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At least 127 records · Page 7Linked to original sources
PubMed1997

Dynamic contrast-enhanced imaging and analysis at high spatial resolution of MCF7 human breast tumors.

High resolution, dynamic GdDTPA-enhanced images of MCF7 human breast tumors in immunodeficient mice were analyzed at pixel resolution. The analysis, based on a physiological model, was performed by applying a nonlinear least-square algorithm using a color coded scale. The final output mapped at pixel resolution capillary permeability times surface area and fraction of extracellular volume, for each tumor slice. In addition, the output included assessment of the fit to the model by determining the proportion of variability (R2) for each pixel. The spatial variation in the R2 values served to identify regions where the predominant mechanism of enhancement was leakage from the intravascular volume to the extracellular volume (R2 close to 1). In regions with low R2 other mechanisms of enhancement appear to be dominating presumably diffusion within the extracellular space. As expected, in necrotic regions lacking microcapillaries and identified by analyzing T2-weighted images of the same tumors, the model failed to fit the dynamic contrast enhanced data. The heterogeneous distribution of the determined pathophysiological features demonstrates the importance of recording and analyzing breast tumor images at high spatial resolution.

Algorithms↗
PubMed2004

Assessment of perfusion by dynamic contrast-enhanced imaging using a deconvolution approach based on regression and singular value decomposition.

The assessment of tissue perfusion by dynamic contrast-enhanced (DCE) imaging involves a deconvolution process. For analysis of DCE imaging data, we implemented a regression approach to select appropriate regularization parameters for deconvolution using the standard and generalized singular value decomposition methods. Monte Carlo simulation experiments were carried out to study the performance and to compare with other existing methods used for deconvolution analysis of DCE imaging data. The present approach is found to be robust and reliable at the levels of noise commonly encountered in DCE imaging, and for different models of the underlying tissue vasculature. The advantages of the present method, as compared with previous methods, include its efficiency of computation, ability to achieve adequate regularization to reproduce less noisy solutions, and that it does not require prior knowledge of the noise condition. The proposed method is applied on actual patient study cases with brain tumors and ischemic stroke, to illustrate its applicability as a clinical tool for diagnosis and assessment of treatment response.

Algorithms↗
PubMed2006

An optimal fuzzy system for color image enhancement.

A Gaussian membership function is proposed to fuzzify the image information in spatial domain. We introduce a global contrast intensification operator (GINT), which contains three parameters, viz., intensification parameter t, fuzzifier fh, and the crossover point mu(c), for enhancement of color images. We define fuzzy contrast-based quality factor Qf and entropy-based quality factor Qe and the corresponding visual factors for the desired appearance of images. By minimizing the fuzzy entropy of the image information with respect to these quality factors, the parameters t, fh, and mu(c) are calculated globally. By using the proposed technique, a visible improvement in the image quality is observed for under exposed images, as the entropy of the output image is decreased. The terminating criterion is decided by both the visual and quality factors. For over exposed and under plus over exposed images, the proposed fuzzification function needs to be modified by taking maximum intensity as the fourth parameter. The type of the images is indicated by the visual factor which is less than 1 for under exposed images and more than 1 for over exposed images.

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↗
PubMed1996

Observer performance in the localization of tubes and catheters on digital chest images: the role of expertise and image enhancement.

RATIONALE AND OBJECTIVES: To determine whether observer performance in the localization of tubes and catheters on computed radiography (CR) chest images can be improved by using an automatic image-processing algorithm. METHODS: Comparisons were made of CR hard-copy, CR soft-copy, and CR enhanced soft-copy images obtained with an image-processing algorithm. The enhanced images used gray-level optimization and nonlinear unsharp masking to emphasize the edges of the devices. Chest radiologists (n = 4), general radiologists (n = 4), and interns (n = 6) read 45 images that contained endotracheal tubes, pulmonary artery catheters, and central venous catheters. RESULTS: Chest radiologists had the smallest mean interobserver localization variability (4 mm), followed by general radiologists (6 mm) and interns (8 mm). Localization variability was greatest for hard-copy images and least for enhanced soft-copy images. CONCLUSION: Use of an automatic imaging-processing algorithm reduced localization variability and enabled the medical interns to perform at approximately the same level as the chest radiologists.

