Extrusions and ball screw actuators help save medical costs

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Bosch Rexroth's MGE aluminium profile range and a CKK linear ball screw actuator have been used by Northern Ireland Regional Medical Physics Department to build six mobile diabetic retinopathy-screening units.

Diabetic retinopathy is the leading cause of blindness and visual impairment in adults in developed societies. A Government initiative in 1990 led to the funding of regional services where screening for this condition could be carried out in church halls and schools rather than in hospitals. Before the regional service was implemented, patients had to travel great distances to hospitals and patients were simply not turning up for their appointments. This is particularly bad news in the case of diabetic retinopathy, as the disease can take hold very rapidly and providing an effective cure at this point is very difficult. However, if the symptoms are detected early, via retinal photoscanning, then the patient can be treated effectively and the disease's progress halted.

The implementation of a mobile regional service helps to solve the problem of patients missing appointments by taking the service to a location near to them; this has the effect of improving attendance. However, there were problems being encountered by the mobile teams, which led to the process being re-evaluated. One of these problems was the sensitivity of the equipment. Retinal photoscanning requires a high-quality camera to capture an image of the patient's eye and these cameras are not designed to be transported.

There is also a good deal of computer hardware needed in the process. Once the camera takes an image, the operative then checks it. This operative is not checking for medical conditions, just the quality of the image. As a mobile scanning unit can be out in the field for a number of days, many hundreds of images can be taken, so a good quality screen and hard drive are needed. Another problem was that the equipment was bulky and had to be manhandled by two people on trolleys, often up inclines. This itself led to cost and time issues. Theft was also a concern, with so much valuable equipment being moved; inevitably at times some equipment was left unattended and was open to being stolen.

A solution was needed that would offer the mobile scanning teams camera position adjustment, ease of transport, computer hardware integration, security and ease of mobility. This was the problem presented to David O'Donnell and Craig Gill, the medical technical officers based at the newly built Cancer Centre at Belfast City Hospital. Other challenges were that the mobile scanning unit should be aesthetically pleasing and easy to clean.

Facing the challenge

Once David and Craig had been given the project they considered all available options. One was a commercially manufactured mobile scanning unit, but neither of the officers was convinced about its robustness.

The unit needed to be robust mainly due to the transportation process that involves it being placed on a tail lift and then in the back of a van. Once in the van, the unit is obviously subject to the vibrations and sudden movements that come with road transportation. David and Craig considered the commercial unit to be too fragile to withstand this method of transport in the long term.

Having decided to design and construct the mobile scanning unit themselves, David and Craig then had to consider the limitations of their own facilities, as Craig explains: "We were looking for a material that we could cut and build in our small workshop. Having used Rexroth equipment in a previous project, when we came to the design and build of this unit we both knew straight away what material we wanted to use."

MGE – Modular profile assembly system

Bosch Rexroth's MGE modular profile assembly system is applicable to virtually all tasks: frames, enclosures, special and series machinery, ESD-capable systems, etc. Rexroth helped to select the most economical components that were then delivered from the local warehouse. This was an important point at the Belfast City Hospital, as storage space for stock is very limited, so the ability to quickly order materials was vital.

Although not used in this instance, Bosch Rexroth offers a free-of-charge 'FM Soft' software package that allows users to plan quickly and efficiently in 3D.

CKK linear ball screw actuator

In addition to the MGE system, Bosch Rexroth's CKK linear ball screw actuator was used as part of a cantilever system to support the photo imaging technology while not attaching to the far profile. The CKK linear ball screw provides the smooth motion that the unit requires in order to make the small adjustments necessary for the operator when taking a picture of a patient's eye. The cantilever supports the equipment and the linear actuator allows the imaging equipment to be lowered into the main body of the unit and stored safely. David O'Donnell says: "As a prototyping system, the MGE material is brilliant. The whole product has been designed around the linear actuator and the shelf."

One very important aspect of the MGE modular profile assembly system is its looks. Craig Gill says: "This equipment has to be taken out into the community and so it has to look the part. The finish of the unit is excellent; for example, the radial corners give it a smoother look and then there is also the practical advantage of not catching on edges."

The first version of the mobile scanning unit was completed in 2005 but David and Craig have used their own experience and end-user feedback to slightly modify the design in subsequent models. The second unit had an additional platform for the computer operator's mouse to sit on and the third version will incorporate a wheelchair motor. David says: "The idea now is that an eight-stone person should be able to manoeuvre the scanning unit with no trouble on their own."

Cost savings

Despite these modifications to the original design, the mobile units are still being produced at around the same cost as the commercially available version. However, one area where Bosch Rexroth's technology has allowed the Belfast City Hospital Trust to make considerable cost savings against other Trusts is in the transportation of the unit. David and Craig have designed and built a docking station inside the vans that simply locks around the two large wheels on the unit. This is made possible by the robustness of the products. In contrast, other areas have had to have the vans converted to accommodate their more sensitive cargo at the cost of many thousands of pounds.

Due to their positive experience with Bosch Rexroth technology and the service and support provided, the NI Regional Medical Physics Agency has also been spotting other potential applications in the hospital. One example was a guarding application on a radiotherapy machine. A bespoke system was going to cost the hospital around £20,000 until David and Craig built their own system using Bosch Rexroth linear slides at not even one-quarter of the cost.

David and Craig have, at this point, delivered three of the six mobile scanning units that have been commissioned. This task is keeping them very busy, as it takes around forty hours to build one unit and, inevitably, being part of a small department, they get diverted onto other tasks. Despite this, their problem-solving aptitude and the other opportunities for Bosch Rexroth technology in the hospital are beginning to be noticed. David says: "We have to build practical items very quickly and the MGE system is perfect for this. We [David and Craig] are hoping that such overt and practical solutions will lead to us being given many more such projects, thus saving the hospital valuable resources."

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