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The aero-optical aberration of conformal dome (AOACD) is difficult to correct and would cause serious image degradation. Wavefront coding (WFC) image technique includes the optics and the digital processing steps to achieve the final high-quality images and it can be used to control the optical aberrations. In this paper, a strategy for correcting the AOACD is presented based on WFC technology. The thermal-structure simulation results of the conformal dome are obtained by using ANSYS. The performance degradation of the conformal optical system affected by aero-optical effect is analyzed by using CODEV. Then, a typical generalized cubic phase mask is inserted into the pupil plane of the conformal optical system to suppress its aero-optical aberration. The simulation results show that (1) the image degradation is mainly caused by the refractive index distribution of the conformal dome rather than its deformation; (2) the utilization of WFC technology could suppress AOACD effectively. This work is of consequence in conformal optics and aero-optics.

To improve the resolution of remote sensing infrared images, infrared scanning oversampling system is employed with information amount quadrupled, which contributes to the target detection. Generally the image data from double-line detector of infrared scanning oversampling system is shuffled to a whole oversampled image to be post-processed, whereas the aliasing between neighboring pixels leads to image degradation with a great impact on target detection. This paper formulates a point target detection method utilizing super-resolution (SR) strategy concerning infrared scanning oversampling system, with an accelerated SR strategy proposed to realize fast de-aliasing of the oversampled image and an adaptive MRF-based regularization designed to achieve the preserving and aggregation of target energy. Extensive experiments demonstrate the superior detection performance, robustness and efficiency of the proposed method compared with other state-of-the-art approaches.

In DSA (Digital Subtraction angiography) image degradation such as prevalence of noise during fusion and blurring of the details is one of the common problems. To improve the performance of the generalized Reisz transform in context of osseous and vascular image fusion it is combined with averaging fusion method. The proposed method is not only able to preserve the spatial consistency of low level features but has also captured the directional structural information. The numerical and the visual assessment clearly depicts that there is negligible amount of noise prevalent in the final fused results which is usually a problem with other state of art fusion methods The performance analysis of the proposed method applied on DSA and mask image fusion demonstrates that it is competitive with state of art fusion methods, especially in combining spatial and structural information. Our proposed method GRWT (Generalized Reisz Wavelet Transform) along with averaging fusion method is able to yield much better results than the GRWT coupled with heuristic fusion model with far less complexity and the computational requirement having a fusion rate of 0.6958.

In conformal optics, the dynamic aberrations of conformal optical system (DACOS) are difficult to correct and would cause serious image degradation. In this work, we propose a method based on wavefront coding (WFC) technology to suppress the DACOS. A conformal dome with highly significant dynamic aberrations (about ± 8 λ ) is established and its aberration characteristics are investigated using Zernike aberration theory. A simple cubic phase mask (CPM) is inserted in its pupil plane to suppress residual dynamic aberrations after preliminary aberration correction. The simulation results show that, the utilization of WFC technology could not only suppress the DACOS efficiently, but also reduce physical imaging elements, which could in turn relax the alignment and fabrication tolerances. This work is of consequence in conformal optical systems design.

In underwater color imaging, the scattering media could cause image blurring and color distortion, which are the two main problems of image degradation. In this paper, we propose a color image recovery method to solve these two problems by considering the crosstalk effects between the RGB channels during estimating the transmittances in RGB channels. The experimental results in turbid water with different colors (blue, green and yellow) show that our method can simultaneously enhance the image contrast and reduce the color distortion to realize the clear underwater vision, which is attributed to the proper estimation of the transmittances in RGB channels by compensating the crosstalk effects.

