Thickness Measurements on Balloon Catheters - Noncontact Measurements of Medical Plastics

Historically, parameters such as angles, lengths and diameters were measured with optical measurement systems because they are accessible. Wall thicknesses were determined by compressing the two tube walls together, measuring with a micrometer gauge and halving the result.

Noncontact measuring systems e.g. by MPT Europe (NR Leek, Netherlands) can not only measure the wall thickness on any area, but also the geometry of an inflated or deflated balloon. As part of this systems, optical sensors (CHRocodile SE by Precitec Optronik) are used for the noncontact measurement of topography and layer thickness.

Additional applications of noncontact measuring techniques include the capability of precisely determining the fill levels of liquids, a requirement for some filling techniques for medications. The wall thicknesses of disposable plastic syringes can be determined. Small medical vials need to be sealed on the upper end. The coatings are so thin that only noncontact systems can validate whether the sealing would last or not.

Furthermore there are new line sensors available, which can process 3D-topographies up to 200 times faster than conventional point sensors. These systems could be used to measure bioresorbable stents, the current end point in a chain of development. Its body wall structure consists of biodegradable polylactic acid (PLA) which completely dissolves after a certain time. The thickness can be measured without any contact and then displayed as a high resolution 3D-topography.