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Ch.3
Digital Radiographic Image Processing and Manipulation
| Question | Answer |
|---|---|
| In both photostimulable phosphor (PSP) and flat-panel detector systems (FPD), after the x-ray photons have been converted into electrical signals, these signals are available for processing and manipulation. | Digital Radiographic Image Processing and Manipulation |
| Takes place in the computer where the algorithms determine the image histogram | Preprocessing |
| Done by the technologist through various user functions | Postprocessing |
| The PSP imaging plate records a wide range of | x-ray exposures |
| in ________, using values at the extreme high and low ends of the exposure range would result in a low-density resolution. | Image Formation |
| Data recognition program searches for anatomy recorded on the imaging plate as follows: | Finding collimation edges Eliminating scatter outside the collimation. |
| Information within the collimated area is the signal use for image data | This is the source for a vendor specific exposure data indicator |
| Failure of the system to find the collimation edges and result in and correct data collection Images may be ..... | To bright or too dark. |
| Equally important is centering anatomy to the center of the imaging plate | Ensures that appropriate recorded densities are located. Failure to do so could result in an image that is too bright or dark. |
| A graphical representation of exposure values collected from the imaging plate | Histogram |
| The value of each tone is represented on the? | Horizontal axis |
| The number of pixels In each tone is represented on the | Vertical axis |
| Values to the left are darker; as the tone vary toward the right, they get ? | Brighter |
| Plate is scanned. Image location and orientation are determined. Size of the signal is determined. Value is placed on each pixel. A histogram is generated from the image data. | Image sampling. |
| Histogram is generated that allows system to find useful signal by locating the minimum ____ and maximum _____ signal within the anatomic regions of interest in the image. | Minimum (S1) and Maximum (S2). |
| Histogram identifies all densities on the imaging plate in the form of a | Graph |
| X-axis is related to amount of | Exposure |
| Y-axis displays the: | Number of pixels for each exposure |
| Graphic representation appears as a series of peaks and valleys and has a pattern that varies for each ____________. | Body part. |
| Low energy (kVp) gives a | Wider histogram |
| High energy (kVp) gives a | Narrow histogram |
| Histogram shows the distribution of: | Pixel values for any given exposure. |
| Pixels have a value of one, two, three, and four for a | Specific exposure |
| Histogram shows the frequency of each of those _______ and actual number of _____ | Values. |
| Histogram sets the _____________ and ______________ “useful” pixel values. | Minimum (S1) and Maximum (S2). |
| Histogram analysis is | Complex |
| Shape of the histogram stays fairly constant for: | Each part exposed (anatomy specific). |
| Shape of __________ for a chest radiograph of a large adult patient looks different from a knee ________ generated from a pediatric knee exam. | Histogram |
| It is important too choose the correct ______________ on the menu before exposing the patient. | Anatomic region. |
| ________________ Used to form the histogram are compared with a “normal” histogram of the same body part by computer. | Raw data |
| In ____, __________ Describe a way to convert analog signals into digital signals that could more accurately transmit over telephone lines. The analog signal could be captured transmitted digitally, and re-created in analog form on the receiver. | 1928, Harry Nyquist. |
| In 1948, Claude Shannon presented a ... | Mathematical proof of the Nyquist’s theory. |
| The Nyquist Theorem is often referred to as | The Sampling Theorem. |
| The Nyquist theorem States that when sampling a signal, | The sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be as close to the original signal as possible. |
| At least twice the number of pixels need to form the image must be | Sampled |
| If too few pixels are sampled, the result is a | Lack of resolution |
| ________ does not result in additional useful information. | Oversampling. |
| The number of conversions in PSP - electrons to light, lights to digital information, digital to analog signal. results in | Loss of detail. |
| Some light is lost during the light to digital conversation because of the | Spreading out of light photons |
| Because there is a small distance between the phosphor plate surface and the photosensitive diode of the photomultiplier, some light spread out there as well, resulting in | Loss of information. |
| Longer the electrons are stored, the more energy they | Lose |
| When laser stimulates electrons, some lower energy electrons escape the | Active layer. |
| If enough energy was lost, some lower energy electrons are not stimulated enough to escape and information is | Lost. |
| All manufacturers suggest that imaging plates be read as soon as possible | To avoid loss of information |
| Both FPD Systems lose fewer signals too light spread than | Conventional radiography. |
