PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Image Enhancement”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1992

Limitations of image enhancement for the visually impaired.

Image enhancement as an aid for the visually impaired may improve visibility of TV programs and provide portable visual aid. This paper describes the current techniques for image enhancement and their underlying models. The limitations of the various techniques and of potential methods of implementation are high-lighted. Initial work in this area was based on a linear model. The finite dynamic range available in the video display and contamination of the enhanced image by high spatial frequency noise limited the model's usefulness. I propose a method to address some limitations of the original model that considers the nonlinear response of the visual system and requires enhancement of subthreshold spatial information only. This modification may increase the dynamic range available by decreasing the range previously used by the linear models to enhance visible details. However, for the modified technique to be most effective, the enhancement has to be continuously tuned, based on the patient's visual loss and the spatial frequency content of the displayed images. The implications of these limitations for the potential implementation in TV are discussed. Implementation of an image-enhancing visual aid in a head-mounted, binocular, full-field, virtual vision device may cause substantial difficulties. Patient adaptation may be difficult due to head movement and interaction of the vestibular system response with the head-mounted display. An alternate, bioptic design is proposed in which the display is positioned above or below the line of sight to be examined intermittently, possibly in a freeze-frame mode. Such implementation is also likely to be less expensive, enabling more users access to the device.

Audiovisual Aids↗
PubMed1989

Evaluation of a commercial mammography image-enhancement system.

A commercial mammography image-enhancement system manufactured by Damon Corporation (Needham, MA) is evaluated. Using a dedicated computer, the system implements a real-time video local adaptive image processing algorithm based on the Wallis equation. Radiographs of a mammographic QA phantom (Nuclear Associates Model 76-001-4) containing five groups of simulated breast microcalcifications ranging in diameter from 0.12 to 0.35 mm were viewed by four investigators under three viewing conditions: on a light box with the unaided eye, on the image enhancer in magnified "bypass" (unenhanced) mode, and on the enhancer using all features for optimum enhancement. A mammogram was then overlaid on the radiographs, and the composite images were viewed under the same three conditions. Using the enhancer, as compared to using a light box alone, average increases of 1.4 and 1.1 microcalcifications per radiograph were observed for the phantom and phantom-with-mammogram radiographs, respectively. High-contrast resolution and spatial distortion were also measured.

Computers↗
PubMed1991

Image enhancement for the visually impaired. Simulations and experimental results.

Digital image enhancement has been proposed as an aid for the visually impaired. The capability of two enhancement techniques to improve recognition of images by patients with central scotoma or cataracts was evaluated using image-processing simulations and direct patient testing. Enhancements and simulations were based on measurements of contrast sensitivity loss for patients with macular disease. Contrast sensitivity loss was measured using Gabor-type localized stimuli and paradigms that are appropriate for analyzing form perception. The simulations using the contrast sensitivity data suggested that patients with moderate visual loss (20/70-20/200) may have difficulty recognizing faces and may benefit from enhancement by both of the techniques used. Ability to recognize celebrities from enhanced images improved for 39 of the 46 patients tested. The improvement was significant (P less than 0.05) for 16 of the 38 patients with central visual loss and for 3 of 8 patients with anterior segment media opacities tested. The simulations suggest that the benefits of image enhancement may be similar or even greater for recognition of other types of images.

Adult↗
PubMed1991

MR differentiation of hepatic haemangioma and hepatocellular carcinoma: value of delayed-phase Gd-DTPA enhanced images.

The efficacy of three different approaches (precontrast and delayed-phase postcontrast T1-weighted (T1-W) images, measurement of T2 value, and dynamic FLASH imaging) for differentiation between hepatic haemangiomas and hepatocellular carcinomas, was compared. Most haemangiomas (89%) showed iso- or hypointensity on precontrast T1-W images and hyperintensity on delayed-phase postcontrast T1-W images. By using both pre/postcontrast T1-W images and T2 measurement, 30 out of 32 lesions (94%) were correctly differentiated. The dynamic FLASH imaging did not significantly improve the overall accuracy although it played a critical role in a few problematic cases. It is concluded that the combination of pre/postcontrast T1-W images is a promising approach for differentiation of small hepatic tumours, and plays a complementary role with T2 measurement.

Adult↗
PubMed1992

Spleen: dynamic enhancement patterns on gradient-echo MR images enhanced with gadopentetate dimeglumine.

To examine the pattern of immediate enhancement with gadopentetate dimeglumine on dynamic magnetic resonance (MR) images of the spleen, this study was divided into two parts: In the first part, the authors retrospectively reviewed the dynamic MR images obtained with a fast low-angle shot (FLASH) sequence in the abdomen immediately after injection of gadopentetate dimeglumine in 137 patients. In the second part, dynamic gadolinium-enhanced FLASH images were prospectively compared with contrast material-enhanced computed tomographic (CT) scans in 17 patients with focal splenic lesions discovered on CT scans. In the first part, 108 patients (79%) had an arciform pattern of contrast enhancement; 22 patients (16%), a uniform pattern of high signal intensity; and seven patients (5%), a uniform pattern of low signal intensity. Most patients had arciform enhancement of the spleen; uniform enhancement occurred in some patients with underlying malignant or inflammatory disease. In the second part, all focal lesions seen on CT scans were seen on dynamic MR images (75 lesions), significantly more than were seen on FLASH images (15 lesions) (P < .001).

