Digital Contrast Enhancement Research Articles

Cystoscopy in the outpatient clinical routine: things to keep in mind

Cystoscopy is an important procedure in the diagnostic evaluation of the lower urinary tract. Standard cystoscopy (white light) undergoes permanent improvement. High-end instruments and video systems are available, supported by PDD (photodynamic diagnostic), NBI (narrow band imaging) and digital contrast enhancement to improve the detection rate of bladder cancer. A correct indication, careful patient education and high expertise are core competencies of our daily business needed to minimise discomfort, keep the complication rate as low as possible and find the correct diagnosis. A severe mismatch is seen between the hygiene requirements in instrument preparation and infrastructure on the one hand and payment on the other. Digital image processing and artificial intelligence will raise the procedure to the next level in the future.

Fast contrast enhancement by adaptive pixel value stretching

In this article, we propose a fast and effective method for digital image contrast enhancement. The gray-level dynamic range of contrast-distorted images is extended maximally via adaptive pixel value stretching. The quantity of saturated pixels is set intelligently according to the perceptual brightness of global images. Adaptive gamma correction is also novelly used to recover the normal luminance in enhancing dimmed images. Different from prior methods, our proposed technique could be enforced automatically without complex manual parameter adjustment per image. Both qualitative and quantitative performance evaluation results show that, comparing with some recent influential contrast enhancement techniques, our proposed method achieves comparative or better enhancement quality at a surprisingly lower computational cost. Besides general computer applications, such merit should also be valuable in low-power scenarios, such as the imaging pipelines used in small mobile terminals and visual sensor network.

Modern endoscopic imaging tools for urothelial carcinoma of the urinary bladder

Cystoscopy is the gold standard for the initial diagnosis of urothelial carcinoma in the urinary bladder (UCB). White light exhibits significant limitations in its ability to detect flat lesions or carcinoma in situ. Photodynamic Diagnosis (PDD) and Narrow Band Imaging (NBI) are established techniques which may improve the detection rates of UCB and reduce the risk of recurrence. Multiple novel tools have been developed in order to improve the diagnostic accuracy of endoscopic procedures, including Digital Contrast Enhancement Technology, Confocal Laser Endomicroscopy (CLE) and Optical Coherence Tomography (OCT). In future, spectral analysis of urothelial lesions may be achieved by Raman spectroscopy, thus providing information about biological alterations in the tissue. Furthermore, molecular imaging may allow specific targeting by fluorescent antibodies or small molecule agents, thus enabling differential diagnosis of suspicious lesions. Software-based approaches have been developed to incorporate computer-aided diagnosis and improve digital documentation of endoscopic findings. This study reviews current and future developments in the field of modern endoscopy of the urinary bladder and discusses the different approaches.

Digital contrast enhancement of (18)Fluorine-fluorodeoxyglucose positron emission tomography images in hepatocellular carcinoma.

Purpose:The role of 18fluorodeoxyglucose positron emission tomography (PET) is limited for detection of primary hepatocellular carcinoma (HCC) due to low contrast to the tumor, and normal hepatocytes (background). The aim of the present study was to improve the contrast between the tumor and background by standardizing the input parameters of a digital contrast enhancement technique.Materials and Methods:A transverse slice of PET image was adjusted for the best possible contrast, and saved in JPEG 2000 format. We processed this image with a contrast enhancement technique using 847 possible combinations of input parameters (threshold “m” and slope “e”). The input parameters which resulted in an image having a high value of 2nd order entropy, and edge content, and low value of absolute mean brightness error, and saturation evaluation metrics, were considered as standardized input parameters. The same process was repeated for total nine PET-computed tomography studies, thus analyzing 7623 images.Results:The selected digital contrast enhancement technique increased the contrast between the HCC tumor and background. In seven out of nine images, the standardized input parameters “m” had values between 150 and 160, and for other two images values were 138 and 175, respectively. The value of slope “e” was 4 in 4 images, 3 in 3 images and 1 in 2 images. It was found that it is important to optimize the input parameters for the best possible contrast for each image; a particular value was not sufficient for all the HCC images.Conclusion:The use of above digital contrast enhancement technique improves the tumor to background ratio in PET images of HCC and appears to be useful. Further clinical validation of this finding is warranted.

