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T1rho Imaging Quantification of Early Intervertebral Disc Degeneration in Pilots on 3.0T Magnetic Resonance
Xiulan Zhang1, Yongmin Bi2, Wanshi Zhang2, and Lizhi Xie3

1Radiology Department, The First People’s Hospital of Jingzhou,Jingzhou, China,People’s Republic of, Jingzhou, People's Republic of China, 2Department of CT&MRI, Air Force General Hospital, Beijing, China, People’s Republic of, 3GE Healthcare, MR Research China, Beijing, China, People’s Republic of

Synopsis

Degenerative disc disease is an occupational disease of the military pilots, which seriously influcenes their health and normal training. Early disc degeneration begins with changes in biochemical compositions which is mainly characterized by proteoglycan lose and cannot be detected on conventional MRI imaging[1-2]. T1rho is a quantitative imaging technique to reflect changes in the extracellular matrix, such as modifications in the intervertebral disc PG content[3]. In this study，Bivariate correlation analysis was performed to compare T1rho values to the degenerative grade, disc space level, age and flight time of the pilots. T1rho values of Lumbar intervertebral discs in pilots demonstrated significantly negative correlations with degenerative grade, age and flight time, except for disk space levels. T1rho can be potentially used as a valid clinical method in the quantitative diagnosis of early intervertebral disc degeneration in asymptomatic Pilots.

Purpose

To evaluate early intervertebral disc degeneration quantified using T1rho imaging technique on 3.0T magnetic resonance in asymptomatic pilots.

Method

A total number of 34 asymptomatic male pilots ranging from 25 to 51 years old (mean 33.47 ± 7.29 years old) underwent examination using a 3.0T MR scanner (GE Discovery MR750) with an 8-channel CTL Target Array Coil. Both sagittal conventional T2- and T1rho-weigted images were acquired at every examination of lumbar disc. T2-weighted imaging were acquired using a fast spin-echo sequence with the following parameters: TR=2556ms, TE=121.3ms, FOV=32×32cm , slice-thickness=4mm, acquisition-matrix=352×320. T1rho-weighted imagings used 3D spoiled gratdient-recalled sequence with parameters as follows: TSL1/TSL2/TSL3/TSL4(time of spin lock)=0/20/40/80ms, Spin Lock Freq=300Hz,TR=4.2ms, TE=min-full, FOV=260×260mm, NEX=1.0, slice-thickness=5mm, acquisition-matrix=160×160, bandwidth=62.5kHz, PE direction=L/R. The original scan data (Figure.1) were transfered to AW4.5 workstation for analyses. The sagittal T1rho maps were reformatted for each disk. Mean T1rho values of the central disk space nucleus pulposus were determined by using post-processing software namely as T2mapping with the Region of Interests that were approximately 49-51mm². The degenerative grade of each lumbar disc was assessed from T2-weighted images according to Pfirrmann degenerative grade. Bivariate correlation analysis was performed to compare T1rho values to the degenerative grade, disc space level, age and flight time of the pilots. All the pilots were divided into three groups according to age, as ＜30 years old, 30~40 years old, and ≥40 years old groups, respectively. Meanwhile, the pilots were subdivided into three groups according to flight time as well, as ＜2000 hours, 2000~3000 hours, and ≥3000 hours groups.

Results

On pseudo-colour imaging of T1rho-map of normal Lumbar intervertebral discs, the central nucleus pulposus was displayed as orange red or yellow, while the surrounding gradually became blue. The annulus fibrosus was homogeneous blue, with a clear boundary between the nucleus pulposus and the annulus fibrous. The nucleus pulposus which degenerated seriously (Pfirrmann Ⅳ, Ⅴ) was homogeneous blue but without a clear boundary.(Figure.2)

The T1rho values of 170 intervertebral discs were achieved and categorized as grade 1 （n=25）, grade 2 （n=29）, grade 3 （n=84）, grade 4 （n=29）, and grade 5 （n=3）. T1rho values were significantly negatively correlated with Pfirrmann grade Ⅰ～Ⅳ(r=-0.901, P＜0.01) and ages (r=-0.709, P＜0.01). There was a significant difference in T1rho values between Pfirrmann grade Ⅰ-Ⅳ(F=277.892,P＜0.01) and among all the age groups (Welch=77.406，P＜0.01). However, there was no significant difference in the T1rho values observed between each level (P＞0.05). T1 rho values were significantly pairwise different among the flight time groups (Welch=41.641，P＜0.01).

Discussion and conclusion

T1rho values of Lumbar intervertebral discs in pilots demonstrated significantly negative correlations with degenerative grade, age and flight time, except for disk space levels. T1rho can be potentially used as a valid clinical method in the quantitative diagnosis of early intervertebral disc degeneration in asymptomatic Pilots.

Acknowledgements

No acknowledgement found.

References

[1] Southern E P, Fye M A, Panjabi M M, et al. Disc degeneration: a human cadaveric study correlating magnetic resonance imaging and quantitative discomanometry. Spine.2000; 25(17): 2171-2175.

[2 ] Luoma K, Vehmas T, Riihimäki H, et al. Disc height and signal intensity of the nucleus pulposus on magnetic resonance imaging as indicators of lumbar disc degeneration. Spine. 2001;26(6): 680-686.

[3 ] Johannessen W, Auerbach J D, Wheaton A J, et al. Assessment of human disc degeneration and proteoglycan content using T1ρ-weighted magnetic resonance imaging. Spine. 2006;31(11): 1253-1257.


Figures

Figure. 1 The sagittal T1rho source imagings were achieved with the TSL as 0,20,40,and 80ms, respectively.

Figure.2 Representative T2-weighted image (left) and corresponding T1rho map (right) of the lumbar discs from a asymptomatic male pilot. Pfirrmann degenerative grades of lumbar intervertebral discs from L1-2 to L5-S1 were Grade Ⅲ，Ⅲ，Ⅱ，Ⅳ and Ⅱ, respectively. Corresponding T1rho values in Grade Ⅱ and Ⅲ were higher than that in Grade Ⅳ. The colour of nucleus pulposus in Grade Ⅱ and Ⅲ was orange red or yellow, but light blue In Grade Ⅳ.

Proc. Intl. Soc. Mag. Reson. Med. 25 (2017)
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