Microscan Systems (Renton, WA)
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Array imagers, such as the MS-4 by Microscan Systems (Renton, WA), read multiple symbologies, including 1-D bar codes and Data Matrix.
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IVD instruments are ultimately only as good as the input they receive. This makes integrated bar code readers very valuable components. Automating data entry with bar coding improves data quality and patient safety while also helping users be more productive.
Recent advances in bar code technology are allowing the performance and productivity of existing IVD applications to be improved and enabling efficient new processes to be developed. Features such as enhanced two-dimensional (2-D) bar code support, more flexible read ranges, improved tolerance for poor symbol quality, and integrated vision and inspection capabilities give reason for diagnostic equipment developers to take a fresh look at how automated bar code entry could enhance their instruments to provide greater value to customers.
Improving Safety and Efficiency
Two of the biggest issues laboratory and healthcare administrators face today are how to maintain adequate staffing levels and how to improve patient safety. Diagnostic equipment can help on both fronts.
Laboratory workers can spend more than half their time doing repetitive preanalytical tasks and another significant portion recording and validating results. Equipment manufacturers can promote lab productivity by building in features that reduce the time required to configure equipment, identify samples, and record results. Labs already rely heavily on laboratory information management systems (LIMS) to maintain productivity. Diagnostic equipment that supports automated, integrated input to LIMS enhances the value of both systems to the users’ benefit.
Bar code scanning is a proven time-saver for sample identification and for entering configuration data and test results—precisely the reason it is also an excellent tool for enhancing patient safety. Much of the data in patient records come from IVD instruments. Manual transcription of test results leads to the occasional error. Also, a small but nonnegligible percentage of laboratory samples are misidentified.
IVD manufacturers can help eliminate a leading source of these errors by building automated data entry capabilities into their equipment. The machines themselves are not usually responsible for erroneous data; mistakes happen when IVD-reported data are transcribed and entered into other systems. Using bar code input and output to remove the need for manual data entry builds safety into processes, too. In 2006, the Joint Commission on the Accreditation of Healthcare Organizations (JCAHO) issued its National Patient Safety Goal, calling for the establishment of means to maintain samples’ identities throughout preanalytical, analytical, and postanalytical processing stages. IVD instruments that support automated data entry and communication can be a valuable aid in JCAHO compliance.
Applications and Opportunities
Bar codes are commonly used to identify both specimens and reagents. Typical instruments and systems that include embedded bar code readers range from blood gas and DNA analyzers to single-tube conveying systems, pipettors, and rack and plate handlers. Although such applications are common, there is still room for innovation.
New bar code reading capabilities enable manufacturers and users alike to develop more-efficient equipment and processes. Array imagers can be integrated into IVD devices to provide full linear and 2-D bar code support plus sensing, inspection, validation, and sortation. The machine vision capabilities of array imagers represent a significant advancement over traditional linear imagers, which themselves had brought a performance leap to integrated scanning by supporting 2-D bar code formats that the laser scanners originally used in medical devices could not read.
A bar code reader is one of the most important components for ensuring device accuracy; however, it can also be one of the most expensive. It is important to understand the key differences between types of readers, the performance and value each provides, their ease of integration, and the effect of each type on total cost of ownership.
Bar Code Reading Options
The challenge in scanning a bar code at close range is achieving a scan width, or field of view, capable of encompassing the entire bar code. The total dimensional space the reader needs to decode a bar code at a specified distance is called the scan envelope. This characteristic of a reader is especially important in space-constrained situations such as embedded applications.
The scan envelope directly affects the space requirement for a scanner that might be mounted within the instrument to read bar codes. The dimensions of the envelope are determined by the depth of the scanner, the scan angle, and the distance between the scanner and the symbol. The depth of the bar code reader is simply the measure of its physical case. The angle of the scan is important because it defines the width of the scanner’s laser beam. The scan distance is the separation of the symbol from the front of the scanner required to achieve a successful read.
For any linear bar code reader to perform properly, the laser line—or the linear field of view in the case of a linear imager—must be aligned perpendicularly to the bars and spaces of the code. The orientation of the bar code and the direction of its travel are very important to systems using linear bar code readers.
Laser scanners historically have been the type of bar code reader most commonly embedded in clinical instruments. Laser technology is unlikely to remain predominant, because it cannot read matrix-type 2-D symbols, including Data Matrix, which is widely used in the pharmaceutical, healthcare, and electronics industries.
To overcome this limitation, instrument manufacturers have turned to linear imagers, which can read Data Matrix and other leading matrix, stacked, and 1-D bar code symbologies such as QR Code, PDF417, GS1 DataBar (formerly known as Reduced Space Symbology, or RSS), Code 128, and Code 39. However, linear imagers also require the bar code to be aligned perpendicularly to the field of view. This technology therefore is unsuitable for applications where the symbol location cannot be controlled or guaranteed.
Array imagers, on the other hand, eliminate the need to orient the symbol. They provide other performance advantages as well. Until recently, 2-D–capable imagers were not always easy to use or cost-effective to integrate into clinical devices. Most were too large and expensive for use as a subsystem in diagnostic instruments. However, new miniature megapixel array imagers are available as cost-effective options for reading 2-D codes while also solving quality and orientation issues. Miniature megapixel imagers are not designed for high-speed applications; they are better suited for slow or stationary applications. But because the majority of analyzers use a stop-and-read system for reading bar codes, this should not pose a serious limitation.