Algorithms↗
PubMed1984

Liposomes loaded with contrast material for image enhancement in computed tomography. Work in progress.

Large unilamellar phospholipid vesicles were prepared and loaded with various radiographic contrast media. Body CT following in vivo administration of these vesicles in the rat demonstrated opacification of organs associated with the reticuloendothelial system. Image enhancement in the spleen and liver was dose dependent and was linearly related within the dose range investigated. Contrast enhancement was observed within five minutes of intravenous administration, was maximal 60 minutes after injection, and declined during the second hour. Clearance of the radiographic contrast material was complete within 24 hours. Diffuse splenic lymphoma following intraperitoneal or intrasplenic injection of lymphoma cells, and solitary lymphoma nodules following intrahepatic injection were readily detected as nonenhanced areas following injection of liposomes.

Animals↗
PubMed1994

Magnetic resonance imaging-enhancing lesions of the labyrinth and facial nerve. Clinical correlation.

OBJECTIVE: Gadolinium-enhanced magnetic resonance imaging (MRI) is useful in assessing inflammatory and neoplastic lesions of the labyrinth and facial nerve. The following cases demonstrate the ability of MRI to differentiate neoplastic from inflammatory lesions within the labyrinth. PATIENTS OR OTHER PARTICIPANTS: Nine patients were selected with enhancing lesions of the labyrinth and the facial nerve identified on MRI. INTERVENTION: Acyclovir and prednisone were prescribed for herpes zoster oticus; surgical removal of neoplastic lesions was performed. MAIN OUTCOME MEASURE: The hypothesis was developed in the course of clinical practice. No planned outcome was emphasized, as this article is based on the differential diagnoses of the cases reported. RESULTS: Gadolinium-enhanced MRI is useful in differentiating neoplastic from inflammatory lesions within the labyrinth. Axial and coronal 3-mm sections with gadolinium enhancement were necessary for identifying these lesions and particularly for recognizing the sharp enhancement of the neoplastic margin in contrast to the dull cloudy margins of an inflammatory lesion. CONCLUSIONS: The MRI differentiation of these lesions is helpful in providing appropriate medical and surgical management of neoplastic and inflammatory lesions of the labyrinth.

Adult↗
PubMed2005

Abdominal CT with low tube voltage: preliminary observations about radiation dose, contrast enhancement, image quality, and noise.

PURPOSE: To prospectively investigate the effect of low tube voltage on radiation dose, contrast enhancement, image quality, and image noise at abdominal dynamic computed tomography (CT). MATERIALS AND METHODS: The institutional review board approved this study. Prior informed consent was obtained from all patients. Forty patients (24 women, 16 men; mean age, 62 years) underwent initial abdominal CT at 120 kV with 100 mL of contrast material (protocol A). Then all patients were randomly assigned to one of two protocols (protocol B, CT at 90 kV with 100 mL contrast material; protocol C, CT at 90 kV with 80 mL contrast material). The CT numbers of their abdominal organs were assessed quantitatively and qualitatively. Statistical analysis was performed by using the two-tailed paired t test, Kruskal-Wallis test, and kappa test of interobserver agreement. The radiation dose was measured with a phantom that consisted of glass-rod dosimeters. RESULTS: Quantitative analysis revealed that protocols B and C yielded significantly better enhancement of the aorta, liver, pancreas, spleen, and kidney than did protocol A (P < .05). With qualitative analysis, the difference among the three protocols in regard to image quality was not significant. At 90 kV versus 120 kV, the radiation dose reduction in the center of the phantom was 56.8% (6.3 vs 14.6 mGy); in the periphery, it was 46.2% (13.6 vs 25.3 mGy). CONCLUSION: By decreasing the tube voltage, the amount of contrast material can be reduced without image quality degradation. In scans obtained with a low tube voltage, the radiation dose can be reduced as much as 56.8%, and higher contrast material enhancement can be achieved.

