Using Solid State Flash Disks as Cure-All for Medical Storage Systems

In collaboration with Wilson Wei Sheng Wang













The medical equipment industry has always remained at the cutting edge of technology to enhance or complement the skills of medical personnel in saving lives. Millions of dollars, and sometimes billions, have been spent by hospitals, medical units and clinics in acquiring the latest equipment. The question is, why does the medical sector invest so much in these equipment? The answer is clear: the medical industry is all about saving lives. Medical equipment are mission critical devices that must not fail under any circumstance despite being deployed in pretty harsh conditions such as ambulances and mobile transportation units. In addition, advances in imaging and data processing have automated diagnostic evaluation, reflecting the need for a storage device that can ensure the high-performance and reliability of such systems.





Critical Issues in Medical Equipment





Size and Weight - Size can be critical in systems destined for use in healthcare environments such as laboratories, emergency rooms, doctors' offices, and ambulances. Therefore, an embedded computer may take up space no greater than the ones used by single-chip microcontrollers. Weight is also an important factor if the equipment is portable or intended for mobile use.





Power Consumption - System reliability is reduced by high heat buildup. Therefore, it is important to minimize power consumption when replacing microcontrollers with embedded PCs. Power consumption and heat generation are important criteria in the design of portable and mobile systems.





Shock and Vibration Resistance - Whether intended for fixed or mobile use, every medical product must be transported from where it is made to where it will be used. Desktop PC motherboards and plug-in cards are notorious for needing adjustment by a trained technician after delivery, prior to use.





Such sensitivity to shock and vibration is not acceptable in embedded applications. In portable or mobile systems, system electronics undergo a wide range of movement during storage, handling, and operation. Vibration and sudden jerking may subject components and solder joints to continual mechanical stress until chips, modules, and boards become partially or fully dislodged or disconnected. In addition, connector pin conductivity can be degraded by corrosion resulting from electrochemical effects that are exacerbated by vibration.





Operating Temperature Range - Most medical systems are used in relatively benign indoor environments. Embedded electronics intended for such use are typically rated for operation at temperatures up to 55°C. However, some medical equipment enclosures need to be fully sealed-to protect against spilled liquids such as blood or chemicals, therefore air vents and cooling fans may not be permissible. In these cases, internal temperature can become elevated, which may require embedded electronics to be rated for operation up to 70°C. In mobile or portable equipment, an extended operating temperature range of -20° to 80°C may be called for.





Environmental Factors





Electrostatic discharge (ESD) and electromagnetic interference (EMI), both generated and received, are key concerns in medical applications. High frequency microprocessor clocks, which for PCs commonly fall in the range of 33-166 MHz, can easily interfere with low-level signal detection or stimulus generation. Additionally, medical systems often must operate in the presence of strong electromagnetic emissions from other devices situated nearby. As a result, components embedded in these systems must be designed with high noise immunity and low noise generation. Consideration also must be given to conductive radiation and susceptibility on power supply and I/O connections. Undesired system resets and data loss must, of course, be prevented, but the potential danger to human lives from high levels of electric, electrostatic, or electromagnetic emissions is a far greater concern in medical applications, requiring designers to incorporate preventive measures.





Quality and Reliability





Naturally, the required level of system quality and reliability depends on the particular application. For example, equipment used in the entry or retrieval of non-critical information can include fewer fail-safe mechanisms than systems performing life-critical patient monitoring or blood chemistry control. However, it is categorically safe to say that medical users are never as forgiving of system malfunctions or crashes as are the users of desktop PCs. Practically every PC user experience messages such as "Fatal error #XYZ" from time to time, but such incidents are totally unacceptable in medical equipment, where consequences can range from loss of critical data to loss of life.





Product Life Span





Regarding product longevity, desktop PC manufacturers and users have a different set of priorities compared with the medical systems industry. Desktop PC vendors strive to bring out new technologies constantly, and the typical half-life (to obsolescence) of PC chipsets is around 1.5 years. Clearly, while it may benefit PC manufacturers to market a new motherboard, video card, disk controller, or network controller every year or so, this situation is unacceptable for medical equipment manufacturers. Medical products typically require two or more years of development, followed by several more years to gain FDA approval. Therefore, medical systems design cannot be based on components with a lifespan of as short as 18 to 24 months.





Medical Diagnosis in the Digital Age





The advent of digital technologies gave birth to a variety of electronic medical equipment requiring high performance and reliability. The following are some examples:





Magnetic resonance imaging (MRI)





MRI is an imaging technique used primarily for diagnostic purposes to produce high quality images of the human body, both internal and external. MRI is based on the principle of nuclear magnetic resonance, a spectroscopic technique used by scientists to obtain microscopic chemical and physical information about molecules.





Computed axial tomography (CAT scan or CT scan)





CAT scan is a computerized x-ray procedure that produces cross-sectional images of the human body. The images are far more detailed than x-ray films, and can reveal disease or abnormalities in tissue and bone. The procedure is usually noninvasive and brief.





Positron emission tomography (PET scan)





PET scan is a test that combines computed tomography (CT) and nuclear scanning. Compared to CT scans and MRI, PET produces less-detailed pictures of an organ. A PET scan is often used to detect and evaluate cancer, such as of the lung or breast. It also can be used to evaluate the heart's metabolism and blood flow and examine brain function.





