Linear Contrast Enhancement Research Articles

CT features in the early and late stages of chronic total coronary occlusions

ObjectivesTo investigate the morphologic characteristics of early and late stages of chronic total coronary artery occlusions (CTO) in coronary computed tomography angiography (coronary CTA). MethodsWe retrospectively analyzed patients who underwent coronary CTA and invasive coronary angiography and had at least one CTO with known duration. The following parameters were obtained in coronary CTA: calcification of the occluded segment; stump morphology; lesion length; remodeling index; presence of intra-occlusion linear contrast enhancement; and density of non-calcified CTO components. CT parameters were compared between patients with early (duration ≤ 12 months) and late (duration > 12 months) stage CTO. ResultsOne-hundred and twelve patients with 124 chronically occluded coronary arteries were analyzed. Fifty nine patients had early stage CTOs (62 lesions) and 53 patients had late stage CTOs (62 lesions). Calcification was more severe in late-stage versus early CTOs (Agatston score: early stage, 27.4 ± 46.7 vs. late stage, 58.3 ± 112.4; p = 0.049). Remodeling index was lower in late-stage CTOs (early stage, 0.96 ± 0.2 vs. late stage, 0.88 ± 0.22; p = 0.034). In patients with late stage CTO, the presence of intra-occlusion linear enhancement was more likely (45.2% vs 14.5%, p < 0.001), and the density of non-calcified components was significantly higher (85.4 ± 27.2 HU vs. 65.7 ± 30.1 HU, p < 0.001). Stump morphology was not different between the two groups. ConclusionsCoronary CTA reveals differences between chronic total coronary occlusions of longer and shorter duration. A long duration is associated with focal calcification and negative remodeling, as well as intra-occlusion enhancement and a higher density of non-calcified components.

Radial contrast enhancement on brain magnetic resonance imaging could be diagnostic of primary angiitis of the central nervous system: a case report and review of the literature

IntroductionPrimary angiitis of the central nervous system is a rare disease of unclear etiology. There is no single test diagnostic of primary angiitis of the central nervous system. We report an unusual pattern on brain magnetic resonance imaging that might be specific for primary angiitis of the central nervous system.Case presentationA 47-year-old Caucasian man developed progressive bilateral hand tremor, difficulty walking, cognitive slowing and headache. A physical examination showed bilateral hand tremor with dysmetria, hyperreflexia and abnormal gait. Magnetic resonance imaging of his brain showed bilateral, symmetrical, increased intensity on T2-weighted images concurrent with linear contrast enhancement in a radial distribution throughout his white matter, sparing subcortical regions in his centrum semiovale, corona radiata, basal ganglia and brainstem. Magnetic resonance spectroscopy demonstrated elevated choline and decreased N-acetyl aspartate. Except for elevated protein and lymphocytic pleocytosis, examination of his cerebrospinal fluid showed no abnormalities. Serological tests for rheumatologic, vasculitic, paraneoplastic, infectious and peroxisomal disorders were negative. A brain biopsy revealed primary angiitis of the central nervous system. Our patient was treated with steroids and intravenous cyclophosphamide, with improvement in signs and symptoms as well as changes on magnetic resonance imaging.ConclusionBilateral, symmetrical, increased intensity on T2-weighted images concurrent with linear contrast enhancement in a radial distribution throughout the white matter on magnetic resonance imaging of the brain should be recognized as a feature of primary angiitis of the central nervous system, and might avoid the need for a brain biopsy to diagnose primary angiitis of the central nervous system.

An integrated approach to map certain palaeochannels of South India using remote sensing, geophysics, and sedimentological techniques

Palaeochannels are important sources of groundwater, economic minerals, and placer deposits. They are also good repositories of palaeoclimate data. To exploit such resources, the first essential step would be to identify and map palaeochannels. This article presents a study in which multi-sensor (optical, thermal, and microwave) image data and satellite-derived digital elevation models (DEM)s of the northern coastal region of Tamilnadu state, south India, were analysed visually and digitally to recognize exposed and buried palaeochannels. Image-enhancement techniques such as linear contrast enhancement of optical data and fusion of microwave and optical image data brought out more information about the palaeochannels. Hill-shading techniques applied to the satellite-derived DEM, further added to the information content on the existence of the palaeochannels. The existence of the newly identified palaeochannels was verified by ground-based techniques such as field checks, sedimentological analysis, and electrical resistivity surveys. The presence of well sorted and rounded grains in the sediment samples and high apparent electrical resistivity values for the thick sandy subsurface strata in these locations confirmed the existence of palaeochannels which were interpreted from the images.

