Accelerated T1rho relaxation quantification in intervertebral disc using limited spin-lock times

Area of Science:

• Biomedical Imaging
• Magnetic Resonance Imaging
• Biochemistry

Background:

• T1rho relaxation mapping is crucial for detecting early biochemical changes in intervertebral discs.
• Traditional T1rho mapping requires multiple spin-lock times (SLT) for accuracy, often around five.
• Reducing the number of SLTs could enhance efficiency without compromising T1rho measurement reliability.

Purpose of the Study:

• To investigate the feasibility of using only three spin-lock times (SLT) for accurate T1rho relaxation time measurements in intervertebral discs.
• To compare the accuracy and robustness of T1rho mapping using three SLTs versus the traditional five SLTs.

Main Methods:

• Lumbar spines from 12 subjects (30-75 years) were scanned using 3-T MRI with a 3D balanced fast field echo (b-FFE) sequence.
• T1rho measurements were performed using a rotary echo spin-lock pulse with spin-lock frequency at 500 Hz and SLTs of 1, 10, 20, 40, and 60 ms.
• T1rho maps were generated using non-negative least-square fitting, comparing reconstructions from all five SLTs with a reduced set of three SLTs (1, 20, 60 ms). Regions of interest included nucleus pulposus (NP) and annulus fibrosus (AF).

Main Results:

• No significant differences in T1rho values were found between the 5-SLT and 3-SLT measurements for both NP (P=0.63) and AF (P=0.31).
• High agreement was observed between 5-SLT and 3-SLT T1rho measurements, with intra-class correlation coefficients (ICC) of 0.991 for NP and 0.981 for AF.
• Bland and Altman analysis indicated minimal mean differences (3.14 ms for NP, 1.83 ms for AF), further supporting the reliability of the 3-SLT approach.

Conclusions:

• Using three spin-lock times (1, 20, and 60 ms) is a feasible and acceptable alternative for intervertebral disc T1rho measurement.
• This reduction in measurement points can potentially streamline the T1rho mapping process for disc degeneration assessment.
• The findings support the optimization of MRI protocols for more efficient biochemical analysis of intervertebral discs.