Yes / The impact of spectral filtration in digital (‘cine’) acquisition was investigated using a flat panel cardiac interventional X-ray imaging system. A 0.1-mm copper (Cu) and 1.0-mm aluminium (Al) filter added to the standard acquisition mode created the filtered mode for comparison. Image sequences of 35 patients were acquired, a double-blind subjective image quality assessment was completed and dose–area product (DAP) rates were calculated. Entrance surface dose (ESD) and effective dose (E) rates were determined for 20- and 30-cm phantoms. Phantom ESD fell by 28 and 41 % and E by 1 and 0.7 %, for the 20- and 30-cm phantoms, respectively, when using the filtration. Patient DAP rates fell by 43 % with no statistically significant difference in clinical image quality. Adding 0.1-mm Cu and 1.0-mm Al filtration in acquisition substantially reduces patient ESD and DAP, with no significant change in E or clinical image quality. / Supported in part by a research grant from Philips Healthcare, The Netherlands.

Yes / The assessment of image quality in medical imaging often requires observers to rate images for some metric or detectability task. These subjective results are used in optimization, radiation dose reduction or system comparison studies and may be compared to objective measures from a computer vision algorithm performing the same task. One popular scoring approach is to use a Likert scale, then assign consecutive numbers to the categories. The mean of these response values is then taken and used for comparison with the objective or second subjective response. Agreement is often assessed using correlation coefficients. We highlight a number of weaknesses in this common approach, including inappropriate analyses of ordinal data and the inability to properly account for correlations caused by repeated images or observers. We suggest alternative data collection and analysis techniques such as amendments to the scale and multilevel proportional odds models. We detail the suitability of each approach depending upon the data structure and demonstrate each method using a medical imaging example. Whilst others have raised some of these issues, we evaluated the entire study from data collection to analysis, suggested sources for software and further reading, and provided a checklist plus flowchart for use with any ordinal data. We hope that raised awareness of the limitations of the current approaches will encourage greater method consideration and the utilization of a more appropriate analysis. More accurate comparisons between measures in medical imaging will lead to a more robust contribution to the imaging literature and ultimately improved patient care. / EU-funded PANORAMA project, funded by grants from Belgium, Italy, France, Netherlands, UK and the ENIAC Joint Undertaking.

Yes / Lumbar radiographs remain a common imaging examination despite strategies to reduce their use. Many authors have demonstrated benefits in changing from traditional supine and recumbent lateral projections to a prone and/or erect orientation. Despite evidence of clinical and radiation dose optimisation, widespread adoption of these strategies has stalled. This article describes the single-centre implementation and evaluation of erect PA and lateral projections. This was an observational study pre- and post-implementation of an erect imaging protocol. Patient BMI, image field size, source image and source object distances and DAP were collected together with assessment of radiographic spinal alignment and disc space demonstration. Effective dose was calculated with organ specific doses. 76 (53.5%) patients were imaged in the supine AP and recumbent lateral position, 66 (46.5%) had erect PA and lateral radiographs. Despite the larger BMI of the erect cohort and similar field sizes, effective dose was lower in the PA position by an average of 20% (p / The full-text of this article will be released for public view at the end of the publisher embargo on 13 May 2024.

The effect of spatial frequency manipulation of color images and its impact on subjective image quality were examined by measuring subjective image quality and the changes in several prominent image quality metrics. The Modulation Transfer Function Area (M1F A), the Square Root Integral (SQRI), the Integrated Contrast Sensitivity (ICS), the Subjective Quality Factor (SQF), and several other acutance-derived image quality metrics were evaluated for their ability to predict image quality. Five distinct spatial frequency filters were applied to each of four pictorial color scenes in the horizontal dimension, the vertical dimension, and in a combined two dimensional format. The same spatial frequency filters also were applied in a circular format. Thirty-two subjects, 24 college students and 8 Eastman Kodak employees, participated in a paired comparison method in which 21 stimuli for each of the four scenes were evaluated for their perceived image quality. Horizontal and vertical modulation transfer functions were acquired by photometric scans of a cross-hair one-pixel wide white line target as well as by luminance profile manipulation of square-waves of differing frequencies, both utilized as input signals. From the modulation transfer functions, values for the various image quality metrics were calculated and related to the subjective image quality data. In the evaluation of perceived image quality, several experimental procedures are available, such as magnitude estimation, rank ordering, rating-scale, categorical judgments, and the method of paired comparison. The method of paired comparison is frequently avoided for its time consuming nature. However, results indicate that with the use of computer automatization it is a powerful and reliable experimental procedure for testing subjective preferences between digital stimuli containing small perceptual differences. The highest correlation between perceived image quality and image quality metrics was obtained for the pictorial scene which contained a uniform and dense set of frequencies in the horizontal and vertical directions. The lowest R 2 values were reported from the pictorial scene that contained more scattered frequencies in both directions. Therefore, it is advised when performing perceived image quality evaluations of frequency-manipulated pictorial stimuli to use those stimuli that contain a broad range and uniform set of spatial frequencies. The impact of frequency manipulation is then more apparent and, in addition, it may provide for a more reliable transfer of results across experiments. Small increases in modulation produced perceived quality increases in the pictorial color images. Furthermore, improved image quality was obtained with low frequency (less than 9 c/deg) modulation enhancement. In addition, vertical filtering produced greater subjective image quality improvement than did horizontal filtering. For all scenes, the two-dimensional filtered images were perceived as possessing equal or better quality than the circular filtered images. Low-frequency enhancement, close to zero spatial frequency, and no high-frequency enhancement, only minutely (if at all), increased perceived image quality; however, continuing the enhancement process from the low frequencies to the higher frequencies significantly improved perceived image quality. The SQRI metric is not recommended for use in the evaluation of image quality when changes in the MTFs occur at spatial frequencies of 3 cycles per degree and higher. The ICS and MTFA behaved in an acceptable manner with changes in subjective image quality and should be considered for their computational accuracy and practicality. The SQF and the acutance metrics were highly recommended for predicting subjective image quality. In addition, the development of a standardized display measurement technique for color CRTs and a standardized verification process of display image quality are recommended. / Ph. D.

