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Biomedical subjects

K S Chuang

Publications and source records attributed to K S Chuang.

17 recordsLinked to original sources
PubMed1999

Shape-based grey-level image interpolation.

The three-dimensional (3D) object data obtained from a CT scanner usually have unequal sampling frequencies in the x-, y- and z-directions. Generally, the 3D data are first interpolated between slices to obtain isotropic resolution, reconstructed, then operated on using object extraction and display algorithms. The traditional grey-level interpolation introduces a layer of intermediate substance and is not suitable for objects that are very different from the opposite background. The shape-based interpolation method transfers a pixel location to a parameter related to the object shape and the interpolation is performed on that parameter. This process is able to achieve a better interpolation but its application is limited to binary images only. In this paper, we present an improved shape-based interpolation method for grey-level images. The new method uses a polygon to approximate the object shape and performs the interpolation using polygon vertices as references. The binary images representing the shape of the object were first generated via image segmentation on the source images. The target object binary image was then created using regular shape-based interpolation. The polygon enclosing the object for each slice can be generated from the shape of that slice. We determined the relative location in the source slices of each pixel inside the target polygon using the vertices of a polygon as the reference. The target slice grey-level was interpolated from the corresponding source image pixels. The image quality of this interpolation method is better and the mean squared difference is smaller than with traditional grey-level interpolation.

Image Enhancement↗
PubMed1994

Noise content analysis in clinical digital images.

Most digital modalities in radiology use 12 bits precision to store the digital images. To determine whether all these bits contain useful information, a statistical method called the Moran test was used to measure the noise level in computed tomographic, magnetic resonance, and digital radiographic images. The test was performed on the bit planes of each pixel. After the noise level was estimated, the pixel data were separated into signal bits and noise bits, and image enhancement techniques were applied on the noise-bits-removed images to demonstrate that the removal of noise bits did not affect image quality. Preliminary results showed no noticeable difference between the original images and the noise-bits-removed images.

Algorithms↗
PubMed1992

Assessment of noise in a digital image using the join-count statistic and the Moran test.

We assume that the data bits of a pixel in digital images can be divided into signal and noise bits. The signal bits occupy the most significant part of the pixel and the noise bits the least significant part. The signal part of each pixel are correlated while the noise parts are uncorrelated. Two statistical methods, the Moran test and the join-count statistic, are used to examine the noise parts. Images from three digital modalities--computerized tomography, magnetic resonance and computed radiography--are used for the evaluation of the noise bits. A residual image is formed by subtracting the original image from its smoothed version. The noise level in the residual image is then identical to that in the original image. Both statistical tests are then performed on the bit planes of the residual image. The results show that most digital images contain only 8-9 bits of correlated information. Both methods are easy to implement and fast to perform.

Magnetic Resonance Imaging↗
PubMed1992

Receiver-operating-characteristic study of chest radiographs in children: digital hard-copy film vs 2K x 2K soft-copy images.

Two methods are commonly used to visualize digital radiologic imaging data: (1) hard-copy viewing, in which the digital data are used to modulate the intensity of a laser beam that exposes an analog film and (2) soft-copy viewing, in which the digital data are converted to an analog video signal and presented on a CRT monitor. The film method allows new digital imaging systems to be easily integrated into conventional radiologic management and viewing methods. The second method, soft-copy viewing, allows digital imaging data to be managed and viewed electronically in a picture archiving and communication system (PACS). These PACS systems are hypothesized to have improved operational efficiency and enhanced image-analysis capabilities. The quality of soft-copy images is still not widely accepted. This article reports on the results of a large-scale receiver-operating-characteristic study comparing observers' performance in detecting various pediatric chest abnormalities on soft-copy 2048 x 2048K byte displays with their performance with digital laser-printed film from computed radiography. The disease categories studied were pneumothorax, linear atelectasis, air bronchogram, and interstitial disease. The selected data set included 239 images; 77 contained no proved abnormality and 162 contained one or more of the abnormalities mentioned. Seven pediatric radiologists participated in the study, two as judges and five as observers. Our results show no significant difference between viewing images on digital hard copy and soft copy for the detection of pneumothoraces and air bronchograms. A slight performance edge for soft copy was seen for interstitial disease and linear atelectasis. This result indicates that computed chest radiographs in children viewed in a soft-copy PACS environment should result in diagnoses similar to or slightly more accurate than those obtained in a laser-printed film-based environment.

Child↗
PubMed1992

Localization of the sympathetic postganglionic neurons innervating cardiac coronary artery with horseradish peroxidase in monkeys.