Adolescent↗
PubMed1992

[Low flip angle spin-echo MR imaging to obtain better Gd-DTPA enhanced imaging with ECG gating].

ECG-gated spin-echo imaging (ECG-SE) can reduce physiological motion artifacts. However, ECG-SE does not provide strong T1-weighted images because repetition time (TR) depends on heart rate (HR). We investigated the usefulness of low flip angle spin-echo imaging (LFSE) in obtaining more T1-dependent contrast with ECG gating. in computer simulation, the predicted image contrast and signal-to-noise ratio (SNR) obtained for each flip angle (0-180 degrees) and each TR (300 msec-1200 msec) were compared with those obtained by conventional T1-weighted spin-echo imaging (CSE: TR = 500 msec, TE = 20 msec). In clinical evaluation, tissue contrast [contrast index (CI): (SI of lesion-SI of muscle)2*100/SI of muscle] obtained by CSE and LFSE were compared in 17 patients. At a TR of 1,000 msec, T1-dependent contrast increased with decreasing flip angle and that at 38 degrees was identical to that with T1-weighted spin-echo. SNR increased with the flip angle until 100 degrees, and that at 53 degrees was identical to that with T1-weighted spin-echo. CI on LFSE (74.0 +/- 52.0) was significantly higher than CI on CSE (40.9 +/- 35.9). ECG-gated LFSE imaging provides better T1-dependent contrast than conventional ECG-SE. This method was especially useful for Gd-DTPA enhanced MR imaging.

Contrast Media↗
PubMedDate not supplied

Image enhancement using computed radiography.

Computed radiography (CR) is emerging as a digital imaging modality for use in conventional radiography. An advantage of CR over film-screen systems is the separation of image acquisition, processing and display. Selection of many different image display characteristics are possible. The system is also able to alter or enhance image details after the radiographic examination has been completed.

Humans↗
PubMed1992

Image enhancement filters significantly improve reading performance for low vision observers.

As people age, so do their photoreceptors; many photoreceptors in central vision stop functioning when a person reaches their late sixties or early seventies. Low vision observers with losses in central vision, those with age-related maculopathies, were studied. Low vision observers no longer see high spatial frequencies, being unable to resolve fine edge detail. We developed image enhancement filters to compensate for the low vision observer's losses in contrast sensitivity to intermediate and high spatial frequencies. The filters work by boosting the amplitude of the less visible intermediate spatial frequencies. The lower spatial frequencies. These image enhancement filters not only reduce the magnification needed for reading by up to 70%, but they also increase the observer's reading speed by 2-4 times. A summary of this research is presented.

Adult↗
PubMed1988

Laminar-specific distribution and infrastructural detail of amyloid in the Alzheimer disease cortex visualized by computer-enhanced imaging of epitopes recognized by monoclonal antibodies.

Monoclonal antibodies to the A4 amyloid polypeptide were used in immunocytochemical staining of the Alzheimer disease prefrontal cortex. Analysis of the resulting staining patterns allowed us to evaluate the amounts and distribution of amyloid-protein deposits exclusive of other senile-plaque components. Previously unappreciated infra-structural details of amyloid in the Alzheimer disease brain became accessible through computer-enhanced imaging procedures. Four discrete morphologic classes of amyloid deposits were observed and classified as punctate, macular, ring, and ring-with-core configurations. Computer imaging indicated that all four classes of immunostained deposits contain internal gradients of density. The classes were nonuniformly distributed with regard to size and location within cortical laminae. Our results support two separate but complementary hypotheses concerning the molecular neuropathology of Alzheimer disease in the prefrontal cortex. (i) Irrespective of cortical layer or morphology, density-gradient analyses suggest that amyloid deposits are elaborated through molecular and cellular events that may involve diffusion or coalescence of the A4 polypeptide. (ii) The distribution and morphology of prefrontal cortical amyloid deposits may be dependent upon underlying laminar-specific structures of the neocortex.

Alzheimer Disease↗
PubMed1990

In vivo 13C imaging enhanced by polarization transfer.

Carbon-13 NMR imaging has been combined with 1H-13C polarization transfer to improve image quality. Natural-abundance carbon images of Fischer rat bodies were obtained within a few minutes. Next 13C-labeled glucose was administered orally to rats, and spatial distributions of glucose and its derivatives were observed with this technique.

Animals↗
PubMed1991

Similar features in Z bands of both skeletal and cardiac muscle revealed by image enhancement.

