Gray Value Differences Research Articles

Evaluation of quantitative contrast harmonic imaging to assess malignancy of liver tumors: A prospective controlled two-center study

To establish the extent to which contrast enhancement with SonoVue in combination with quantitative evaluation of contrast-medium dynamics facilitates the detection of hepatic tumors. One hundred patients with histologically confirmed malignant or benign hepatic tumor (maximum size 5 cm) were analyzed. Contrast-enhanced ultrasound (bolus injection 2.5 mL SonoVue) was carried out with intermittent breath-holding technique using a multifrequency transducer (2.5-4 MHz). Native vascularization was analyzed with power Doppler. The contrast-enhanced dynamic ultrasound investigation was carried out with contrast harmonic imaging in true detection mode during the arterial, portal venous and late phases. Mechanical index was set at 0.15. Perfusion analysis was performed by post-processing of the raw data [time intensity curve (TIC) analysis]. The cut-off of the gray value differences between tumor and normal liver tissue was established using Receiver Operating Characteristic (ROC) analysis 64-line multi-slice computed tomography served as reference method in all cases. Magnetic resonance tomography was used additionally in 19 cases. One hundred patients with 59 malignant (43 colon, 5 breast, 2 endocrine metastases, 7 hepatocellular carcinomas and 2 kidney cancers) and 41 benign (15 hemangiomas, 7 focal nodular hyperplasias, 5 complicated cysts, 2 abscesses and 12 circumscribed fatty changes) tumors were included. The late venous phase proved to be the most sensitive for classification of the tumor type. Fifty-eight of the 59 malignant tumors were classified as true positive, and one as false negative. This resulted in a sensitivity of 98.3%. Of the 41 benign tumors, 37 were classified as true negative and 4 as false negative, which corresponds to a specificity of 90.2%. Altogether, 95.0% of the diagnoses were classified as correct on the basis of the histological classification. No investigator-dependency (P = 0.23) was noted. The results show the possibility of accurate prediction of malignancy of hepatic tumors with a positive prognostic value of 93.5% using advanced contrast-enhanced ultrasound. Contrast enhancement with SonoVue in combination with quantitative evaluation of contrast-medium dynamics is a valuable tool to discriminate hepatic tumors.

Input parameter sensitivity analysis and comparison of quantification models for continuous arterial spin labeling

The regional cerebral blood flow (rCBF) values determined using continuous arterial spin labeling (CASL) are subject to several sources of variability, including natural physiologic variations, sensitivity to the input parameters, and the use of different quantification models. To date, a thorough analysis of the impact of input parameters and the choice of quantification model has not been performed. These sources of variability were investigated through computer simulations using bootstrap techniques on actual CASL data. Coefficients of variation for representative single voxels were 6.7% for gray matter and 29% for white matter, and for eight-voxel regions of interest they were 4.5% for gray matter and 23% for white matter. Comparison of nine CASL quantification models showed differences in gray matter rCBF values of up to 42%. An analysis of the sensitivity of the rCBF to input parameters for each of the nine quantification models demonstrated that accurate quantification of the inversion efficiency, tissue and arterial blood longitudinal relaxation times, and transit times were critical in calculating precise rCBF values. The large potential variations in rCBF and the effect of the choice of quantification model suggest that interpreting absolute rCBF values in CASL studies can be challenging and requires great care.

High-Dimensional Deformation Fields for Longitudinal Intraindividual Volumetry of Cerebral Infarction

The aim of this study is the analysis of 3D morphological changes of human brains after cerebral infarction. The change of brain volume caused by the infarction is measured by high-dimensional transformations. These are determined by a multiresolution full multigrid (FMG) movement model [4], resulting in a precise correlation of homologous structures. Thus, volume changes are detected with subvoxel accuracy to determine volume changes between the infarct and remote brain regions without manual interaction. High-dimensional transformations are determined by application of the theory according to Navier-Lamee. Volumes are modelled as an elastic medium. For complex deformations the elastic model is extended to a movement model and the total spatial differences are divided into discrete steps. The gray-value forces driving the movement of each voxel in the source object are determined by minimizing the gray-value difference between source and reference volume. The movement of each voxel is controlled by the data itself and smoothed with respect to noise by the elasticity properties defined by the Lamee parameters for each step. The numerical effort is overcome by a combined multiresolution, full-multigrid method and the correlation of homologous structures improved by application of the Scale-Space theory. To avoid rotational transformations, coarse and fine alignment is achieved by the extended principle axes theory [2, 3] and by a cross-correlation based procedure using a matrix-norm [1]. The MRI data sets are acquired at different times, enabling the determination of morphological changes over time. The application of the FMG model enables the investigation of morphological brain changes over time. Furthermore, it is possible to detect ischemia-induced spatial distortions and plastic alterations, as the changes of the volume are exactly determined by the deformation fields. The results show, that even small infarcts result in morphological changes not only adjacent to the ischemic area but also in remote areas and in some cases the contralateral hemisphere. Supported by the Deutsche Forschungsgemeinschaft (SFB 194 A6, A13, B2).