Localization of the sympathetic postganglionic neurons innervating the cardiac coronary arteries in monkeys was investigated by using retrograde axonal transport of horseradish peroxidase (HRP). HRP was applied to the main trunk of the left and right coronary arteries, and to the terminal branches of the ventral and dorsal descending vessels of the left and right coronary arteries, respectively. The animals were sacrificed 84-96 hours later and perfused via the left ventricle. The paravertebral sympathetic ganglia from the superior cervical, middle cervical and stellate ganglia to the T9 ganglia, and nodose ganglia were removed and processed for HRP identification. After HRP was applied into the main trunk of the right coronary artery, and into the main trunk and the terminal branches of the descending vessels of the left coronary artery, the HRP-labeled sympathetic neurons were localized predominantly in the right superior cervical ganglion, and next in the left superior cervical ganglia. However, labeled cells were found in the stellate ganglia bilaterally. After HRP applications to the terminal branches of the dorsal descending vessels of the right coronary artery, HRP-labeled cells were mainly present in the left superior cervical ganglion and next in the right superior cervical ganglion. Some labeled cells were found in the middle cervical and stellate ganglia. No labeled cell was found in ganglia below the second thoracic ganglia on either side in these four groups.

Animals↗
PubMed1991

Surface and volume rendering in three-dimensional imaging: a comparison.

Many surface rendering techniques are currently available for the three-dimensional display of structure data captured by imaging devices. Comparatively fewer volume rendering techniques are also available for the same purpose. The relative performance of these two methodologies in visualization tasks has been a subject of much discussion recently. Although it is very desirable to establish, based on observer studies, objective guidelines stating the relative merits of the two methodologies even for specific situations, it is impossible to conduct meaningful observer studies that take into account the numerousness of the techniques in each methodology, and within each technique, the numerousness of the parameters and their values that control the outcome of the technique. Our aim in this article is to compare the two methodologies purely on a technical basis in an attempt to understand their common weaknesses and disparate strengths. The purpose of this article is twofold--to report a new surface rendering technique and to compare it with two volume rendering techniques reported recently in the literature. The bases of comparison are: ability to portray thin bones; clarity of portrayal of sutures, fractures, fine textures, and gyrations; smoothness of natural ridges and silhouettes; and computational time and storage requirements. We analyze the underlying algorithms to study how they behave under each of these comparative criteria. Our conclusion is that, at the current state of development, the surface method has a slight edge over the volume methods for portrayal of information of the type described above and a significant advantage considering time and storage requirements, for implementations in identical environments.

Algorithms↗
PubMed1988

Sympathetic postganglionic innervation of the cardiac coronary artery in cats.

The localization of the sympathetic postganglionic neurons innervating the cardiac coronary arteries of the cat was investigated using retrograde axonal transport with horseradish peroxidase. We found after the enzyme was applied to the main trunk of the right coronary artery, and to the main trunk and the terminal branch of the ventral descending vessels of the left coronary artery, the peroxidase-labeled sympathetic neurons were localized predominantly in the right stellate ganglia, with a few cells in the left stellate ganglia. There were very few labeled cells in the middle cervical, superior cervical, and T4-7 ganglia on both sides. After peroxidase application to the terminal branch of the dorsal descending vessels of the right coronary artery, labeled cells were mainly in the left stellate ganglia, with only a few cells in the right stellate ganglia.

Animals↗
PubMed1988

New stereotactic technique for percutaneous thermocoagulation upper thoracic ganglionectomy in cases of palmar hyperhidrosis.

To perform unilateral or bilateral upper thoracic ganglionectomy, we established a three-dimensional system of coordinates for T2 and T3 ganglia. For this purpose, the spatial relations were represented by drawings obtained from 50 Chinese cadavers. A simple stereotactic frame was constructed as an aid in performing the procedure. Then, according to the established three-dimensional system of coordinates, percutaneous thermocoagulation of both T2 and T3 ganglia was performed on 10 patients (20 sides) with palmar hyperhidrosis, under local anesthesia and fluoroscopic guidance at the posteroanterior projection. Excellent relief of abnormal sweating in 19 of the 20 hands was achieved. Partial relief was obtained in the remaining hand. No complication was observed in our patients. The technique has been proved to be safe, effective, and simpler than other methods now in use.

Animals↗
PubMed1985

Horseradish peroxidase localization of the sympathetic postganglionic neurons innervating the cat heart.

The localization of the sympathetic postganglionic neurons innervating the cat heart has been investigated by using retrograde axonal transport of horseradish peroxidase (HRP). HRP was injected into the subepicardial layers of 4 different cardiac regions. The animals were sacrificed 72-96 h later and fixed by perfusion via the left ventricle. The paravertebral sympathetic ganglia from the superior cervical, middle cervical and stellate ganglia to T10 ganglia were removed and processed for HRP identification. Following injections of HRP into the apex of the heart, the sinoatrial (SA) nodal region and the ventral wall of the right ventricle, we observed that HRP-labeled sympathetic neurons were localized predominantly in the right stellate ganglia, and to a lesser extent, in the right superior and middle cervical ganglia, and left stellate ganglia. Fewer labeled cells were found in the right T4-T6. T8 and T9. After HRP injection into the dorsal wall of the left ventricle, HRP-labeled cells were present mainly in the left stellate ganglia.

Animals↗
PubMed1985

Spinal intramedullary pseudocyst. Case report.

