Tango

Markers were casted out of silicone. A mold was 3D printed using a Fortus 250MC (Stratasys, Ltd.) printer with a rubber-like print material, Tango (Stratasys, Ltd.). This resulted in a flexible mold that allowed releasing the markers from the mold after curing. The resulting marker is a disk of 2 mm thick and 5 mm in diameter. Initially, a marker of 10 mm in diameter was produced and was only used on the first two patients. The marker’s material is Ecoflex™ GEL (Smooth-on Inc.) which is commercially available and tested skin safe that conform with the OECD TG 439 test guidelines which are closely related to the ISO 10993 standards for medical devices [15 (link)]. For this pilot study, we rely on these test results and patients were asked to report any adverse events. The two components of uncured silicone were mixed, stirred, and carefully poured into the mold. Any excess material was scraped off. The markers were left to cure for 4 h of which the first hour in a vacuum chamber at 100 mbar to extrude any trapped air. After curing, the markers were removed from the mold and stored on a plastic sheet for later application. The permanently sticky silicone allowed for long-term storage of the marker without changes to geometrical or acoustic properties.