scholarly journals The Ever-Changing Work That is Digital Preservation

2020 ◽  
Vol 2020 (1) ◽  
pp. 1-5
Author(s):  
Leslie Johnston
Keyword(s):  
Image Quality ◽  
Multispectral Imaging ◽  
Visible Spectrum ◽  
Quality Criteria ◽  
Color Difference ◽  
Low Noise ◽  
Transformation Matrix ◽  
Reflectance Factor ◽  
Tristimulus Values ◽  
Color Transformation

Conventional color imaging has three channels—R, G, and B. In multispectral imaging within the visible spectrum, the number of channels increases in order to improve color accuracy and estimate spectral reflectance factor. Image quality criteria important in multispectral imaging include colorimetric accuracy, sharpness, registration, and low noise. The color transformation matrix, connecting camera signals with CIE tristimulus values, affects color accuracy and the visibility of image noise and misregistration when the multiple channels are combined to a colormanaged image. When the final goal is a color-accurate image for one set of illuminating and viewing conditions, the color transformation is often derived directly using nonlinear optimization minimizing the average color difference between spectrophotometer- and camera-based colorimetric coordinates. Optimization requires starting values and least squares minimizing spectral or tristimulus RMS error is typically used. Although it is effective for achieving convergence, the optimized matrix can result in a large reduction in image quality caused by noise propagation via the color transformation matrix. These concepts are reviewed.

scholarly journals Establishing a quality assurance baseline for radiological protection of patients undergoing diagnostic radiology

2011 ◽  
Vol 15 (3) ◽  
pp. 70 ◽  
Author(s):  
Geoffrey K Korir ◽  
Jeska Sidika Wambani ◽  
Ian K Korir
Keyword(s):  
Quality Control ◽  
Quality Assurance ◽  
Image Quality ◽  
Radiation Exposure ◽  
High Speed ◽  
Quality Criteria ◽  
Patient Dose ◽  
Radiological Protection ◽  
X Ray ◽  
High Speed Film

Background. The wide use of ionising radiation in medical care has resulted in the largest man-made cause of radiation exposure. In recent years, diagnostic departments in Kenya have adapted the high-speed film/screen combination without well-established quality control, objective image quality criteria, and assessment of patient dose. The safety of patients in terms of justification and the as-low-as-reasonably-achievable (ALARA) principle is inadequate without quality assurance measures. Aim. This study assessed the level of film rejects, device performance, image quality and patient dose in 4 representative hospitals using high-speed film/screen combination. Results. The X-ray equipment quality control tests performance range was 67% to 90%, and 63% of the radiographs were of good diagnostic value. The measured prevalent chest examination entrance surface dose (ESD) showed levels above the international diagnostic reference levels (DRLs), while lumbar spine and pelvis examination was the largest source of radiation exposure to patients. Conclusion. The optimisation of patient protection can be achieved with optimally performing X-ray equipment, the application of good radiographic technique, and continuous assessment of radiographic image quality.

Image Quality Criteria Applied to Digital Radiography

1995 ◽  
Vol 57 (1-4) ◽  
pp. 139-140
Author(s):  
H.P. Busch ◽  
K. Faulkner ◽  
J.F. Malone
Keyword(s):  
Image Quality ◽  
Digital Radiography ◽  
Quality Criteria

scholarly journals Study on the effect of heat treatment on amethyst color and the cause of coloration

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Renping Cheng ◽  
Ying Guo
Keyword(s):  
Heat Treatment ◽  
Significant Relationship ◽  
Color Change ◽  
Heating Temperature ◽  
Visible Spectrum ◽  
Crystallinity Index ◽  
Color Difference ◽  
Cell Parameters ◽  
Initial Color ◽  
A Charge

Abstract The effect of heat treatment on amethyst color was studied from a new perspective of chromaticity of gemstones and the cause of amethyst coloration was discussed based on the results of X-ray diffraction, ultraviolet–visible spectroscopy. The results show that the amethyst color has no significant relationship with cell parameters but the crystallinity index decreases as temperature rises. The absorption band at 545 nm in the UV–visible spectrum can be related to a charge-transfer transition of Fe3+ and O2−, which has a significant relationship with amethyst lightness and chroma. The color at different temperatures can be divided into three stages: The amethyst stage with temperature below 420 °C, the prasiolite stage with temperature between 420 and 440 °C where the color center is the most unstable, the citrine stage with temperature above 440 °C. The color change degree of heated amethyst is related to its initial color. When the initial color is darker, the color difference of heated amethyst is larger, and the easier it is to change the color after heat treatment. A more appropriate heating temperature to obtain citrine by heating amethyst is about 560 °C.

Quality Control and Image Quality Criteria in Computed Tomography

1995 ◽  
Vol 57 (1-4) ◽  
pp. 125-127
Author(s):  
J. Albrechtsen ◽  
J. Hansen ◽  
L.C. Jensen ◽  
K.A. Jessen ◽  
A.G. Jurik
Keyword(s):  
Computed Tomography ◽  
Quality Control ◽  
Image Quality ◽  
Quality Criteria

Reduction of absorbed dose in storage phosphor urography by significant lowering of tube voltage and adjustment of image display parameters

2005 ◽  
Vol 46 (4) ◽  
pp. 391-395 ◽  
Author(s):  
H. J. Wiltz ◽  
U. Petersen ◽  
B. Axelsson
Keyword(s):  
Image Quality ◽  
Contrast Media ◽  
Absorbed Dose ◽  
Quality Criteria ◽  
Patient Dose ◽  
Image Display ◽  
Modified Technique ◽  
Tube Voltage ◽  
Storage Phosphor ◽  
Dose Area Product

Purpose: To investigate whether image quality in storage phosphor urography can be maintained when the X‐ray tube voltage is significantly lowered to give a lower patient dose. Material and Methods: Initial phantom studies were used to establish exposure settings at 53 kV that gave signal‐to‐noise ratios for contrast media structures equivalent to those obtained at the reference kilovoltage of 69 kV. Dose area product and image quality, assessed by image quality criteria and visual grading, were then recorded for 44 patients drawn at random to be examined by either the standard or modified technique. Results: Absorbed dose could be reduced by more than 30% without any significant change in image quality in manually controlled exposures and by 13% in exposures controlled by AEC. Conclusion: It might be possible to lower the tube voltage in digital examinations involving contrast media as a means of lowering patient dose. The image display parameters need to be adjusted to maintain image quality.

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