Intensity Loss (intensity + loss)

Distribution by Scientific Domains


Selected Abstracts


Nonalcoholic fatty liver disease: Quantitative assessment of liver fat content by computed tomography, magnetic resonance imaging and proton magnetic resonance spectroscopy

JOURNAL OF DIGESTIVE DISEASES, Issue 4 2009
Liang ZHONG
OBJECTIVE: The purpose of this study was to evaluate the clinical application of imaging technology in the quantitative assessment of fatty liver with magnetic resonance imaging (MRI) and proton MR spectroscopy. METHODS: Overall 36 patients with diffuse fatty liver who had undertaken the computed tomography (CT) scan, MRI and proton MR spectroscopy (1H MRS) were analyzed. Their body mass index (BMI) was measured and their liver to spleen CT ratio (L/S) calculated on the plain CT scan. MR T1-weighted imaging (T1WI) was obtained with in-phase (IP) and out-of-phase (OP) images. T2-weighted imaging (T2WI) was acquired with or without the fat-suppression technique. The liver fat content (LFC) was quantified as the percentage of relative signal intensity loss on T1WI or T2WI images. The intrahepatic content of lipid (IHCL) was expressed as the percentage of peak value ratio of lipid to water by 1H MRS. RESULTS: The results of BMI measurement, CT L/S ratio, LFC calculated from MR T1WI and T2WI images, as well as IHCL measured by 1H MRS were 27.26 ± 3.01 kg/m2, 0.88 ± 0.26, 13.80 ± 9.92%, 40.67 ± 16.04% and 30.98 ± 20.43%, respectively. The LFC calculated from MR T1WI, T2WI images and IHCL measured by 1H MRS correlated significantly with the CT L/S ratio (r=,0.830, P= 0.000; r=,0.736, P= 0.000; r=,0.461, P= 0.005, respectively). BMI correlated significantly only with the liver fat contents measured by T1WI IP/OP and 1H MRS (r=,0.347, P= 0.038; r=,0.374, P= 0.025, respectively). CONCLUSION: CT, MR imaging and 1H MRS were effective methods for the quantitative assessment of LFC. The MR imaging, especially 1H MRS, would be used more frequently in the clinical evaluation of fatty liver and 1H MRS could more accurately reflect the severity of fatty liver. [source]


Fully automated intensity compensation for confocal microscopic images

JOURNAL OF MICROSCOPY, Issue 1 2005
H.-X. WU
Summary One well-recognized problem in three-dimensional (3D) confocal microscopic images is that the intensities in deeper slices are generally weaker than those in shallower slices. The loss of intensity with depth hampers both qualitative observation and quantitative measurement of specimens. Two major types of methods exist to compensate for this intensity loss: the first is based on the geometrical optics inside the specimen, and the second applies an empirical parametric intensity decay function (IDF) of depth. A common feature shared by both methods is that they are parameter-dependent. However, for the optics-based method there are as yet no fully automated parameter-setting approaches; and for the IDF method the traditional profile-fitting approach cannot provide proper parameters if the presumed IDF model does not match the experimental intensity,depth profile of the 3D image. In this paper, we propose a novel maximum-entropy (ME) approach to fully automated parameter-setting. In principle the ME approach is suitable for any compensation method as long as it is parameter-dependent. The basic assumption is that without intensity loss an ideal 3D image should be generally homogeneous with respect to depth and this axial homogeneity can be represented by the entropy of a normalized intensity,depth profile. Experiments on real confocal images showed that such a profile was consistent with visual evaluation of axial intensity homogeneity and that the ME approach could provide proper parameters for both compensation methods mentioned above. Moreover, for the IDF method, experiments on both real and simulated data showed that the ME approach could provide more precise parameters than with traditional profile-fitting. The Appendix provides a proof that under certain conditions the global maximization of the profile-entropy is guaranteed. [source]


Artefacts in restored images due to intensity loss in three-dimensional fluorescence microscopy

JOURNAL OF MICROSCOPY, Issue 2 2001
J. Markham
Computational algorithms for three-dimensional deconvolution have proven successful in reducing blurring and improving the resolution of fluorescence microscopic images. However, discrepancies between the imaging conditions and the models on which such deconvolution algorithms are based may lead to artefacts and/or distortions in the images restored by application of the algorithms. In this paper, artefacts associated with a decrease of fluorescence intensity with time or slice in three-dimensional wide-field images are demonstrated using simulated images. Loss of intensity, whether due to photobleaching or other factors, leads to artefacts in the form of bands or stripes in the restored images. An empirical method for correcting the intensity losses in wide-field images has been implemented and used to correct biological images. This method is based on fitting a decreasing function to the slice intensity curve computed by summing all pixel values in each slice. The fitted curve is then used for the calculation of correction factors for each slice. [source]