Seminar 2007 10 10 Image Guidance
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CISST ERC Seminar
Image Guidance during Minimally Invasive Interventions: Beyond Fluoroscopy
Date: Wednesday, October 10, 2007
Time: 12:00pm
Place: CSEB B17 (Lunch will be served)
Speaker: Rebecca Fahrig
Standford University
Title: Image Guidance during Minimally Invasive Interventions: Beyond Fluoroscopy
Presentation: PDF, not yet uploaded
Abstract
There has been a dramatic increase in both the number and type of minimally invasive procedures carried out using image guidance. At Stanford Hospital, the number of vascular and interventional radiology procedures over the past 8 years has increased at an average rate of 20% per year. Under some conditions, the existence of an appropriate imaging modality and devices enable treatment where none was previously available. Medicine has continued to evolve and we are now looking at a class of procedures that currently use x-ray fluoroscopy to guide the placement of a catheter, followed by a phase of the procedure in which x-ray fluoroscopy provides little to no information on the treatment. This is true for current procedures such as hepatic artery chemoembolization and mechanical or chemical thrombolysis for stroke treatment. It is also true for promising new therapies that are being developed such as cardiac stem cell treatment and percutaneous valve replacement. There is a recognized need for soft tissue guidance within a catheter-based procedure.
The development of practical large-field-of-view flat panel x-ray detectors has facilitated the development of new hybrid imaging systems, and our work to implement and streamline two such systems, fluoroscopy/C-arm CT and fluoroscopy/MR will be described. C-arm CT has been under development since the early 90�s, but has recently entered a new phase as the ability to visualize soft tissue and low-contrast lesions improves. Our methods for addressing non-idealities such as x-ray scatter, detector lag, limited field-of-view or angular coverage, data insufficiency and noise will be discussed. The implementation of retrospective gating in combination with multi-sweep acquisitions for cardiac imaging using a C-arm system is a new development, and our work to improve image quality and optimize image acquisition protocols, as well as first clinical images, will be presented. The close integration of fluoroscopy with MR is also facilitated by the new flat-panel detectors since they are essentially immune to magnetic fields. The engineering challenges and solutions required to closely integrate an x-ray system into the bore of a 0.5T GE Signa SP magnet will be described, including local shimming for magnetic inhomogeneity caused by the detector and x-ray tube modifications. Our vision for the next-generation XMR system, placed directly adjacent to a wide short-bore interventional magnet, will be presented, including new designs for an MR-compatible rotating-anode x-ray tube.
True integration of imaging modalities within the interventional suite continues to present significant challenges, with the need to maintain excellent image quality of both modalities while allowing easy switching between them, and providing a combined navigation interface. Further investigations such as how best to present, interact with and visualize image data, are also ongoing.