Care required when PXI serves medicine

The design and manufacture of medical devices follow tightly controlled processes.

By Richard A. Quinnell, Contributing Technical Editor -- Test & Measurement World, 9/1/2010 12:00:00 AM

Instrumentation development and manufacturing test for medical equipment are growing application areas for PXI technology. Engineers working in these fields face unique challenges, though, because of regulations that require the design and manufacture of medical devices to follow tightly controlled processes. Design techniques that use off-the-shelf modules, such as PXI, require extra care from the design team and extra support from their vendors.

PXI helped speed the prototyping and software development of this Active Diagnostics neurosimulator for training physicians on the human nervous system's response to surgery. Courtesy of National Instruments.

There are many reasons why PXI is appealing to the medical industry, according to John Hottenroth, market development manager for scientific and biotechnology instrumentation at National Instruments. One key appeal is the ability that PXI gives medical developers to quickly create prototypes. "Many of these customers are experts in their medical field looking for design help," says Hottenroth. "With PXI, they are able to take their ideas and form prototypes to prove the ideas out, then quickly bring the product to market."

One recent example is a neurosimulator that Active Diagnostics developed for surgical training of neurophysiologists. In an application note on the NI Website (Ref. 1), David Miller and Michael Russell of Active Diagnostics explained that PXI "hardware and software tools provided an easy-to-use solution that allowed us to quickly prototype and reuse much of the code in our final deployment."

This ability to quickly develop prototypes can also be valuable in obtaining funding, especially when a company is just starting out. "There's no shortage of venture capital for medical companies," Hottenroth explained, "but having a working demo helps them win backing."

Once the prototype is ready, the role of PXI in production can vary based on anticipated volume, noted Hottenroth. Low-volume production, such as for high-cost systems that sell in the tens per year, may well employ off-the-shelf PXI as an embedded system. For higher volumes, customers are more likely to want the custom form factors and reduced pricing available by using OEM components such as backplanes rather than assembled systems.

However PXI enters production in the medical industry, though, developers face the same regulatory challenge: required controls on the design and manufacture of their products. In the US, the FDA's (Food and Drug Administration's) regulations on this control appear in the Code of Federal Regulations, Title 21 (21 CFR), part 820. Further, once the design is complete, it must receive certification from the FDA and cannot change without notification to—and in some cases recertification by—the FDA.

This requirement for control and certification creates challenges for medical-device designers using off-the-shelf modules and software such as PXI products. The solution involves help from the PXI vendor. Certification is the medical device developer's responsibility, but the vendor can help by supplying complete information on the design and manufacture of its products to streamline the certification process. By designing, building, and testing its products in conformance to industry standards, a vendor also helps ease the subsequent certification efforts of its medical customers.

Because the manufacture of medical products requires tight controls, PXI vendors should provide medical instrumentation customers with advance notice of changes to their hardware. This notification allows those customers to inform the FDA and to anticipate that a product might require recertification. Another option is for the vendor to set aside parts to continue building the original version for the medical customer when a design changes, such as for an upgrade in processor. Vendors could also offer customers lifetime buys of products that will undergo substantial change or will be removed from the market.

Developers interested in applying PXI to the medical field can gain insight into the impact of this choice by reading the FDA's guidance on the use of off-the-shelf software (Ref. 2). The developer's best help, however, will come from working with a vendor experienced in applying PXI to medical care.

REFERENCES
1. "Prototyping and Deploying a Neurosurgery Training Device Using NI LabVIEW, R Series, and Embedded Hardware," application note, National Instruments. sine.ni.com/cs/app/doc/p/id/cs-12572.
2. "Off-The-Shelf Software Use in Medical Devices," US Food and Drug Administration, September 9, 1999. www.fda.gov.