Evolution of anuran brains: disentangling ecological and phylogenetic sources of variation.

Variation in ecological selection pressures has been implicated to explain variation in brain size and architecture in fishes, birds and mammals, but little is known in this respect about amphibians. Likewise, the relative importance of constraint vs. mosaic hypotheses of brain evolution in explaining variation in brain size and architecture remains contentious. Using phylogenetic comparative methods, we studied interspecific variation in brain size and size of different brain parts among 43 Chinese anuran frogs and explored how much of this variation was explainable by variation in ecological factors (viz. habitat type, diet and predation risk). We also evaluated which of the two above-mentioned hypotheses best explains the observed patterns. Although variation in brain size explained on average 80.5% of the variation in size of different brain parts (supporting the constraint hypothesis), none of the three ecological factors were found to explain variation in overall brain size. However, habitat and diet type explained a significant amount of variation in telencephalon size, as well in three composite measures of brain architecture. Likewise, predation risk explained a significant amount of variation in bulbus olfactorius and optic tecta size. Our results show that evolution of anuran brain accommodates features compatible with both constraint (viz. strong allometry among brain parts) and mosaic (viz. independent size changes in response to ecological factors in certain brain parts) models of brain size evolution.

Authenticity and integrity of digital mammography images.

Data security becomes more and more important in telemammography which uses a public high-speed wide area network connecting the examination site with the mammography expert center. Generally, security is characterized in terms of privacy, authenticity and integrity of digital data. Privacy is a network access issue and is not considered in this paper. We present a method, authenticity and integrity of digital mammography, here which can meet the requirements of authenticity and integrity for mammography image (IM) transmission. The authenticity and integrity for mammography (AIDM) consists of the following four modules. 1) Image preprocessing: To segment breast pixels from background and extract patient information from digital imaging and communication in medicine (DICOM) image header. 2) Image hashing: To compute an image hash value of the mammogram using the MD5 hash algorithm. 3) Data encryption: To produce a digital envelope containing the encrypted image hash value (digital signature) and corresponding patient information. 4) Data embedding: To embed the digital envelope into the image. This is done by replacing the least significant bit of a random pixel of the mammogram by one bit of the digital envelope bit stream and repeating for all bits in the bit stream. Experiments with digital IMs demonstrate the following. 1) In the expert center, only the user who knows the private key can open the digital envelope and read the patient information data and the digital signature of the mammogram transmitted from the examination site. 2) Data integrity can be verified by matching the image hash value decrypted from the digital signature with that computed from the transmitted image. 3) No visual quality degradation is detected in the embedded image compared with the original. Our preliminary results demonstrate that AIDM is an effective method for image authenticity and integrity in telemammography application.

Real-time teleconsultation with high-resolution and large-volume medical images for collaborative healthcare.

Real-time consultation between referring physicians or radiologists with an expert is critical for timely and adequate management of problem cases. During consultation, both sides need to: 1) synchronously manipulate high-resolution digital radiographic images or large volume MR/CT images; 2) perform interpretation interactively; and 3) converse with audio. We present a specifically designed teleconsultation system in a digital imaging and communication in medicine picture archiving and communication systems clinical environment. The system uses bidirectional remote control technology to meet critical teleconsultation application requirements with high-resolution and large-volume medical images operated in a limited-bandwidth network setting. We give the system design and implementation methods, and also describe the teleconsultation procedure and protocol used in this system. Finally, laboratory and clinical evaluation results are discussed.

Automatic breast region extraction from digital mammograms for PACS and telemammography applications.

High spatial resolution results in very large digital mammogram file sizes. For telemammography, and picture archiving and communication systems, the large file issue introduces technical difficulties in image transmission, storage, and display. We propose extracting the breast region from the mammogram to reduce the image file size. The challenge is on how to faithfully extract breast regions from digital mammograms generated from different types of acquisition systems that contain various imaged compositions. We report an algorithm to automatically identify the orientation of breast region and extract the breast region from mammograms. Breast regions extracted from full-field digital mammograms reduce file sizes by three to five folds.

An automated PACS image acquisition and recovery scheme for image integrity based on the DICOM standard.

The data quality and completeness of acquired images, which we refer to as integrity, is considered as the most important requirement in the image acquisition design of the Picture Archiving and Communication System (PACS). The Digital Imaging and Communications in Medicine (DICOM) standard significantly simplifies the task of acquiring radiological images from a DICOM compliant imaging system into the PACS. However, human interaction with the imaging system by changing the DICOM communication settings can result in missing images during the PACS image acquisition. A scheme based on the DICOM Query and Retrieve (Q/R) service class was developed to automatically identify and recover missing images. In addition, grouping sequential scanned images such as a CT and MR image series is another potential process that can miss images because of no indication of the end of series. Two methods are presented for determining the end of series and the pros and cons of each method are discussed in detail. Two experiments in a real clinical environment were conducted; one with and one without the Q/R implementation. The statistical results indicate two highlights from this work. First, the Q/R scheme faithfully recovered all missing images caused by human interaction with the DICOM compliant imaging system. Second, there was no single image slice missed when grouping slices into a series using the presented grouping algorithm in the two experimental periods.

