X-Ray Technology in Medical Device Manufacturing
29 July 2010
X-ray screening to inspect the quality of products has been instrumental in ensuring the safety and efficacy of medical devices. As devices become more sophisticated and complex, the capabilities of X-ray technology continue to advance.
Finding internal faults
Traditionally, in the wider medical sector, X-rays have been used for straightforward tasks such as simple presence or absence testing in blister packs and other medical supplies. However, the main application for X-rays in the medical device sector is testing for latent faults. Whether a device works from a purely functional point of view can be easily tested at the end of the production line. Whether that device has been manufactured to remain functional for the period of its designed life may only be validated with X-rays. The components, objects or systems are often opaque, or products need to be examined internally in a way that would be impossible with the naked eye or visible light inspection systems. For example, without X-rays it would be impossible to see faults such as short fills in the plastic components within a device, which may cause complications long after it has left the factory.
Seeing fine detail faster
However, as manufacturing processes have improved and accelerated, so X-ray inspection has had to keep pace. In the medical device sector this is particularly challenging because it is an industry where sample testing is usually an inadequate measure. Wherever possible it is clearly better to perform 100% inspection of all the devices that come off the production line to ensure that no faulty component ever reaches the end user. Thus, in recent years the ability to see finer detail faster has led to significant advances in X-ray technology.
Systems capable of taking more than 30 measurements with resolutions of better than 100 micron in two or three seconds are now achievable. For example, a system originally developed for battery inspection can measure the position of multiple complex features in a device to ensure no latent faults are present. It can accurately measure internal linear distances, alignments, the quality of internal electrical contacts, short circuits and misaligned components. With a rotational and translation stage incorporated, 360 degree inspection of a device can take place in seconds.
X-ray detector technology has improved dramatically and there are now completely new ways of acquiring images that did not exist before. These include high resolution full field and linear detector arrays that use
PIN photodiodes, typically in the 200 micron pixel pitch range
amorphous silicon or, more recently, amorphous selenium, typically in the 100 micron pixel pitch range
charge-coupled device (CCD) X-ray detectors, typically in the 20 micron pixel pitch range.
Even in well-established X-ray techniques such as line or area scan imaging, there have been improvements in advanced digital processing techniques. For example, time delay integration is a technique in which the CCD detector readout electronics helps to compensate for the motion of an object. Typically used in computer tomography scanners, in-line X-ray inspection and sorting systems, it provides high speed and high sensitivity.
Sensor materials have led to higher performance and more sensitive detectors, but almost as important have been the rapid improvements in processing power available to X-ray engineers. To achieve in-line inspection it is not only necessary to acquire the data, but also to process that data and make an informed decision such as a simple yes/no or a more complex measurement that is sent to the statistical process control software. The increased amount of processing power available to X-ray scanners has accelerated the data analysis phase of X-ray screening. This has opened up new avenues for X-ray
specialists to explore such as the integration of advanced, high speed, in-line inspection systems into production lines. Systems such as the one descrbed above can now be placed on a production line to perform inspection. In addition, the continuing popularity of X-ray technology in the broader healthcare and security sectors has helped to drive down costs for developing and manufacturing X-ray technology.
Medical device manufacturers have also been asking for improvements because of a growing regulatory push on manufacturing processes. A paper based quality system is no longer necessarily seen as completely acceptable for the certification of a device. Manufacturers have to prove the efficacy of their entire manufacturing process to regulators and as a result physical testing is again experiencing a major resurgence.
In less highly regulated sectors, if a fault develops during manufacture, companies would simply change the manufacturing process to prevent that fault occurring again, and it is common to see many minor adjustments being made to a production line to optimise manufacture. However, for medical device manufacturers a change to the manufacturing process may require new regulatory approval that would involve delays to manufacturing and incur a large cost. Consequently, medical device manufacturers often increase inspection as the most cost-effective solution to protect the end user.
Help with increasing complexity
X-ray testing not only helps manufacturers monitor and control their production facility by reducing waste and scrapage, but also provides the benefits of maintaining customer confidence in products and significantly reduces the corporate risk of faulty products reaching the marketplace. More recently, these manufacturing concerns have combined with increasingly complex medical devices to result in an increase in the use of X-ray screening to perform more detailed checks. For example, inhalers are becoming more intricate in their design, moving away from simple push-button release valves to sophisticated measured dose delivery systems that may even incorporate microelectromechanical systems (MEMS) components.
FIGURE 1: Inhaler scan. More parts and more challenging designs increase the chances of latent faults.
With more parts and more challenging designs, there is always the increased chance of devices being manufactured with latent faults. This has led to X-rays being deployed to accurately measure elements inside devices to ensure, for example that the right components are present, that they are the correct size and shape and positioned correctly. Even with simple items such as lancets (Figure 2), there is scope for needles to be misaligned or positioned wrongly, thereby presenting hazards to the clinician and patient.
X-rays can also be used as an efficient means to ensure that devices have been packaged correctly. This is particularly useful when a device is not one solid item, but made up of several component parts, and their use can confirm that the patient instructions have been included. The improvements in processing power and detector technology X-ray screening mean that is it possible to perform these checks quickly and accurately, without holding up the production line. Depending on the equipment deployed, this can take as little as a few seconds.
FIGURE 2: Even simple items such as a lancet can have serious faults.
The technology keeps pace
The trend of increasing device complexity and the complicated inspection requirements that result, is set to continue into the future. The incorporation of MEMs technology into devices to meet the needs of the end user requires ever more sophisticated test and quality regimes to ensure that the devices that end up with clinicians and patients are safe, reliable and effective. As these design trends develop and grow, so X-ray technology has to keep pace to enable the medical device sector’s manufacturing capability to progress safely.
is Chief Technology Officer at
Units 16 and 18, Hayhill Industrial Estate
Barrow-upon-Soar LE12 8LD, UK
tel. +44 1509 817 400
Published in European Medical Device Technology, March 2010, Volume 1, No. 3