Parametric Generalized Linear System Based on the Notion of the T-Norm

By using the triangular norm, we propose two methods for the construction of generalized linear systems, and show new insights into the relationship between typical systems. Using the Hamacher and Frank t-norm, we propose a parametric log-ratio model, which is a generalization of the log-ratio model and is more flexible in algorithmic development. We develop a generalized linear contrast enhancement algorithm based on the proposed parametric log-ratio model. We show that the performance of the proposed algorithm is effective and robust for different types of images.

Interpretation of aero-magnetic data and satellite imagery to delineate structure — a case study for uranium exploration from Gwalior Basin, India

The Paleo-Meso Proterozoic Gwalior basin (E - W), lying to NW fringe of Bundelkhand massif is represented by litho-package of lower arenaceous Par Formation and upper chemogenic Morar Formation. It is bounded by Indo-Gangetic alluvium in north and east, Kaimur sediments in west and Bundelkhand granitoids in south. Gwalior Basin has been the exploration target for uranium mineralization right from early 60’s. Surface radioactivity anomalies due to uranium has been reported in both Par and Morar Formations of Gwalior Group and Vindhyan sediments. Besides presence of syngenetic uranium in the system, presence of post-depositional faults and fractures are the favorable factors. Aeromagnetic survey was carried out by AMD in 2002 with N-S lines of 500 m interval covering 9406 line km. The data with sampling interval of 0.1 sec was corrected for spikes, diurnal variation, IGRF, heading and lag. Final processed images are prepared after suitable leveling and gridding. First vertical derivative of TMI-RTP and tilt-angle derivative images are used to map the litho-contacts, lineaments and structural features. Numerous NE-SW trending low amplitude and NW-SE trending high amplitude magnetic linears corroborate with quartz reefs and basic dykes respectively. Besides, E-W to WNW-ESE and ENE-WSW trending fractures are also evident from the processed image maps. Further, the Euler’s depth solution of gridded aeromagnetic data calculated for structural indices of 0 and 1 are very consistent in locating the position of the causative sources. Based on the amplitude and textural character of processed aeromagnetic data, alteration zone is delineated well within the Morar Formation. Enhanced Thematic Mapper (ETM+) image with 30m resolution was merged with IRS PAN 1D (5.8 m resolution) for better spatial/radiometric resolution to extract litho-contacts and lineament patterns. Merged PAN band-4 after linear contrast and edge enhancement techniques deciphered detailed lineament pattern, which corroborate the magnetic data. Merged ETM+ (RGB 751) and PC (PC1-PC2-PC5) images depict litho-logical contrast. Integration of aeromagnetic and satellite imagery data helped in understanding the structural fabric of the Gwalior Basin and to identify favorable loci of uranium mineralization.

IMAGING DIAGNOSIS—VENTRICULO‐PERITONEAL SHUNT ASSOCIATED INFECTION IN A DOG

Ventriculo-peritoneal shunting is a surgical treatment for hydrocephalus. Complications of this procedure are not well described in dogs. The most common complication in humans is infection, which can be fatal if not diagnosed and treated quickly. We describe the magnetic resonance (MR) imaging characteristics of a shunt-associated cerebral infection in a dog. The MR features of the infection included hyperintensity of the lining of the ventricular system visible on a T2-weighted FLAIR sequence and marked linear contrast enhancement of the ependymal layer on T1-weighted sequences, similar to that described in people.

Quiste óseo aneurismático frontal. Caso clínico y revisión de la bibliografía

Cranial aneurysmal bone cyst (ABC) is a rare pathological finding that is usually diagnosed in young patients. It is defined as a benign lesion made up of intervillous spaces limited by connective bone tissue septa and osteoclast-type giant cells; these histological characteristics are common to extracranial ABC. Clinically, in most patients, they manifest as cranial tumours which may be painful and vary in size. About 100 cases of cranial ABC have been reported in the literature. We present a literature review of the cases of frontal ABC reported to date, including one that was recently treated in our own service. A 29-year-old female, with no history of traumatic brain injury, who was examined due to the presence of a fixed, painless frontal cranial lesion on the right-hand side. The results of a radiological study revealed the presence of a lytic cranial lesion with well-delimited edges and marginal sclerosis; peripheral and linear contrast enhancement was also observed in the magnetic resonance imaging of the brain. The patient was submitted to a surgical intervention and the entire lesion was removed. There were no incidents in the post-operative period and the definitive pathological diagnosis was cranial ABC. Cranial ABC is a pathological condition with well-defined histological and radiological characteristics, despite the fact that its aetiopathogenesis is still not fully understood. Complete excision of the tumour is considered to be the preferred treatment, which often leads to full recovery of the patient and also offers a good long-term prognosis.