We have shown previously that the small square (ss) and basket weave (bw) states of the Z band lattice in cardiac and skeletal muscle are related to the contractile state of the muscle. We have used two-dimensional image processing techniques on digitized electron micrographs to enhance the structural features of each projected lattice form in cardiac and skeletal muscle. Four different processing techniques were employed to assess the effect of enhancement artifacts on the resulting Z band images. We observed only slight differences between enhanced images of a particular Z band form produced by the four different techniques. Every enhanced image showed an approximate four-fold symmetry independent of muscle type or Z band lattice form. Each enhanced image showed four cross-connecting Z-filaments which appeared to connect each axial filament to the four nearest axial filaments. In bw images from both cardiac and skeletal muscle, axial filaments had a greater apparent diameter and a greater interaxial filament spacing than in the ss images. In both muscle types, the cross-connecting Z-filaments appeared to overlap half-way between axial filaments in the ss images while the bw images showed no such overlap. These structural features are consistent with a dynamic Z band lattice that participates in muscle contraction.

Algorithms↗
PubMed1978

Digital image enhancement of cephalograms.

Quantification of cephalometric X-rays requires the use of hand tracings of the structures to delineate points, lines, and angles. The structures, especially soft tissue, are often obscure and are therefore approximated. Recent biomedical application of image enhancement by digital computer promises a method whereby landmarks in the cranium are more clearly defined. Development of this technique will enable a more extensive and accurate utilization of cephalometric radiographs for diagnostic and research purposes.

Cephalometry↗
PubMed1991

Developing spinal column: gadolinium-enhanced MR imaging.

Enhancement characteristics of the normally developing spinal column were examined in magnetic resonance (MR) images obtained in 58 children aged 7 days to 9 years. With a 1.5-T imager, short-repetition-time spin-echo images were obtained before and after the administration of 0.1 mmol/kg gadopentetate dimeglumine. Enhancement of normal bone marrow was seen in all patients aged less than 7 years; it was marked only in patients aged less than 2 years. Enhancement of normal cartilage, seen in all patients aged less than 1 1/2 years, may be the most striking feature of enhanced MR images of the infant spine. Enhancement of both bone marrow and cartilage in children appears to be due to the unusual prominence of vasculature, associated with permeability of the capillary endothelium and a plentiful extravascular space. Although marked and diffuse enhancement of vertebral bodies in adults is often thought to indicate a pathologic marrow state, caution must be used before the same criteria are applied to children.

Age Factors↗
PubMed1990

Video enhanced imaging of the fluorescent Na+ probe SBFI indicates that colonic crypts absorb fluid by generating a hypertonic interstitial fluid.

Extracellular accumulation of Na+ detected by video-enhanced microscopic imaging of the impermeant fluorescent probe SBFI confirms the view that colonic crypts produce a hypertonic ascorbate ca 1000 mOsm.kg-1, thereby generating a large osmotic pressure across the crypt wall. This creates a high fluid tension within the crypt lumen, sufficient to dehydrate faeces. When bathed in Tyrode the SBFI.Na+ fluorescence indicates a [Na+] ca 750 mM within the interstitial space of metabolizing rat descending colon. There is no evidence of interstitial Na+ accumulation in octanol (2 mM) or in rabbit colon incubated with 1.0 mM ouabain and no evidence of Na+ secretion via the crypt lumen during absorption.

Animals↗
PubMed1990

Hepatic cirrhosis and hepatitis: MR imaging enhanced with superparamagnetic iron oxide.

Superparamagnetic iron oxide was applied as a reticuloendothelial contrast agent in the diagnosis of cirrhosis and hepatitis in seven patients. Three patients had compensated cirrhosis, and four had active hepatitis. T1- and T2-weighted spin-echo magnetic resonance images were obtained before and 1 hour after the administration of iron oxide. Eight patients without diffuse liver disease served as a control group. Normal liver tissue showed a 75% +/- 9% reduction in signal intensity after the administration of iron oxide, and the liver appeared homogeneously hypointense. Cirrhotic liver tissue showed a smaller response (P less than .05) to iron oxide, with a 52% +/- 13% reduction in liver signal intensity. Inhomogeneous structures could be observed in enhanced images and are thought to represent fibrous bands or regenerating nodules. Liver tissue with active hepatitis showed a markedly reduced response to iron oxide (11% +/- 2%) (P less than .05), and the parenchyma appeared homogeneous. The authors conclude that the uptake of iron oxide particles is inhomogeneously altered in cirrhosis because of structural changes and homogeneously decreased in hepatitis because of functional changes of hepatic parenchyma.

Contrast Media↗
PubMed1979

Image enhancement by digital-analog filtration. I. Technical description of device.

A device for general (10 x 10 pixels) image filtration of 24 cm x 30 cm roentgenograms in the image domain (10(6) pixels) is described. It combines analog and digital techniques and records the processed image on film in the same scale as the original. Results from preliminary tests of the equipment are reported and it is concluded that it yields images with increased perceptibility of large-scale objects of low photographic contrast in the presence of disturbing structures of high spatial frequency and comparably high photographic contrast.

Bone and Bones↗