Abstract:
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Purpose: To propose and validate a new ultrafast spin echo based MRI
technique that provides for each sequential slice a T2 weighted, heavily T2
weighted and T1 weighted image
Methods and Materials: The new MR sequence is a new spin echo based sequence. After
a 90° RF excitation pulse, a first echo train is acquired for a Half Fourier
TSE image. The same echo is sampled once more to generate a second heavily T2
weighted image. In the mean time, these measurements act as a saturation pulse
to the tissue of the particular slice. After a time delay of 400ms, a new 90°
RF pulse is given, followed by a reordered half Fourier acquisition. Theory
predicts this image to have a T1 weighted image contrast. The sequence was
implemented on a 1.5T system (Sonata, Siemens, Germany). The weighting of the
images has been validated on a phantom and in selected abdominal MRI
examinations. °
Results: The implementation of the sequence required dedicated pulse sequence
programming. Three images with FOV 225 x 320 mm and 80% scan percentage are
obtained in a total time of 1.3s, using only 171 RF pulses for 3 images.
Phantom experiments confirmed the T2 and heavily T2 weighted image contrast of
the first images, and the T1 weighted contrast of the third image. A whole
upper abdomen could be scanned in less than 1 minute. Breath hold was not
necessary. Restrictions on specific absorption rate led to the use of 108°
refocusing pulses, but image contrast was still appropriate. There was no
sensation of warmth during the measurements. Problems of partial volume effects
were overcome: the same anatomical slice is being evaluated for 3 image
contrasts. The image quality of the T1 weighted image was acceptable. The
sequence was successfully used to study the perfusion of the kidneys and any
enhancing lesion after contrast injection. Image quality of the T1 weighted
image could be further improved by parallel imaging and the use of shorter echo
spacing. Keyhole imaging could be applied to further reduce the number of RF
pulses.
Conclusion: A new sequential scanning technique that provides T2 weighted,
heavily T2 weighted and T1 weighted images was successfully implemented. First
validation studies underlined the potential of this technique for rapid
scanning of a large anatomical region with T1 and t2 weighted imaging in a
single run.
(J.M. is an employee of Siemens.)
Questions about this event email: hilde.bosmans@uz.kuleuven.ac.be
Bosmans PhD, H,
A New Sequence for Ultrafast Sequential Multicontrast MRI Screening. Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL.
http://archive.rsna.org/2003/3103731.html