| The Nyquist theorem is still applied to ensure that sufficient signal is | Sampled |
| Because sampling is three process by the computer immediately, signal loss is ........ | Minimized but still occurs. |
| Occurs in digital imaging when: | Spatial frequency is greater than the Nyquist frequency |
| Sampling occurs less than twice per cycle: | Information is lost. Fluctuating signal is produced. Also know as fold over or biasing |
| A wraparound images produced, and the image appears as __________ slightly out of alignment. | To superimposed images |
| Aliasing results in a | Moire effect. The same effect can occur with grid error. |
| Automatic rescaling | When exposure is greater than or less than what is needed to produce an image. |
| Automatic rescaling occurs in an effort to display the Pixels of the area of | Interest |
| Images are produce that have uniform ________ and _________ regardless of the amount of exposure. | Brightness and contrast. |
| Too little exposure results in | Quantum mottle |
| Too much exposure result in | Loss of contrast, and loss of distinct edges because of detector saturation. |
| Rescaling is ____________ for appropriate technical factors. | No substitute |
| Danger exists of using higher than necessary mAs values because doses will | “Creep” up over time. |
| A histogram of the luminance values derived during image acquisition. Used as a cross reference to transform the raw information. | Look up table (LUT) |
| Has a mapping function: | All pixels or change to a new gray value. Image will have appropriate appearance and brightness and contrast. Provided for every anatomic part. |
| LUT can be graph as follows: | Plotting that original values ranging from 0 to 255 on the horizontal axis. Plotting new values also ranging from 0 to 255 on the vertical axis. |
| Contrast can be increased or decreased by changing the ? | Slope of the graph. |
| Brightness (density) can be increased or decreased by moving the ........ | Line up and down the y-axis. |
| Image processing parameters Contrast manipulation Spatial frequency resolution Spatial frequency filtering * edge enhancement *smoothing | Quality control workstation functions |
| Digital systems have a greater dynamic range then | Film/Screen imaging |
| Initial digital image appears _______ when graphed because all shades of gray are visible. | Linear |
| Digitalization gives the image a | Wide latitude |
| If all shades we’re left in the image, contrast would be too low. To avoid this digital systems make use of ...... | Various contrast - enhancement parameters. |
| Contrast enhancement parameters convert the digital input data to and image with appropriate | Brightness and contrast |
| Image contrast is controlled by using a parameters that changes the | Steepness of the exposure gradient. |
| Brightness can be varied at the toe and shoulder at the curve, removing the extremely low and extremely high density values using | A different parameter. |
| Parameters should only be used to | Enhance an image |
| No amount of adjustment takes place of: | Proper technical factor selection. |
| What is spatial frequency resolution? | Refers to detail or sharpness of the image |
| Digital imaging processing parameters allow the technologist to: | Choose the structure to be enhanced. Control the degree of enhancement for each density to reduce image graininess. Adjust how much edge enhancement is applied. |
| Image Information is _______ if improper algorithms are applied. | Degraded |
| _____ ___________ Before sending to the (PACS) reduces the amount of manipulation radiologist can do | Image manipulation |
| After the images stored in PACS | All post processing results in a loss of information from the original image. |
| Spatial frequency filtering | Edge enhancement. Smoothing. |
| After the signal is obtained for each pixel, averaging of the signal occurs too shorten processing time and storage. | Edge enhancement |
| The more pixels involved in the averaging | The smoother the image appears |
| Signal strength of one pixel is average with | The strength of adjacent pixels or neighborhood pixels |
| Edge enhancement occurs when fewer pixels in the neighborhood are included in the | Signal average |
| The smaller the neighborhood | The greater the enhancement |
| When frequencies of areas of interest are known, they can be amplied, and other frequencies can be | Suppressed |
| Amplification, also known as ________________ results in an increase of contrast and edge enhancement. | High pass filtering |
| Suppression of frequencies, also known as _________, can result in loss of small details. | Masking This technique is useful for enhancing large structures, such as organs and soft tissues, but can be noisy. |
| Also known as low passing Filtering Results from averaging the frequency of each pixel with surrounding pixel values to remove high frequency noise Result is a reduction of noise and contrast Useful for viewing small structures (fine bone tissue) | Smoothing |
| Window level and window width. Background removal or shutter. Image orientation. Image stitching. Image annotation. Magnification. | Image manipulation |