Reproducibility of Immunostaining Quantification and Description of a New Digital Image Processing Procedure for Quantitative Evaluation of Immunohistochemistry in Pathology

Quantification of immunostaining is a widely used technique in pathology. Nonetheless, techniques that rely on human vision are prone to inter- and intraobserver variability, and they are tedious and time consuming. Digital image analysis (DIA), now available in a variety of platforms, improves quantification performance: however, the stability of these different DIA systems is largely unknown. Here, we describe a method to measure the reproducibility of DIA systems. In addition, we describe a new image-processing strategy for quantitative evaluation of immunostained tissue sections using DAB/hematoxylin-stained slides. This approach is based on image subtraction, using a blue low pass filter in the optical train, followed by digital contrast and brightness enhancement. Results showed that our DIA system yields stable counts, and that this method can be used to evaluate the performance of DIA systems. The new image-processing approach creates an image that aids both human visual observation and DIA systems in assessing immunostained slides, delivers a quantitative performance similar to that of bright field imaging, gives thresholds with smaller ranges, and allows the segmentation of strongly immunostained areas, all resulting in a higher probability of representing specific staining. We believe that our approach offers important advantages to immunostaining quantification in pathology.

High-Resolution Video-Enhanced Differential Interference Contrast Light Microscopy

Publisher Summary This chapter describes the basic concepts of differential interference contrast (DIC) image formation and analog and digital contrast enhancement, the practical aspects of component selection, alignment and specimen chambers for VE-DIC, and several test specimens for measuring microscope and video performance. A DIC microscope is a dual beam interferometer that uses a brightfield polarizing microscope containing polarizer, analyzer, and rotating stage. Contrast enhancement is produced by subtracting voltage from the video signal and amplifying the difference for each horizontal line scan of the video raster image. Increasing the analog contrast enhancement to the levels necessary to give distinct images of microtubules induces a new set of technical problems. Image quality becomes limited by noise from several sources, which is amplified as gain is increased. Fixed pattern noise could be eliminated from the video image by subtracting a stored background image, using a digital image processor operating at video rates. The background is obtained by defocusing the microscope until the microtubule image disappears. Achieving high-resolution, high-contrast VE-DIC images requires the highest performance of both the optical and video components of the video microscope system. Test specimens for microscope and video performance, such as diatom test slide, squamous cheek cell, and embedded skeletal muscle thin section, are also described in the chapter.

Interactive computer-assisted position acquisition procedure designed for the analysis of organelle movement in pollen tubes.

An interactive computer-assisted video microscopy method has been developed for the acquisition of extensive data on the sequential positions of pollen tube organelles, which cannot be automatically tracked using geometric or motion patterns. The method consists of video microscopy, analog and digital contrast enhancement, digital time-lapsing of the images, and interactive selection of positions in a coordinate system corresponding to the cell shape and real size. Data on 15,000 positions acquired with this method have been used to make quantitative analyses of the movement patterns of the organelles. From these analyses and the reconstruction of 900 trajectories, it appears that movements are random in the tip of the pollen tube but become more directed in distal regions of the cell, indicating an increase in axial arrangement of the actin filaments. (All custom-made software is available from the authors on request.)

Chapter 9 High-Resolution Video-Enhanced Differential Interference Contrast (VE-DIC) Light Microscopy

Publisher Summary Differential interference contrast (DIC) light microscopy was an immediate success after its introduction in the 1960s because it could produce high-contrast optical images of the edges of objects and fine-structural detail within transparent specimens. DIC contrast depends on gradients in optical path and not on absolute values of optical path (OP). As a result, DIC methods can produce clear optical sections of relatively thick transparent specimens. Resolution in DIC microscopy is also superior to phase contrast. VE–DIC has been important in many aspects of cell biology, including measuring the assembly dynamics of individual microtubules and forced production by microtubule assembly/disassembly. The quality of images in VE–DIC microscopy depends critically on both the quality of the image projected onto the camera detector by the microscope as well as on the electronic contrast enhancement capabilities of the camera. The chapter describes the basic concepts of DIC image formation and analog and digital contrast enhancement, the practical aspects of component selection, alignment and specimen chambers for VE–DIC, and several test specimens for measuring microscope and video performance.

