Fei Cao

Fault-tolerant back-up archive using an ASP model for disaster recovery

A single point of failure in PACS during a disaster scenario is the main archive storage and server. When a major disaster occurs, it is possible to lose an entire hospitals PACS data. Few current PACS archives feature disaster recovery, but the design is limited at best. These drawbacks include the frequency with which the back-up is physically removed to an offsite facility, the operational costs associated to maintain the back-up, the ease-of-use to perform the backup consistently and efficiently, and the ease-of-use to perform the PACS image data recovery. This paper describes a novel approach towards a fault-tolerant solution for disaster recovery of short-term PACS image data using an Application Service Provider model for service. The ASP back-up archive provides instantaneous, automatic backup of acquired PACS image data and instantaneous recovery of stored PACS image data all at a low operational cost. A back-up archive server and RAID storage device is implemented offsite from the main PACS archive location. In the example of this particular hospital, it was determined that at least 2 months worth of PACS image exams were needed for back-up. Clinical data from a hospital PACS is sent to this ASP storage server in parallel to the exams being archived in the main server. A disaster scenario was simulated and the PACS exams were sent from the offsite ASP storage server back to the hospital PACS. Initially, connectivity between the main archive and the ASP storage server is established via a T-1 connection. In the future, other more cost-effective means of connectivity will be researched such as the Internet 2. A disaster scenario was initiated and the disaster recovery process using the ASP back-up archive server was success in repopulating the clinical PACS within a short period of time. The ASP back-up archive was able to recover two months of PACS image data for comparison studies with no complex operational procedures. Furthermore, no image data loss was encountered during the recovery.

Fault-tolerant PACS server

Failure of a PACS archive server could cripple an entire PACS operation. Last year we demonstrated that it was possible to design a fault-tolerant (FT) server with 99.999% uptime. The FT design was based on a triple modular redundancy with a simple majority vote to automatically detect and mask a faulty module. The purpose of this presentation is to report on its continuous developments in integrating with external mass storage devices, and to delineate laboratory failover experiments. An FT PACS Simulator with generic PACS software has been used in the experiment. To simulate a PACS clinical operation, image examinations are transmitted continuously from the modality simulator to the DICOM gateway and then to the FT PACS server and workstations. The hardware failures in network, FT server module, disk, RAID, and DLT are manually induced to observe the failover recovery of the FT PACS to resume its normal data flow. We then test and evaluate the FT PACS server in its reliability, functionality, and performance.

Fault-tolerant PACS server design

A single point of hardware failure in PACS is at the PACS controller, or the main archive server. When it occurs, it renders the entire PACS inoperable and crippled until the problem is diagnosed and resolved. Many current PACS do not have a fault-tolerant design or adequate back-up system for the main archive server due to several issues including cost. Several large scale PACs utilize the Tandem or cluster design but are very costly and have not been critically tested for their degree of fault tolerance. This paper describes a novel, portable, and scalable fault-tolerant PACS controller design that is affordable for most PACS implementations.

Educational RIS/PACS simulator

Many educational courses have been designed for training radiologists and allied healthcare providers to operate PACS workstations. There are yet tools available for educational training of PACS concepts and workflow analysis. We have designed and implemented a RIS/PACS Simulator for this purpose. The RIS/PACS Simulator consists of six key components simulating a typical clinical RIS/PACS: RIS simulator, acquisition modality Simulator (AMS), DICOM gateway, PACS controller (UNIX-based), clinical viewing workstation, and network infrastructure with a 100mbits/sec Ethernet switch connecting to all these components. A generic RIS and a generic DICOM compliant PACS software package are used to simulate normal clinical data flow. Using this simulator, trainees can: 1. Observe clinical RIS/PACS operation, component by component 2. Trace image flow through each component 3. Identify PACS data flow bottle neck 4. Induce failure in a component to observe its impact on the PACS workflow and operation RIS/PACS simulator is a valuable tool for participants to gain knowledge of the complexity of RIS/PACS data flow with hands-on experience. As a stand-alone system, it also becomes a good test bed for evaluation of medical imaging applications without interrupting clinical workflow.

Fault-tolerant PACS server design and evaluation

Abstract A single point of hardware failure in picture archiving and communication system (PACS) is at the PACS controller, or the main archive server. When it occurs, it renders the entire PACS inoperable and crippled until the problem is diagnosed and resolved. Many current PACS do not have a fault-tolerant design or adequate backup system for the main archive server due to several issues including cost. This paper describes a novel, portable, and scalable fault-tolerant PACS controller design that is affordable for most PACS implementations. Currently, most PACS controllers are based on UNIX servers. The UNIX server can be replaced by a specially designed Continuous Availability Server (CAS) consisting of three identical machines as the UNIX server that run the same operating system and application software simultaneously and independently. Hardware failure of any one or multiple components in a machine in the CAS, including the power supply, processors, SCSI ports, network ports, RAID controller, and disk controllers, was simulated. A series of clinical scenarios were performed while executing a simulated failure of the key hardware components within the CAS. No interruption of PACS data flow passing through the CAS was observed. Therefore, the result is a continuous availability server immune to a single point of hardware failure.

