Magnetic wire for retrieval and elimination of calculus from the urinary tract

Inventors

Ge, Tianjia Jessie • Conti, Simon • Liao, Joseph C. • Sheth, Kunj Raju • Wang, Shan X.

Assignees

US Department of Veterans Affairs • Leland Stanford Junior University

Abstract

A medical device for retrieval of kidney stone fragments from a urinary tract is provided. The medical device has a plurality of magnets arranged within a flexible sheath forming a flexible wire. The magnets are magnetically attached end-to-end and arranged with their magnetic polarities alternating in direction. The magnetization direction of each of the magnets is orthogonal to the length axis of the flexible wire. A removable inner stylet is situated within the flexible sheath allowing for modifiable flexibility of the wire. The medical device is dimensioned to be introduced into the urinary tract and standard endoscopic devices. The medical device is further dimensioned to allow for the wire with magnetically attached stone fragments to be retrieved from the urinary tract. The magnetic field along the length axis is sufficient to attract to the surface of the flexible wire superparamagnetic nanoparticles which have bound themselves to kidney stone fragments.

Core Innovation

The described invention relates to removing calculi from a urinary tract by introducing superparamagnetic particles that bind themselves to calculi, where the calculi are calcium, uric acid, struvite, cystine, or a combination thereof. A flexible magnet wire is then inserted such that a magnetic field along the length of the flexible magnet wire is sufficient to attract, to the surface of the flexible magnet wire, the superparamagnetic particles that have bound themselves to the calculi.

The flexible magnet wire is positioned at an end of a flexible wire that is not magnetic, and includes a plurality of magnets arranged within a flexible sheath. The magnets are magnetically attached end-to-end and arranged with their magnetic polarities alternating in direction, forming a multi-magnet magnetic structure inside the flexible sheath.

Retention and capture of stone fragments are further addressed by magnetically labeled fragments and by structural elements such as bristles/shield or a basket configuration. In additional embodiments, a hydrogel-based delivery concept is described in which a hydrogel precursor polymer cross-links with superparamagnetic particles bound to calculi to form a magnetic hydrogel that coats and binds the calculi.

Claims Coverage

The partial content includes two independent method claims. Both claims share the core sequence of binding calculi with superparamagnetic particles and using a flexible magnet wire to magnetically attract the bound particles to a wire surface for removal from a urinary tract, with claim-specific emphasis on calcium oxalate versus calcium, and on ureteroscope working-channel delivery in claim 14. Across the independent claims, the inventive features focus on the superparamagnetic binding, the flexible magnet wire structure with alternating polarities inside a flexible sheath, and sufficient magnetic field attraction along the wire length.

Across the independent claims, coverage centers on binding urinary tract calculi with superparamagnetic particles and using a flexible magnet wire to magnetically attract the bound superparamagnetic particles to the flexible magnet wire surface. Claim 1 emphasizes a flexible magnet wire with a plurality of magnets arranged end-to-end with alternating magnetic polarities inside a flexible sheath and a sufficient magnetic field along the wire length. Claim 14 further emphasizes ureteroscope working-channel delivery of the flexible magnet wire, extension into the urinary tract, and removal of the flexible magnet wire carrying the attracted, calculi-bound particles for removal of the calculi from the urinary tract.

Stated Advantages

Documented Applications