Neuroradiology workstation reading in an inter-hospital environment: a nineteen month study.

Two workstations (WS) each with two, 2500 line display monitors were installed in the in-patient and the out-patient neuroradiology reading areas for inter-hospital workstation readings. These WSs are part of the display component of a hospital-integrated picture archiving and communication system (PACS). Direct digital neuro images from 10 CT and MR scanners located at various buildings from two medical centers are first transmitted to the PACS database and then distributed to these two WSs automatically. This paper attempts to answer two questions. First, do the WSs facilitate neuroradiology operation? Second, does it cost less for preparing WS reading than that for the traditional film reading? Two parameters, the "time required before images become available for reading after the examination" and a "workstation utilization index" were derived as a means for answering these two questions. Nineteen months of clinical data were collected and analyzed. The results demonstrate that the workstation utilization index goes up from 40% in September 1994 when the WS was first introduced to over 80% in March 1996. This upward trend substantiates the hypothesis that these WSs do facilitate the neuroradiology operation. The derived results also exhibit that it costs much less to prepare images for WS reading than for film reading. Other indirect results derived from this study including the WS utilization hours, WS functions used, and the time duration of each WS session are also presented.

Full-field direct digital telemammography: technical components, study protocols, and preliminary results.

The early detection of breast cancer increases the survival rate in women. Today, film-screen mammography is the most common and effective technique for the detection of breast cancer. However, the film-screen image recording system of current mammography has several technical limitations that can reduce the breast cancer diagnostic accuracy. A state-of-the-art technology, full-field direct digital mammography (FFDDM) has the potential to increase the sensitivity of clinical and screening examinations and emerge as a film-screen mammography replacement. It is believed that efficiently delivering the superior image quality of FFDDM to expert mammographers will significantly increase the breast cancer diagnostic accuracy. This concept motivates the studies of FFDDM telemammography. In this paper, we will report the FFDDM telemammography project that is being conducted in our facility. The fundamental technology of the FFDDM system and the characteristics of FFDDM images are described. Our research approach is through three protocols: telediagnosis, teleconsultation, and telemanagement. Each of these study protocols is defined. To conduct this FFDDM telemammography project, an asynchronous transfer-mode-network-based telemammography system is developed across two remote campuses in our facility. The architecture of this system is detailed. Unlike other medical imaging modalities, the matrix of an FFDDM image is huge. How to present the image information to mammographers via currently available display media is a challenging task. Our display approaches for the FFDDM images are described. Some preliminary study results from the current phase of this study are reported.

Workstation design. Image manipulation, image set handling, and display issues.

The importance of this article is fourfold. First, the introduction of workstation technology and the types of image workstations provides readers with a better understanding of the state-of-the-art and availability of digital image-display workstations in the market-place. Second, this article identifies primary processes related to image viewing in radiology daily operations. This is crucial because it illustrates the important concepts of the Folder Manger with image preprocessing, patient folder organization, and automatic image display sequencing. With these features incorporated in the workstation design, the number of steps required for a radiologist to interact with a workstation is minimized. Third, the discussions on how to present and manipulate images on the workstations suggest methods concerning the issue of displaying large volumes of image sets on a limited number of monitor screens. Lastly, examples of automatic image sequencing, high-resolution color monitors, and voice-based user interface illustrate current research topics in the future of digital workstation design.

Design and implementation of a picture archiving and communication system: the second time.

This report describes the authors' experience in the design and implementation of two large scale picture archiving and communication systems (PACS) during the past 10 years. The first system, which is in daily clinical operation was developed at University of California, Los Angeles from 1983 to 1992. The second system, which continues evolving, has been in development at University of California, San Francisco (UCSF) since 1992. The report highlights the differences between the two systems and points out the gradual change in the PACS design concept during the past 10 years from a closed architecture to an open hospital-integrated system. Both systems focus on system reliability and data integrity, with 24-hour on-line service and no loss of images. The major difference between the two systems is that the UCSF PACS infrastructure design is a completely open architecture and the system implementation uses more advanced technologies in computer software, digital communication, system interface, and stable industry standards. Such a PACS can withstand future technology changes without rendering the system obsolete, an essential criterion in any PACS design.

Methods of automatically acquiring images from digital medical systems.

Automated image acquisition plays an important role in a picture archiving and communication system (PACS). However, there is no single solution for automated data acquisition from existing digital medical imaging systems. We have gained a great deal of experience on automatic acquiring data by interfacing imaging scanners of major manufacturers. In this paper, we categorize the interface methods supported by the current image scanners. This categorization consists of five architectural models: (a) sequential chain; (b) direct interface; (c) memory access; (d) shared disk; and (e) interconnected network. The cost, rate of data transfer, and ease of implementation of each model are discussed. To ensure the integrity and availability of patient images in a PACS system, automated fault tolerance design in image acquisition is required. Based upon our field data, we report common scenarios which cause the acquisition to fail. We also describe techniques employed to automatically restart the operations which include recovery from acquisition processes' errors and traps, image acquisition computer down-time occurrence, and shutdown occurrence of medical imaging system.

