Using NI PXI and SCXI hardware to build a test system for medical stents

Author(s):
Dave Weisberg - Cal-Bay Systems

Industry:
Biotechnology

Products:
LabVIEW, Signal Conditioning, PXI/CompactPCI

The Challenge:
Provide a medical device manufacturer with an automated production test system for analyzing medical stents (a device placed inside an artery to support the vessel wall) and increase test throughput by 10 times.

The Solution:
By simulating the movement of a vascular stent when implanted in the human body and measuring its expansion characteristics, an automated testing system was established that can test 30 vascular stents simultaneously.

The medical field is changing rapidly, and the pace of medical research and development is advancing rapidly. The use of various devices implanted in the human body to assist in functioning or maintaining life is increasing. For patients with aneurysms, the arterial walls become weak and prone to rupture. There is currently an arterial wall device used for patients with aneurysms. It is very effective, but how can this device be inserted into the artery (some arteries are only the diameter of a coin) without interfering with sensitive areas and causing the aneurysm to rupture prematurely?

A device called a stent can support an artery weakened by an aneurysm. A stent is a small, compressed, supercooled spring that is inserted into the artery from a convenient location, usually the inner thigh. The stent is then passed through the artery and expanded to the appropriate diameter to support the artery wall. Stents must meet strict product specifications and expand to the appropriate size at the appropriate speed. Any failure can be life-threatening.

Cal-Bay Systems designed, developed, and implemented a fully automated test system using NI PXI and SCXI hardware to measure and compare the deployment rate and maximum deployment diameter of medical stents at different temperatures. This system replaced the previous traditional test system and increased the amount of stents that can be tested at one time by 10 times.

system

Cal-Bay Systems designed a state-of-the-art production test system using NI LabVIEW, PXI, and SCXI data acquisition hardware. The system uses linear variable displacement transducers (LVDTs) to test the deployment of 30 vascular stents simultaneously to determine how the diameter of the stent changes when it is heated from a supercooled state to normal body temperature.

The PC running the LabVIEW application collects the data and displays the expansion of each stent under test in real time as a graph of temperature. The user can select up to three stents to view at a time. At the end of the test, when the test bath reaches body temperature, the displacement curve is analyzed to determine whether the stent meets the standard specifications. A report is created after each test.

The software also controls the temperature of the test fluid and the pneumatic valve that lowers the LVDT sensor into the bracket under test.

The new test system can test 30 stents at a time, while the old system can only test 3 stents at a time.

FDA approved

The software for this test equipment needed to be approved by the U.S. Food and Drug Administration (FDA), so we wrote an application using LabVIEW to test every input and output of the system. We provided the FDA with complete files of calculations, expected results, and actual results.

Because the use of medical stents to assist patients with aneurysms has been well received and recently approved by the FDA, the production of stents has increased dramatically. With the automated testing system designed by Cal-Bay Systems, 30 stents can be tested at a time, increasing the test volume by a full 10 times. There are currently 5 types of production testing systems used in the market.