Ultra-Fine Tubing Smoothes the Way for Miniaturized Medical Devices
Mini medical instruments require highly specialized metal tubing and innovative suppliers with ultra-fine finishing capabilities
The increased miniaturization of medical devices such as surgical instruments and imaging tools continues to proliferate, paying off in many ways. The driving force behind this development, which began several decades ago, is to make surgery, including exploratory procedures, less invasive.
Today, as science and industry continue to miniaturize instruments, procedures that were once considered futuristic are now 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.
One of the integral items that have helped to facilitate the use of miniaturized medical devices has been the metal tube through which these devices pass, and that perform vital associated tasks such as aspiration, the cleanout of debris, and injection of fluids such as medications.
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 miniscule implants.
"While these small metal tubes are probably considered ancillary to many miniaturized medical applications, they have certainly facilitated them," says Lance Heft, CEO of International Tube (Pottstown, PA). "Yet this is a highly specialized 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."
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 needed diameter. Perhaps more important, the tube must have an even, smooth ID. Also, specialized shapes may be essential, requiring swaging, flaring or threading a portion of a tube, or making a one-piece component to avoid field failure.
For example, International Tube was involved in the development of a radioactive "seed" used in the localized treatment of tumors 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.
"Essentially, the fabrication of the seeds requires that a titanium tube that is about four pin-heads thick be welded closed on one end," Heft explains. "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 tumor. The radiation seeps through the metal, into the cancerous tissue next to the seeds."
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 final design was accomplished. At that point, International Tube began fabricating 250,000 seed tubes at a time, which required the use of merely about 1,000 ft. of tight tolerance small diameter titanium tubing.
Heft emphasizes 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 fiber optic cameras used in microsurgery applications. Due to the delicate and pliable nature of fiber optics, the device manufacturer got reports that the fibers were occasionally getting snagged in the tubes. Worse yet, this snagging sometimes resulted 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," Heft says. "They were very concerned about any possibility of patient discomfort as well as the performance of their fiber optic equipment."
"The problem was that the tube ID surface was not smooth enough for this virtually micro-level application," he explains. "So our engineers analyzed the requirements and designed an ultra-smooth and ultra clean interior tube surface. The new tube design not only solved the snagging and shorting problems, but also saved the manufacturer almost 50 percent on expenditures for replacement fiber optics."
Heft cautions that 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 or tools or medication passing through it to deflect or get trapped.
Heft adds that International Tube also worked with customer engineers to develop its Ultra Clean tube line to facilitate microsurgery applications that include the removal of debris during surgery. The smoothness ensures that tissue and tool debris created during procedures will no longer tend to collect in clean-out tubes, thereby reducing the need to clear or change tubes during operations.
Achieving an ultra-smooth tubing ID as small as 0.009 in. is no simple feat. Heft's mill developed a proprietary "floating plug" design to continuously smooth the ID of tubes as they are drawn.
Even the lubrication used in the fabricating of the tube can affect performance. The right lubricant may be vital to the manufacturing of the tube to give it the smooth ID. Often this super smooth ID is a requirement to facilitate the passage of a medical device or component such as a stent, seed, or even a balloon. Yet it's essential that the lubricant used does not interfere or interact with a medicine or chemical that is dispensed through the tube. "Challenges that occur small diameter, tight tolerance tubing are not even considered in larger sizes", Heft states. Many variables are required to be resolved before a tube is ready for use in a device, partnering with a tube mill that is highly specialized in this area of manufacture is key.
International Tube is a specialty metal tubing and fabrication company supplying the medical, electronic and industrial markets with high quality products and personalized service in combination with cost-effective solutions.
For additional information please contact info@internationaltube.com