Asynchronous transfer mode technology for radiologic image communication.

Image communication is an important component in picture archiving and communication systems (PACS) and teleradiology applications. Currently, local area networks (LANs) and wide area networks (WANs) use different technologies for image communication. Asynchronous transfer mode (ATM) is an emerging technology that can be used for both LANs and WANs. This article describes experimental results using an ATM network to transmit CT scans and digitized radiographs between the University of California, San Francisco (UCSF) and Mount Zion Hospital, an affiliated community hospital in the San Francisco Bay area. The WAN connection between the two hospitals is via an ATM main switch at Pacific Bell, a local communication carrier located in Oakland, CA, which uses single-mode optical fibers. Preliminary results show that, using the ATM Optical Carrier Level 3 (OC3) (155 Mbits/sec) specification, it takes 1.3 sec and 2.7 sec to transmit a 10-Mbyte digitized radiograph and a 20-Mbyte CT scan, respectively, between the two locations. Encouraged by these results, we have designed and implemented an ATM WAN and LAN between UCSF and Mount Zion Hospital. This is the first of a three-phase project of installing a WAN serving four hospitals and one clinic in the San Francisco Bay area.

Multimedia in the radiology environment: current concept.

Multimedia has different meanings according to its context. Here, multimedia in the radiology environment is defined as the integration of multiple radiology and medical information systems to facilitate the practice of radiology. These information systems include the hospital information system, radiology information system, picture archiving and communication systems, voice reporting, library information systems, and electronic mail and file systems. The concept of multimedia within the context of integration of these database systems will be presented. An example is given on how to access these information systems by a radiologist's desktop personal computer.

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.

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.

Projection domain compensation of missing angles for fan-beam CT reconstruction.

An improved method is proposed for fan-beam computed tomographic (CT) reconstruction from data with limited views. Compensation for the missing projections for fan-beam CT can be partially accomplished by using the coincident ray or by an interpolation technique using circular sample theory. In this article, the authors propose a more accurate compensation method for the missing projections whether the coincident ray pairs exist or not. The fan-beam reprojection algorithm, which is the inverse operator of the convolution filter, was extended from the projection space iteration reconstruction-reprojection (PSIRR) in parallel beam geometry. In addition, this algorithm was validated by applying the Shepp-Logan phantom for a computer simulation in the equi-angular fan-beam CT geometry.

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.

Full-frame transform compression of CT and MR images.

Compression algorithms based on full-frame discrete cosine transforms have achieved compression ratios as high as 10:1 to 20:1 with almost imperceptible image degradation, when applied to projection radiographs digitized with 2,048 X 2,048 X 8-bit matrices. Compared with such radiographs, images obtained with computed tomography (CT) and magnetic resonance (MR) are smaller in size, have lower signal-to-noise ratios, and, in the case of CT, have a larger dynamic range. These differences result in qualitatively different spectral properties. The authors studied the efficiency of the full-frame technique when applied to CT and MR images. They achieved excellent results, with compression ratios in the neighborhood of 5:1. The study was performed with the use of a hardware implementation of the authors' algorithm, which can compress a 512 X 512 X 12-bit image in less than 1.5 seconds.

Radiological image compression using full-frame cosine transform with adaptive bit-allocation.

We report a new bit-allocation scheme based on the full-frame cosine transform for radiological image compression. The new technique differs from a previously reported method in its use of a two-dimensional bit-allocation table to encode the compression data. This allows for an improved treatment of high frequency components in the transform domain. Consequently, it has the capability of faithfully reproducing limited numbers of high-contrast sharp edges in the image. Previously reported artifacts, induced in the reconstructed image by sharp edges in the original, have been eliminated. Experiments with 10 radiological chest images show almost no perceivable degradation in the reconstructed image at compression ratios below 10:1. Image quality at a fixed compression ratio is, in every case, comparable or superior to results using the old method. Furthermore, the new algorithm lends itself to hardware implementations that are both simple and fast.

Radiological image compression using error-free irreversible two-dimensional direct-cosine-transform coding techniques.

Some error-free and irreversible two-dimensional direct-cosine-transform (2D-DCT) coding, image-compression techniques applied to radiological images are discussed in this paper. Run-length coding and Huffman coding are described, and examples are given for error-free image compression. In the case of irreversible 2D-DCT coding, the block-quantization technique and the full-frame bit-allocation (FFBA) technique are described. Error-free image compression can achieve a compression ratio from 2:1 to 3:1, whereas the irreversible 2D-DCT coding compression technique can, in general, achieve a much higher acceptable compression ratio. The currently available block-quantization hardware may lead to visible block artifacts at certain compression ratios, but FFBA may be employed with the same or higher compression ratios without generating such artifacts. An even higher compression ratio can be achieved if the image is compressed by using first FFBA and then Huffman coding. The disadvantages of FFBA are that it is sensitive to sharp edges and no hardware is available. This paper also describes the design of the FFBA technique.