MR fluoroscopy: Technical feasibility

Abstract

A method of magnetic resonance image acquisition and reconstruction is described in which high imaging rates and fast reconstruction times are allowed. The acquisition is a modification of the basic FLASH sequence but with a restricted number N of phase encodings. The encodings are applied sequentially, periodically, and continuously. Images are formed by sliding a window of width N encodings along the acquired data and reconstructing an image for each position of the window. In general the acquisition time per image exceeds the time between successive images, and the method thus has a temporal lag. Experimental studies were performed with a dynamic phantom using 48 phase encodings and a TR of 20 ms, for an image acquisition time of about 1 s. The image display rate in the reconstructed sequence was 12.5 images/s, and the image sequence portrayed the motion of the phantom. Additional studies were done with 24 encodings. It is shown how the sliding window technique lends itself to high-speed reconstruction, with each newly acquired echo used to quickly update the image on display. The combination of the acquisition technique described and a hardware implementation of the reconstruction algorithm can result in realtime MR image acquisition and reconstruction.

Combination of 2D sensitivity encoding and 2D partial fourier techniques for improved acceleration in 3D contrast‐enhanced MR angiography

“…We expect that both the 2D-SENSE and the combined 2D-SENSE-PF techniques presented here are directly compatible with time-resolved imaging, by simple resampling of the previously sampled views, alternating the collection of vanes, or using view sharing (27)(28)(29). The principal assumption is that the a priori calculated coil sensitivity profiles for SENSE, and the overall phase maps used for homodyne reconstruction do not change over the time course of the dynamic process being imaged.…”

Multiple field of view MR fluoroscopy

“…Consecutive sets can be combined for an increased FOV at the expense of reduced temporal resolution. Although the temporal resolution of larger FOV images is lower, they can be updated as each new set is acquired at intervals of 8 ϫ TR, providing a smoother transition over time (11).…”

“…MR fluoroscopy (11,12) has been used to increase temporal resolution in both interventional (13,14) and noninterventional (15)(16)(17) procedures. Fluoroscopic methods are frequently combined with dedicated real-time reconstruction hardware or algorithms, and some researchers (18 -20) have devised techniques to actively track the tip of interventional devices.…”

Reconstruction of Cardiac Cine MR Images from Partial k-Space

“…These techniques have been used for dynamic imaging as well. In an attempt to further increase the acquisition rate by reducing the amount of acquired data by a given factor, referred to as the reduction factor, several methods dedicated to dynamic MR images reconstruction have been reported in the literature [9][10][11][12][13][14][15]. Even though parallel imaging is commonly used to acquire cine MRI, few reconstruction methods have been proposed for reconstructing cardiac cine images [16].…”