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Results for “Image Enhancement”

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At least 73 records · Page 4Linked to original sources
PubMed1999

Safety, tolerance, biodistribution, and MR imaging enhancement of the liver with gadobenate dimeglumine: results of clinical pharmacologic and pilot imaging studies in nonpatient and patient volunteers.

PURPOSE: The purpose of this study was to assess safety, tolerance, biodistribution, and magnetic resonance (MR) imaging enhancement of the liver with gadobenate dimeglumine. MATERIALS AND METHODS: Phase I single-blind studies were performed in 53 healthy volunteers, of whom 39 received gadobenate dimeglumine and 14 placebo. Another 106 patients with focal liver disease received gadobenate dimeglumine in parallel-group, open-label, phase II studies. The imaging potential of gadobenate dimeglumine was assessed in all 106 patients plus 11 healthy volunteers, whereas pharmacokinetics were determined for 42 healthy volunteers. Safety was assessed for all subjects enrolled in the study. Imaging protocols for healthy volunteers were similar to those for patients and comprised predose T2-weighted sequences and pre- and postinjection T1-weighted spin-echo and gradient-echo sequences. RESULTS: Gadobenate dimeglumine was safe and well tolerated in healthy volunteers and patients, with pharmacokinetics described adequately as a distribution phase and an elimination phase. Most of the injected dose of gadobenate was excreted unchanged in urine within 24 hours, although a fraction corresponding to 0.6%-4.0% of the injected dose was eliminated with the bile and recovered in the feces. The gadobenate dimeglumine-enhanced signal intensity of liver parenchyma was dose-related and constant for 120 minutes. Gadobenate dimeglumine-enhanced MR imaging was superior to nonenhanced MR imaging in more than 50% of patient studies, with more lesions seen in 26%-38% of patients and smaller lesions in 21%-33% of patients. In general, image sets acquired 40-180 minutes after administration of a dose were preferred, whereas images acquired during the dynamic phase after administration were typical of those obtained with extracellular fluid contrast agents. CONCLUSION: Gadobenate dimeglumine is a safe and efficacious MR imaging contrast agent suitable for both delayed and dynamic imaging of the liver.

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↗
PubMed2000

Enhanced image detail using continuity in the MIP Z-buffer: applications to magnetic resonance angiography.

In this paper a new algorithm is presented for the segmentation and display of blood vessels from images obtained with magnetic resonance angiography (MRA) and other three-dimensional (3D) angiographic imaging techniques. The algorithm developed is based on the observation that vessels are strongly evident in the maximum intensity projection (MIP) Z-buffer as regions of high continuity and low local roughness. Roughness is measured here by the minimum chi2 value of a low-order local least-squares fit in the principal directions through each point in the MIP Z-buffer. Although some background pixels in the Z-buffer exhibit low local roughness, the size of the connected region is nearly always much smaller than even the very smallest vessels that appear in the MIP image. It is shown that by applying connectivity to the regions of low roughness, there is nearly complete separation between vascular detail and background. When connectivity is further applied in the original 3D image, vascular bed segmentation becomes nearly complete. The algorithm consists of three basic steps: a) determination of the minimum local roughness at each point in the MIP Z-buffer; b) connection of all neighboring points of low local roughness; and c) connection of all points in the original 3D image matrix that are connected to the points determined in the MIP Z-buffer and that are above an intensity threshold. The algorithm as presented is not optimized but demonstrates a very strong potential for improved portrayal of vascular detail.

Algorithms↗
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

Optimization of ionizing radiation usage in medical imaging by means of image enhancement techniques.

This paper focuses attention on the fact that images considered unsatisfactory for medical analysis may be rendered usable following various image enhancement techniques. In those cases where this form of image processing can sufficiently improve otherwise unusable images, the necessity of repetitive administration of radionuclides to patients may be avoided with a concomitant reduction in ionizing radiation dosages. Application of these techniques in a clinical situation reduced the dose in thallium studies by 50%. Similar results may be obtainable with other nuclear medicine procedures.

Bone and Bones↗
PubMed1994

A method of using noise as a test pattern for determining image enhancement filters.