To investigate the value of 4 different protocols for prospectively triggered 256-slice coronary computed tomography angiography (coronary CTA).Two hundred and ten patients underwent prospectively triggered coronary CTA for suspected or known coronary artery disease (CAD). Patients with heart rate75 bps before the scan despite ß-blocker administration and with arrhythmia were excluded. From January to September 2010, 60 patients underwent coronary CTA using a non-tailored protocol (120 kV; 200 mAs) and served as our 'control' group. From September 2010 to April 2012, based on the body mass index (BMI) of the examined patients (BMI subgroups of25; 25-28; 28-30, and ≥ 30 kg/m(2)) current tube voltage and tube current were: (1) slightly, (2) moderately or (3) strongly reduced, resulting into the 3 following BMI-adapted acquisition groups: (1) a 'standard' (100/120 kV; 100-200 mAs; n=50), 2) a 'low dose' (100/120 kV; 75-150 mAs; n=50), and 3) an 'ultra-low dose' (100/120 kV; 50-100 mAs; n=50) protocol.Patients examined using the non-tailored protocol exhibited the highest radiation exposure (3.2 ± 0.4 mSv), followed by the standard (1.6 ± 0.7 mSv), low-dose (1.2 ± 0.6 mSv) and ultra-low dose protocol (0.7 ± 0.3 mSv) (radiation savings of 50%, 63% and 78% respectively). Overall image quality was similar with standard dose (1.9 ± 0.6) and low-dose (2.0 ± 0.5) compared to the non-tailored group (1.9 ± 0.5) (p=NS for all). In the ultra-low dose group however, image quality was significant reduced (2.7 ± 0.6), p0.05 versus all other groups).Using BMI-adapted low dose acquisitions image quality can be maintained with simultaneous radiation savings of ∼65% (dose of ∼1 mSv). This appears to be the lower limit for diagnostic coronary CTA, whereas ultra-low dose acquisitions result in significant image degradation.

Respiratory and cardiac motion are a known source of image degradation and quantification impairment in positron emission tomography (PET). In this study we use near-realistic PET/MRI data acquired using a custom-built human torso phantom capable of simulating respiratory and cardiac motion. We demonstrate that a significant reduction in motion-induced artifacts in PET data is possible using MR-derived motion estimates.

Respiratory and cardiac motions represent important sources of image degradation in both PET and computed tomography (CT) studies that need to be taken into account and compensated to improve image quality and quantitative accuracy. This review describes the hardware needed to perform respiratory and cardiac gating with PET and PET/CT systems. In particular, most of the proposed motion-tracking devices for the management of respiratory, cardiac, and multidimensional movements are described and compared. Some advanced applications in PET and PET/CT made possible by the gating technology are considered and analyzed.

To compare visualization using whole-heart coronary magnetic resonance angiography (CMRA) acquired during a single breath-hold (BH) with that using conventional respiratory-gated (RG) CMRA.The CMRAs of 14 healthy subjects under either BH or RG conditions were studied using a 1.5 T system equipped with a whole-body phased-array coil and 16-channel receivers. The BH examination was accelerated using parallel imaging (PI) by factors of 2.5 and 2 in the phase and section directions, respectively. For the RG examination, a PI factor of 2 was used only in the phase direction. The visualization quality of 15 coronary segments using each condition was evaluated with a five-point scale (0-4). Differences between two conditions were compared at segments with an average score greater than 2 in RG-CMRA.The average examination time for BH and RG acquisition scans was 34 s and 11 min 31 s, respectively. Ten segments (segments 1-3, 5-9, 11, and 13) had average scores higher than 2 in RG-CMRA. Of these, BH-CMRA had significantly lower scores than RG-CMRA at six segments (segments 1, 5-8, and 11) after correction for multiple comparisons (p0.005). However, in BH-CMRA, proximal segments (segments 1-2, 5-7, and 11) showed average scores over 2, indicating marginally acceptable image quality.Compared with the relatively limited degree of image degradation with RG-CMRA, the present data suggest that BH-CMRA would be useful for screening and as an adjunct to RG-CMRA that is occasionally incomplete.

In the system of X-ray radiograph, the scattered X-ray induces the depression and degradation of the image quality, and badly influences the detecting sensitivity. After studying mechanism of image degradation, and analyzing the scattering polarization, a new restoration method based on the blind separation and wavelet transform was raised. An ICA (Independent Component Analysis) model was firstly constituted based on the radiograph mechanism. To satisfy to the statistically independence of blind separation, the sub-band images by wavelet transform were utilized as estimating source. We utilized the least mutual information entropy as the criteria for blind separation and deduced to the optimization estimation. The experimental results show that the method can effectively depress the scattering and improve the contrast.

