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PubMed2002

Diffraction enhanced imaging contrast mechanisms in breast cancer specimens.

We have investigated the contrast mechanisms of the refraction angle, and the apparent absorption images obtained from the diffraction enhanced imaging technique (DEI) and have correlated them with the absorption contrast of conventional radiography. The contrast of both the DEI refraction angle image and the radiograph have the same dependence on density differences of the tissues in the visualization of cancer; in radiography these differences directly relate to the contrast while in the DEI refraction angle image it is the density difference and thickness gradient that gives the refraction angle. We show that the density difference of fibrils in breast cancer as measured by absorption images correlate well with the density difference derived from refraction angle images of DEI. In addition we find that the DEI apparent absorption image and the image obtained with the DEI system at the top of the reflectivity curve have much greater contrast than that of the normal radiograph (x8 to 33-fold higher). This is due to the rejection of small angle scattering (extinction) from the fibrils enhancing the contrast.

Absorption↗
PubMed2005

Reliability of diffraction enhanced imaging for assessment of cartilage lesions, ex vivo.

OBJECTIVE: The assessment of articular cartilage integrity is of value for the detection of early degenerative joint disease in both the clinical and the research settings. It was the purpose of this study to determine the accuracy and reliability of identifying articular cartilage defects through Diffraction Enhanced Imaging (DEI), a high contrast radiographic imaging technique. DEI provides two new sources of image contrast to radiography: refraction and scatter rejection, besides the absorption of conventional radiography. DESIGN: Cadaveric tali were DEI imaged in the anterior-posterior position at the National Synchrotron Light Source. Two independent observers provided gross score evaluations (on a five point scale) of the trochlear surfaces. The DEI image of each trochlear surface was then graded (on a five point scale) by two additional independent observers who were blinded with regard to the gross evaluation of the articular surfaces. Inter-observer agreement for DEI grades was assessed with the weighted kappa statistic. Correlation of diffraction enhanced image score to the gross score was assessed with Spearman correlation coefficient. RESULTS: The defects of articular cartilage of talar trochleae could be visualized through DEI. The Spearman correlation of gross grades with DEI grades on the 165 talar regions for observers 1 and 2 were 0.91 and 0.91, respectively. The overall weighted kappa value for inter-observer agreement was 0.93, thus considered high agreement. CONCLUSIONS: DEI is accurate and reliable for detection of articular cartilage defects ex vivo. Even early stages of degeneration of cartilage can be visualized with this high contrast technique. Future studies will focus on the application of DEI to the identification of such lesions in vivo.

Aged↗
PubMed2005

Computational methods to produce enhanced images out of given SNOM raw data.

We propose to produce enhanced images out of given raw data read out by SNOM through (i) improved image formation from the raw data; (ii) wavelet de-noising of the image; and (iii) resolution enhancement by deconvolution. Our methods of improvement are based on refined models for the reduction of noise present in SNOM images and on a linear model for the imaging process. They are successfully demonstrated on (magneto-)optical SNOM images of suitable test samples, but yet they are applicable to other scanning probe microscopy techniques.

Journal Article↗
PubMed2005

Digital image enhancement for in vivo laser scanning microscopy.

BACKGROUND/PURPOSE: In vivo confocal laser scanning microscopy (CLSM) is a new method that provides skin images in horizontal plane at a level of resolution that allows to view microanatomic structures. This study examines whether certain digital image-processing steps can increase the visibility of various structures in CLSM. STUDY DESIGN: Fifty images were taken from normal skin of 25 probands, and 39 image enhancement procedures were created. Eight procedures that seemed to provide some quality enhancement were deliberately selected for further evaluation. Subsequently, a collection of random pairs of the original image and an image submitted to any of the eight selected procedures was rated by five independent observers. RESULTS: In three of the eight procedures tested, the modified image was significantly preferred to the original image (chi2-test,: P< or =0.001). In particular, smoothing, shading correction, delineate and grey-level normalization in various combinations were helpful in showing the characteristic honeycomb pattern, pigmented basal cell layer, cell borders and the nuclei more clearly. CONCLUSION: Digital image processing may help to increase visibility of in vivo CLSM images.

Adolescent↗
PubMed2002

Calibration and accuracy testing for image-enhanced endoscopy.

New surgical navigation techniques may combine the use of live video from a surgical endoscope with 3D volumetrically-reconstructed images of a patient's anatomy. This image-enhanced endoscopy requires calibration of the endoscope to ensure that the mapping of the real endoscope image to its virtual counterpart is properly performed. The application of a technique to calibrate an endoscope prior to use in a diagnostic or therapeutic procedure is described, as well as a simple yet effective linear method for lens-distortion compensation. The results of accuracy testing of the calibration technique using a dedicated testing apparatus are reported.