The use of moving contrast sweep to increase the effectiveness of linear, non-linear and midtone shift contrast enhancement in mammography

Low contrast in mammographic image has always made detection of subtle signs such as the presence of micro calcification within dense tissue a challenge. Therefore, numerous researches have been conducted on contrast enhancement technique for mammographic images. However, most of these methods focus on enhancing specific range of intensity level producing an enhanced version of the original image. This paper proposes a new approach in dealing with contrast enhancement for mammographic images. Instead of producing just a single image, the approach proposed here will generate multiple different images where each of them corresponds to a different range of intensity level. These images will then be combined together to form frames of a moving video which would display seamless transition from one intensity level to another. As a result, the radiologist who is performing visual inspection of the image can sweep through the entire range of intensity level of the image which has been contrast enhanced.

Effect of Transient and Permanent Permeability Transition Pore Opening on NAD(P)H Localization in Intact Cells

To study the effect of mitochondrial permeability transition pore (PTP) opening on NAD(P)H localization, intact cells were exposed to the Ca(2+) ionophore A23187. PTP opening, mitochondrial membrane potential, mitochondrial volume, and NAD(P)H localization were assessed by time-lapse laser confocal microscopy using the calcein-cobalt technique, tetramethylrhodamine methyl ester, MitoTracker, and NAD(P)H autofluorescence, respectively. Concomitant with PTP opening, NAD(P)H fluorescence increased outside mitochondria. These events occurred in all cells and were prevented by cyclosporin A. Mitochondrial membrane potential was not systematically collapsed, whereas mitochondrial volume did not change, confirming that A23187 induced transient PTP opening in a subpopulation of cells and suggesting that mitochondrial swelling did not immediately occur after PTP opening in intact cells. NAD(P)H autofluorescence remained elevated after PTP opening, particularly after membrane potential had been collapsed by an uncoupler. Extraction of nucleotide for NAD(P)H quantification confirmed that PTP opening led to an increase in NAD(P)H content. Because the oxygen consumption rate decreased, whereas the lactate/pyruvate ratio increased after PTP opening in intact cells, we conclude that PTP opening inhibits respiration and dramatically affects the cytosolic redox potential in intact cells.

Contrast–dose relation in first‐pass myocardial MR perfusion imaging

To determine the regime of linear contrast enhancement in human first-pass perfusion cardiovascular magnetic resonance (CMR) imaging to improve accuracy in myocardial perfusion quantification. A total of 10 healthy subjects were studied on a clinical 1.5T MR scanner. Seven doses of Gd-DTPA ranging from 0.00125 to 0.1 mmol/kg of body weight (b.w.) were administered as equal volumes by rapid bolus injection (6 mL/second). Resting periods of 15 minutes were introduced after delivery of Gd doses >0.01 mmol/kg b.w. For each subject, two series of rest perfusion scans were performed using two different multislice saturation-recovery perfusion sequences. Maximum contrast enhancement and maximum upslope were obtained in the blood pool of the left ventricular (LV) cavity and in the myocardium. The range of linear contrast-dose relation was determined by linear regression analysis. MR signal intensity increased linearly for contrast agent concentrations up to 0.01 mmol/kg b.w. in the LV blood pool and up to 0.05 mmol/kg b.w. in the myocardium. For Gd concentrations exceeding these thresholds the signal intensity response was not linear with respect to the contrast agent dose. Quantitative evaluation of cardiac MR perfusion data needs to account for signal saturation in both the LV blood pool and the myocardium.

Chronic epigastric blood collection after coronary artery bypass grafting: Case report

A clinical case of epigastric pain 3 months after coronary artery bypass grafting (CABG) is presented. The CT finding of an abdominal mass with thick wall, internal horizontal by-gravity level and linear contrast enhancement at the border between the two different components was correctly interpreted for a chronic hematoma with separation of the formed blood elements from blood serum; in particular, the linear contrast enhancement was related to an artery-feeding vessel.

Magnetic resonance imaging characteristics of posterior scleritis mimicking choroidal mass

We present imaging findings in a case of posterior scleritis, which may mimic tumoral mass lesion resulting in unnecessary enucleation. Magnetic resonance imaging was remarkable for a subretinal mass hypointense on T2 and hyperintense on T1 weighted images. A peripheral rim of hypointensity was noteworthy, suggestive of sclerouveal thickening. There was an ill-defined area of increased T2 signal intensity adjacent to globe at the site of nodular lesion implying an inflammatory process. A linear contrast enhancement was seen within the bulbus oculi which may represent detached retina by exudation or displaced retina due to thickened sclera and choroidal layers. The CSF space around the optic nerve was enlarged.

