Assessing the Characteristics of Modern Valvuloplasty Balloons Using a Robotic Non-Contact Optical Approach

Background: Balloon aortic valvuloplasty is a procedure for treating aortic stenosis, as well as being a preliminary step before transcatheter aortic valve implantation. Balloon aortic valvuloplasty requires inserting a balloon catheter into the aortic valve and repeatedly inflating it to widen the narrowed valve. With a wide range of equipment, operators rely on manufacturer data to guide the balloon use during surgery. However, such data can have variations of up to 10%, which can affect the procedures’ efficacy. Methods: In this paper, we report a bench-top proof-of-concept, automated, non-contact optical system that combines a linear delta robot (ROMI) equipped with a bright-field microscopy system, image stitching, and passive autofocusing algorithms to measure the diameters of aortic valvuloplasty balloons inflated using clinically relevant pressures. The system also introduces a laser projection system, enabling the use of passive autofocus algorithms to allow measuring transparent balloons. We evaluate three balloon brands (TRUE Dilatation, Edwards, and Z-MED II) across commonly used sizes and compare the measured diameters with vendor specifications. The developed system allows us to systematically determine the balloons’ diameters with submillimeter-level accuracy. Results: The experimental data shows that the TRUE Dilatation balloon presented the smallest deviations from the manufacturers’ data, even though the 22 and 24 mm balloons exceeded the 1% tolerance by +2.26% (over-inflation) and −1.56% (under-inflation), respectively. The Edwards Lifesciences and Z-MED II balloons presented inflation diameter variations ranging from −5.97% to + 8.81%, which led to a deviation of the specified balloon diameter of 1.76 mm. The standard error value obtained within our measurements revealed that the balloon diameters were consistent despite multiple inflations and were also resilient to repeated inflations up to the rated burst pressure. Conclusions: These results demonstrate the potential of the system presented herein to be adapted for in situ, contactless pre-operative balloon assessment in clinical settings.