Tracking kidney stones during shock wave lithotripsy

Boston University (Charles River Campus), Boston MA

Investigators

Linked publications & trials

Abstract

DESCRIPTION (provided by applicant): This application addresses broad Challenge Area (06) Enabling Technologies and specific Challenge Topic, 06-DK-104 Enabling technology for the prevention and treatment of diseases within the NIDDK mission. . In particular, it addresses the three priority areas mentioned in this challenge topic 1/ better tools for minimally invasive ... urologic surgeries, to minimize complications 2/ improvement of lithotripters to minimize complications. 3/ Creation of new or improved mechanical designs and control algorithms Shock wave lithotripsy (SWL) is a non-invasive procedure by which focused shock waves are used to fragment kidney stones into pieces that are small enough to be passed naturally. In the United States targeting is normally accomplished using X-ray imaging before treatment starts. A typical treatment uses on the order of 2000 shock waves delivered over a 30 minute period and targeting is checked occasionally during this time. However, due to respiration (and other patient movement) the stone is not in the focus of the lithotripter the entire time and therefore many shock waves miss the stone. These mis-targeted shock waves result in trauma to the surrounding tissue without any therapeutic benefit. The trauma induced by shock wave lithotripsy has been associated with both acute and chronic complications. We propose to develop a real-time tracking system that can be retro-fitted onto clinical lithotripters and gate the lithotripter so that it fires a shock wave only when the stone is on target. In the case where a stone has permanently moved from the focal region the system will signal to the urologist that alignment should be reassessed with conventional imaging. By eliminating the mis-targeted shock waves the system will reduce the potential for trauma without affecting the fragmentation efficiency. Aim 1: Optimize tracking algorithm We have preliminary data to show that we can track kidney stones in an in vitro environment (artificial stone and artificial tissue). The algorithm will be improved to track multiple fragments and then a prototype system that can be retro-fitted to a clinical lithotripter will be constructed and tested. Aim 2: Evaluate tracking using an in vivo model The tracking system will be deployed on a clinical lithotripter and used to track the motion of kidney stones in a pig model. In the first step the accuracy of the system to track a stone under controlled motion will be assessed. In the second step the system will be used on two different lithotripters to track a stone and gate SW delivery during treatment and assess the impact of gating on fragmentation and tissue injury. The deliverable from this project will be prototype stone tracking system that can be retro-fitted onto a clinical lithotripter. The performance of this new tool will have been assessed in particular its ability to reduce trauma to kidney tissue while still being able to fragment stones. At the end of the two year project we will be in a position to plan clinical trials. PUBLIC HEALTH REVEVANCE: Shock wave lithotripsy (SWL) is a common non-invasive technique for breaking up kidney stones by shock waves. During SWL the stone moves due to respiration and presently many shock waves miss the stone and damage the surrounding tissue. Our goal is to develop an ultrasound based tracking system which will only allow the lithotripter to fire a shock waves when the stone is on target and therefore spare the surrounding tissue.