Adult↗
PubMed1985

Gadolinium oxide: a protoype agent for contrast enhanced imaging of the liver and spleen with magnetic resonance.

Gd2O3 particles (less than 2 microns) in suspension were evaluated as a potential contrast agent for liver-spleen imaging with magnetic resonance. The agent was administered IV to rabbits in doses ranging from 10 to 120 mumol/kg and the tissues removed after sacrifice for in vitro T1 and T2 analysis. The temporal response was determined in liver and spleen samples of rabbits given a fixed dose (60 mumol/kg) and sacrificed at intervals from 15 min to 60 hr later. Documentation of the subanatomic location of Gd2O3 particles in tissue was accomplished by electron microscopy and x-ray dispersion microanalysis. T1 weighted images were obtained at 0.12T on a prototype resistive scanner. The liver, spleen, and lung relaxation times are very responsive to Gd2O3 IV and the effect is dose related. A peak effect is observed between 3-7 hr after injection and relaxation times may normalize by 60 hr. By electron microscopic and x-ray analysis, Gd2O3 is most prominently found in the hepatic and splenic sinusoids. The images show marked enhancement of liver and splenic tissues, aiding in the clear delineation of these tissues from neighboring structures.

Animals↗
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↗
PubMed2006

Diffraction enhanced imaging of controlled defects within bone, including bone-metal gaps.

Gap regions between a bone and an implant, whether existing upon insertion or developing over time, can lead to implant failure. Currently, planar x-ray imaging and CT are the most commonly used methods to evaluate the gap region. An alternative to these available clinical imaging modalities could help to better evaluate bone resorption. Previous experiments with diffraction enhanced imaging (DEI) have shown significant contrast advantages over monochromatic synchrotron radiation (SR) imaging. DEI and planar SR radiography images of bone samples with drill holes and gap regions of known geometry were acquired at the NSLS beamline X15A (Upton, NY, USA). The images acquired with DEI show measurable contrast-to-noise gains when compared to the images acquired using SR radiography.

Animals↗
PubMed1997

Image enhancement of severely hypoperfused myocardia for computation of tomographic ejection fraction.

UNLABELLED: Ejection fractions computed from 99mTc-sestamibi myocardial perfusion gated tomograms have demonstrated a high degree of accuracy and reproducibility. Although automated algorithms appear to provide reasonable endocardial outlines for patients over a broad spectrum of cardiac diseases, in cases of severe hypoperfusion, it is necessary to manually adjust contrast and brightness to judge whether borders are correct or must be altered. METHODS: Midventricular horizontal and vertical long axis gated tomograms were generated for 116 studies chosen on the basis of extensive, severe myocardial perfusion defects. Automated software transformed cinematic tomograms into images demonstrating uniform appearance of the myocardium throughout the cardiac cycle. Transformed images were introduced to edge detection algorithms for subsequent calculation of ventricular volumes and ejection fractions. RESULTS: Linear regression analysis demonstrated excellent intraobserver reproducibility for ejection fractions (r = 0.95) and volumes (r = 0.98). There was also good agreement of ejection fractions (r = 0.86) and volumes (r = 0.94) with values derived from an expert's manual drawings. In a subgroup of 22 patients, automated ejection fractions from transformed images demonstrated better agreement with independent first-pass values (r = 0.90) than did manual measurements derived from original data (r = 0.85). CONCLUSION: Image enhancement algorithms succeeded in providing accurate, reproducible gated SPECT ejection fractions in the most difficult class of patients exhibiting severe hypoperfusion.

Aged↗
PubMedDate not supplied

Lumbar degenerative disk disease: prospective comparison of conventional T2-weighted spin-echo imaging and T2-weighted rapid acquisition relaxation-enhanced imaging.