Rapid engineering developments in electronic imaging during the last decade have led to the widespread use of color CRT displays. misconvergence among the primary colors of a shadow-mask CRT is a principle human factors concern for applications of this technology. The major objectives of this research were: (1) to determine the effect of misconvergence on visual search performance (i.e., search time and error), (2) to examine the effects of misconvergence on subjective image quality estimates, and (3) to examine the interactions among target size, nontarget density, and misconvergence type and degree upon subjective and objective human performance indices. Ten participants performed a visual "search-and-select" task on a color CRT computer workstation. Following each trial in this procedure, participants subjectively rated the image quality of the display screen using a 9-point scale. Reducing target size increased selection errors and response times, while increasing nontarget density generally increased response times. Type and degree of shadow-mask CRT misconvergence had almost no effect on visual search performance, suggesting that low levels (1 to 2 arcmin) of misconvergence may be acceptable in effective color CRT applications. However, misconvergence adversely affected subjective image quality ratings, indicating that color CRT usage should be avoided where their use is not essential. / Master of Science

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<p>This study is a thesis for the Master of Science degree in Media Technology and Engineering at the Department of Science and Technology, Linkoping University. It was accomplished from November 2002 to May 2003. </p><p>Objective image quality measures play an important role in various image processing applications. In this paper quality measures applied on halftoned images are aimed to be in focus. Digital halftoning is the process of generating a pattern of binary pixels that create the illusion of a continuous- tone image. Algorithms built on this technique produce results of very different quality and characteristics. To evaluate and improve their performance, it is important to have robust and reliable image quality measures. This literature survey is to give a general description in digital halftoning and halftone image quality methods.</p>

This study is a thesis for the Master of Science degree in Media Technology and Engineering at the Department of Science and Technology, Linkoping University. It was accomplished from November 2002 to May 2003. Objective image quality measures play an important role in various image processing applications. In this paper quality measures applied on halftoned images are aimed to be in focus. Digital halftoning is the process of generating a pattern of binary pixels that create the illusion of a continuous- tone image. Algorithms built on this technique produce results of very different quality and characteristics. To evaluate and improve their performance, it is important to have robust and reliable image quality measures. This literature survey is to give a general description in digital halftoning and halftone image quality methods.

Yes / Dynamic X-ray imaging systems are used for interventional cardiac procedures to treat coronary heart disease. X-ray settings are controlled automatically by specially-designed X-ray dose control mechanisms whose role is to ensure an adequate level of image quality is maintained with an acceptable radiation dose to the patient. Current commonplace dose control designs quantify image quality by performing a simple technical measurement directly from the image. However, the utility of cardiac X-ray images is in their interpretation by a cardiologist during an interventional procedure, rather than in a technical measurement. With the long term goal of devising a clinically-relevant image quality metric for an intelligent dose control system, we aim to investigate the relationship of image noise with clinical professionals’ perception of dynamic image sequences. Computer-generated noise was added, in incremental amounts, to angiograms of five different patients selected to represent the range of adult cardiac patient sizes. A two alternative forced choice staircase experiment was used to determine the amount of noise which can be added to a patient image sequences without changing image quality as perceived by clinical professionals. Twenty-five viewing sessions (five for each patient) were completed by thirteen observers. Results demonstrated scope to increase the noise of cardiac X-ray images by up to 21% ± 8% before it is noticeable by clinical professionals. This indicates a potential for 21% radiation dose reduction since X-ray image noise and radiation dose are directly related; this would be beneficial to both patients and personnel. / This work was funded by Philips Healthcare, NL. Part of this work has been performed in the project PANORAMA, cofunded by grants from Belgium, Italy, France, the Netherlands, and the United Kingdom, and the ENIAC Joint Undertaking.

An edge-based segmentation scheme (i.e. boundary detector) for nuclear medicine images has been developed and consists of a multiresolutional Gaussian-based edge detector working in conjunction with a modified version of Nilsson's A* graph-search algorithm. A multiresolution technique of analyzing the edge-signature plot (edge gradient versus resolution scale) allows the edge detector to match an appropriately sized edge operator to the edge structure in order to measure the full extent of the edge and thus gain the best compromise between noise suppression and edge localization. The graph-search algorithm uses the output from the multiresolution edge detector as the primary component in a cost function which is then minimized to obtain the boundary path. The cost function can be adapted to include global information such as boundary curvature, shape, and similarity to prototype to help guide the boundary detection process in the absence of good edge information.