GRASE (gradient- and spin-echo) MR imaging: a new fast clinical imaging technique

Area of Science:

• Radiology
• Medical Imaging

Background:

• Conventional spin-echo (SE) magnetic resonance (MR) imaging provides high-quality T2-weighted images but suffers from long acquisition times.
• Rapid acquisition techniques like RARE (rapid acquisition with relaxation enhancement) have been developed to accelerate imaging, but may have limitations.

Purpose of the Study:

• To introduce and evaluate a novel magnetic resonance imaging technique combining gradient-echo and spin-echo (GRASE) methods.
• To assess the potential of GRASE for significantly reducing imaging time while preserving image quality and contrast mechanisms.

Main Methods:

• The GRASE technique integrates multiple Hahn spin echoes with short gradient-echo trains.
• Image acquisition parameters were demonstrated for body and brain imaging, achieving 11 multisection body images in 18 seconds and 22 brain images in 36 seconds.
• GRASE was compared to RARE, noting advantages in acquisition speed and radio-frequency power deposition.

Main Results:

• GRASE achieves T2-weighted multisection imaging up to 24 times faster than conventional SE imaging.
• The technique maintains the contrast mechanisms and high spatial resolution characteristic of SE imaging.
• GRASE overcomes common artifacts associated with echo-planar imaging, such as chemical shift and signal loss due to field inhomogeneity.
• Breath-holding during 18-second GRASE scans effectively eliminates respiratory motion artifacts in T2-weighted abdominal images.

Conclusions:

• The GRASE technique represents a significant advancement in accelerating T2-weighted MR imaging.
• It offers a promising alternative to existing rapid imaging methods, with potential for improved patient comfort and diagnostic utility, particularly in abdominal imaging.