Many digitally based medical imaging systems include both reconstruction algorithms and additional image filters designed to enhance certain image features. However, the manufacturers usually consider these algorithms and filters to be proprietory information. The purpose of this note is to describe a simple procedure for determining the spatial frequency response of these proprietary enhancement filters. The technique uses image noise as a test pattern. The procedure consists of acquiring a small number of noise-only data sets (say 10) of a uniform phantom and reconstructing the images using the different filters with repeated use of the noise data sets. A straightforward analysis then yields the enhancement filter frequency responses.

Algorithms↗
PubMed1995

An algorithm for MR angiography image enhancement.

This study describes a three-dimensional (3D) filtering algorithm for magnetic resonance angiography (MRA) image enhancement. Based on the properties of 3D MRA data, the algorithm uses the dispersion range of the 13 outputs of a 3D directional low-pass filter bank to identify the vessel structure and control the processing of MRA data. Vascular structures in the data are preserved while the components of static tissues and isolated noise impulses are reduced by the processing. As a result, the small vessels have been enhanced and visibility of vessels in the projected image has been improved.

Algorithms↗
PubMed2006

Computerized evaluation of echocardiographic stress tests in patients with poorly visualized endocardium using analysis of color-encoded contrast-enhanced images.

AIMS: We hypothesized that real-time color encoding of contrast-enhanced images would allow objective detection of stress-induced wall motion abnormalities (WMA). METHODS: We studied 117 patients with poorly visualized endocardium undergoing dobutamine stress tests. Color-encoded images (Philips, color kinesis) were obtained at rest and peak stress in four standard views during i.v. infusion of Definity. Images were reviewed without color overlays by two expert readers, who graded regional wall motion as normal or abnormal. In 101/117 patients (86%), in whom contrast enhancement allowed endocardial tracking, regional fractional area changes were calculated from the color overlays, and thresholds for calling a stress-induced WMA were optimized in a randomly selected subgroup of 34 patients (ROC analysis) to achieve maximum agreement with expert grades. This computerized detection of stress-induced WMA was then tested prospectively in the remaining 67 patients, using the expert grades as a "gold standard". RESULTS: 20/67 patients had resting WMA and 13/67 patients developed WMA at peak stress. The automated technique detected stress-induced WMA in at least one vascular territory with a sensitivity, specificity and accuracy of 0.80, 0.65 and 0.69, while the level of agreement between the two experts was 0.62, 0.91 and 0.85, respectively. CONCLUSION: Analysis of color-encoded, contrast-enhanced images allows objective, accurate, automated detection of stress-induced WMA in patients with poor acoustic windows.

Cardiotonic Agents↗
PubMed2003

How we perform delayed enhancement imaging.

Recently, numerous studies have demonstrated the effectiveness of a segmented inversion recovery fast gradient echo (seg IR-FGE) sequence for differentiating injured from normal myocardium. This technique for delayed enhancement imaging has been shown to be effective in identifying the presence and extent of myocardial infarction, as well as predicting improvement in contractile function after coronary revascularization. In this article we outline the procedure of delayed enhancement imaging performed at our center, describe the seg IR-FGE sequence in more detail, including our process for choosing sequence settings, review our process of image interpretation, and highlight potential pitfalls (and techniques to overcome them) that we have encountered in our experience with performing the technique in over 1500 patients.

Contrast Media↗
PubMed2005

Quantitative comparison between two phase contrast techniques: diffraction enhanced imaging and phase propagation imaging.

Two x-ray phase contrast imaging techniques are compared in a quantitative way for future mammographic applications: diffraction enhanced imaging (DEI) and phase propagation imaging (PPI). DEI involves, downstream of the sample, an analyser crystal acting as an angular filter for x-rays refracted by the sample. PPI simply uses the propagation (Fresnel diffraction) of the monochromatic and partially coherent x-ray beam over large distances. The information given by the two techniques is assessed by theoretical simulations and compared at the level of the experimental results for different kinds of samples (phantoms and real tissues). The imaging parameters such as the energy, the angular position of the analyser crystal in the DEI case or the sample to detector distance in the PPI case were varied in order to optimize the image quality in terms of contrast, visibility and figure of merit.

Breast Neoplasms↗
PubMed2000

Nondiffuse fatty change of the liver: discerning pseudotumor on MR images enhanced with ferumoxides-initial observations.