Comparison of Laparoscopic Imaging Systems and Conditions Using a Knot-Tying Task

Pilot experiments to determine the important factors in the engineering of laparoscopic (videoscopic) imaging systems are described in this paper. In the first set of experiments, three videoscopic systems were compared by using a knot-tying task: monoscopic, monoscopic with digital contrast enhancement, and stereoscopic. Direct viewing was used as a control. In both experienced and novice subject groups, no difference was found in completion time or errors between the videoscopic conditions. Performance with direct viewing was significantly better, however, indicating that there are factors in videoscopic imaging that degrade perception or distort the relationship between vision and motor response. In the second set of experiments, the effects of contrast and spatial resolution were examined by varying working distance and camera exposure while experienced subjects tied knots on high-and low-contrast surfaces. Good contrast was found to be most important at longer working distances. This result shows that performance of knot tying, a complex task, is affected by contrast sensitivity, which is a fundamental property of human vision.

Comparison of laparoscopic imaging systems and conditions using a knot-tying task

Pilot experiments to determine the important factors in the engineering of laparoscopic (videoscopic) imaging systems are described in this paper. In the first set of experiments, three videoscopic systems were compared by using a knot-tying task: monoscopic, monoscopic with digital contrast enhancement, and stereoscopic. Direct viewing was used as a control. In both experienced and novice subject groups, no difference was found in completion time or errors between the videoscopic conditions. Performance with direct viewing was significantly better, however, indicating that there are factors in videoscopic imaging that degrade perception or distort the relationship between vision and motor response. In the second set of experiments, the effects of contrast and spatial resolution were examined by varying working distance and camera exposure while experienced subjects tied knots on high- and low-contrast surfaces. Good contrast was found to be most important at longer working distances. This result shows that performance of knot tying, a complex task, is affected by contrast sensitivity, which is a fundamental property of human vision.

Real-time digital contrast enhancement and magnification in the assessment of acute elbow injuries

The elbow is a common site of injury and missed fractures may lead to disability and litigation. An assessment was made of a commercially available desk-top digital contrast enhancement and magnification unit (DETECT system) in a series of 320 patients with an acute elbow injury. Five radiologists of varying experience independently viewed elbow radiographs on a conventional light-box, and subsequently using the digitizer, indicating the presence or absence of a fracture. The overall results demonstrated no difference in performance when using the unit, though small improvements in the confidence with which a definite diagnosis was made were observed. Assessment of soft tissues with the digitizer was less reliable.

Real-time digital contrast enhancement and magnification in the assessment of scaphoid and other wrist injuries

A study on the value of a commercially available desk-top digital magnifier-contrast enhancer (DETECT System) was made in a series of 550 patients presenting with an acute wrist injury. Four radiologists, of varying experience, independently reviewed the radiographs on a conventional lightbox and later with the digitizer. In the scaphoid series (350 cases), the performance of the two more experienced radiologists was marginally better with the digitizer, whereas the less experienced radiologists performed slightly worse. Overall the digitizer improved the confidence of the radiologists in diagnosing correctly the presence of a scaphoid fracture but, for the less experienced radiologists, this was at the expense of identifying normality. In the wrist series (200 cases), the use of the digitizer resulted in a minor increase in the true positive and decrease in the false negative observations, but this was offset by a concomitant minor increase in the false positive and decrease in the true negative categories. Evaluation of the soft-tissue planes around the wrist joint showed a limited value in the identification of a scaphoid fracture with an overall positive predictive value of 0.26. Correlation of soft-tissue changes and the presence or absence of a scaphoid fracture was slightly worse with the digitizer. Possible causes for the apparently poorer performance of the digitizer are discussed, as well as the relative merits and potential value of the unit.

Real time digital contrast enhancement and magnification in the assessment of elbow injuries

Real time digital contrast enhancement and magnification in the assessment of elbow injuries

Interpretation of Bone Scans Using a Video Display

Digital processing, storing, and interpretation of scintigraphic images from a PACS system has been postulated as an efficient, cost-saving measure that may obviate the need for analog film. In order to replace analog film, documentation that images can be interpreted from a digital video display with accuracy at least equal to film must be obtained. Analog film was compared with video images in 28 patients with cancer suspected to be metastatic to bone. Images were acquired with a gamma camera and processed in 256 x 256 word mode by the use of the Medical Data Systems A3 computer. Adjustment of gray scales provided operator-controlled digital contrast enhancement. Video and film images were independently interpreted by two experienced nuclear medicine physicians, each blinded to the other modality. A linear four-color scale was then substituted for the gray scale, and images again interpreted. Lesions were interpreted as positive or equivocal and verified through follow-up scans over a minimum of six months. Of the 28 patients, 22 proved to have metastases, in whom 129 lesions were confirmed by follow-up scintigrams. 124 of these lesions (96.1%) were detectable on both analog film and video images. An additional three proven metastatic lesions on video images were absent or equivocal on analog studies, increasing sensitivity for video images to 98.4%. Five further lesions seen on the video screen represented rib fractures and regressed on follow-up examination. All lesions seen on black-and-white video were also seen when the color scale was applied.(ABSTRACT TRUNCATED AT 250 WORDS)

Digital contrast enhancement for online portal imaging.