Ultrasound (Sonography)





This diagnostic imaging technique uses high-frequency sound waves and a computer to create images of blood vessels, tissues, and organs. Ultrasounds are used to view internal organs as they function, and to assess blood flow through various vessels.








Electronic Records Management





The recent boom in the global healthcare industry has ramped up demand not only for healthcare professionals but also for related IT equipment. Government regulations such as the Health Insurance Portability and Accountability Act (HIPAA) are gradually forcing healthcare providers to upgrade legacy information systems with the latest in laboratory information management, picture archiving and communication, as well as medical records systems.





Laboratory information management system (LIMS)





According to market research firm Frost & Sullivan, regulatory compliance as well as the standardization of business practices and have catapulted the LIMS market into the growth stage, with market revenues likely to increase from US$209 million in 2003 to US$328 million in 2009. The development of LIMS has been influenced by the trend toward the maintenance of electronic records in lieu of paper-based documents. LIMS assists lab workers in handling structured data records such as samples, tests performed, and their results.





Picture archiving and communication system (PACS)





PACS is an electronics system that uses an image server to exchange X-rays, CT scans and other medical images over a network. Due to its legal mandate under the provisions of the HIPAA, market research firm Frost & Sullivan projects that 65.2 percent of all hospitals and 12.3 percent of U.S imaging centers will install PACS by 2007. This is not surprising considering that PACS offers several benefits. The film-less system speeds up the turnaround time required for delivering images/x-rays to the attending physicians, since they will no longer need to wait for film images to be processed and delivered before they are analyzed. As a result, doctors will be able to make quick decisions in emergency or life-threatening medical cases.





LIMS and PACS both require a high level of performance, availability and reliability, as immediate access to patient information is critical in emergency scenarios.





The Solid State Disk Advantage





So what do solid state flash disks offer for these applications?





Medical imaging systems are performance-hungry applications that require real-time performance and higher resolutions while medical information systems need reliable components to minimize downtime. All of these requirements can be easily met by utilizing flash-based solid state disk for storage or as a cache solution. High transfer rates allow immediate delivery of real time information, while the ruggedized packaging of certain solid state disk models, such as BiTMICRO's E-Disk SSD, immunizes the storage device from hazardous ESD and EMI. Moreover, the VME and cPCI architectures are most commonly used in medical imaging systems, and E-Disk solid state disks are tailor fit for any VME, cPCI, PMC storage module.





Solid state flash disks are capable of much higher transfer rates and IOPS relative to other storage mediums such as magnetic disk drives. Flash-based solid state disks inherently consume less power and generate a smaller amount of heat due to the absence of spindle motors. ESD and EMI, both generated and received, will be minimized with flash drive implementation. On top of that, the non-volatile nature of flash memory makes it resistant to shock and vibration, a useful feature in rugged mobile environments.





BiTMICRO's E-Disk solid state flash disk has a unique feature that sets it apart from its DRAM-SSD and HDD counterparts. E-Disk's patented PowerGuard® provides temporary power in the event of a power loss, allowing the disk to flush all the content in the cache into the flash memory, ensuring data reliability and availability in mobile medical systems.





It is also noteworthy to mention BiTMICRO's extended warranty support programs in support for non-obsolescence and quality control of computerized medical equipment. Extended warranty ensures timely and original or functionally equivalent replacements for BiTMICRO products that need repair or attention, up to a period covering 10 years after original purchase.





Price Trend





Now that we've established the technical viability of solid state flash disks in medical systems, let's examine the practicality of flash disk deployment in enterprise storage. Though there still is a price premium for solid state disks over rotational drives, the gap between HDD and solid state flash disk quotes is seen to narrow significantly-with a difference of only about $0.05 per MByte in 2007-despite the huge performance advantages of solid state disks (at 100x-150x over magnetic drives in terms of sustained transfers and IOPS).





Web-Feet Research also projects a major decline in the solid state flash disk/HDD cost ratio by approximately four times, from 433:1 ($0.078 vs. $0.0018 per MByte) in 2003 to 107:1 ($0.096 vs. $0.0009 per MByte) in 2006. Solid state flash disks will also maintain its cost-per-MByte advantage over DRAM-based SSDs.





One thing the solid state disk industry has benefited from is the continued decline in flash memory prices. High demand for portable electronic devices such as MMS-capable phones, digital cameras, and MP3 players has driven semiconductor manufacturers to boost flash memory density and output. Market research firm Web-Feet Research predicts that the price per MByte of solid state flash disk will fall by an average of 80.86 percent annually within a 5-year period starting 2004.











Figure 1: Disk drive comparison, $ / MB





Conclusion





The digitization of diagnostics and records management procedures in the medical industry has facilitated the evaluation, sharing, and archiving of patient images and information. However, these data intensive applications require storage components that can operate in an environment where IT system downtime can be fatal. Solid state flash disk is the ideal solution for medical systems, providing fast throughput and scalability at a price that belies its wide performance lead over magnetic disk drives.





For more information, visit the E-Disk Technology Center at www.e-disk.com.