Calibration↗
PubMed1996

Use of image enhancement during lithotripsy.

Renal excursion during breathing is inevitable and is a cause of poor localization during extracorporeal shock-wave lithotripsy (SWL), which in theory might lead to poor treatment results. Eighty-one patients underwent lithotripsy treatment with and without the use of an image enhancement system designed for use with the Dornier MPL9000 lithotripter. This device contains a memory incorporated into a separate differential grayscale monitor, which allows the stone image to be stored. Shockwave release is enabled only when this image corresponds to the real-time image on the lithotripter ultrasound monitor. No improvement in success rates was found using this system, although upper-pole stones appeared to be fragmented more successfully. Overall, the results were favorable in both groups after a single treatment. Further work is needed to establish whether image enhancement is capable of improving the success rates and reducing the side effects of lithotripsy by better targeting.

Adult↗
PubMed1996

Computed tomography image enhancement using the concept of fuzzy logic.

Diagnostic features in computed tomography (CT) images vary widely due to the vague nature (fuzziness) of functional characteristics in organ pathologies. Classical image enhancement techniques cannot adapt to the characteristics of this nature. A method based on fuzzy logic is given in this paper. In this method the image of interest is transformed into a fuzzy plane using fuzzifiers which can be changed to select a crossover point. A contrast intensification operator (INT) is then applied. The operator increases the grade of membership of those values which lie above the crossover point and decreases the same for those pixels which lie below it, thereby increasing the contrast and reducing the fuzziness. Quantitative measures of fuzziness which reflect a sort of quantitative measure of image quality have also been studied. Using digitized CT images it has been shown that at early stages of a disease, when the contrast of the pathological tissues is very low, the visibility of the disease could be considerably improved using this technique.

Fuzzy Logic↗
PubMed2006

Mononuclear subsets in the peripheral blood of multiple sclerosis patients in relation to results of brain gadolinium- enhancing imaging.

UNLABELLED: Very little is known about processes which are leading to the development of new multiple sclerosis (MS) plaques. Therefore, the problem of correlating immunological disequilibrium in MS patients with the onset of a relapse and with other markers of the disease seems to be of great importance. In our studies we have evaluated the mononuclear subsets in the peripheral blood of multiple sclerosis patients in relation to results of brain gadolinium-enhancing imaging. A positive magnetic resonance imaging (MRI) gadolinium enhancement indicates an ongoing inflammation and activity of the MS process, whereas gadolinium (Gd) negative imaging should be considered as a sign of stabilization of the MS process. MATERIAL AND METHODS: Peripheral blood was taken from 70 MS patients, fulfilling the criteria of McDonald et al [8]. Brain MRI was performed using a Magneton Impact 1.0 T (Siemens) machine. Enhanced T1 images were obtained after administration of 0.1 mmol/kg gadolinium - DTPA. Lymphocyte subsets were analyzed by flow cytometry with the aid of specific monoclonal antibodies. RESULTS: The relative percentage of the white blood cell count as well as the absolute number of mononuclears and of CD3+ lymphocyte were significantly lowered only in the group of gadolinium negative MS cases. The CD4+ relative percentage was significantly higher both in the total as well as in gadolinium positive and negative subgroups. The ratio of CD4/CD8 was significantly higher in MS patients. The absolute number of CD4 lymphocytes was the lowest in gadolinium negative MS cases. CONCLUSION: An appropriate regulation of the Th /T helper/ cells seems to be critical in the control and prevention of diverse states of the disease. In the course of an acute process, gadolinium positive imaging as well as immunological events, represented by mononuclear subsets in the peripheral blood may proceed and change very quickly, whereas gadolinium negative findings reflecting a stabilization of processes, are changing more slowly and therefore may be detected more easily in peripheral blood cell counts.

Adult↗
PubMed1996

Observers' use of image enhancement in assessing caries in radiographs taken by four intra-oral digital systems.