| Patient demographics input Manual send Archieve query. | Image management |
| Window level | Controls how light or dark the image is |
| Window width | Controls the ratio of black to white, or contrast. |
| Unexposed borders around the collimation edges allowed excess light to enter the eye is called | Veil glare |
| Causes oversensitization of a chemical within the eye called | Rhodopsin The results in temporary white light blindness |
| Eye recovers quickly enough so that the viewer recognizes only that the light was very bright. | Veil glare is a great distraction that interferes with image reception by the eye. |
| In digital imaging, _________ is used to blacking out the white collimation borders | Automatic shuttering |
| Shuttering is a _________ technique only | Viewing |
| Shuttering should never be used to mask poor __________ practices | Collimation |
| Removal of the white unexpose borders results in an overall smaller number of pixels | This reduce the amount of information to be stored. |
| The way the anatomy is oriented on the imaging plate. | Image orientation |
| There image reader must be informed of the part location | Head versus feet Left versus right |
| The image is displayed exactly as read ..... | Unless the reader is informed otherwise |
| The cassette must be oriented so that image is processed to display as expected. | Vendors mark the cassettes in different ways. Fuji uses a tape type orientation marker Kodak carestream uses a sticker. |
| With FPD systems the position of the part should correspond with the | Marked top and sides of the detector. |
| ___________ is used for anatomy or areas of interest to large to fit on one Cassatt | Stitching. |
| Multiple images can be “________” together | Stitched |
| Sometimes special cassettes holders are used in position vertically, corresponding to | Foot to hip, or entire spine studies. |
| Images are processed in ________________ that nearly seamlessly join the anatomy. | Computer programs |
| Computer displays | One single image. |
| Process eliminates the need for large (36 inch) cassettes previously used in | Film/Screen radiography. |
| Information other than standard identification must be added to the image. | Image annotation. |
| In Screen/film radiography, additional information is marked by the following: | Time and stickers. Grease pencils. Permanent markers. |
| Allows selection of preset terms or manual text input. Can be useful when such additional information is necessary. Overlay that image as bitmap images. May not transferred to PACS. | Annotation function |
| Input of annotation for identification of the patients left or right side should never be used as a substitute for the | Technologist’s anatomy markers. |
| What are the two basic types of magnification techniques are standard with digital systems ? | Magnifying glass and zoom. |
| A box is place over a small segment of anatomy on the main image. The book shows a magnified version of the underlying anatomy. The size of the magnified area and the amount of magnification can be made larger or smaller. | Magnifying glass |
| Allows magnification of the entire image. Image can be enlarge enough that only parts of it are visible on the screen. Those parts can be seen through mouse navigation. | Zoom. |
| Patient demographics input Manual send Archieve query | Image management |
| Proper identification of the patient is even more critical with digital imaging. | Patient demographics input |
| Retrieval can be nearly impossible if the image is not | Properly and accurately identified |
| Name Health care facility Patient identification number Date of birth Exam date Other pertinent information | Demographic information about the patient. |
| Information should be input or linked via _______________ before the start of the exam and before the processing phase. | Barcode label scans |
| Function should be track to link the technologist with alternation for accuracy and accountability | The patients name must be entered the same for each visit or exam. |
| Suppose a patient gives a middle name or initial and previous exams have only hindrance for me first name. | The system will save each version of the name as a different patient. Merging of files can be difficult. Retrieval of previous files will be difficult. |
| The right images must be placed in the correct | Data files |
| Because the quality control workstation is networked to the PACS, it also has the capability to send images to | Local network workstations |
| The manual send function allows the quality control technologist to select one or more | Local computers to receive images. |
| PACS archieve can be queried for | Historical images |
| Function allow retrieval of images from the PACS system based on the following: | Date of exam. Patient name or number. Exam number. Pathologic condition. Anatomic area. |
| Technologist could query ________ to retrieve all chest radiographs for a particular date or range of dates. | PACS |
| Technologist could query retrieval of all of a certain | Patient’s images |
| Multiple combinations of query fields can ...... that include many categories of information or a few specific ones. | Generate reports from storage |
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