Rationale and objectives The purpose of this study is to determine whether sagittal reformations of volumetric high-resolution computed tomography (CT) provide additional information in evaluating lung abnormalities compared to axial high-resolution CT images. Materials and methods Twenty-two consecutive patients who underwent combined inspiratory and expiratory volumetric high-resolution CT from May to July 2003 were studied. Using end-inspiratory and end-expiratory sagittal reformatted images, respiratory motion artifacts were evaluated at upper, middle, and lower lung areas bilaterally. Diaphragmatic motion artifacts were evaluated bilaterally. The detection of major and minor fissures was assessed. Additional findings on sagittal reformations were graded using a three-point scale: grade 1 = no additional findings; grade 2 = additional findings of no diagnostic significance; grade 3 = additional findings of diagnostic significance. Results Respiratory motion artifacts were either imperceptible or present but not diagnostically limiting except for one case, in which diagnostically limiting image degradation was noted in the bilateral lower lung areas. Diaphragmatic motion artifacts were frequently present: 95% (21/22) at end-inspiration, and 86% (19/22) at end-expiration; however, diagnostically limiting artifacts were observed in only two cases. The grading of additional findings on sagittal reformatted images was statistically significant (grade 1, n = 13; grade 2, n = 7; grade 3, n = 2; median, 1; P = .004) compared to axial images. Additional findings included relationship between mass/nodules and fissure/pleura/pericardium (grade 2, n = 4; grade 3, n = 2), distribution of interstitial abnormalities of the lung (grade 2, n = 2), and diaphragmatic eventration (grade 2, n = 1). Conclusion Sagittal reformatted images of volumetric high-resolution CT provided additional information compared to volumetric axial images alone with statistical significance.

Aim To evaluate retrospectively the impact of injection flow rate on arterial phase image degradation in liver magnetic resonance imaging (MRI) with gadoxetic acid (Gd-EOB-DTPA) compared to gadobutrol. Materials and methods Two hundred consecutive patients who had undergone liver MRI were enrolled in this Health Insurance Portability and Accountability Act (HIPAA)-compliant institutional review board (IRB)-approved study and were divided into three groups. Group 1 (50 patients) and 2 (50 patients) had undergone MRI performed with gadoxetic acid (fixed 10 ml) at flow rate of 1 and 2 ml/s, respectively. Group 3 (100 patients) had undergone MRI performed with gadobutrol (0.1 mmol/kg) at 1 ml/s. Precontrast and post-contrast (arterial, portal venous, and hepatic venous phases) image degradation was assessed by two blinded independent readers using a four-point rating scale. The numbers of patients with arterial phase image degradation were compared using the Fisher exact test among the three groups. Results The incidence of arterial phase image degradation was 12% (6/50) in group 1 and 16% (8/50) in group 2 for both readers, 6% (6/100) for reader 1 and 5% (5/100) for reader 2 in group 3. Group 2 had a higher incidence of arterial phase image degradation when compared with group 3 for reader 2 (p=0.032). Severe arterial phase image degradation, resulting in non-diagnostic image quality, occurred in 4% (2/50) of patients when performed with gadoxetic acid administration at 2 ml/s and 2% (1/50) at 1 ml/s. Conclusion A slower injection flow rate has a trend to reduce the incidence and severity of arterial phase image degradation during liver MRI with gadoxetic acid when compared to gadobutrol.

A single parameter value that represents the difference between the original and the digitized characters is determined from a binary scan of a test chart. It represents the combined effect of the point spread function diameter and the binary intensity threshold and is used to generate synthetic characters that are similar to characters scanned under the same conditions as the test chart.