The authors describe a case of a spinal intramedullary pseudocyst at T-1 that did not communicate with the surrounding spaces. The cystic wall was composed of dense connective tissue without epithelial or neoplastic cells. The patient's condition improved dramatically after surgical removal of the cyst. The literature on spinal intramedullary cystic lesions is reviewed and the etiology of pseudocysts is discussed. This case is believed to be the first in which a pseudocyst has been demonstrated within the spinal cord.

Adult↗
PubMed1984

Both dopaminergic and adrenergic receptors in the brain are involved in the behavioural excitation induced by dibutyryl 3',5'-adenosine monophosphate and aminophylline in the rat.

Following administration of dibutyryl cyclic-AMP or aminophylline, but not vehicle solution, into the lateral cerebral ventricle of rats produced locomotor stimulation, head and body rearing, circling, (as indicated by an enhancement of gross movement), increased grooming, head swaying and scratching (as indicated by an enhancement of fine movement), tail elevation, piloerection and convulsion. The behavioural excitation produced by either dibutyryl cyclic-AMP or aminophylline was antagonized by pretreatment with intraventricular injection of either two alpha-adrenergic antagonists (phentolamine and yohimbine) or a dopaminergic antagonist (haloperidol), but not with either a beta-adrenergic antagonist (propranolol) or a narcotic antagonist (naloxone). In addition, direct administration of dibutyryl cyclic-AMP into either the anterior hypothalamus, the nucleus accumbens or the caudate-putamen complex of rats produced the same behavioural responses as those produced by the intraventricular injection. Again, the behavioural responses induced by intracerebral injection of dibutyryl cyclic-AMP was antagonized by pretreatment with either alpha-adrenergic antagonists or a dopaminergic antagonist. The present data indicate that both the dopaminergic and the adrenergic receptors in the brain are involved in the behavioural excitation induced by dibutyryl cyclic-AMP and aminophylline in the rat.

Aminophylline↗
PubMedDate not supplied

Implementation of a large-scale picture archiving and communication system.

This paper describes the implementation of a large-scale picture archiving and communication system (PACS) in a clinical environment. The system consists of a PACS infrastructure, composed of a PACS controller, a database management system, communication networks, and optical disk archive. It connects to three MR units, four CT scanners, three computed radiography systems, and two laser film digitizers. Seven display stations are on line 24 h/day, 7 days/wk in genitourinary radiology (2K), pediatric radiology in-patient (1K and 2K) and outpatient (2K), neuroradiology (2K), pediatric ICU (1K), coronary care unit (1K), and one laser film printing station. The PACS is integrated with the hospital information system and the radiology information system. The system has been in operation since February 1992. We have integrated this PACS as a clinical component in daily radiology practice. It archives an average of 2.0-gigabyte image data per workday. A 3-mo system performance of various components are tabulated. The deployment of this large-scale PACS signifies a milestone in our PACS research and development effort. Radiologists, fellows, residents, and clinicians use it for case review, conferences, and occasionally for primary diagnosis. With this large-scale PACS in place, it will allow us to investigate the two critical issues raised when PACS research first started 10 yrs ago: system performance and cost effectiveness between a digital-based and a film-based system.

Computer Communication Networks↗
PubMedDate not supplied

A fast dual-energy computational method using isotransmission lines and table lookup.

An efficient method has been developed to speed up the computational time required for tissue separation after the dual-energy scan in computerized tomography and digital radiography. This method consists of two steps. First, an isotransmission line method is used to replace the iterative algorithm for solving the two nonlinear equations, which is computationally noisy and sensitive. Second, two tables, one for the aluminum component and the other for the plastic component, are derived from calibration data in order to replace calculation by a table lookup. Results from this method are compared with the conventional method.

Models, Structural↗
PubMedDate not supplied

Evaluation of inherent gray-level dynamic range in a digital image using the runs test and join-count statistics.

The dynamic range of the gray level of a digital image is limited by the noise it contains. Two statistical methods called "runs test" and "join-count statistic" are used to measure the noise level in a digital image. A residual image is formed by subtracting an original image from its smoothed version. Theoretically, the noise level in the residual image should be identical to that in the original image. The noise level is determined by examining each bit plane of the residual image individually starting from the least significant bit up to the bit plane whose statistic does not show a random pattern. Images from three digital modalities: computerized tomography, magnetic resonance, and computed radiography are used to evaluate the gray-level dynamic range. Both methods are easy to implement and fast to perform.

Biometry↗
PubMedDate not supplied

Effects of stellate ganglionectomy on the cat cardiovascular function.

The effects of stellate ganglionectomy on cardiovascular function were assessed in pentobarbital-anesthetized cats. A right stellectomy produced much more profound bradycardiac effects than a left stellectomy. This finding demonstrated that the stellate ganglion exerted a lateralized influence on heart beat in the cat. The cardiovascular response of intact cats to phase 4 (overshoot) of the Valsalva-like maneuver (VM) was reflex bradycardia. In response to VM, however, reflex bradycardia was completely abolished by a right or bilateral stellectomy, or by pretreatment with propranolol, but not by a left stellectomy alone or with phentolamine. The data indicated that the right stellate ganglion in cats makes a major contribution to cardiovascular control, especially over reflex bradycardia mechanisms.

Animals↗