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CT compatible needle positioning system

 

The usual therapy for combatting liver cancer is to remove the liver tumour surgically. Inevitably this intervention also removes a lot of healthy liver tissue because of the complexity of the procedure. An alternative method is to ablate (or burn away) the tumour with radio frequency or microwave radiation. In this local therapy, the surgeon inserts a needle through the skin and into the tumour manually, using the images in a CT scanner. The advantages of this procedure are that a major operation is unnecessary, and very little healthy liver tissue is damaged. A disadvantage is that it is difficult for the surgeon to position the needle correctly in the tumour in one attempt. It generally needs several repetitions: insert the needle, produce a CT scan, reorientate and reintroduce the needle etc., until the right position has been achieved. This makes the procedure time-consuming and onerous for the patient.

https://www.demcon.nl/wp-content/uploads/2016/04/Demcon_needle_positioning_2015-06-30.mp4

Dozens of solutions to this problem have already been implemented worldwide, from simple tools through to a robot which introduces the needle entirely automatically. In practice however most doctors still do it manually, because these systems are awkward to use and/or they don’t do their job well. In a European research project with partners like Philips and Nucletron, DEMCON spotted an opportunity for an approach which positions the needle correctly at the first attempt, and which fits well in the doctor’s workflow. In developing this patient and doctor-friendly solution, DEMCON worked closely alongside specialists from the University Medical Center Groningen and the Erasmus MC in Rotterdam.

The starting point was to retain the current workflow as closely as possible, and only to automate the step which is critical for the speed and result (‘first time right’) of the procedure. The critical step is determining the angle at which the needle enters the body. DEMCON developed a system comprising a head with a needle-guidance mechanism which can be positioned around the patient manually, and an arm which secures the head in relation to the operating table with one press of a button. Once the system has been positioned around the patient, it accompanies the patient into the CT scanner. The position of the patient’s tumour in relation to the head is established in this way, and the system automatically steers the needle-guidance mechanism to assign it the required direction. The needle is then clamped into the guidance mechanism and is inserted into the body by the doctor himself.

The design threw up a range of challenges for DEMCON’s developers. The system architecture, for one, based on the current medical workflow, had to produce as few barriers as possible to being used by the doctor, both literally and figuratively. A second challenge was the design factor. The system of arm + head had to fit in the (tight) space between the patient and the CT scanner’s ring. However the biggest hurdle was CT compatibility. The bulk of the system would enter the scanner’s X-ray field, but should not disrupt the imaging. That meant the usual materials like steel, copper and titanium could not be used.

DEMCON worked with several suppliers including Ceratec (ceramics) and Futura Composites to develop alternatives. A variety of materials were used in the components, such as composites (for rigid construction parts and flexible elements), ceramics (for highly-stressed precision parts and ball bearings), Dyneema fibres (for rotating cable drives), carbon nanotubes (for power wires and switches) and plastic optic fibres (to read out encoder positions remotely).

These solutions imparted high rigidity to the construction, reducing any transmission play to a minimum. The result is a system which can guide the needle correctly and precisely, with a margin of error of less than 2 mm at a depth of 25 cm. The added value of the system has also been clinically demonstrated in collaboration with the UMCG. This means the patient suffers only minimal tissue damage, the medical team can complete the procedure more quickly (and thus more economically), and the doctor remains ‘in control’.

 

 

 

Nikki Tahapary
"Multiple material innovations"

Our view was that we wanted to change as little as possible in the way the doctor currently positions a needle, and that we only wanted to help him with this one critical task. We first explored the current solutions, and learned how not to do it from these attempts. We then elaborated on the current, manual workflow.

What is unique about this system is that it looks simple on the outside, and that operating it is extremely easy, even though its development took a great deal of time and effort. Particularly from a mechanical aspect, it’s a complicated device. Central to the design process were the multiple material innovations needed to make the system CT-compatible.

The device had to do exactly what the user needed, and no more. As mechatronic engineers we could of course have added a drive to insert the needle. But it was this responsible job in particular which we wanted to leave to the doctor, who can sense as he goes along just which tissues the needle is penetrating and when he has reached the tumour. Most surgeons still want to exercise this degree of control themselves, and that’s why the system doesn’t introduce any unnecessary intervention in the current workflow and the doctor’s responsibilities. This means the system can quickly be accepted into practice, so that this approach yields a cost-effective system immediately.

To gain good acceptance it was also important that the design should become a serious product immediately, and that its appearance would match the level of the CT scanner in which it is applied. Given the costs of the components, we worked in accordance with the ‘first time right’ concept, and succeeded!

Nikki Tahapary
Mechatronic System Engineer

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About Demcon

Demcon is a high-end technology supplier of products and systems. In a world in which technology increasingly plays a role in solving contemporary social issues, Demcon supports clients with a wide range of competencies. As a system supplier, Demcon can meet the entire needs of its clients, from initial idea and concept, to prototyping, industrialization and (series) production. In addition, Demcon develops its own products and, through an innovation program, investments are made in both start-ups and established companies. Demcon is certified for ISO 9001:2015 and ISO 13485:2016.

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