers |
Devices that convert alternating current into direct current. |
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Half wave rectification |
The negative pulse of each cycle of alternating current is prevented from going across the X-ray tubes. |
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Full wave rectification |
The negative pulse of current is redirected through a series of valve tubes in order to be applied to the cathode side of the X-ray tube. |
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High frequency |
Voltage ripple is 1% since the voltage waveform is nearly constant. |
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Contrast Resolution |
The ability to detect subtle changes in the grayscale. |
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Image intensifier function |
To convert the xray beam into a bright visible light. |
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Input phosphor |
Converts the incoming xray photons. Typically made of cesium iodide. |
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Photocathode |
Converts light photons from the input phosphor into free electrons. |
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Anode |
Allows the electrons to pass through the output phosphor. |
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Output Phosphor |
Converts electrons sent from the photocathode into light photons. Typically made of zinc cadmium sulfide. |
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XLELM |
Xrays-light-electrons-light-monitor |
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Brightness Gain |
The expression of the ability of an image intensifier tube to convert xray energy into light energy and increase the brightness of the image in the process. |
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Cone Cells |
Bright light vision (phototopic) |
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Rods Cells |
Low light or night vision (scotopic) |
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Vignetting (Pin Cushion Distortion) |
The apparent loss of detail and fall off of brightness along the edge of the flouroscopic image. |
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DEL (detector element) |
Size is used with direct capture radiography (cassette less). Spatial resolution is determined by the DEL. As the DEL increases, spatial res decreases. |
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Cine Fluoroscopic Device |
Exposed by light from the output end of the image intensification tube. Gives highest pt dose. |
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Automatic brightness control (ABC) or Automatic Exposure Rate Control (AERC) |
A function of the fluoroscopic unit that maintains the overall appearance of the image by automatically adjusting the KVP, mA, or both. |
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Magnifying the fluoroscopic image results in... |
Increased patient dose, but yields better spatial resolution and better contrast resolution. |
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Fluoroscopy is the... |
Single greatest source of acute radiation exposure to the patient in the diagnostic radiology environment. |
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Cassette Based (digital detectors) |
Photostimuable phosphor plate (PSP) |
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Cassetteless (digital detector) |
Flat panel detector/thin film transistor (FPD/TFT) |
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Phosphor or Active Layer |
This layer contains the photostimuable phosphor that “traps” electrons during the radiographic exposure. |
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Violet light is viewed by? |
A very sensitive photomultiplier |
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S or Sensitivity Numbers |
have an inverse or indirect relationship to the amount of exposure. |
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EI or Exposure Index |
Has a direct relationship to the amount of exposure. |
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quantum mottle |
Type of noise that results when too few xrays reach the IR causing the image to be underexposed. (Contrast loss) |
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Lgm or logirithum |
Median exposure has a direct relationship to the amount of exposure. |
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Flat panel detector: indirect |
scintillator based systems use cesium iodide (CSI) or gadolinium oxysulfide. The scintillator converts xray photo into light photons. |
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Flat panel detector: direct |
Non-scintillator based system. This system uses amorphous selenium (a-Se), which converts the xray beam into electrons. |
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Charged couple device (CCD) |
A light sensitive semi-conducting device that generates an electrical charge when stimulated by light and stores this charge in a capacitor. |
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Complimentary Metal Oxide Semiconductor (CMOS) |
A scintillator device made of a crystalline silicon matrix. |
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Low S |
Overexposed |
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High S |
Underexposed |
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Analog to digital converter (ADC) |
A device that takes the analog signal and divides it into a number of bits that the computer “understands.” |
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Histograms |
Used to represent a graphical representation of optimal densities during an exposure, and recognition of exposure data requires processing only by optimal receptor exposure exposures. |
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Rescaling |
A digital reprocessing technique that is used to modify an overexposed or underexposed image. |
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Contrasts Resolution/Dynamic Range |
The range of exposure intensities that an image receptor can respond to and squire image data. Greater dynamic range will yield in greater contrast resolution. |
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Equalization |
Method of image processing using the histogram of the image to adjust contrast. To improve image display range. |
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Electronic Collimation |
Masking (Subtraction) |
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Stitching |
Computer programs an “stitch” images together to combine multiple images for anatomy that is too large for a single exposure. |
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Shuttering |
Removes or replaces the background |
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Spatial Resolution |
Ability to distinguish between adjacent objects on the radiographic image. (Small recorded detail) |
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Windowing |
Ability to alter the receptor exposure and contrast of a digital image following processing. |
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Hounesfield unit |
Value related to the attenuation characteristic of the tissue in the voxel but not an attenuation coefficient. |
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FOV |
Diameter of the image reconstruction. |
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Window leveling |
Determines brightness |
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Window width |
Determines the gray-scale, image contrast. |
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Signal to Noise Ratio (SNR) AKA Contrast Noise Ratio (CNR) or Signal Difference to Noise Ratio (SDNR) |
Ratio between “signal” or meaningful information and “noise” or background. (The more signal, the greater the spatial resolution) |
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Wider window widths |
Results in long gray scale (low image contrast) |
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Narrow window widths |
Produce a narrow gray-scale (high image contrast) |
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Digital imaging and communication in medicine (DICOM) |
Accepted standard for networked medical devices to exchange the images and information. |
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Picture archival and communication system (pacs) |
Consists of digital acquisition equipment, workstations for display and manipulation of images and interconnected storage devices that communicate over a network in the same language. |
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Teleradiology |
Process of remote transmission and viewing of images. |
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Hospital Information System (HIS) |
Contains full patient information |
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Radiology information system (RIS) |
Contains radiology specific information about a patient including the radiologist’s report. |
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What is the amount of change in mas necessary to yield a noticeable difference in receptor exposure change within the radiographic image? |
30% |
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SNR |
As noise increases it is more difficult to visualize small objects. |
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The five things that must be present on a radiograph are: |
1) Pt Name 2) PT ID # 3) Markers 4) Exam date 5) Institutional Name
DOB and DIGITAL markers are not mandated. |
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Dynamic Range |
The range of exposures that can be captured by a receptor. |
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Exposure latitude |
The range of exposure that produce quality images at an appropriate patient dose. |
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Quantization |
Is the process of turning electrical signal into a DIGITAL image. |
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Bit Depth |
The total number of possible brightness levels that an be assigned to any given pixel in the digital image. |
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Histogram |
Frequency of recorded exposures. (Graph form) |
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Rescaling |
Adjusts histogram to expected values. This makes of for any small technique errors the tech may have made. |
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Histogram analysis |
Identifies the values of interest (VOI) |
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Look Up Table (LUT) |
used to correct brightness and contrast |
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Correct body part and correct collimation = ? |
The correct histogram processing. |