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Exposures Ch.20
Scatter Radiation
| Question | Answer |
|---|---|
| ____________ measurements and observations should be instituted for all digital display devices | AAPM TG 18. |
| Photometric Evaluation | Of digital display devices and ambient light levels is essential to digital QC. |
| ____________ reflection appears as specular or diffuse | Digital display. |
| Digital image date arrive at the digital display device as _________ transformed into digital driving levels and viewed as _________________. | P-values; Luminance levels. |
| The best digital image viewing is ______________. | Straight on. |
| The ____________ test pattern should be viewed regularly | TG 18-QC. |
| Luminance Nonuniformity | The maximum variation of luminance across the display area when a uniform pattern is displayed. |
| P-values | The pixel values are also grey-scale values and they are sent to a digital display device as presentation values or ________________. |
| Geometric Distortion | Arises from problems that cause the displayed image to be geometrically different from the original image. This can affect the relative size and shape of image features. |
| The Society of Motion Picture and Television Engineers (SMPTE) | Uses format, dimensions, and contrast characteristics of a pattern and measures the resolution of display systems. |
| The American College of Radiology and the National Electrical Manufacturers Association (NEMA) - (DICOM) Digital Imaging and Communication | Created a standard for DICOM (Digital imaging and communication. |
| Image Quality Assurance in X-ray Diagnostics; Acceptance Testing for Image Display Devices (DIN 2001) | Acceptance testing for requirements for digital display devices. |
| Video Electronics Standard Association (VESA) | Set of instructions in the evaluation of performance of system due to compliance standards. |
| The American Association of Physicists in Medicine (AAPM TG 18) | Ensures clinical performance using a set of test patterns. |
| Luminance Meter | The luminance response of monitors and luminance uniformity measurements require the use of a properly calibrated photometer. |
| Reflection | Ambient light significantly contributes to the light reflected by the display device, which in turn depends on the display characteristics of the display device. |
| Reflection: | Usually as specular and diffuse. Specular results in mirror images of light sources surrounding the monitor. Diffuse is randomly scattered on the digital display device. |
| Luminance Response | The image is acquired by a digital modality and is stored as an array of pixel values. |
| Display Noise | Any high frequency fluctuations or patterns that interfere with detection of the true signal. |
| Display Resolution | Spatial resolution is the quantitive measure of the ability of the digital display device to produce separable images of different points of an object with high fidelity. |
| Veiling Glare or Flare | Caused by light reflected from the window of the output phosphor, which reduces image contrast. Occurs when moving from one portion of the patients anatomy to another, (like chest and moving down to abdomen) causing a sudden increase in image brightness. |
| Pincushion Distortion | Barrel distortion, projecting an image from a curved surface (input phosphor) onto a flat surface (output phosphor)(example: carnival mirror that distorts appearance. |
| Vignetting | A decrease in image brightness at the lateral portions of the image and is caused by a combination of pincushion distortion and the coupling of the tv to the output phosphor. |
| S distortion | Warping of the image along an s shaped axis and is caused by strong magnetic fields changing the electrons moving across the image intensifier tube. |
| Spatial Resolution | Is the quantitative measure of the ability of the ddd to produce separable images of different points of an object with high fidelity. |
| Lookup Table (LUT) | Ideal" histogram for every part imaged. In the final phase of processing, automatic rescaling of the image occurs |
| AAPM TG 18 | Evaluates a digital display device with test patterns in Task group Report 18 ensuring acceptable clinical performance. |
| TG 18 QC & TG 18 LPV/LPH | Visual assessment of geometric distortion by filling up the entire screen with a test pattern, you can see if there is an appearance of a pincushion and barrel-like distortion. |
| TG 18 AD | Checks specular reflection on monitors. Consists of pattern with varying low contrast. Observe those under ambient light and in total darkness on the digital monitor. |
| TG 18 CT | Test pattern for the luminance response of a digital display device. |
| TG 18 LN | External photometer that test the luminance of a digital display. |
| TG 18 UN | By observing there test patterns across the display screen; gross variations in uniformity can be observed. |
| TG UNL 10 & TG 18 UNL80 | External photometers evaluation of luminance uniformity. Luminance is measured at 5 different locations of the monitor. |
| TG 18 CX & TG 18 QC | Patterns to evaluate display resolution. The CX patterns in the middle and in the corners can be evaluated with a magnifying glass and compared. |
| TG 18 PX | Pattern can be used to evaluate resolution uniformity. |
| TG 18 AFC | Any high frequency fluctuations or patterns that interfere with detection of the true signal are classified as noise. |
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