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Biomedical subjects

H K Huang

Publications and source records attributed to H K Huang.

At least 19 recordsLinked to original sources
PubMed1992

Orientation correction for chest images.

This report presents an automatic procedure that determines the orientation of computed radiography (CR) chest images and rotates them to a standard position to be viewed by radiologists. As an input, CR images of a normalized size of 1,000 x 1,000 or 2,000 x 2,000 pixels are used. The analysis is performed in three steps. First, the orientation of the spine within the image is determined. Then, a function searches for upper extremities and the subdiaphragm. Finally, the lungs are extracted and their areas are compared. This indicates whether the image needs to be y-axis flipped. These three steps set the value of three parameters on the basis of which the final rotation angle is determined. The procedure has been implemented in the clinics at UCLA. The rate of correctly rotated images is 95.4%.

Algorithms↗
PubMed1992

Subsystem throughputs of a clinical picture archiving and communications system.

We measured the throughtput rates of individual picture archiving and communications system (PACS) subsystems including the acquisition, archive, display, and communication network as a basis of evaluation the overall throughput of our clinical PACS. The throughput rate of each PACS subsystem was measured in terms of average residence time of individual images in the subsystem. The residence time of an image in a PACS subsystem was determined by the total time the image was required to be processed within the subsystem. The overall throughput of the PACS was measured as the total residence time of an image in the various subsystems. We also measured throughputs of the PACS subsystems using three types of networks (Ethernet; fiber distributed data interface; and UltraNet, UltraNetwork Technologies, San Jose, CA), and the results were compared. Approximately 200 gigabytes of data transactions including magnetic resonance, computed tomography and computed radiography images from our PACS were analyzed. Results showed that PACS throughput was limited by three major factors: (1) low-speed data interface used in the radiologic imaging devices and archive devices; (2) competition for systems processing time among the PACS processes; and (3) network degradation caused by heavy network traffic. We concluded that PACS performance could be improved with a well-designed network architecture, a job prioritizing mechanism, and an image routing strategy. However, device-dependent low-speed data interface has limited PACS performance.

Computer Communication Networks↗
PubMed1992

A fiber-optic broadband CT/MR video communication system.

Our department operates three magnetic resonance (MR) and three computed tomography (CT) scanners that are located in three different buildings up to 2 km apart. We have designed and implemented a multichannel, fiber-optic broadband video communication system as a remote scanner monitoring network. This system consists of baseband and broadband fiberoptic transmitters, receivers, and multiplexers. The structure of the video network is supported by two strategically located headends (distributors) connecting local/remote scanners and monitoring stations. The system is capable of serving up to 5 km from each headend. The video signal from each scanner is sent through a baseband fiber-optic link to a headend, where it is frequency modulated, multiplexed with other scanner video signals, and distributed over broadband fiber-optic links to monitoring stations. Each receiver consists of a demodulator, a channel selectable tuner, and a video monitor. The current design provides up to 16 scanner channels and 16 remote monitoring station connections. Monitoring stations are placed in 14 clinical locations including the following reading rooms: thoracic, neuro, abdomen, musculoskeletal, gastrointestinal, genitourinary, and pediatric radiology. A radiologist can use any of these 14 monitoring stations to view a patient's CT/MR images in real-time as they appear on any of the six scanner consoles. By selecting the proper channel assigned to a patient's scanner, the radiologist may monitor the examination while using the telephone to communicate with the technologist at the scanner site. This fiber-optic broadband video communication system has been integrated into daily clinical use for over 6 months.

Computer Communication Networks↗
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

Image preprocessing for a picture archiving and communication system.

OBJECTIVES AND RATIONALE: In a picture archiving and communication system (PACS), images are acquired from multiple modalities and displayed on an electronic workstation. Each modality has different image characteristics. This variability must be addressed before the image is displayed. METHODS: The authors developed methods to automatically process magnetic resonance (MR), computed tomographic (CT), and computed radiography (CR) images before display and subjectively evaluated their effectiveness. RESULTS: Unwanted background successfully was automatically removed from 89.5% of 615 CR images. Of 803 chest, abdomen, and hand images 93% were automatically rotated to the correct orientation. CONCLUSIONS: Automated preprocessing of PACS images can be performed successfully, improving speed and convenience for the radiologist interpreting images at an electronic workstation.

Image Processing, Computer-Assisted↗
PubMed1992

Magnetic resonance image synthesis from analytic solutions of spin-echo and radio frequency-spoiled gradient-echo images.

