Cervical spine: MR imaging with a partial flip angle, gradient-refocused pulse sequence. Part II. Spinal cord disease

Area of Science:

• Radiology
• Medical Imaging
• Neurology

Background:

• Cervical cord disease detection can be challenging, especially when minimal cord enlargement is present.
• Gradient Recalled Acquisition in the Steady State (GRASS) is a magnetic resonance imaging (MRI) pulse sequence with potential for improved lesion conspicuity.

Purpose of the Study:

• To prospectively evaluate the GRASS MRI sequence for detecting cervical cord disease with minimal or no cord enlargement.
• To determine the optimal GRASS imaging parameters (flip angle, repetition time [TR], echo time [TE]) for signal-to-noise ratio (S/N) and contrast.

Main Methods:

• Eight patients with suspected cervical cord disease underwent sagittal T2-weighted, cerebrospinal fluid (CSF)-gated MRI, and sagittal and axial GRASS MRI.
• GRASS parameters including flip angle (4-18 degrees), TR (22-50 msec), and TE (12.5-25 msec) were manipulated to assess their impact on S/N and contrast.

Main Results:

• Flip angle demonstrated the most significant effect on S/N and contrast.
• No significant difference was observed between axial and sagittal GRASS imaging for spinal cord or lesion visualization.
• Cerebrospinal fluid (CSF) signal intensity varied between sagittal and axial GRASS, influencing lesion conspicuity and optimal flip angle ranges.

Conclusions:

• While GRASS MRI is valuable, CSF-gated sagittal images were superior for initial lesion detection in all patients.
• Axial GRASS imaging is best utilized to confirm spinal cord disease initially detected on sagittal CSF-gated images.
• A balanced GRASS approach (TR=40ms, TE=20ms, flip angles 4-6° sagittal, 6-8° axial) is suggested for confirmation.