Term
| Digital image processing can be used to change what characteristics of the image? (3) |
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Definition
1. Reduce image noise
2. Increase visibility of detail
3. Adjust and optimize the image contrast characteristics |
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Term
| What two processing methods can be used to adjust the contrast characteristics of an image? |
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Definition
1. Look-up table (LUT) processing
2. Windowing |
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Term
| Contrast is changed by changing _____ values. |
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Definition
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Term
| _____-__ _____ are data stored in the computer that is used to substitute new values for each pixel during the processing. |
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Definition
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Term
| The appropriate LUT for an exam is ____________ selected to give the desired contrast characteristics to match the type of procedure (chest, extremity, etc) that is designated by the operator. |
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Definition
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Term
| Digital radiographic receptors have a ____ dynamic exposure range and a _____ response. |
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Definition
wide range
linear response |
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Term
| Why is the wide dynamic exposure range and linear response of DR a desirable characteristic? |
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Definition
| Because a wide range of exposure is recorded and the digital receptor does not suppress or cutoff the contrast in some of the exposure range as happens w/ images recorded directly on film |
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Term
| An inverted image is sometimes called what? What can a conventional image sometimes be called? |
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Definition
inverted - black bone image
conventional - white bone image |
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Term
| _________ is the process of selecting some segment of the total pixel value range (the wide dynamic range of the receptor) and then displaying the pixel values within that segment over the full brightness (shades of gray) range from white to black. |
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Definition
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Term
| Contrast will be visible only for the pixel values that are within the selected window. All pixel values that are either below or above the window will be all ______ or all ______ and display no contrast. |
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Definition
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Term
| The person controlling the display can adjust both the ______ and the ______ of the window. The combination of these two parameters determine the range of pixel values that will be displayed with contrast in the image. |
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Definition
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Term
| With _________ we can create many displayed images, each one "focusing on" a specific range of pixel values. |
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Definition
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Term
| When the window is set to cover the lower segment of total pixel value range, we see good contrast in the _______ areas like the mediastinum. |
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Definition
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Term
| Setting the window to the higher segment of total pixel value range produces good contrast in the _______ areas like the lungs. |
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Definition
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Term
| A _______ ____ _________ procedure is performed in order to increase the visibility (contrast) of some objects, especially where the visibility of the objects is somewhat limited by large area contrast as in chest imaging. |
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Definition
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Term
| What are the two distinct steps to a blurred mask subtraction procedure? |
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Definition
1. A blurred copy of the original image is produced
2. The computer subtracts the blurred mask image from the original image to produce the final result - an image w/ enhanced visibility of detail |
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Term
| What is the end result of a blurred mask subtraction procedure? |
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Definition
| The result is that the final image has an enhanced contrast and visibility of detail (small objects and structures) |
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Term
| The basic photometric unit is the ______. |
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Definition
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Term
| The lumen is scaled to the maximum photopic eye response at ____ nm. |
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Definition
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Term
| What are the four important properties of the lumen? |
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Definition
1. Luminous flux
2. Illuminance
3. Luminance intensity
4. Luminance |
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Term
| Is the total intensity of light from a light source: |
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Definition
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Term
| Is the intensity of light incident on a surface: |
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Definition
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Term
| One lumen of luminous flux incident on a single square foot is known as a: |
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Definition
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Term
| One lumen per square meter is known as a: |
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Definition
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Term
| Is the luminous flux that is emitted into the entire viewing area by a view-box or a digital display device. It is measured in lumens per candela: |
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Definition
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Term
| In DR, the _______ ________ is the amount of light emitted by the monitor. |
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Definition
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Term
| ________ is similar to luminous intensity and is expressed as units of candela per meter squared; also known as a nit. |
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Definition
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Term
| Candela per meter squared is also known as a ___. |
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Definition
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Term
| What are the two fundamental laws that are associated w/ photometry? |
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Definition
1. the inverse square law
2. the cosine law |
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Term
| The ______ ______ law states that the luminous intensity of a device decreases in proportion to the inverse square of the distance from the source. |
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Definition
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Term
| The ______ ____ is particularly relevant to digital display devices. When a monitor is viewed straight on, Luminous intensity is at its max; however, when viewed from an angle the luminous intensity is reduced, following the mathematical function of a ______. |
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Definition
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Term
| What is another name for an active matrix liquid crystal display (AMLCD) monitor? |
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Definition
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Term
| (True or False) AMLCD monitors are inferior to cathode ray tubes (CRTs). |
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Definition
| False - AMLCD monitors are superior |
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Term
| AMLCD monitors are fashioned pixel by pixel using a very intense ____ back-light that illuminates each pixel. |
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Definition
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Term
| AMLCD monitors come into two types. What are they? |
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Definition
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Term
| Medical flat panel monitors are typically of the _________ type, and they are identified by the number of ______ in the AMLCD. |
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Definition
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Term
| The higher the pixel value of a monitor, the greater its _______ ________. |
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Definition
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Term
| The RAD monitors for radiography typically have a _____ pixel value. |
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Definition
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Term
| The RAD monitors for mammo typically have a _____ pixel value. |
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Definition
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Term
| The AMLCD is a very inefficient device, in that only about __% of the back-light is transmitted through a monochrome monitor. |
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Definition
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Term
| How come only about 10% of the back-light is transmitted through a monochrome AMLCD monitor? |
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Definition
| Because of the light absorption in the filters and polarizer devices w/in the monitor, along w/ the TFTs which block a substantial portion of each pixel |
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Term
| The portion of the pixel face that is available to transmit light is the ________ ratio. |
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Definition
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Term
| What is the typical aperture ratio in AMLCD monitors? |
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Definition
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Term
| The term ______ in AMLCD is reference to the ability to control each pixel of the digital display device individually. |
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Definition
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Term
For a DR receptor, the pixel "fill factor" _______ radiation.