RATIONALE AND OBJECTIVES: To synthesize magnetic resonance images (MRI) in real-time using a minimal data set obtained with routine clinical protocols and stored in a picture archiving and communication system (PACS) database. METHODS: Analytic solutions for T1 and T2 were obtained from a double and a single spin-echo set, with routine parameters. Analytic solutions from radio frequency-spoiled gradient-echo images, with TRs as low as 33 mseconds, also were used to synthesize gradient-echo images. RESULTS: Phantom studies showed that the errors in the synthesized images were significantly smaller than the errors in the T1- and T2-calculated images and similar to the source images. The gradient-echo images resulted in significant scan time savings. CONCLUSION: MRI synthesis from analytic solutions of T1, T2, and rho saves computational time and yields accurate values for the intrinsic parameters while allowing the use of routine clinical protocols. The availability of clinical images in the PACS database and the ability to synthesize images in real-time has allowed the development of a practical interactive teaching module.

Brain↗
PubMed1992

Three methods of implementing a picture archiving and communication system.

A picture archiving and communication system (PACS) is a system integration of many components, including radiologic image acquisition devices, computers, communication networks, image display workstations, and data base management systems. The author describes three general approaches to implementing a PACS. In the first approach, the department or institution acts as a systems integrator, designing and implementing the PACS. In the second approach, the PACS is planned on the basis of the department's operations and environment and then a manufacturer is contracted to design and build the system. The third approach is to purchase a turnkey system, with some modifications provided by the manufacturer for a specific clinical application. The author provides examples of each approach in the clinical environment and presents the disadvantages and advantages of each.

Computer Systems↗
PubMed1992

Subperiosteal resorption: effect of full-frame image compression of hand radiographs on diagnostic accuracy.

Image compression is essential to handle a large volume of digital images, including computed tomographic, magnetic resonance, computed radiographic, and digitized images in a digital radiology operation. Developed during the past few years, full-frame bit allocation performed with the cosine transform technique has been proved to be an excellent irreversible image compression method. This article describes the effect, on the accuracy of diagnosis of subperiosteal resorption, of using the hardware compression module to produce hand radiographs. Receiver operating characteristic analysis of the interpretation of 71 radiographs by five observers demonstrated that there is no statistically significant difference in diagnostic accuracy between the original radiographs and compressed and reconstructed images obtained with a compression ratio as high as 20:1.

Bone Resorption↗
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

Infrastructure design of a picture archiving and communication system.

A picture archiving and communication system (PACS) infrastructure is the necessary framework to integrate distributed and heterogeneous imaging systems, provide intelligent data-base management of all radiology-related information, arrange an efficient means of viewing, analyzing, and documenting study results, and furnish a mechanism for effectively communicating study results to the referring physician. The PACS infrastructure consists of a basic skeleton of hardware components integrated by standardized, flexible software subsystems. This review describes these concepts and basic building blocks drawn from our original investigation, past experience, and the current clinical system in our radiology department.

Computer Systems↗
PubMed1992

A PACS-based interactive teaching module for radiologic sciences.

This article describes an interactive teaching module, linked to a picture archiving and communications system (PACS) data base, for teaching radiology. The module is currently tailored to MR images but can be adapted to any other imaging technique. An algorithm has been developed that allows the use of MR images acquired with routine clinical protocols and stored in the data base to yield, in real time, images at any other arbitrary TE and TR. In the browse mode, the user can study either the effect of different scan parameters or clinical cases on synthesized or acquired images. The quiz mode has multiple-choice questions and answers, accompanied by images. In the teaching mode, the instructor has access to the clinical data base and WRITE privileges for setting up the browse or quiz mode. The module achieves considerable flexibility when linked to the PACS, with access to all archived images and the ability to subsequently synthesize MR images at arbitrary TE and TR values in real time. The module is also "dynamic" in character, in that the instructor can easily add new cases and comments to the teaching files, both to enhance its clinical aspects and to reflect advances in technology.

Algorithms↗
PubMed1992

Digital archive center: implementation for a radiology department.

OBJECTIVE: In this article, we describe the implementation of a digital archive center for a radiology department in a 700-bed teaching hospital. MATERIALS AND METHODS: The archive center consists of two identical archive systems, each comprising five components: an archive server, a data-base server, an optical disk library, a stand-alone optical disk drive, and a communication network. An image management system controls the image traffic from acquisition devices to display stations. A fault-tolerant mechanism was built into the archive center to achieve a 100% uptime. RESULTS: The center has been in operation for over 6 months. We have not experienced a single total system failure during this period. It currently archives all digital images from three MR units and four CT scanners and selected images from three computed radiographic systems and two laser film digitizers. The center archives between 1.5 and 2.0 gigabytes of images per workday. CONCLUSION: With its built-in fault-tolerant mechanism, we believe that the implemented archive center is very reliable and is suitable for a radiology department to archive its digital images.

Hospital Bed Capacity, 500 and over↗
PubMed1992

Assessment of a neuroradiology picture archiving and communication system in clinical practice.

