2012 AAPM Annual Meeting
Charles Mistretta, PhD, University of Wisconsin, Madison, WI, 53792-3252, United States

During the past decade the use of undersampled acquisition and constrained reconstruction have led to significant increases in data acquisition speed, SNR, spatial resolution and temporal resolution in MR imaging. When a separately acquired constraining image is combined with an angiographic time series the traditional tradeoff between spatial and temporal resolution is greatly reduced. Artifacts and limited resolution that would normally be associated with a rapid highly undersampled temporal image series are mitigated by the constrained reconstruction process which transfers the SNR and spatial resolution of the constraining image to the individual time frames.

In rotational C-Arm DSA a 3D image volume is formed from all the projections acquired during the C-Arm rotation. Although the individual projections contain temporal information, the reconstructed 3D image has no temporal information and represents a composite of the vascular filling that has occurred during the iodine injection. However, the 3D cone beam CT reconstruction can be used to constrain the reconstruction of one 3D volume for each of the rotational projections. This extends the traditional DSA time series of 2D images to a series of 3D volumes at rates up to 30 per second.

Similar techniques can be used to provide fluoroscopy that can be embedded in the 3D space of the constraining volume and viewed from arbitrary angles without gantry motion. This overcomes the problem of forbidden views and guarantees that an intervention can be done without having to send patients to surgery. Unlike 4D DSA which requires only one source and receptor, 4D Fluoroscopy requires a bi-plane fluoroscopy system.

Learning objective
To understand the application of undersampling and constrained reconstruction to 4D DSA and Fluoroscopy.

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