PURPOSE: To compare conventional T2-weighted spin-echo imaging with a rapid acquisition relaxation enhanced (RARE) technique in the routine evaluation of lumbar degenerative disk disease. METHODS: Thirty consecutive patients referred for evaluation of the lumbar spine for suspected degenerative disk disease were evaluated with sagittal and axial T1-weighted spin-echo, conventional T2-weighted spin-echo, and T2-weighted RARE "turbo spin-echo" sequences (4000/93/2 (repetition time/echo time/excitations), 192 x 256, echo train length of 8). Conventional T2-weighted and RARE images were evaluated independently by two neuroradiologists for image quality, presence of artifacts, cerebrospinal fluid signal intensity, extradural interface conspicuity, intradural nerve root conspicuity, soft-tissue detail, and signal intensity of normal and degenerated intervertebral disks. RESULTS: Both readers rated the cerebrospinal fluid signal higher, the extradural interface conspicuity higher, and the nerve root detail greater on the turbo spin-echo than on conventional spin-echo images. Neither reader had a significant difference in ranking "normal" or "degenerated" disk signal on the two sequences. Both readers rated soft-tissue detail higher for conventional than for turbo spin-echo. CONCLUSION: RARE sequences can replace conventional T2-weighted spin-echo sagittal studies for degenerative lumbar disk disease.

Artifacts↗
PubMed2000

Triple-dose contrast-enhanced images in neurologically symptomatic HIV-positive patients.

Our purpose was to determine whether triple-dose delayed contrast-enhanced images would improve lesion detection in patients with symptomatic human immunodeficiency virus (HIV) infection. We reviewed 33 MRI studies on 29 patients. Single-dose immediate T1-weighted spin-echo (1x-T1) images were compared with delayed triple-dose images (D3x-T1). Two neuroradiologists decided which technique showed more lesions, increased lesion conspicuity and/or altered the radiologic diagnosis. The D3x-T1 technique improved lesion detection in 14 of 29 patients (48%). In two patients (7%), the improvement changed the radiologic diagnosis by showing new meningeal lesions.

Adult↗
PubMed2000

The application of computer-enhanced imaging to improve preoperative counselling and informed consent in children considering bone anchored auricular prosthesis surgery.

OBJECTIVES: Bone anchored auricular prostheses have become a valuable option in the treatment of congenital and acquired deformities of the pinna. However, preoperative counselling and informed consent remains a challenging issue. Until recently it has been difficult to provide the child with a realistic prediction of their own postoperative appearance. This is particularly relevant when a remnant pinna needs to be excised prior to the second stage. The potential for psychological repercussions and the possibility that remnant excision might compromise future autologous tissue reconstruction make it imperative that the decision to proceed with surgery is founded on the best possible information. METHODS: The authors describe the use of computer enhanced images using the Adobe Photoshop (Apple Mac. Inc.) software package to provide such a preview. This technique is used in the outpatient clinic as an adjunct to counselling provided by clinic staff and is reinforced by meeting children who have already enrolled on to the implant programme. Children are encouraged to follow the stages of their planned operation on the computer screen, providing an accurate insight into the physical consequences of surgery. RESULTS: Our experiences suggest that this approach has encouraged a better qualitative understanding of implant surgery which has helped to foster the on-going commitment that is required to maintain a long-lasting, trouble-free implant site. CONCLUSIONS: This application of the Adobe Photoshop package has strengthened our basis for a personal informed consent and has provided an opportunity to lessen the adverse psychological consequences of such irreversible surgery. It is commended for its simplicity as it employs established software to enhance photographic prints or slides taken from the child's clinical records.

Child↗
PubMed1998

Image enhancement improves reading performance in age-related macular degeneration patients.

We wanted to determine whether the 2- to 4-fold increases in reading speed found for patients with age-related macular degeneration (ARMD) when reading filtered text, presented one word at a time in the middle of the display would also be found when filtered text was scrolled across the screen. Reading speeds for filtered text that compensates for an observer's reduced contrast sensitivity function (CSF) were compared with the reading speeds for unfiltered text, when continuous, non-repeating text was scrolled across the display. The reading speeds of the ARMD observers tested were 1.7-4.5-times faster when reading filtered text, than when reading unfiltered text that was scrolled across the screen. The largest increments, over a 4-fold increase, were obtained in those subjects with the lowest unfiltered reading rates and the greatest loss of central vision. This study illustrates the usefulness of individualized text filtering for image enhancement in digitally based viewing devices to provide low vision remediation.

Aged↗