Image matching as a diagnostic support tool

We have developed and evaluated a novel image-matching method for medical images. This method allows the radiologist to search through - in a matter of seconds - large medical databases containing thousands of patients. To illustrate the usefulness of this method in a clinical setting, we have employed this method as a diagnostic support tool for pediatric brain diseases. To this aim, we have assembled a database containing Magnetic Resonance (MR) brain images of 2500 patients between ages 0 and 18 with known brain lesions. As the images are added to the database, they are registered to a global coordinate system. In addition, regions of interests (ROI) are labeled, and sophisticated image processing techniques are used to extract image parameters from the ROIs and from the entire MR image. To perform a clinically realistic search through this database, we have established a training testbed at Childrens Hospital Los Angeles for acquiring MR images from our PACS server of patients with unknown lesions. We have matched these images with the images in the pediatric brain MR database containing known lesions using our image-matching method. An expert pediatric neuroradiologist evaluated the search results. We found that in most cases, our image-matching method is able to retrieve images with relevant diagnostic content, making it highly attractive as a diagnostic support tool.

Digital image envelope: method and evaluation

Health data security, characterized in terms of data privacy, authenticity, and integrity, is a vital issue when digital images and other patient information are transmitted through public networks in telehealth applications such as teleradiology. Mandates for ensuring health data security have been extensively discussed (for example The Health Insurance Portability and Accountability Act, HIPAA) and health informatics guidelines (such as the DICOM standard) are beginning to focus on issues of data continue to be published by organizing bodies in healthcare; however, there has not been a systematic method developed to ensure data security in medical imaging Because data privacy and authenticity are often managed primarily with firewall and password protection, we have focused our research and development on data integrity. We have developed a systematic method of ensuring medical image data integrity across public networks using the concept of the digital envelope. When a medical image is generated regardless of the modality, three processes are performed: the image signature is obtained, the DICOM image header is encrypted, and a digital envelope is formed by combining the signature and the encrypted header. The envelope is encrypted and embedded in the original image. This assures the security of both the image and the patient ID. The embedded image is encrypted again and transmitted across the network. The reverse process is performed at the receiving site. The result is two digital signatures, one from the original image before transmission, and second from the image after transmission. If the signatures are identical, there has been no alteration of the image. This paper concentrates in the method and evaluation of the digital image envelope.

Complete continuous-availability PACS archive server solution

Failure of PACS archive server would cripple the entire PACS operation. Last year we demonstrated that it was possible to design a fault-tolerant (FT) server with 99.999% uptime. The FT design was based on a triple modular redundancy with a simple majority vote to automatically detect and mask a faulty module. The purpose of this presentation is to report on its continuous developments in integrating with external mass storage devices, and applying as an Application Service Provider (ASP) back-up archive server. ASP back-up archive is to provide instantaneous automatic backup of PACS image data and instantaneous recovery of PACS image data in the event of disaster. FT server is used as an off-site backup-archive PACS server from the main PACS archive locations. Clinical data from a hospital PACS is sent to the FT server in parallel to the exams being archived in the main server. A disaster scenario is simulated and the PACS data is sent from the offsite FT server back to the hospital PACS. The reliability, functionality and performance of the FT server and external mass storage devices are evaluated during the simulation.

Wireless-PDA-controlled image workflow from PACS: the next trend in the health care enterprise?

Image workflow in todays Picture Archiving and Communication Systems (PACS) is controlled from fixed Display Workstations (DW) using proprietary control interfaces. A remote access to the Hospital Information System (HIS) and Radiology Information System (RIS) for urgent patient information retrieval does not exist or gradually become available. The lack for remote access and workflow control for HIS and RIS is especially true when it comes to medical images of a PACS on Department or Hospital level. As images become more complex and data sizes expand rapidly with new image techniques like functional MRI, Mammography or routine spiral CT to name a few, the access and manageability becomes an important issue. Long image downloads or incomplete work lists cannot be tolerated in a busy health care environment. In addition, the domain of the PACS is no longer limited to the imaging department and PACS is also being used in the ER and emergency care units. Thus a prompt and secure access and manageability not only by the radiologist, but also from the physician becomes crucial to optimally utilize the PACS in the health care enterprise of the new millennium. The purpose of this paper is to introduce a concept and its implementation of a remote access and workflow control of the PACS combining wireless, Internet and Internet2 technologies. A wireless device, the Personal Digital Assistant (PDA), is used to communicate to a PACS web server that acts as a gateway controlling the commands for which the user has access to the PACS server. The commands implemented for this test-bed are query/retrieve of the patient list and study list including modality, examination, series and image selection and pushing any list items to a selected DW on the PACS network.

NGI performance for teleradiology applications

Tele-medical imaging applications require low cost, and high-speed backbone wide area networks (WAN) to carry large amount of imaging data for rapid turn around interpretation. Current low cost commercially WAN is too slow for medical imaging applications, while high speed WAN is too costly. The next generation Internet (NGI) or Internet2 is federal initiatives for the integration of higher speed backbone communication networks (up to 2.4 Gbits/sec) as a means to replace the current inadequate Internet for many applications including medical imaging. This paper describes our preliminary experience of connecting to Internet2 for teleradiology application. A case study is given for the NGI WAN connection between Childrens Hospital Los Angeles and National Library of Medicine. NGI WAN performance for different image modalities, measured in throughput rate and application response time, were obtained and then compared to the T1 WAN connection between Childrens Hospital Los Angeles and Saint Johns Health Center Santa Monica.