Can an intermittent pneumatic compression system monitor venous filling in the leg?

Rapid prototyping compliant arterial phantoms for in-vitro studies and device testing

BACKGROUND

Compliant vascular phantoms are desirable for in-vitro patient-specific experiments and device testing. TangoPlus FullCure 930 is a commercially available rubber-like material that can be used for PolyJet rapid prototyping. This work aims to gather preliminary data on the distensibility of this material, in order to assess the feasibility of its use in the context of experimental cardiovascular modelling.

METHODS

The descending aorta anatomy of a volunteer was modelled in 3D from cardiovascular magnetic resonance (CMR) images and rapid prototyped using TangoPlus. The model was printed with a range of increasing wall thicknesses (0.6, 0.7, 0.8, 1.0 and 1.5 mm), keeping the lumen of the vessel constant. Models were also printed in both vertical and horizontal orientations, thus resulting in a total of ten specimens. Compliance tests were performed by monitoring pressure variations while gradually increasing and decreasing internal volume. Knowledge of distensibility was thus derived and then implemented with CMR data to test two applications. Firstly, a patient-specific compliant model of hypoplastic aorta suitable for connection in a mock circulatory loop for in-vitro tests was manufactured. Secondly, the right ventricular outflow tract (RVOT) of a patient necessitating pulmonary valve replacement was printed in order to physically test device insertion and assess patient's suitability for percutaneous pulmonary valve intervention.

RESULTS

The distensibility of the material was identified in a range from 6.5 × 10(-3) mmHg(-1) for the 0.6 mm case, to 3.0 × 10(-3) mmHg(-1) for the 1.5 mm case. The models printed in the vertical orientation were always more compliant than their horizontal counterpart. Rapid prototyping of a compliant hypoplastic aorta and of a RVOT anatomical model were both feasible. Device insertion in the RVOT model was successful.

CONCLUSION

Values of distensibility, compared with literature data, show that TangoPlus is suitable for manufacturing arterial phantoms, with the added benefit of being compatible with PolyJet printing, thus guaranteeing representative anatomical finishing, and quick and inexpensive fabrication. The appealing possibility of printing models of non-uniform wall thickness, resembling more closely certain physiological scenarios, can also be explored. However, this material appears to be too stiff for modelling the more compliant systemic venous system.