Ultrasound-guided minimally invasive grinding for clearing blood clots: promises and challenges

Mechanical removal of blood clots is a promising approach towards the treatment of vascular diseases caused by pathological clot formation in the circulatory system. These clots can form and travel to deep seated regions in the circulatory system and result in significant problems as blood flow past the clot is obstructed. A microscopically small helical microrobot (Fig. 1a) offers great promise in the minimally-invasive removal of these clots. The simple design of the microrobot, which was originally presented at Tohoku University by Ishiyama et al., enables fabrication at micro and nano scales [1]. The incorporation of a magnetic material to the helical microrobots allows them to controllably navigate using an external source of magnetic field and feedback control [2]. The external source of magnetic field has been provided using a configuration of electromagnetic coils or rotating permanent magnets, while several research groups have relied on visual feedback to design feedback control systems.