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.
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. 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’.