title: Active microcoil tracking in the lungs using a semisolid rubber as signal source.
abstract: A new method to localize and track medical devices in air-filled body cavities is proposed that uses active microcoils with a semisolid filling. In air spaces, e.g., the lung, microcoils require an independent signal source, which should be made of a biocompatible, solid and sterilizable material with a long shelf time. In a measurement of the T(1) and T*(2) and the relative spin density of several semisolid materials, latex was identified as a suitable material from which a prototype catheter was constructed with a microcoil at its tip. In a dual-echo tracking pulse sequence, the very short T*(2) of the rubber material allowed suppressing the background signal from surrounding tissue with a subtraction technique and additional dephasing gradients. With a roadmapping reconstruction, the microcoil's trajectory could be visualized on a previously acquired reference image set with a tracking rate of up to 60 Hz at a spatial resolution of better than 2mm. In a real-time tracking implementation, an image update rate of 4 Hz was achieved by combining the tracking with a fast real-time imaging sequence. Both methods were successfully applied in vivo to track the catheter in the lung of a pig.
authors.affiliation: German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Alt
authors.forename: Ann-Kathrin
authors.initials: AK
authors.lastname: Homagk
authors.forename: Reiner
authors.initials: R
authors.lastname: Umathum
authors.forename: Wolfhard
authors.initials: W
authors.lastname: Semmler
authors.forename: Michael
authors.initials: M
authors.lastname: Bock
mesh_terms: D000818:Animals; D001672:Biocompatible Materials; D002404:Catheterization / Q000295:instrumentation* / Q000379:methods*; D008168:Lung / Q000000981:diagnostic imaging*; D053783:Magnetic Resonance Imaging, Interventional / Q000379:methods*; D008297:Male; D011859:Radiography; D012408:Rubber; D013552:Swine
chemical_list: D001672:Biocompatible Materials; D012408:Rubber