Image processing and analysis for determination of concentrations of powder mixtures

The quality of the pharmaceutical powder mixing strongly influences the potency and properties of the tablets. Furthermore, in order to optimize powder mixing processes, fast and accurate methods are sought for determining the concentration of powder mixtures. This work describes an optical method based on an image processing system to determine concentration of powders in a mixture that can be sensed by its gray-level values. The methodology was developed utilizing univariate and multivariate gray image analysis. The effect of difference in mean gray value (DMGV) on the precision and accuracy of the vision system was determined. The results that were obtained from the vision system were compared to those obtained with near-infrared spectroscopy. The multivariate gray image analysis methodology using frequency of each gray-level value ( Φ) of gray scale as the independent variables obtained the best predictions. The vision system produced high precision with a standard deviation of about 1.7% w/w and a 2.6% relative standard deviation. The accuracy indicated by the root mean standard error of prediction (RMSEP) was around 1.7% w/w. The mixtures analyzed with the vision system and the near-infrared spectrometer yielded similar results. Analysis of all results confirms that the vision system is an adequate technology for determination of powder mixture concentrations.

홍삼 내공검출을 위한 X-선 영상처리기술 (II) - 내공검출결과 -

Red ginsengs are inspected manually by examining those in the dark room with back light illumination. Manual inspection is often influenced by physical condition of inspectors. Sometimes. the best grade, heaven. has some inner holes though it was inspected by a specialist. In order to resolve this problem, this study was performed to develop image processing algorithm to detect the inner holes in the x-ray image of ginseng. Because of little gray value difference between background and ginseng in the image. simple thresholding method was not appropriate. Modified watershed algorithm was used to differentiate the inner holes from background and normal ginseng body. Inner hole edge region detected by watershed algorithm consists of many number of blobs including normal portions. With line profile analysis with scanning one line at a time beginning the starting point. it shelved two peaks both ends representing extracting each blobs. in which setting threshold value as of lower peak value enabled us to obtain inner hole image. Once this procedure has to be done till the finishing point it is completing inner hole detection for one blob. Thus. conducting ail blobs by this procedure is completing inner detection of one whole ginseng. Detection results of the inner holes fer various size of red ginsengs were good even though there was small detection variation. 6.2%. according to position of x-rat tube.

Spinal Deformity Detection from Moiré Images Based on Differences in Gray Values on the Left and Right Sides

Spinal Deformity Detection from Moiré Images Based on Differences in Gray Values on the Left and Right Sides

홍삼 내공검출을 위한 X-선 영상처리기술(I) - 내공검출에 적합한 전처리기법 -

Quality evaluation of red ginsengs is determined by outer shape and inner qualities. Especially, the inner qualities are main grading criteria. Currently, red ginsengs are classified into 3-grades; heaven, earth and good. The best heaven grade must not include inner holes and sponge tissues. This study was conducted to develop a red ginseng sorting system using x-ray image processing technique. Because of lens characteristic, gray values of the central region in the x-ray image are higher and gradually decreased towards the edge regions. This difference of gray values gives trouble in segmentation and detection of inner holes in red ginseng image, so preprocessing technique is necessary. The preprocessing was done by subtracting source image from an empty background image. But, simple subtraction was not quite appropriate because of too small contrast between inner holes and sound part. Scaled subtraction images were obtained by multiplying all gray values by some numbers. However this method could not help to set threshold value because the gray values of root part are generally lower than body part when red ginseng is exposed to the x-ray. To determine threshold value for detecting inner holes, an algorithm was developed by increasing overall gray values of less clear images.

Edge Detection in Range Images using Nonlinear Laplacian Operators

In this paper, application of a nonlinear laplacian operator for edge detection in range images is discussed. The nonlinear laplace operator which had earlier been shown to be effective for edge detection in intensity images with low and medium signal-to-noise ratios is modified to detect the roof edges in range images. Differences in surface normal in a neighborhood around a pixel in the image is used here in contrast to the differences in gray values used in intensity images. The images are smoothened using median filters of suitable size before applying the laplace operator. Results with synthetic and natural range images are presented.

