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Exposures Ch.21
Medical Image Descriptors
| Question | Answer |
|---|---|
| Digital radiographic image receptors have unique artifacts associated with ________________. | Pixel failure. |
| Environmental radiation can contribute to ___________________. | Ghost artifacts. |
| Interpolation | is the process of assigning a value to a dead pixel based on the recorded values of adjacent pixels. |
| Flatfielding | Is a software correction that is performed to equalize the response of each pixel to a uniform x-ray beam. |
| Lossless Compression | Up to 3:1 generally is considered acceptable and helpful in digital radiographic image management. |
| Histogram | Is a graph of frequency of occurrence versus digital value intervals. |
| ______ is essentail for artifact-free images | Automatic radiation field. |
| ______________ & ______________ prevent histogram errors that can lead to artifacts. | Proper collimation; centering point. |
| _______________ of multiple digital images on a single IP results in proper separation and collimation of each image | Partitioning. |
| Printer Errors | - Caused by malfunction of dry laser printer. - One common artifact is "shading". - Another common artifact is "corduroy effect". |
| CR Scanner Malfunction | - Malfunction of laser scanner in Image Reader Unit. - Can also be caused by memory problems, digitization problems or communication errors. |
| Increased Sensitivity to Scatter | - Decrease in image contrast due to image receptor being more sensitive to scattered radiation. - Can be minimized by proper collimation, grids, smallest possible field size, and use of air gap technique. |
| Phantom or Ghost Image Artifact | - Caused by incomplete erasure of imaging plate in CR systems. - Can appear in DR systems when images are taken too close together in time. |
| Defects in Imaging Plate | Scratches, scuff marks or cracks in image plate can cause areas of increased brightness. |
| Quantum Mottle | - Blotchy appearance of image due to insufficient mAs. - Sometimes referred to as image noise. |
| Object Artifacts: | - Image Histogram. - Collimation & Partition. - Alignment. |
| Software Artifacts: | - Preprocessing. - Image Compression. |
| CAD | - Not computer-aided detection or imaging archiving. - Require uncompressed for processing images. |
| When the chest radiograph is digital each region of the image can be represented by the ______________ of the digital values of each pixel. | Frequency distribution. |
| There is no such thing as _______________ on these IP's. | Radiation fatigue. |
| Compression | Rakes advantage of redundant of data, as occurs with exposure to the raw x-ray beam when all values are the same. Described as lossless or lossy. |
| Partitioning | Allows two or more images to be projected on a single IP. |
| Lossy Compression | Can provide compression factors of up to 100:1 or greater, can be used on images in which exact measurement or fine detail is not required. |
| Lossless Compression | Reduces the file to 10% (10:1) to 50% (2:1) of the original file. |
Created by:
sassyrad
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