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Medical LAN cards Achieving Compliance in Network Connections

13/06/2011


Manufacturers of medical technology or IT vendors integrating applications into hospital network environments are faced with the problem of having to supply network connections that are suitable for medical devices. That is no easy job if expensive and risky external insulators are to be avoided. Claus Giebert of Kontron describes how a new IEC60601-1 compliant LAN card makes it possible to replace the existing costly and risky tandem approach of standard LAN card and external insulator.

Networks in hospitals, rehabilitation centres and medical practices are constantly expanding and taking on more and more devices. The aim is to improve efficiency in the whole clinic process by means of integrated systems and increased communication. For example, X-ray pictures can be transmitted to desktop PCs and smartphones, information from hundreds of sensors and actuators at the point-of-care can be accessed by workstations on the hospital wards, and data from operations is stored on central servers for documentation purposes. Even the patient emergency call will in future be run over the network. There is literally hardly any application, and certainly not any undergoing current development, that is destined to be operated on a stand-alone basis. The IT backbone is Ethernet-based, or wireless connections are used for mobile peripherals. That explains why an increasingly colourful jumble of conventional IT and medical technology devices is currently "at large" in hospitals.

Protection in both directions is needed

Two cases need special attention when this type of hybrid networking is addressed:

-There are normal IT systems, i.e. central servers of workplace PCs, which generally do not conform to the leakage current standards for medical devices. Medical device networks have to be protected from leakage current "infections" via these devices.

-Medical devices with a network connection have to be protected from insecure networks.
 
The established practice is that insulators are inserted between the device and the network to protect the medical device from the network or vice versa the medical network from the simple IT system. This is an effective solution, but often one with unexpectedly high costs. More than anything this solution is quite fault-prone: if for whatever reason the insulator is forgotten between the network and the device then all protection fails. There is practically no possibility to check whether a clip-on insulator has been implemented or not in the infrastructure. Thus the more cost-efficient and secure solution is for the network connection of the medical device or IT system to be protected right from the word go.

IEC60601-1 conforming network connection

When a network connection is being designed IEC60601-1 and IEC60602-XX standards have to be adhered to ‚€" as also applies to the whole system. For example, medical technology devices have to ensure protection for the operation against 1500 volt by one Means of Operator Protection (MOOP) or against 2500 volt by two MOOPs. Two MOOPs are always necessary when the medical device is connected to a patient and a user interface is available for the doctor, attendant or patient. That is basically always the case for integrated devices with PC technology. Conventional LAN cards, however, according to IT EN 60950-1 are only guaranteed to protect against up to 1500 volt. Therefore, they do not meet the requirements of the medical environment. A LAN interface design that is suitable for medical devices is mandatory. When selecting the right components the list of requirements that have to be fulfilled is a long one.

Closed adapter connection

The physical connection of the Ethernet connector must have a closed housing. This is imperative because the wiring that lies between the connector and the PCB has to be dust- and dirt-proof. A large range of this type of coupler is available. However only a very small number of manufacturers guarantee the dust-proof qualities of the coupler's housing. If standard couplers are taken apart, it becomes apparent why they cannot withstand overvoltage of 2500 volt. They are not long-term dust-proof and also the whole construction of the coupler is not designed to cope with 2500 volt as can be seen on the windings and solderings (Figure 1). An Ethernet coupler that is apparently encapsulated is in no way a guarantee of long-term secure insulation.






Figure 1: Normal Ethernet couplers are not dust-proof and cannot withstand voltage peaks of 2500 volt in the long run








Distance of the solder contacts to the screen

To guarantee secure insulation to the board IEC60601-1 states that the distance of the insulation (grounding) to the signal line to avoid leakage current in the air should be 4 mm and on a PCB mm. Today, most Ethernet couplers with metallic shielding only have a pin distance of about 2 mm. In addition it must be noted that it is not a question of the distance of the pins from centre to the centre, but the pin distance between the edges of the respective solder contacts and the edges of the PCB tracks. The pin distance between insulation and signal line itself has to be significantly larger than 4 mm. But due to increasing miniaturisation and SMT mounting of the layouts these distances are no longer available.

