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Power Point questions

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Answer
show the ability of the detector to detect and respond to very low levels of visible light or radiation. Similar to DQE Important because it affects patient dose  
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Describe DYNAMIC RANGE - detector   show
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show DIRECT the more sensitive the detector, the higher the DQE  
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What is a CCD?   show
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show Orth p307 detective quantum efficiency a measurement of overall efficiency with with the detector can convert the x-ray input signal into a useful output image  
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show Increased dynamic range/wide exposure latitude Greater contrast resolution immediate results improved workflow  
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show lower spatial resolution image quality depends on processing and display monitor characteristics  
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show Signal to Noise ratio white noise interferes w/digital image; measure of translation of latent image to electronic image; measures contrast resolution P p48 std method to express noise vs signal strength  
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show contrast to noise ratio; ratio between image contrast and image noise; can be used to describe image quality how well the latent image subject contrast translates to image contrast  
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What impacts spatial resolution in detector?   show
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What is sampling ?   show
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What is sampling frequency?   show
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How does pixel pitch affect pixel size?   show
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What is fixed sampling versus fixed matrix?   show
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show a layer of photostimulable phosphor that interacts with the x-rays to create the latent image in CR - commonly used BaFl and Europium  
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How does DEL/dexel size affect spatial resolution of the detector?   show
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What is fill factor?   show
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What is the relationship of spatial resolution to DEL size?   show
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Define LUMINESCENCE   show
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show emission of visible light during and after stimulation  
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Define FLUORESCENCE   show
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show Random size and spread of crystals - creates light spread - lower spatial resolution Most CR phosphors are turbid  
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What is structured phosphor and how does it affect spatial resolution?   show
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show BOTH direct and indirect all have TFT array/AMA array composed of dexels/DELs  
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show decrease DEL size to increase SR nn increase in mAs to get enough SNR If we make the dexels smaller, the fill factor will go down. The 20% part cannot be made smaller, so we need to increase the mAs to decrease the SNR from the smaller fill factor  
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Describe DR plate elements.   show
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show Orth p307 the material that captures the x-ray photons in CR, it is the photostimulable phosphor in DR, it is the NaI, CsI, and GdOS for indirect Direct DR - amorphous Selenium  
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What is conducting element?   show
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What is collecting element?   show
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Describe elements of CR plates   show
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Describe elements of early Indirect DR plates.   show
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show Capture element - CsI and GdOS p274 Orth Coupling element - contact layer (amorphous silicon semiconductor) painted onto the glass substrate Collecting element - TFT  
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Describe elements of Direct DR   show
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show photomultiplier tube - a light sensitive device used to convert the light into electronic signal  
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show secondary release of light; phosphor releases trapped energy as light when re-excited by infrared or visible light Helium Neon laser causes this in CR reader  
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show invisible image captured on IP (CR or FPD (until activated by CR reader or processed by digital system to become visible image)  
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show a. segmentation/exposure field recognition/data recognition b. Histogram analysis c. Automatic rescaling/normalization (RISK of FAILURE) d. LUT  
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show Thin-film transistor - a charge collection electrode (senses ELECTRONS) - it is a switch that is closed during exposure, allowing the charge in each DEL to be collected and stored.  