Rapid Three-Dimensional Myocardial Contrast Echocardiography: Volumetric Quantitation of Nonperfused Myocardium After Intravenous Contrast Administration.

Current acquisition methods for quantitative three-dimensional myocardial contrast echocardiography require long acquisition times and therefore require the invasive administration of deposit contrast agents administered intra-arterially or into the left atrium. This study addressed the feasibility of obtaining accurate and precise quantitative volumetric measurements of nonperfused myocardium after an intravenous bolus of echocardiographic contrast agent using a rapid three-dimensional myocardial contrast echocardiographic acquisition technique. An open-chest pig model of acute left anterior descending coronary artery (LAD) occlusion was used. After LAD ligature, an intravenous bolus of contrast agent was given and images were obtained over a 12-second period using a continuously rotating transducer placed at the apical position. There was no significant microbubble destruction during the rotational acquisition period as measured by differences in mean gray scale values of apical, mid, and basal myocardial regions between the first and last image frames of acquisition. Calculated volumes of nonperfused myocardium demonstrated significant agreement and correlation (mean difference +/- SD = -0.30 +/- 1.71 cm(3); r = 0.89; P < 0.01; y = 1.06x - 1.08) with anatomic specimens. When expressed as percent of total LV volume being nonperfused, the mean difference +/- SD was 2.1 +/- 3.6%, r = 0.94, P < 0.01, and y = 1.33x - 4.08. We conclude that accurate and precise measurements of nonperfused myocardium after an acute LAD coronary artery occlusion can be obtained after the intravenous bolus administration of a contrast material when a rapid 12-second acquisition with a continuously rotating transducer is used.

Extraction of Stroke Feature Based on Gray Value Distribution and Application to Judgement of Classic Works by Writing-Brush

It is a point in dispute whether “Shinsou-Senjimon”, which is one of ancient manuscripts written by writing-brushes, is a work that was written originally or a traced one. On the other hand, it is clearly handed down that “Souranjo” was written by “toumo” which was one of unknown skilled techniques for copying. In this paper, we compare several characters from these two ancient manuscripts by writing-brushes from viewpoints of the distribution of gray values and their gradient in the direction of making strokes by writing-brush. It is observed from the result of comparison that in the case of characters in Sinsou-Senjimon the difference in gray values of pixels in each character is large compared with that in the Souranjo.

Anoxia during kainate status epilepticus shortens behavioral convulsions but generates hippocampal neuron loss and supragranular mossy fiber sprouting.

In rats, this study determined the impact of systemic hypoxia during late kainate-induced status epilepticus on hippocampal neuron loss and mossy fiber sprouting. Non-fasted Sprague Dawley rats were prepared as follows: Naive controls (n=5); rats placed 2 min in a hypoxia chamber (hypoxia only; n=6); rats that seized for more than 6 h from kainic acid (KA-status; 12 mg/kg; i.p.; n=7); and another KA-status group placed into the hypoxia chamber 75 min after the convulsions started (KA-status/hypoxia; n=16). All rats, except for half of the KA-status/hypoxia animals, were perfused 2 weeks later (short-term). The other 8 KA-status/hypoxia rats were perfused after 2 months (long-term). Hippocampal sections were studied for neuron densities and aberrant mossy fiber sprouting at three ventral to dorsal levels. Fascia dentata (FD) mossy fiber sprouting was quantified as an increase in the inner minus outer molecular layer (IML-OML) gray value (GV) difference. Behaviorally, KA-status/hypoxia rats had a shorter duration of convulsive status epilepticus than KA-status animals without anoxia. Hippocampal sections showed that compared to controls: (1) hypoxia-only rats showed no differences in ventral neuron densities and neo-Timm's stained IML-OML GVs; (2) KA-status rats had decreased CA3 densities and a non-significant increase in ventral IML-OML GV differences; and (3) KA-status/hypoxia short-term animals showed decreased hilar, CA3 and CA1 densities and increased ventral IML-OML GV differences. Compared to KA-status/hypoxia short-term rats, long-term animals showed no differences in ventral hippocampal neuron densities, but middle and dorsal sections demonstrated increased IML-OML GV differences and animals were observed to have spontaneous limbic epilepsy. These results indicate that rats exposed to kainate-induced status epilepticus for over 1 h and then a hypoxic insult had a shorter duration of convulsive status, decreased hippocampal neuron densities and greater FD mossy fiber sprouting than controls and the amount of neuronal damage and sprouting was slightly more than animals subjected to 6 h of kainate-induced status. This supports the hypothesis that a physiologic insult during status can shorten the convulsive episode, but still produce hippocampal pathology with a number of clinical and pathologic similarities to human mesial temporal lobe epilepsy (MTLE).