No coupler with the front panel

It does not suffice to use a closed, dust-resistant coupler. The coupler has to be insulated from the
front panel of the component group. For this reason common couplers that end immediately at the front panel are not suitable because they cannot comply with the required 6 mm (PCB) or 4 mm (air) (Figure 2). Consequently, a coupler that protrudes out of the front panel must be used in order to adhere to the required distance. This also applies to the Ethernet transformer. Most currently available Ethernet transformers only have a distance of 5 mm from pad to pad due to the small form factors (SFF) trends. But 6 mm is still the required distance. Therefore, a suitable transformer has to be designed-in.



Figure 2: 6 mm is the required distance from the edges of the insulation/grounding to the signal lines; most components on standard LAN cards such as couplers and transformers are built with a smaller pin distance







Ethernet plug connectors without LEDs

Another feature of Ethernet interfaces that is unsuitable for IEC60601-1 compliance is the LED status display of the Ethernet connection as it is built into nearly all Ethernet interfaces, at least when the LEDs have to be integrated in the coupler. This has to do with the physical size of couplers. Why? For cost purposes LEDs are galvanically coupled with the component group's grounding. Because these do not comply with the distance required to the signal leading lines you can recognise IEC60601-1 compliant Ethernet interfaces by, amongst other things, the fact that there are no LEDs on the connector itself. These few but essential features are important for a design-in and should not pose too large a problem.

However, that is not the end of the list of requirements. The construction of the coupler affects the design of the transformer. The PHY configuration also has to be adapted, which would require access to the PHY chip manufacturer's NDA documents. These necessary alterations have, in turn, influence on the range of use, which has to be kept at 100 meters to comply with the Ethernet specification. Any changes made to the card have an influence on the component group's shielding, which again affects ESD and EMC tests, so that producing a medical LAN card from a standard Ethernet card is in no way a straight forward issue.

Although the requirements in terms of design are relatively easy to master, additional costs for certifications must be taken into consideration. Laboratory costs for tests can be calculated at approximately 15,000 euro; for certificates such as UL listing around 3000 euro; and for full CE certification they are around 5000 euro. All in all approximately 18 000 euro must be additionally invested just for exchanging the coupler and the transceiver in comparison to a "normal" LAN card. Thus, it comes as no surprise that a large number of medical devices and IT systems are still employing standard LAN cards and using external insulators: this approach presents no initial costs because these investments have to date not been made by any manufacturers. Now that the Kontron PCIe Medical LAN Card (Figure 3) has become available it is possible to replace this relatively pricey tandem consisting of a standard LAN card and external insulator with an IEC60601-1 compliant component group, which also increases the level of operational safety as unsafe network connections are eliminated.


Figure 3: Pad to pad distance on the Kontron Medical LAN Card is > 6 mm with no conducting paths running through; the design of the PCB of the LAN card allows for one or two Ethernet interfaces; on the right the pads for the transceiver of the second interface are visible









Kontron PCIe medical LAN card

Application areas for the IEC60601-1 compliant PCIe Gigabit Ethernet card are clinics, rehabilitation centres, medical practices and any scenario where medical devices have to be integrated into a network with conventional desktop PCs or high availability archiving, backup or storage solutions. The PCIe 2.0 compliant PCIe Medical LAN Card has been designed to fit into any PCI Express x1 compatible card slot. Slot brackets for full height or low profile mounting are included in the delivery. The card has one or two insulated Ethernet 1000Base-T interfaces via RJ45 connectors. Both versions are based on the Intel 82574L GbE controller, which guarantees high compatibility and high transfer rates. If a card with two Ethernet interfaces is chosen, users need no longer worry about which coupler has the insecure network connection and which has the secure one, because both are secure (Figure 4).



Figure 4: The status LEDs are separated from the coupler to keep the required distance; the coupler has no metal shielding and protrudes out of the front panel









Kontron offers the PCIe Medical LAN Card together with support for all Windows operating systems starting from Windows XP/Windows 2000 and from Linux kernel 2.4.18.


Claus Giebert is Business Development Manager at Kontron,
www.kontron.com



   

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