Minimally Invasive Surgery Places New Demands on Testing and Inspection Equipment

Originally Published MPMN April 2007

PRODUCT UPDATE

Minimally Invasive Surgery Places New Demands on Testing and Inspection Equipment

As minimally invasive cardiac procedures continue to gain popularity, use of testing and inspection equipment catering to the devices is emerging

As the leading cause of death in the United States, heart disease poses an enormous threat to the general population and remains a major concern of the medical industry. In fact, the American Heart Association estimates that in 2004, more than 79 million people suffered from one or more forms of cardiovascular disease. Although statistics remain grim, researchers have made headway in the treatment of heart disease over the years, most notably in the practice of minimally invasive surgery. Minimally invasive cardiac procedures typically result in less trauma to the patient’s body and quicker recovery times than open-heart surgery.

The rising preference for minimally invasive cardiac surgeries has produced a larger market for such devices as catheters, balloons, and stents. However, the demand for these devices has also generated an expanding market dedicated to the rigorous testing and inspection of these critical products. This article examines testing and inspection equipment used for devices employed in minimally invasive cardiac procedures. A Buyers Guide highlighting suppliers of testing and inspection equipment and services for a broad range of applications follows on page 42.

Stent Coating Test System

More than a million angioplasties were performed in the United States in 2004, according to the American Heart Association. Owing to the increasing turn to angioplasty over traditional open-heart surgery, the medical industry has witnessed a subsequent growing demand for quality stents, which are used in the procedure. As a result, more-effective and more-accurate stent-testing methods are required.

The second-generation Coating Durability Tester (CDT) offered by Dynatek dalta (Galena, MO) simulates real-life conditions when conducting durability testing on drug-eluting and other coated stents. The system creates a pulsating test environment that allows the stent to expand and contract as it would in the body. In turn, the system can accurately evaluate particulate loss and durability in real time, according to the company.

The precise time period in which the particles are shed, as well as the size and number of shed particles, are provided. Operators can set parameters, which consist of selecting the size of particles to be detected and opting to group the particles by size range. Capable of testing up to five samples at once, the product has a particle size range from 4 to 250 µm and a particle count range from 4 to 1000. The CDT is equipped with a bypass filtration system that removes the filters without affecting the test. This updated model also allows for a range of sample lengths and diameters, as well as for complicated sample designs.

Peripheral Artery Stent Test Instrument

Peripheral artery disease is the most common type of peripheral vascular disease and affects up to 12 million Americans, according to the American Heart Association. Stents deployed in these areas experience a great deal of stress and strain, owing to peripheral arteries’ tendencies to bend, stretch, and twist more than other arteries. Because of the complex loading that stents undergo in peripheral arteries, it is imperative that testing applications aptly simulate actual in vivo conditions.

Responding to this need, Bose Corp., ElectroForce Systems Group (Eden Prairie, MN) has developed a multiaxis test instrument designed specifically for stents used in the peripheral arteries, which include the renal, carotid, and femoral-popliteal arteries. The system can combine dynamic bending, rotation, extension and compression, and radial distension on multiple stents under controlled conditions. Moreover, the instrument can also conduct an accelerated 10-year durability test in an estimated 90–120 days for stents used in the superficial femoral or carotid artery, or 135–180 days for stents used in the renal artery.

Noncontact Thickness Measurement System

Along with stents, devices such as catheters and balloons are often used in cardiac minimally invasive surgical procedures. Lumetrics (Rochester, NY) licensed a thin-film measurement technology from Eastman Kodak to create the OptiGauge precision thickness measurement system. In collaboration with Advanced Polymers Inc. (Salem, NH), Lumetrics has applied its technology to develop an automated catheter and balloon measurement system, which measures catheters and the cones of balloons in a noncontact, nondestructive manner.

To measure the thickness of angioplasty balloon walls, a person would traditionally collapse them and use a pincher gauge, then divide the measurement in half. However, this method can yield inaccurate results because the two walls may not have the same thickness, according to the company. Moreover, such physical measurement procedures can also produce inaccuracies due to pressure on the plastic that causes compression.

Using the firm’s nondestructive system, engineers don’t need to cut or collapse the walls of the devices in order to obtain measurements. The technology allows users to rotate a balloon and measure its thickness down to 12 µm. It is also capable of measuring multiple-layer materials, such as tubing. The upper wall, lower wall, and inside diameter of tubes with diameters smaller than 8 mm can be measured.

Vision System

Catheters, stents, and tubing are among the noncontact measurement applications to which the Galileo EZ, offered by the L.S. Starrett Co. (Athol, MA), lends itself. Featuring live video camera feed and automatic edge detection, the compact manual vision system is suited for quality assurance inspection and measurement applications.

Video edge detection automatically detects and targets edge points by scanning the image area within a circle around the crosshairs on the display. The vision system has a precision mechanical bearing with an x-y-z measuring stage of 8 × 4 × 6 in., plus 6-to-1 zoom video optics and dual-output 150-W fiber-optic illumination for the fiber-optic ring and collimated substage light. In addition, the system has an accuracy of E1=2.5+7L/100 and x-y resolution of 0.00002 in. Engineered to support a workload of up to 20 lb, the system is available with such options as 1¼2 to 2× auxiliary lenses, 150-mm line standard for system calibration verification, coaxial illumination, and a three-light illuminator.

The system is equipped with the Metronics QC300 digital readout, which displays x-y-z digital readout display and measurement data; however, it is also compatible with the industry-standard QC200 readout system.

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