Seven digital contrast enhancement algorithms were implemented and evaluated for application to images obtained with an online video portal imaging system. An objective quantitative comparison shows that superior contrast enhancement is obtained using histogram modification techniques. Additional tests made on an image of a humanoid phantom indicate that local (adaptive) histogram modification methods can produce a better contrast in detail than their global counterparts, if the original image is nonuniform in intensity.

First direct magneto-optical observations of quasi-néel walls in double permalloy films

The first observations of quasi-walls have been performed in the double Permalloy layers separated by a thin carbon layer. This structure was brought to light due to the high-resolution Kerr effect with digital contrast enhancement. The experimental results are in good agreement with the theoretical predictions.

Contrast enhancement of noisy images by windowing: Limitations due to the finite dynamic range of the display system

A theoretical model has been developed to explain the effects of simple linear windowing on the apparent contrasts of signals in displayed digital images. The model predicts, and experimental results demonstrate, that the effective displayed contrast of a digital radiographic signal depends in a complex way upon interactions among the endpoints of the display scale, the signal contrast and noise level of the original data, the window center and display center selected, and the contrast enhancement factor applied. The results obtained from this work apply quantitatively to the highly idealized situation in which (i) a uniform signal is superimposed on a uniform background containing Gaussian pixel-value noise, and (ii) a linear (or exponential) relationship exists between the optical density of a film display (or the light intensity of a luminous display) and pixel value in some finite range. However, the qualitative effects demonstrated here may be expected to arise in a broad variety of situations involving strong digital contrast enhancement.

DOMAIN TIPS : STRUCTURE AND MOBILITY IN UNIAXIAL AMORPHOUS THIN FILMS

Statics and dynamics of domain tips have been investigated by high resolution Kerr effect using digital contrast enhancement. The magnetic structure is affected by demagnetizing effect. The internal wall structure is visible and a transition between asymmetric Bloch wall to Neel one is shown. Tip propagation along the easy axis is measured.

Digital subtraction angiography (DSA) in renal and renovascular hypertension: diagnostic value and application in follow-up studies after PTA.

Diagnosis of renovascular hypertension is of particular interest because it is curable by vascular surgery or percutaneous transluminal angioplasty (PTA). Transvenous digital subtraction angiography (DSA) is a minimally invasive method of importance in detecting renal hypertension of different origins (pre-, intra-, postrenal). This study was carried out to assess the value of transvenous DSA in analyzing the renal arteries and renal parenchyma, in detecting renal artery stenosis, and in controlling PTA results. Our results demonstrate that image quality of transvenous DSA of the renal arteries was excellent (diagnostic in 474 of 510 cases, 93%). A large number (62%) could be analyzed following one injection of contrast medium, in 25% a second, and 6% a third injection was necessary. In follow-up studies after PTA (1 week to 24 months) patients with normalized blood pressure values (16/33) had a completely reopened arterial segment and normal parenchyma of both kidneys. In persistent or recurrent hypertension (17/33) restenosis could be detected by transvenous DSA in 2 cases and renal parenchymal lesions in 8 cases. Reversible intimal dissections observed immediately following PTA had no influence on blood pressure results. Intra-arterial DSA is recommended when renal artery stenosis is to be evaluated for PTA and when the result of balloon catheter dilatation is to be evaluated. Intra-arterial DSA is indicated to exclude stenosis following kidney transplantation and to determine perfusion of the graft (parenchyma and venous return) taking advantage of small volumes and concentrations of contrast material made possible by digital contrast enhancement.

A preprocessing method for the contrast enhancement of tv-scanned electron microscopic images

Preprocessing TV-scanned images in transmission electron microscopy improves the results of subsequent digital contrast enhancement. The method takes into account noise, system artifacts and the image forming modes of darkfield and brightfield.