Embedding biological macromolecules or molecular assemblies in amorphous ice provides natural surroundings for them which probably leaves their structure intact. However, it has been difficult in practice to get high-resolution information from such non-conducting, beam-sensitive samples. In this work graphite embedded in amorphous ice in the presence of detergent was used to investigate whether image degradation occurs also with a beam-insensitive object. Lattice images showing the 0.34 nm spacing were obtained but the choice of imaging conditions was important in determining the success rate. The best results were obtained using spot-scan with a beam diameter of 150 nm, under conditions which minimize the effects of charging of the specimen. Thus there is no intrinsic problem to obtaining high-resolution images of an object due solely to being embedded in amorphous ice. It should therefore be possible to get high-resolution information from biological objects, if the problem of charging can be overcome.

The limiting sensitivities of coded-aperture imaging telescopes employing fixed masks are derived for continuum and line emission from cosmic point sources. The sensitivities are calculated for a single-source observation and do not take into consideration the many advantages offered by a multiplex system; for instance, low susceptibility to secular background changes and the ability to observe more than one source during an observation period. For the nuclear transition energy region, it is shown that the utilization of a coded-aperture mask by a particular detection system does not significantly degrade its performance relative to conventional, sequential scanning instruments. It is further shown that for short source observation times (e.g., typical of those obtained from stratospheric balloons), the coded-aperture imaging technique can be particularly advantageous. The effects of a non-uniform instrumental background on the imaging process are discussed and a correction procedure suggested. It is found that by careful planning of the observing program coupled with a stable instrument design, image degradation due to background non-uniformities can be made arbitrarily small and the resulting performance made to approach that predicted for an equivalent mask-antimask system.

Psychophysical procedures were used to determine increment-threshold spectral sensitivity functions for monkeys with either stimulus deprivation amblyopia produced by monocular lid suture or anisometropic amblyopia produced by optical defocus. The spectral sensitivity functions obtained from all of the non-treated control eyes had 3 sensitivity maxima at approximately 445, 520 and 610 nm, and were typical of functions for humans and monkeys with normal trichromatic vision. Relative to their paired control eyes, the amblyopic eyes of all of the lid-sutured monkeys demonstrated reductions in absolute sensitivity. In addition, the amblyopic eyes of the monkeys form-deprived at 1 month of age exhibited alterations in the shapes of their spectral sensitivity functions. The pattern of spectral sensitivity deficits observed in the monkeys form-deprived at 1 month of age varied with the duration of deprivation and indicated that the spectral characteristics of the neural mechanisms mediating stimulus detection in these lid-sutured monkeys' amblyopic and control eyes were substantially different. In contrast, none of the anisometropic amblyopes demonstrated any alterations in the shapes of their spectral sensitivity functions and only one anisometropic subject exhibited a reduction in sensitivity. A comparison of the spectral sensitivity deficits observed in our lid-sutured and anisometropic monkeys reveals that when lid suture and optical defocus are initiated early in life for equivalent periods of time, lid suture produces abnormalities which are both qualitatively and quantitively different from the abnormalities produced by optical defocus. Therefore, in addition to factors such as the age of onset and the duration of deprivation, it is concluded that the degree of image degradation is important in determining which visual functions are affected and to what extent they are affected.

Summary MRI is a diagnostic technique that employs a strong magnetic field and RFs to generate images. The magnetic field provides interesting challenges to members of the anesthesia team: prohibitive use of any ferromagnetic material (which is attracted to the magnet), image degradation from monitoring equipment, and malfunction of routine electronic monitors kept within the vicinity of the scanner. Therefore, major changes are needed regarding the choice of anesthetic and monitoring equipment to ensure the safe delivery of anesthesia. This review highlights these problems and offers some solutions. MRI is also being used as an investigative tool to define the action and kinetics of the potent inhalation anesthetics. It is therefore of critical importance that we learn more about this exciting new frontier in imaging.

The linespread profile after double passage through the eye has been measured previously. We show that one cannot separate the contributions of the optics of the eye and of the retina to image degradation with this last method. We present here a new method which allows just such a separation. We have measured the modulation transfer function of the optics of the eye in the visual axis and oblique axes, and a function which characterizes light scattering in different portions of the living retina.

If we make a sampled hologram of an object with space-bandwidth product N but we use only M (⪡ N ) samples, the image will be degraded. The type of degradation (resolution or signal-to-noise ratio is determined by the type of sampling.