Spectral Image Quality Research Articles

A Novel Technique of Spectral Image Quality Assessment Based on Structural Similarity Measure

A Novel Technique of Spectral Image Quality Assessment Based on Structural Similarity Measure

Image Quality Analysis for Visible Spectral Imaging Systems

An image quality investigation of visible spectral imaging systems was performed. Spectral images were simulated using different combinations of imaging system parameters with different numbers of imaging channels, wavelength steps, and noise levels based on two practical spectral imaging systems. A mean opinion score (MOS) was determined from a subjective visual assessment scale experiment for image quality of spectral images, rendered to a three-channel LCD display. A set of image distortion measures, including color difference for color images, were defined based on image quality concerns. The relationships between the distortion factors and the combinations of parameters in spectral imaging systems are discussed in detail. The MOS values and distortion measures were highly correlated. The results indicate that the image quality of spectral imaging systems was significantly affected by the number of channels used with noise in the image capture stage. The selection of wavelength steps had no significant impact on final image quality, especially when there was no noise involved. The results also showed that the contrast factor indicates a different impact on image quality for human portraits compared to other relatively complex scene images. An empirical metric is proposed to estimate the scaled image quality. The correlation between this metric and the subjective measure, MOS, was 0.97. The results also indicate that two distortion factor eigenvectors were sufficient to represent four distortion factors used in this experiment. This suggests that further research needs to be performed to find more efficient distortion factors.

Medved M, et al. The effect of varying spectral resolution on the quality of high spectral and spatial resolution magnetic resonance images of the breast. J Magn Reson Imaging 2003;18:442–448.

AbstractThe original article to which this Erratum refers was published in Journal of Magnetic Resonance Imaging (2002) 18(4) 442–448.

The effect of varying spectral resolution on the quality of high spectral and spatial resolution magnetic resonance images of the breast.

To evaluate the effect of varying spectral resolution on image quality of high spectral and spatial resolution (HiSS) images. Eight women with suspicious breast lesions and six healthy volunteers were scanned using echo-planar spectroscopic imaging (EPSI) at 1.5 Tesla with 0.75- to 1-mm in-plane resolution and 2.3- to 2.6-Hz spectral resolution. Time domain data were truncated to obtain proton spectra in each voxel with varying (2.6-83.3 Hz) resolution. Images with intensity proportional to water signal peak heights were synthesized. Changes in water signal line shape following contrast injection were analyzed. Fat suppression is optimized at approximately 10-Hz spectral resolution and is significantly improved by removal of wings of the fat resonance. This was accomplished by subtracting a Lorentzian fit to the fat resonance from the proton spectrum. The water resonance is often inhomogeneously broadened, and very high spectral resolution is necessary to resolve individual components. High spectral resolution is required for optimal contrast in anatomic features with very high T(2)* (e.g., within a lesion) and for detection of often subtle effects of contrast agents on water signal line shape. Despite a trade-off between the spectral resolution and signal-to-noise ratio, it is beneficial to acquire data at the highest spectral resolution currently attainable at 1.5 Tesla.

Ultraviolet conical diffraction: a near-stigmatic tandem grating mounting spectrometer

Conical diffraction grating mounts (gratings used off-plane) offer many new possibilities in the ultraviolet and extreme ultraviolet wavelength domain. Up to now, single conical diffraction gratings, whether coupled or not to grazing incidence gratings, have had limited spectral resolution and disadvantages owing to the simultaneous monochromatic slit image rotation with the grating rotation during the wavelength scan. Here we propose a tandem conical diffraction mount that improves the spectral resolution and nearly eliminates the monochromatic slit image rotation. This results in the improvement of spectral image quality. Through the example of a complete solar telescope-spectrometer instrumentation, the qualities (spectral and angular resolution-2 pm and 1 sec of arc) and limits (lower efficiency) of the mounting are compared to other recent solar instrumentations proposed in the 30-135-nm wavelength range.

Mechanically ruled aberration-corrected concave grating for high resolution Seya-Namioka monochromator.

An aberration-corrected concave grating especially for reducing coma-type aberration has been developed to improve the resolution of Seya-Namioka monochromators by utilizing the technology of varied groove spacings. The optimum amount of space variation is calculated by using the light path function, and the concave grating is ruled with a numerically controlled ruling engine. A concave grating with 1/600 mm average spacing and 500 mm radius of curvature was designed and ruled for a Seya-Namioka monochromator which covers the spectral wavelength range of 200-800 nm. The quality of spectral images obtained with the new concave grating was examined both theoretically and experimentally and the results show the effectiveness of aberration correction in the resolution and luminosity of the monochromator.