OBJECTIVES: To evaluate observers' use of image-enhancement facilities and time consumption in assessing caries in radiographs taken with four digital systems. METHODS: In total, 131 extracted human premolars and molars were mounted three in a line. Radiographs were taken using four digital systems: Digora (DIG), Radio VisioGraphy (RVG), Sens-A-Ray (SAR) and Visualix (VIX), and imported into a programme with routines for adjustment of brightness, contrast and gamma curve. Sixteen images from each digital system were compressed (JPEG, irreversible compression). The 588 images were scored by six observers for approximal and occlusal caries on a five-point confidence scale using enhancement as they pleased. The programme automatically recorded any enhancement made without the observers knowing this. RESULTS: Some form of digital enhancement was used in almost all images, with the gamma curve being the most frequent. The VIX images were enhanced most followed by SAR, DIG and RVG images. The differences were significant (p < 0.01) except between DIG and SAR images. The compressed images were enhanced significantly more than their uncompressed counterparts (p = 0.02). The average time spent recording one image was 24 s. On average, significantly less time was spent with the DIG images than the other systems (p < 0.01), while there were no significant differences between the CCD-based systems (p > 0.2). There was no relationship between time spent and number of manipulations performed. CONCLUSIONS: The observers took advantage of the facilities available for enhancement of density and contrast in digital images. The potential of gamma curve manipulation requires further investigation.

Dental Caries↗
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↗
PubMed2005

Generic and customized digital image enhancement filters for the visually impaired.

This study compares the effectiveness of various image enhancement filters for improving the perceived visibility of coloured digital natural images for people with visual impairment. Generic filters were compared with Peli's adaptive enhancement and adaptive thresholding and custom-devised filters based on each subject's contrast sensitivity loss. Subjects with low vision made within filter rankings followed by between filter ratings. In general, subjects preferred filters with lower gains. Unsharp masking resulted in a significant increase in perceived visibility for some image types (p < or = 0.05) while Peli's adaptive enhancement, edge enhancement and histogram equalization resulted in borderline improvements. Adaptive thresholding and the custom devised filter did not result in overall improvements in perceived visibility.

Adult↗
PubMed2006

Image enhancement for multilayer information retrieval by using full-field optical coherence tomography.

When a full-field optical coherence tomography (OCT) system is used to extract tomographic images from a multilayer information carrier, the resulting images may suffer from interlayer modulations and parasitic patterns derived from interference fringes. We describe and analyze these negative influences that degrade the quality of extracted tomographic images and propose practical algorithms and methods to minimize them. The emphasis of the discussion will be the removal of the parasitic fringes produced by the imperfection of a CCD camera. The simulative and experimental results of image enhancement for multilayer tomography extraction using full-field OCT are provided.

Algorithms↗
PubMed1999

Using helical CT to evaluate renal cell carcinoma in patients undergoing hemodialysis: value of early enhanced images.

OBJECTIVE: The purpose of this study was to evaluate early and delayed enhanced helical CT for revealing renal cell carcinoma in patients undergoing hemodialysis. MATERIALS AND METHODS: Over the course of 3 years, 630 chronic hemodialysis patients underwent early and delayed contrast-enhanced and unenhanced helical CT to detect renal cell carcinoma. Retrospective review showed that 23 of these patients later underwent either unilateral or bilateral nephrectomy. Two radiologists, unaware of the pathology results, independently reviewed these 23 examinations. The sensitivity and specificity of each early and delayed scan for revealing neoplasms were determined using pathology as the gold standard. The mean attenuation values of the neoplasms and parenchymas of end-stage kidneys on both early and delayed enhanced images were also compared. RESULTS: Helical CT revealed 225 lesions, 24 of which were found to be renal cell carcinomas at pathology. Delayed enhanced helical CT failed to detect one papillary carcinoma in an end-stage kidney with acquired cysts. Three nonpapillary carcinomas were not detected on delayed scans, and one was missed on an early scan of a patient without acquired cysts. The sensitivity and specificity of early enhanced CT for revealing renal cell carcinoma were 96% and 95%, respectively. In contrast, delayed enhanced CT achieved a sensitivity of 83% and a specificity of 94%. A significant difference in mean attenuation values between carcinomas and renal parenchymas was observed on the images with early enhancement but not on those with delayed enhancement (p < .0001). CONCLUSION: Early enhanced helical CT is superior to delayed enhanced helical CT for revealing renal cell carcinoma in end-stage kidneys.

Carcinoma, Renal Cell↗
PubMed1998

Image enhancement by noncontrast harmonic echocardiography. Part II. Quantitative assessment with use of contrast-to-speckle ratio.

