2097 Automated tracking of a passive intramyocardial needle with off-resonance mri: a feasibility study
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KeywordsPositive Contrast Automate Tracking Deformable Template Siemens Sonata Tesla Siemens
Direct intramyocardial therapies aimed at treating myocardial regions affected by severe ischemia may benefit from CMR-guided interventional procedures. Although interventional MR approaches using active devices are considered to be the method of choice, potential tissue heating and altered mechanical properties are some of their limitations. Methods that have the capacity to visualize MR-compatible passive devices may overcome many of these obstacles. Recently, an off-resonance-based real-time positive contrast method (FLAPS) was used to visualize the passage of an intramyocardial needle (PIN) through the aorta and into the heart of swine [1, 2]. We envision this procedure may benefit from computer assisted strategies that track the needle's location throughout the MR procedure. However, the feasibility of real-time automated tracking of a PIN has not been established.
To test the feasibility of automated off-resonance MRI-based tracking of a passive intramyocardial needle in a realistic phantom of the thoracic aorta.
Experimental Setup & Imaging
Needle Tip Tracking Algorithm
Two orthogonal MR images, O(x, y) and E(z, y), of the phantom were used simultaneously to track the needle tip with an image processing algorithm. The algorithm took input of the initial location of the needle (regions of positive contrast) from the first frames and detected the needle in subsequent frames using a template method. The template methodology used information from the previous frame and was flexible, allowing for rotation and scaling to adapt to the dynamic MR footprint of the needle. A real-time filter was used to smooth the data and all observations were combined to improve the accuracy of the needle's position.
Discussion and conclusion
The feasibility to track a PIN with off-resonance positive contrast was demonstrated in a phantom of an aorta. Although the image processing was performed retrospectively in this study, given the real-time capacity of the template tracking method, it should be readily adaptable for prospective guidance. Future studies need to extend this work to in vivo conditions in order to assess the capacity of the technique within the heart and aorta.
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This article is published under license to BioMed Central Ltd.