Data hiding in images via multiple-based number conversion and lossy compression

A novel and easy method to embed any form of secret messages into a cover image with controlled distortion is proposed. Any lossy image compressor may be applied first to a cover image to produce a lossily-processed result as the basis for embedding data in the cover image. The stego-image is produced by embedding data in each pixel of a cover image by changing its gray value without excessing the range of the gray value difference of the corresponding pixels of the cover image and its lossily-processed one. The quantity of distortion that is caused by embedding data is never in excess of that is caused by the lossy compressor. A multiple-based number system is proposed to convert the information in the secret bit stream into values to be embedded in the choosing pixels of the cover image. Pseudo-random mechanisms may be used to achieve cryptography. It is found from experiments that the values of the peaks of the signal-to-noise ratio of the stego-images are larger than those yielded by the chosen compressor, which means that the distortion in the embedding result is more imperceptible than that in the compressed one.

Neuron loss, mossy fiber sprouting, and interictal spikes after intrahippocampal kainate in developing rats.

This study determined neuron losses, mossy fiber sprouting, and interictal spike frequencies in adult rats following intrahippocampal kainic acid (KA) injections during postnatal (PN) development. KA (0.4 micrograms/0.2 microliters; n = 64) was injected into one hippocampus and saline into the contralateral side between PN 7 to 30 days. Animals were sacrificed 28 to 256 days later, along with age-matched naive animals (controls; n = 20). Hippocampi were studied for: (1) Fascia dentata granule cell, hilar, and CA3c neuron counts; (2) neo-Timm's stained supragranular mossy fiber sprouting; and (3) hippocampal and intracerebral interictal spike densities (n = 13). Mossy fiber sprouting was quantified as the gray value differences between the inner and outer molecular layer. Statistically significant results (p < 0.05) showed the following: (1) Compared to controls, CA3c and hilar neuron counts were reduced in KA-hippocampi with injections at PN 7-10 and PN 12-14 respectively and counts decreased with older PN injections. Granule cell densities on the KA-side and saline injected hippocampi were not reduced compared to controls. (2) In adult rats, supragranular mossy fiber sprouting was observed in 2 of 7 PN 7 injected animals. Compared to controls, increased gray value differences, indicating mossy fiber sprouting, were found on the KA-side beginning with injuries at PN 12-14 and increasing with older PN injections. On the saline-side only PN 30 animals showed minimal sprouting. (3) Mossy fiber sprouting progressively increased on the KA-side with longer survivals in rats injured after PN 15. Sprouting correlated positively with later PN injections and longer post-injection survival intervals, and not with reduced hilar or CA3c neuron counts. (4) On the KA-side, mossy fiber gray value differences correlated positively with in vivo intrahippocampal interictal spike densities. These results indicate that during postnatal rat development intrahippocampal kainate excitotoxicity can occur as early as PN 7 and increases with older ages at injection. This rat model reproduces many of the pathologic, behavioral, and electrophysiologic features of human mesial temporal lobe epilepsy, and supports the hypothesis that hippocampal sclerosis can be the consequence of focal injury during early postnatal development that progressively evolves into a pathologic and epileptic focus.

New geodosic distance transforms for gray-scale images

In this paper, two new geodesic distance transforms for gray-scale images are presented. The first transform, the Distance Transform on Curved Space (DTOCS), performs the calculation with integer numbers. The second transform, the Weighted Distance Transform on Curved Space (WDTOCS), gives a weighted distance map with real numbers for an arbitrary gray-value image. Both transforms give a distance map in which the distance value of a single point corresponds to the length of the shortest discrete 8-path to the nearest background point. Both differ from the previously presented gray-level distance transforms by not weighting the distance values directly by the gray-values, but by gray-value differences.

Automatic Analysis of Moving Images

Cine film and videotape are used to record a variety of natural processes in biology, medicine, meteorology, etc. This paper describes a system which detects and tracks moving objects from these records to obtain meaningful measures of their movements, such as linear and angular velocities. Features of the system are as follows. 1) In order to detect moving objects that are usually blurred, temporal differences of gray values (differences between consecutive frames) are used to separate moving objects from stationary objects, in addition to spatial differences of gray values. 2) The results of previous frames are used to guide feature extraction process of the next frame so that efficient processing of moving pictures which consists of a large number of frames is possible. 3) Uncertain parts in the current frame, such as occluded objects, are deduced using information of previous frames. 4) Misinterpreted or unknown parts in previous frames are reanalyzed using the results of later frames where those parts could be found.