OBJECTIVE: To ascertain whether "harmonic imaging"--use of ultrasound signals with the frequency twice that of the transmitted signal for ultrasound image generation--can improve image contrast while reducing noise. METHODS: Technically difficult echocardiograms (nonvisualization of 2 or more endocardial segments in a 16-segment model) from 25 patients were analyzed. Corresponding fundamental and harmonic images of the left ventricle in the apical four-chamber, two-chamber, and long-axis views were divided into basal, mid, and apical regions. The difference in image quality between fundamental and harmonic scans was assessed by using the muscle-to-cavity contrast-to-speckle ratio (CSRmc). RESULTS: The mean CSRmc values of pooled data revealed significant image enhancement by harmonic scanning (CSRmc increased from 0.84 to 1.06; P < 0.0001). Regression analysis showed that harmonic imaging improved the CSRmc values in 68% of all scans. Regional analysis indicated the most enhancement in basal regions (CSRmc increased from 0.96 to 1.34; P < 0.0001), followed by the mid (CSRmc increased from 0.84 to 1.04; P < 0.0001) and apical (CSRmc increased from 0.68 to 0.74; P = 0.0138) left ventricular regions. CONCLUSION: Noncontrast harmonic imaging significantly enhances suboptimal echocardiographic images, particularly in the regions distant from the transducer.

Adult↗
PubMed2000

Undersampled projection-reconstruction imaging for time-resolved contrast-enhanced imaging.

In time-resolved contrast-enhanced 3D MR angiography, spatial resolution is traded for high temporal resolution. A hybrid method is presented that attempts to reduce this tradeoff in two of the spatial dimensions. It combines an undersampled projection acquisition in two dimensions with variable rate k-space sampling in the third. Spatial resolution in the projection plane is determined by readout resolution and is limited primarily by signal-to-noise ratio. Oversampling the center of k-space combined with temporal k-space interpolation provides time frames with minimal venous contamination. Results demonstrating improved resolution in phantoms and volunteers are presented using angular undersampling factors up to eight with acceptable projection reconstruction artifacts.

Abdomen↗
PubMed1994

Hepatic tumors: detection and characterization at 1-T MR imaging enhanced with AMI-25.

PURPOSE: To evaluate the ability of magnetic resonance (MR) imaging enhanced with AMI-25 to depict and characterize hepatic tumors. MATERIALS AND METHODS: Sixty-four patients (41 men and 23 women, aged 24-65 years [mean, 55 years]) underwent 1-T MR imaging: 22 had metastatic disease; 10, hepatocellular carcinoma; seven, hemangioma; three, focal nodular hyperplasia; three, gallbladder adenocarcinoma; two, lymphoma; one, adenoma; and 16, no tumor. Pre- and postcontrast images (alone and in combination) were analyzed by three independent radiologists. Receiver operating characteristic curves were constructed to compare tumor characterization. RESULTS: Signal intensity was decreased in all benign tumors but not in malignant tumors. The number of tumors depicted (nonenhanced images, 657 tumors; enhanced, 753; and combined, 760) was not statistically different. Receiver operating characteristic curves did not show improved characterization with AMI-25. CONCLUSION: AMI-25 does not improve depiction of hepatic tumors. Although characterization of hepatic tumors was not improved with AMI-25, uptake of AMI-25 seems specific for hepatic tumors at MR imaging.

Carcinoma, Hepatocellular↗
PubMed1994

A method for determination of optimal image enhancement for the detection of mammographic abnormalities.

We present a paradigm for empirical evaluation of digital image enhancement algorithms for mammography that uses psychophysical methods for implementation and analysis of a clinically relevant detection task. In the experiment, the observer is asked to detect and assign to a quadrant, or indicate the absence of, a simulated mammographic structure characteristic of cancer embedded in a background image of normal breast tissue. Responses are indicated interactively on a computer workstation. The parameter values for the enhancement applied to the composite image may be varied on each trial, and structure detection performance is estimated for each enhancement condition. Preliminary investigations have provided insight into an appropriate viewing duration, and furthermore, suggest that nonradiologists may be used under this methodology for the tasks investigated thus far, for predicting parameter values for clinical investigation. We are presently using this method in evaluating several contrast enhancement algorithms of possible benefit in mammography. These methods enable an objective, clinically relevant evaluation, for the purpose of optimal parameter determination or performance assessment, of digital image-processing methods potentially used in mammography.

Algorithms↗
PubMed1993

Use of charge-coupled device (CCD) image-enhancement for rapid screening and monitoring of prokaryotic promoter expression.

Charge-coupled device (CCD) image-enhancement was used for rapid screening of genomic libraries and allowed selection of promoters with differing characteristics. In addition, both the CCD and luminometry were used to monitor and characterize the expression from two Pseudomonas syringae pv. phaseolicola promoters. The same pattern of gene expression was indicated by the two methods but the CCD enabled the rapid non-destructive in situ monitoring of a microbial population, over a prolonged period.

Cloning, Molecular↗