PURPOSE: To clarify the findings of nondiffuse fatty change of the liver on ferumoxides-enhanced magnetic resonance (MR) images. MATERIALS AND METHODS: Of 202 patients who underwent ferumoxides-enhanced MR imaging, eight who had nondiffuse fatty change of the liver at computed tomography (CT) were examined as study subjects. MR imaging findings before and 1 hour after ferumoxides administration were compared with CT findings. RESULTS: Focal fatty areas of the liver showing low attenuation on CT images were depicted as areas of relatively high intensity on the ferumoxides-enhanced T1-weighted images in all patients. On enhanced T2-weighted images, focal fatty change showed relatively high intensity in three and isointensity in one of the four patients. Focal spared areas appearing as areas of relatively high attenuation on CT images were depicted as areas of relatively low intensity on the ferumoxides-enhanced T1- and T2-weighted images in all patients. CONCLUSION: Although prior reports of hepatic MR imaging with ferumoxides indicated that there is accumulation of ferumoxides within focal fatty areas that are no longer seen after the administration of contrast medium, this study revealed that focal fatty change and focal spared areas of fatty liver may be pseudotumors because of the relatively high intensity of fatty areas of the liver. Radiologists can distinguish these conditions from hepatic tumors by using the opposed-phase gradient-echo sequence or the fat-saturation technique.

Aged↗
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↗
PubMed2003

Chromosome image enhancement using multiscale differential operators.

Chromosome banding patterns are very important features for karyotyping, based on which cytogenetic diagnosis procedures are conducted. Due to cell culture, staining, and imaging conditions, image enhancement is a desirable preprocessing step before performing chromosome classification. In this paper, we apply a family of differential wavelet transforms (Wang and Lee, 1998), (Wang, 1999) for this purpose. The proposed differential filters facilitate the extraction of multiscale geometric features of chromosome images. Moreover, desirable fast computation can be realized. We study the behavior of both banding edge pattern and noise in the wavelet transform domain. Based on the fact that image geometrical features like edges are correlated across different scales in the wavelet representation, a multiscale point-wise product (MPP) is used to characterize the correlation of the image features in the scale-space. A novel algorithm is proposed for the enhancement of banding patterns in a chromosome image. In order to compare objectively the performance of the proposed algorithm against several existing image-enhancement techniques, a quantitative criteria, the contrast improvement ratio (CIR), has been adopted to evaluate the enhancement results. The experimental results indicate that the proposed method consistently outperforms existing techniques in terms of the CIR measure, as well as in visual effect. The effect of enhancement on cytogenetic diagnosis is further investigated by classification tests conducted prior to and following the chromosome image enhancement. In comparison with conventional techniques, the proposed method leads to better classification results, thereby benefiting the subsequent cytogenetic diagnosis.

Algorithms↗
PubMed1999

Indocyanine green angiography: an evaluation of image enhancement for the identification of occult choroidal neovascular membranes.

PURPOSE: To determine the diagnostic yield of occult choroidal neovascularization from examination of nonenhanced digital indocyanine green (ICG) angiograms versus examination of both nonenhanced and contrast-enhanced angiograms. METHODS: Fifty consecutive occult choroidal neovascular membranes were examined using ICG angiography at the Queen's University Eye Department. These studies were retrospectively reviewed in a masked fashion using the nonenhanced images. A subsequent examination of the same images was then performed using both the nonenhanced and contrast-enhanced images. Each study was graded as focal hyperfluorescence, plaque hyperfluorescence, isofluorescence, or hypofluorescence. RESULTS: Of the cases reviewed, only 36% (18/50) of the membranes were well-defined on nonenhanced ICG angiography, compared with 58% (28/50) using image enhancement in addition to the nonenhanced images. This was a statistically significant difference in image definition between the two groups (chi-square test; P < 0.005). CONCLUSION: Contrast-enhanced angiograms, when used in conjunction with nonenhanced ICG images, allowed for a significantly higher diagnostic yield when compared with the study of nonenhanced images alone.

Aged↗
PubMed2004

Fingerprint image enhancement by differential hysteresis processing.

A new method to enhance defective fingerprints images through image digital processing tools is presented in this work. When the fingerprints have been taken without any care, blurred and in some cases mostly illegible, as in the case presented here, their classification and comparison becomes nearly impossible. A combination of spatial domain filters, including a technique called differential hysteresis processing (DHP), is applied to improve these kind of images. This set of filtering methods proved to be satisfactory in a wide range of cases by uncovering hidden details that helped to identify persons. Dactyloscopy experts from Policia Federal Argentina and the EAAF have validated these results.

Dermatoglyphics↗