The main goal of this project is the development of a fast dynamic 3D MRI method using adaptive spatial encoding that can acquire a high resolution MRI dates (256x256x256) operating in near real-time as possible (1 dataset per 1-2 seconds) with minimal hardware modifications to a standard MRI scanner. This goal lies well outside the possibilities of current MRI methods like echo planar techniques that employ Fourier encoding and specialized gradient hardware. A number of applications of interventional MRI, a focus in our hospital, have the specific requirement for dynamic 3D MRI that can operate on an "open" MR scanner with no specialized gradient coils. The most important of these applications is the MRI monitoring of the timecourse of thermal therapies during which non-uniform heating of tissue occurs due to tissue heterogeneity and nearby vessels. Another important application is the near real-time 3D tracking of probes and catheters used for minimally invasive therapies. Specifically, we propose to develop, implement, test and optimize a dynamic 3D MRI method that encodes adaptively in two directions using high flip angle 2D spatially selective RF excitations to implement a minimal set of near-optimal encodes computed from the multidimensional Singular Value Decomposition (MSVD) of a 3D image estimate (formed from recently acquired data) computed per acquisition, combined with frequency encoding in the third direction. The accomplishment of the main objective of this project is only possible due to three significant technological advances. First, and most important regarding spatial encoding, the applicants reported recently having developed the MSVD, a powerful numerical mathematical tool that can determine near-optimal 3D spatial encoding. Second, a simple fast numerical procedure has been developed in their laboratory for the computation of RF pulse waveforms for implementing non-Fourier encodings using high flip angles ( 90=A1) for high SNR scans. Third, at their facility, they have the operating capability for near real-time adaptive 2D MRI using a commercial MR system with the minor modification of an additional attached workstation.