Oral Presentation 51st International Society for the Study of the Lumbar Spine Annual Meeting 2025

The effect of unloaded rest and time of day on MRI measurements of disc T2 time and height   (115454)

Mackenzie N Conner 1 , Harrah R Newman 1 , Edward J Vresilovic 2 , Dawn M Elliott 1
  1. Biomedical Engineering, University of Delaware, Newark , Delaware
  2. University of Delaware, Newark

Introduction

Disc degeneration is often quantified by magnetic resonance imaging (MRI) measures of T2 relaxation time and disc height [1], [2]. While disc hydration and height loss occur throughout the day [1], [3], it is unknown whether the time MRI is acquired affects these outcome measures. To mitigate potential diurnal effects, many studies scan after an unloaded rest period or early in the morning [1], [3], however, the effectiveness of these efforts is unknown. Therefore, we evaluated T2 time before and after unloaded rest, and T2 time and disc height across the day. We hypothesized T2 time would increase after unloaded rest while both T2 time and disc height would decrease throughout the day.

Methods

T2 time and disc height were measured from lumbar spine (L1-S1) MRI of asymptomatic participants (23-37 years old, n=8) [1, 4]. Participants were scanned at ~8:00 am, before and after 45 minutes of unloaded, supine rest. This was repeated every three hours, with regular activity between timepoints. A mixed ANOVA evaluated effects of rest and time of day, with post hoc Bonferroni corrected paired t-tests.

Results

Unloaded rest  T2 time changes were normally distributed (Fig 1A). Although the T2 time significantly decreased (-4 ± 18 ms) after unloaded rest, ~half of the discs decreased while ~half increased (Fig 1A, B).

The difference in T2 time across the day was not significantly different, except for between 11:00 am and 2:00 pm (-10 ± 17 ms) (Figure 2A, B). Disc height significantly decreased ~1.8% between each subsequent timepoint, for a total decrease of 5.4%. (Figure 2C, D).

Discussion

While T2 time following rest significantly changed on average by 4 ms, half of the discs decreased and half increased, and there was high variation as the standard deviation was 18ms. Therefore, it is unnecessary to have a subject lie supine, to allow for re-hydration, before MRI evaluation of T2 time.

Across time of day, T2 times changes were variable and mostly insignificant, moreover the single significant change in T2 time was small. Therefore, it may not be necessary to control for time of day when measuring T2 time. Although T2 time is partially dependent on water content which appears to be diminishing due to the disc height loss, the minimal changes in T2 time over the day suggest proteoglycans and collagens likely contribute to T2 time measurement.

Consistent with previous studies [3], disc height decreased by 5.4% over 9 hours, ~1.8% every three hours, due to water loss. Therefore, it is necessary to control for time of day when measuring disc height, but since height loss was linear, it may be possible to account for time of day using a correction factor. 

Ultimately, contrary to our hypothesis, T2 time was not meaningfully changed with unloaded rest and time of day. Consistent with prior work, disc height decreased throughout the day. This work established the effects of time of day and unloaded rest on T2 time, which should be considered in designing MRI studies to improve scanning consistency.

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  2. T. Videman, M. C. Battié, L. E. Gibbons, and K. Gill, “Aging changes in lumbar discs and vertebrae and their interaction: a 15-year follow-up study,” Spine J. Off. J. North Am. Spine Soc., vol. 14, no. 3, pp. 469–478, Mar. 2014, doi: 10.1016/j.spinee.2013.11.018.
  3. J. T. Martin et al., “Lumbar intervertebral disc diurnal deformations and T2 and T1rho relaxation times vary by spinal level and disc region,” Eur. Spine J., vol. 31, no. 3, pp. 746–754, Mar. 2022, doi: 10.1007/s00586-021-07097-4.
  4. K. D. Meadows, C. L. Johnson, J. M. Peloquin, R. G. Spencer, E. J. Vresilovic, and D. M. Elliott, “Impact of pulse sequence, analysis method, and signal to noise ratio on the accuracy of intervertebral disc T 2 measurement,” JOR SPINE, vol. 3, no. 3, p. e1102, Sep. 2020, doi: 10.1002/jsp2.1102.