Contrast-enhancement techniques for particle-image velocimetry

In video-based particle-image velocimetry (PIV) systems for fluid mechanics research, it is sometimes desirable to image seed particles to be smaller than a camera pixel. However, imaging to this size can lead to marginal image contrast such that significant numbers of erroneous velocity vectors can be computed, even for simple flow fields. A variety of image-enhancement techniques suitable for a low-cost PIV system that uses video cameras are examined and tested on three representative flows. Techniques such as linear contrast enhancement and histogram hyperbolization are shown to have good potential for improving the image contrast and hence the accuracy of the data-reduction process with only a 15% increase in the computational time. Some other schemes that were examined appear to be of little practical value in PIV applications. An automated shifting algorithm based on mass conservation is shown to be useful for displacing the second interrogation region in the direction of flow, which minimizes the number of uncorrelated particle images that contribute noise to the data-reduction process.

Meningeal Carcinomatosis of the Cerebellopontine Angle and Internal Auditory Canal

Most CPA and IAC region neoplasms are benign. Malignant tumour represent about 2% of the lesions and metastatic lesions account for 0.2 to 2% of all neoplasms of this region. In a group of 82 patients with meningeal carcinomatosis, 11 patients (16%) with PCA and IAC metastatic lesions were identified. In three cases the original tumour was a breast carcinoma, while in the other eight cases it was a sarcoma, PNET, glioma, leukaemia, lymphoma, medulloblastoma and one tumour of unknown origin. In five cases both PCA and IAC presented abnormal contrast enhancement of nodular type; in four patients only IAC and in two only PCA were involved. IACs were involved bilaterally or monolaterally in four cases each, while PCAs presented bilateral involvement in five cases and monolateral in one. In two cases bilateral Vth cranial nerves and cavernous sinuses were present and all the patients had dural or leptomeningeal carcinomatosis outside the PCAs and IACs. Unlike literature reports in which only 25% of IACs carcinomatosis have a negative clinical picture, we found clinically tested hearing pathology, in only 1/11 patients, and involvement of other cranial nerves in only 2/11 patients. From the MR point of view, CPA and IAC carcinomatosis is characterized by bilateral or, less frequently monolateral nodular or linear contrast enhancement inside the IAC and along the dural lining of the CPA and it usually not visible in non contrast SE T1 and T2 sequences. Carcinomatosis is always associated with more diffuse dural or leptomeningeal secondary neoplastic involvement, but the association with other cranial nerve carcinomatosis is not the rule. The more frequent involvement of these regions may depend on the length of the VIIth and VIIIth cranial nerves (and this observation may also explain the more frequent association with Vth cranial nerve carcinomatosis) and on the volume of the CPA cistern, that allows a more diffuse and longer contact between the nerves and the meninges and the metastatic lesions floating in the cerebrospinal fluid.

3D-FT MRI of the facial nerve

Contrast-enhanced 3D-FT MRI of the intrapetrous facial nerve was obtained in 38 patients with facial nerve disease, using a 1.0 T magnet and fast gradient-echo acquisition sequences. Contiguous millimetric sections were obtained, which could be reformatted in any desired plane. Acutely ill patients, were examined within the first 2 months, included: 24 with Bell's palsy and 6 with other acute disorders (Herpes zoster, trauma, neuroma, meningeal metastasis, middle ear granuloma). Six patients investigated more than a year after the onset of symptoms included 3 with congenital cholesteatoma, 2 with neuromas and one with a chronic Bell's palsy. The lesion was found incidentally in two cases (a suspected neurofibroma and a presumed drop metastasis from an astrocytoma). Patients with tumours had nodular, focally-enhancing lesions, except for the leptomeningeal metastasis in which the enhancement was linear. Linear, diffuse contrast enhancement of the facial nerve was found in trauma, and in the patient with a middle ear granuloma. Of the 24 patients with an acute Bell's palsy 15 exhibited linear contrast enhancement of the facial nerve. Three of these were lost to follow-up, but correlation of clinical outcome and contrast enhancement showed that only 4 of the 11 patients who made a complete recovery and all 10 patients with incomplete recovery demonstrated enhancement. Possible explanations for these findings are suggested by pathological data from the literature. 3D-FT imaging of the facial nerve thus yields direct information about the of the nerve condition and defines the morphological abnormalities. It can also demonstrate contrast enhancement which seems to have some prognostic value in acute idiopathic Bell's palsy.