For an AMLCD monitor, the pixel "aperture ratio" _______ light. |
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Definition
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Term
| Name the advantages of AMLCD monitors over CRT monitors: |
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Definition
| 1. AMLCDs have better gray-scale definition 2. They have better contrast resolution because they are not limited by veiling glare or reflection on the face plate 3. Intrinsic noise is less 4. They are influenced less by ambient light |
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Term
| What is the major disadvantage of AMLCD monitors? |
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Definition
| AMLCD monitors are very angular dependent when viewing an image, i.e., contrast resolution greatly decreases as the viewing angle increases |
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Term
| Pre and post processing of the digital image alters the appearance for the purpose of improving: |
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Definition
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Term
| _________ of the digital image is largely automatic, and is designed to produce artifact-free images. |
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Definition
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Term
| _____ images and _____ images are automatic calibration images designed to make the response of the IR uniform. |
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Definition
| offset images & gain images |
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Term
| Offset/Gain: ______ images are generated every few months, while ______ images are generated many times each day. |
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Definition
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Term
| Signal _________ is used to correct the effect of defective pixels. The response of pixels surrounding a defective pixel are averaged, and the value is assigned to the defective pixel. |
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Definition
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Term
| Each type of digital image receptor (detector) generates an electronic latent image that may not be made completely visible; this is known as image ___. |
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Definition
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Term
| What is the solution to image lag? |
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Definition
| The application of an offset voltage before the next image is acquired |
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Term
| Variations in voltage along the buses that drive each pixel is called: |
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Definition
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Term
| ____ _____ causes linear artifacts to appear on the final image. |
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Definition
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Term
| ____ _____ can be resolved by application of a voltage correction from a row or column of pixels in a dark, unirradiated portion of the IR. |
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Definition
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Term
| Unlike preprocessing, postprocessing is largely ______ and is accomplished typically by the technologist or radiologist. |
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Definition
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Term
| __________ is performed to optimize the appearance of the image for the purpose of better detection of pathology. |
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Definition
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Term
| ________ is the process of adding text to the image. |
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Definition
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Term
| Digital images can contain up to _____ levels of gray. However, the human eye can only see about __ shades of gray. |
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Definition
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Term
| ________ and _______ can make all 65,536 shades of gray visible. |
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Definition
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Term
| The amplification of image _______ may be the most important feature of digital imaging. |
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Definition
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Term
| __________ is the process of electronically depicting small objects as larger objects, similar to using a magnifying glass on a screen-film image. |
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Definition
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Term
| _____ ____ capability is an electronic tool that the RT or RAD can use to change the horizontal or vertical orientation of the image. |
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Definition
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Term
| Image ________ can be used to change the contrast rendition of an image so that the normally light areas are dark, and the normally dark areas are light. Some types of pathology are more easily visualized in this manner. |
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Definition
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Term
| When a subtraction image is misregistered because of motion during the procedure, it can be corrected by the use of a ______ ______. |
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Definition
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Term
| What does a pixel shift do? |
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Definition
| It re-registers the image so that it is in correct alignment w/ the image undergoing subtraction. |
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Term
| Identifying a specific region of interest is a postprocessing technique that allows the operator to select a defined area for computer analysis using the numeric value of the pixels w/in the defined area. This is known as a ________ _______ technique. |
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Definition
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Term
| ____ _________ uses the computer to enhance the periphery of bones and small, high contrast tissues. It is used to detect small fractures and other pathology that might not otherwise be visualized. |
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Definition
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Term
| __________ is used to identify diffuse, non-focal disease processes and pathology. |
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Definition
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Term
| ___, ____, and ____ allow for better visualization of precise regions of an image. RADs use this feature often when identifying small areas of pathology. |
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Definition
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Term
| Offset images and gain images are automatic calibration images designed to make the response of the IR uniform. These preprocessing techniques are called: |
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Definition
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