TPi November 2013

smal l diameter, high precision tubes

Ultra-fine tubing in medical applications The driving force behind the increasing miniaturisation of medical devices is to make surgery, including exploratory procedures, less invasive.

As science and industry continue to miniaturise instruments, procedures that were once considered futuristic are becoming more accessible and affordable, ranging from tiny X-ray systems used for exploration of brain tissue to radioactive ‘seeds’ used to treat prostate cancer. An integral item that helps facilitate the use of miniaturised medical devices is the metal tube through which the devices pass, and that performs vital associated tasks such as aspiration, cleanout of debris, and injection of fluids such as medication. Composed of medical-grade metal in sizes commonly as thin as a pin, these tubes are used for a wide assortment of miniature medical procedures ranging from ultra-fine catheters to minuscule implants. “While these slender tubes are probably considered ancillary to many miniaturised medical applications they have certainly facilitated them,” said Lance Heft, CEO of International Tube. “Yet this is a highly specialised area that requires both sophisticated metallurgical expertise as well as unique fabrication skills. Those capabilities are necessary not only to produce custom products while avoiding unnecessary costs, but the key requirement is to eliminate any possibility of failure during use.” Mr Heft says that when designing and fabricating tubing for medical applications – especially the miniature ones – it is vital to be able to draw the necessary material to the required diameter. Perhaps more importantly, the tube must have an even, smooth ID. Specialised shapes may be essential, requiring swaging, flaring or threading a portion of a tube, or making it a one- piece component. For example, International Tube was involved in the development of a radioactive ‘seed’ used in the localised treatment of tumours in prostate cancer cases. Known as brachytherapy, the treatment requires the manufacture of very small titanium tubes that are similar to a pinhead in size and shape.

Medical instruments are becoming increasingly miniaturised

manufacturer got reports that the fibres were occasionally getting snagged in the tubes. This snagging sometimes resulted in metal-to-metal contact, which produced distressing shocks to the surgical patients. “Of course, this snagging problem was very disconcerting to the medical device manufacturer,” said Mr Heft. “They were concerned about any possibility of patient discomfort as well as the performance of their fibre optic equipment. The problem was that the tube ID surface was not smooth enough for this virtually micro- level application. So our engineers analysed the requirements and designed an ultra-smooth interior tube surface. The new tube design not only solved the snagging and shorting problems, but also saved the manufacturer almost 50 per cent on expenditures for replacement fibre optics.” If the tube application is aspirating or clearing a surgical area, the performance is going to depend on the smooth operation of the tube. If the tube ID does not support the operation, it can collapse or congest, causing debris, tools or medication passing through it to deflect or get trapped.

“Essentially, the fabrication of the seeds requires that a titanium tube that is about four pin-heads thick be welded closed on one end,” Mr Heft explained. “A radioactive isotope is placed into the enclosure, which is then closed at the open end. Depending on the treatment requirements, up to 100 tiny seeds are inserted into or near the prostate tumour. The radiation seeps through the metal, into the cancerous tissue next to the seeds.” Mr Heft says his firm provided the seed ‘hulls’ for one of the first suppliers of radioactive seeds used for prostate cancer. He was involved with the design and assisted with multiple FDA trials and approvals, using multiple sizes of tubing until the final design was accomplished. At that point, International Tube began fabricating 250,000 seed tubes at a time, which required the use of about 1,000ft of very narrow titanium tubing. Mr Heft emphasised the need for a smooth, clean ID with very low RMS (roughness) readings for many micro medical applications. His firm was called on to improve the safety in small- diameter tubes used for insertion of the fibre optic cameras used in microsurgery applications. Due to the delicate and pliable nature of fibre optics, the device

International Tube – USA info@internationaltube.com www.internationaltube.com

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Tube Products International November 2013

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