Array imagers used to cost $5000 or more, which was significantly more than the price of a linear imager or laser scanner. Today, though, megapixel array imagers have list prices starting around $2000—still higher than linear imagers and lasers, but not by so much. Each technology has its own specific capabilities and limitations, however, so direct price comparisons among technologies do not provide a true measure of value. Radio-frequency identification (RFID) readers illustrate very well why component cost is not a true indication of value. RFID provides suitable performance for sample identification, and OEM reader costs are comparable to those of bar code readers, if not better. However, the RFID tags used to identify samples cost much more than the application of bar codes. Therefore, the operating costs associated with RFID readers are high.
Through a combination of solid-state technology and a light source based on light-emitting diodes (LEDs), megapixel imagers typically have a longer life expectancy than a laser diode scanner. Solid-state technology means that the product consists mainly of semiconducting materials, components, and related devices with no moving parts. Laser scanners do have moving parts, including a motor that rotates or moves a mirror to sweep a laser across an object and direct the returning energy. In comparison, imagers illuminate an object with an array of LEDs and use a lens to focus the target image onto a complementary metal oxide semiconductor/charge-coupled device image sensor.
Imaging Applications
Array imagers support legacy bar code formats and processes and also enable new imaging-based applications, such as cap inspection. Over the past four years, most array imagers have read at VGA resolution with 307,200 pixels (video graphics array; 640 ¥ 480 pixels). This has forced instrument designers to choose between resolution and field of view. The introduction of miniature megapixel imagers offers QXGA (quad extended graphics array) resolution with an array of more than 1 million pixels, delivering a much larger field of view without sacrificing resolution. This enables imagers to read up to 100 2-D or Data Matrix symbols within a single image capture and to process the data in real time. Array imagers thus provide an alternative to RFID for high-speed multiple-sample identification.
Because of their enhanced resolution and capabilities, array imagers can replace other components used for inspection and validation. Now, a single reliable component can be used to read bar codes, identify specimen containers, read color-coded tube caps, and capture measurements in order to perform cap and container inspection to aid sortation, identify misses by the decapper, and consequently prevent damage to pipettors. Besides reading both linear bar codes and 2-D symbols, an imager can serve as a presence/absence detector for tubes and caps; capture cap diameter information in order to direct piercing, decapping, and sorting operations; and identify caps by color code, as well as perform other functions.
Component Selection
Thus, reading method, reliability, and operating cost are some important differentiators among technology and product options for sample identification. Others include tolerance for environmental and bar code variables, speed, input/output capabilities, power draw, and space requirements.
Environmental Considerations. The manufacturer should evaluate the environment in which the bar code reader will be operating. Temperature, ambient lighting, electrical noise, and dust or water exposure are all potential sources of reading problems. The equipment designer should make sure the housing of the reader qualifies for necessary industrial rating or else should build an enclosure to protect the reader from its immediate environment.
Lighting is a very important consideration in technology and product selection. Imagers perform very well in low-light conditions, and they may include an integrated light source for illuminating the bar code symbol.
Electrical functions, such as power requirements, connectivity cables, and trigger methods, should be considered by any instrumentation manufacturer planning the integration of a bar code reader. Most readers require electricity of 5–28 V. Those designed with minimal power requirements will drain the host instrument less. The routing of connectivity cables should be carefully designed to minimize the risk of damage.
Scanning Considerations. Designers value compact components, and bar code readers are no exception. However, more important than the size of the reader is the space available for reading. Designers need to calculate the scan envelope before specifying a bar code reader. Smaller scan envelopes offer the design advantage of requiring less physical space between the reader and the bar code.
For someone assessing readers’ specifications comparatively, the speed parameter can be misleading. A scanner’s decode rate often is more important than the more commonly cited read rate for embedded applications, because it determines how fast the scanner will be able to process the encoded data and send it to the host.
Interface Considerations. Triggers that tell the scanner when to look for the bar code are divided into two categories: discrete (external) and serial (software). Which type to include generally depends on the designer’s preference for programming or wiring. Discrete triggers are separate sensors, or object detectors, that can be wired directly into the reader. They typically require much less programming than serial triggers. Serial triggers are dispatched from an external device, such as a programmable logic controller or host personal computer, that tells the reader to look for a bar code. Serial triggers are often used in embedded applications to provide greater control.
Once the bar code is decoded, the reader can output the data in the particular format required for a specific process. Interface software should be designed to initialize the reader, check for status, and create a robust real-time communication protocol between reader and host.
Conclusion
Bar codes have proven their value for ensuring the accuracy of medical information and protecting patient safety. The value of bar code reader components for IVD manufacturers is changing because of recent technology advances. Now is a good time for instrumentation manufacturers to reexamine available bar code component technology in order to see whether these advances can provide performance or total-cost-of-ownership advantages in embedded designs. The use of bar codes in laboratories and hospitals continues to increase, so IVD equipment must evolve to meet growing needs.