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Where is the risk of failure?   show
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Describe SEGMENTATION/EXPOSURE FIELD RECOGNITION.   show
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Describe HISTOGRAM ANALYSIS/construction.   show
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Describe HISTOGRAM ERROR.   show
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Describe SEGMENTATION for CR.   show
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describe CR - image artifacts   show
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show errors creating image during segmentation because system doesn't recognize actual exposure field. Place the part as much as possible in the CENTER aligned lengthwise. when views are non-symmetrical -  
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Describe histogram construction   show
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Describe histogram graph.   show
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Are collimated field borders important to image processing?   show
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show PP p5 formula or set of rules for solving problem  
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show PP p5 graphical representation of different body tissues SPATIAL RESOLUTION  
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show PP p5 Look Up Table histogram of luminance values (image display) for pixel values CONTRAST p165 Papp maps the image grayscale values into some visible output intensity on the monitor  
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Describe Segmentation. lecture 2hr 20min   show
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show Selecting correct exam (choose unique histogram) tells system how to process image. If choose incorrect exam, system must post-process data resulting in loss of info, unless repeat; choose correct technique; Steps - select exam, histogram applied, LUT  
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Describe Ideal, appropriate and inappropriate collimated fields.   show
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Describe HISTOGRAM ALGORITHM function.   show
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Describe LUT ALGORITHM function.   show
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show system compares image data histogram with stored image histogram reads data from left to right (low to high)(white to black)  
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show White grays are on the left side and represent collimation, scatter then bone Possible prosthesis/Barium which can cause histogram analysis error - use correct HISTOGRAM  
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On a histogram graph, what does the black side represent?   show
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Describe histogram elements.   show
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What is exposure latitude in a histogram?   show
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Describe histogram contrast.   show
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show attenuation is loss of energy of photons  
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What is VOI?   show
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show region of interest - occurs on computer  
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show Increase kVp decreases subject contrast - flattens and widens histogram (fewer peaks/valleys - flat) Decrease kVp increases subject contrast - more peaks/valleys, narrower histogram  
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show Shape stays fairly constant for each part exposed (anatomy specific IE - Shape of histogram for a chest radiograph on a large adult is different than a ped knee  
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show image acquisition processing takes place in computer using processing algorithms (segmentation, histo analysis, auto-rescale, LUT) that analyze and ID components and characteristics of image  
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show all manipulation and adjustments done by the tech through various user functions after pre-processing has occurred (once visible image is displayed) Tech must be careful not to POST PROCESS necessary data from image.  
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show Only the detector plate (CR uses IRD/CR reader) All other steps are the same SEGMENTATION HISTOGRAM ANALYSIS AUTO RESCALE LUT  
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show p298/299 Orth/p164 Papp to display image with appropriate brightness level regardless of the exposure tech FAILURE possible here - select correct TECHNIQUE (ALARA)  
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show auto rescaling process  
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Why does the image initially appear as a washed out gray image?   show
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show exposure of 500% over ideal and 60% below ideal  
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What does auto-rescaling do?   show
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When does auto rescaling fail?   show
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What is a LUT?   show
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show A Priori 1. Extremity model - type 1 (common) 2. General model - type 2 (common) 3. Metal model - type 3 (fixed algorithm) Neural - AI  
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show any error where system does not recognize data or collimation  
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show to correct values of pixels; to give desired final image contrast  
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What is mapping function of LUT? KNOW THIS   show
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How is LUT graphed?   show
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What is window width?   show
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What is window level?   show
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show The range of techniques that will produce a quality image that has an acceptable appearance (low noise) and does not violate ALARA  
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What is the biggest difference between digital and film screen?   show
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Describe WINDOW WIDTH.   show
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What is electronic collimation?   show
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What are the effects of excessive processing?   show
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show PIXEL BIT DEPTH  
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show LOCAL spatial frequency adjustment generating image that is pleasing to observer Includes - contrast, edge, spatial and frequency filtering, image combining and noise reduction  
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show Local spatial frequency processing to make changes to contrast and brightness of an image Window width - CONTRAST Window level - BRIGHTNESS  
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What is Edge Enhancement (high pass filtering)   show
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What is smoothing (low pass filtering)?   show
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What is unsharp masking?   show
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What is DOSE CREEP?   show
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show p288 Orth 1. kVp 15% rule 2. kVp is seen as exposure and provides adequate data to computer 3. Increasing kVp maintains contrast resolution while decreasing patient dose 4. Very low kVp = quantum mottle = repeat  
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show p298 Orth/PP p8/graph 22.6 p299 processing stretches values toward optimal exposure (values that are more appropriate for specified anatomy) brings blacks to grays SUBTRACTS values from pixels in image to align with stored histo  
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What does autorescaling do to an underexposed image?   show
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What is rescaling image brightness?   show
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show Any unwanted image on pic - may obscure anatomic info - PLUS density (B) MINUS density (W) GHOST/2x exp's Scratches/tears fogging noise heat blur histo error non-parallel collimation linear scanning artifacts Moire Aliasing Light bulb  
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show blacks on image  
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show whites on image  
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What is GHOST artifact?   show
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What is MOIRE pattern?   show
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Tell me about Quantum Noise.   show
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What are exposure indicator scales?   show
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Describe inversely proportional scales (S#).   show
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show Based on 300 point system Increase EI by 300 = 2x exp Decrease EI by 300 + 1/2 exp to double receptor exposure, double the mAs to halve receptor exposure, 1/2 mAs  
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