The goal of this study was to determine if our neuroradiology picture archiving and communication system (PACS) is capable of improving the efficiency and function of the management and review of neuroradiologic images. A neuroradiology PACS module developed in our department was evaluated in the clinical environment from February 1990 through July 1991. The overall evaluation focused on three aspects: (1) image delivery performance, (2) system availability, and (3) user acceptance. Image delivery performance was evaluated by analyzing the time spent on each modularized task with both the film-based system and the PACS system. The system availability was examined by observing the downtime occurrence and uptime probability of individual hardware components in the PACS module. User acceptance was evaluated through a survey done with the display workstation. Under regular operating conditions, the PACS outperforms the current film-based operation. The overall PACS module availability is more than 92%, with the display workstation available more than 99% of the time. The overall user acceptance of the system is 3.4 on a four-point ranking scale. This study has demonstrated the full functionality and clinical usefulness of our neuroradiology PACS. On the basis of the results of this study, a large-scale PACS has been designed and implemented in our department.

Computers↗
PubMed1991

Clinical experience in the use of photostimulable phosphor radiographic systems.

The experience with CR systems gained at the three institutions described in this report demonstrates numerous advantages over the conventional screen-film system. These include: (1) a reduction in the radiation exposure delivered to the patient (25% to 50%); (2) a decrease in the number of repeat examinations needed, especially in portable units where technical difficulties are common with screen-film examinations; this is attributable to the linear, wider dynamic range of CR systems compared with screen-film combinations; (3) the capability to archive electronically all images by means of a digital optical storage system; (4) automatic electronic setting of the laser scanner for the latitude and sensitivity on each image; (5) the digital images are available for transmission to all image display workstations on a local or wide-area network; and (6) the ability to adjust interactively the display parameters to best depict images and pathology as well as salvage technically suboptimal examinations. Several disadvantages of CR systems compared with conventional screen-film examinations have also been identified.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1991

Design and implementation of full-frame, bit-allocation image-compression hardware module. Work in progress.

A hardware module was designed and built to implement the full-frame, bit-allocation image-compression algorithm in a clinical setting. The algorithm transforms an entire image without prepartitioning into small subimages. This adaptation eliminates block artifacts at subimage borders that can mimic relevant pathologic conditions. The quality of 1,024- and 2,048-pixel images compressed at a rate up to 10:1 with a custom-designed processor board (which contains four digital signal processors that transform and quantize separate rows and columns of an image independently with a two-pass cosine transform) and a 16-Mbyte frame buffer was found to be diagnostically acceptable in preliminary receiver operating characteristic studies. The module can compress a 1,024-pixel image in 4 seconds in a general-purpose computer system; images can be compressed in 1 second with the addition of a custom-designed data transporter. Copies of the compression module are being installed in the authors' department and in collaborating hospitals for laboratory and clinical evaluation.

Computers↗
PubMed1991

An ultrafast network for communication of radiologic images.

The three most difficult problems in making picture archiving and communication systems (PACS) a clinical reality in radiology are image archiving, very high-resolution display stations, and high-speed networking. This article considers high-speed image transmission through a high-capacity network. Our laboratory has tested several commercially available high-speed networks over the past year. Only one of these networks (UltraNet) has adequate throughput and capacity potential necessary for our PACS. The focus of this experiment is to determine the throughput and capacity characteristics of this star topology networking scheme as they relate to the operation of a PACS in the clinical environment. A large-scale test was done to gauge network performance for three networking configurations modeling those in a PACS: duplex, parallel, and relay. Ten computers used in our PACS (Sun 3 and 4 computers) were connected with UltraNet. For point-to-point throughput (half-duplex model), the network delivers up to 3.1 megabytes/sec for Sun 3 computers and 6.8 megabytes/sec for the Sun Sparcserver 490. As regards capacity considerations (parallel model), five parallel image transfer processes generated a maximum of 13.9 megabytes/sec through the network. Only a slight degradation in individual process throughput was observed (1.4%). With regard to shared access to high-contention resources on the PACS network (e.g., archive servers), this network demonstrated equal sharing of server networking capacity between the various client computers. With the encouraging results of this experiment, we believe that the UltraNet network will be sufficient for the image communication requirements of our PACS. We are proceeding with the implementation of UltraNet as the high-speed backbone of our extended PACS network.

Computers↗
PubMed1990

Advances in medical imaging.

The field of medical imaging, stimulated by advances in digital and communication technologies, has grown tremendously. New imaging techniques that reveal greater anatomical detail are available in most diagnostic radiology departments. We discuss vascular imaging with ultrasound, high-resolution computed tomography of the thorax, magnetic resonance imaging applications, and picture archiving and communication systems. Vascular imaging with ultrasound requires duplex and color flow Doppler, which combine gray-scale ultrasound and the Doppler phenomenon. High-resolution computed tomography modifies conventional computed tomography technology and results in images with higher spatial resolution. Magnetic resonance imaging applications for all areas of the body are being investigated and are replacing older roentgenographic techniques such as computed tomography, arthrography, myelography, and even angiography in a growing number of indications. With these new digital imaging modalities, image management has become an important consideration that can be addressed by picture archiving and communication systems.

Diagnostic Imaging↗