GLOMERULAR FILTRATION RATE & EXTRACTION FRACTION OF GD DTPA IN KIDNEYS W/ MRI

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Introduction: Magnetic Resonance imaging (MRI) has become an important imaging modality for the management of cancer patients due to its excellent soft tissue contrast. However, MRI has so far been restricted primarily to the detection of cancer, with only a limited role in subsequent tissue biopsy, and no direct role in therapy. This is all changing with the recent generation of "open" MRI systems which promise less invasive biopsy and the possibility for replacing generalized or systemic therapy with local therapy. Interventional MRI (iMRI) procedures involve the use of devices such as biopsy needles, catheters, or ablation devices using RF, lasers, or cryotherapy. Since MRI is extremely sensitive to perturbations in magnetic field, the presence of these devices often produces image distortions and signal voids. Efforts to improve image quality have focused on designing interventional device materials that produce minimal artifacts with conventional imaging methods. Our goal is to develop advanced MR imaging methods that are designed specifically for imaging in the presence of interventional devices, and integrate these methods into a rapid, interactive, and flexible system. Methods/Results: We have developed a method to remove image distortions by the use of view angle tilting. This method is dependent on the application of a gradient with magnitude equal to that of the slice select gradient, applied during data collection. The additional gradient ensures that off resonance spins appear to be registered in the image. We have also developed methods to increase needle artifacts on spin echo images which have inherently little needle contrast due to the rf refocussing. This method takes advantage of the fact that spins adjacent to the needle resonant far off-resonance. Conclusions: Open MR systems provide tremendous clinical opportunities for minimally invasive therapies. An essential requirement will be the ability to rapidly obtain high quality images in the presence of interventional devices. In this work, we are developing an array of elements that allow the imaging of interventional devices to be improved and controlled.