Multiple medullary venous malformations decreasing cerebral blood flow: Case report

A rare case of multiple medullary venous malformations in the right cerebral hemisphere is reported. The literature review yielded only one case of multiple medullary venous malformations. Computed tomography scan showed multiple calcified lesions with linear contrast enhancement representing abnormal dilated vessels and mild atrophic change of the right cerebral hemisphere. Single-photon emission computed tomography using N- isopropyl-p-( 123 I) iodoamphetamine demonstrated decreased cerebral blood flow in the right cerebral hemisphere.

Contrast enhancement of landsat data on multispectral data analysis system

Contrast enhancement, one of the image processing techiques, is developed on the Multispectral Data Analysis System (MDAS) for enhancing the LANDSAT data. The purpose of image processing for enhancement is to improve the obscure objects data in the image to stand out more readily for good sensing to the human eye. It is observed on MDAS that some of the LANDSAT scenes when examined on the color display, give inadequate information for the required objective of interpretation. This is due to poor tonal contrast in the scene because of prevailing climatological conditions at the time of satellite pass over that area. Also, the LANDSAT data usually occupy a small subset of the total brightness range 0–127. To provide optimal contrast and variation for color compositing, contrast enhancement may by performed on the data before going to trie information processing (categolization) on the landsat scene. This paper describes the algorithms of parametric linear and non linear contrast enhancement techniques. A typical example to differentiate the degree of salinity in the soils was tested with the suggested algorithms and the results are tabulated in the form of photographs. The test area is selected from Haryana (frame no. 158-040 dated 2nd May, 1977) for testing the algorithms. The enhancement software developed on the MDAS stretches all the four Landsat bands and generates an output tape with the format similar to LANDSAT computer compatible tape (CCT). The stretched results of 5 and 7 bands are displayed in this paper. A false color composite which appears as on the color displya could also be generated from 4, 5 and 7 bands. The enhanced output was found to be useful for easily categorizing the data into various categories on MDAS.

Eros Data Center Landsat Digital Enhancement Techniques and Imagery Availability, 1977

SUMMARYThe US Geological Survey's EROS Data Center (EDC) is experimenting with the production of digitally enhanced Landsat imagery. Advanced digital image processing techniques are used to perform geometric and radiometric corrections and to perform contrast and edge enhancements. The enhanced image product is produced from digitally preprocessed Landsat computer compatible tapes (CCT's) on a laser beam film recording system.Landsat CCT data have several geometric distortions which are corrected when NASA produces the standard film products. When producing film images from CCT's, geometric correction of the data is required. The EDC Digital Image Enhancement System (EDIES) compensates for geometric distortions introduced by Earth's rotation, variable line length, non-uniform mirror scan velocity, and detector misregistration.Radiometric anomalies such as bad data lines and striping are common to many Landsat film products and are also in the CCT data. Bad data lines or line segments with more than 150 contiguous bad pixels are corrected by inserting data from the previous line in place of the bad data. Striping, caused by variations in detector gain and offset, is removed with a destriping algorithm applied after digitally enhancing the data.Image enhancement is performed by applying a linear contrast stretch and an edge enhancement algorithm. The linear contrast enhancement algorithm is designed to expand digitally the full range of useful data recorded on the CCT over the range of 256 digital counts. This minimizes the effect of atmospheric scattering and saturates the relative brightness of highly reflecting features such as clouds or snow. It is the intent that no meaningful terrain data are eliminated by the digital processing.The edge enhancement algorithm is designed to enhance boundaries between terrain features that exhibit subtle differences in brightness values along edges of features.After the digital data have been processed, data for each Landsat band are recorded on black-and-white film with a laser beam film recorder (LBR). The LBR corrects for aspect ratio distortions as the digital data are recorded on the recording film over a preselected density range. Positive transparencies of MSS bands 4, 5, and 7 produced by the LBR are used to make color composite transparencies. Color film positives are made photographically from first generation black-and-white products generated on the LBR.

Image processing of galaxy photographs

New computer techniques for analyzing and processing photographic images of galaxies are presented, with interesting scientific findings gleaned from the processed photographic data. Discovery and enhancement of very faint and low-contrast nebulous features, improved resolution of near-limit detail in nebulous and stellar images, and relative colors of a group of nebulosities in the field are attained by the methods. Digital algorithms, nonlinear pattern-recognition filters, linear convolution filters, plate averaging and contrast enhancement techniques, and an atmospheric deconvolution technique are described. New detail is revealed in images of NGC 7331, Stephan's Quintet, Seyfert's Sextet, and the jet in M87, via processes of addition of plates, star removal, contrast enhancement, standard deviation filtering, and computer ratioing to bring out qualitative color differences.