| Objective: To evaluate early intervertebral disc degeneration quantified by T1?-and T2-weighted magnetic resonance imaging(MRI)at 3.0T in asymptomatic pilots compared with a health control group and to correlate T1? value with Pfirrmann degenerative grade,age,level and flight time.Materials and Methods: Total 69 Health volunteers,ranging in age from 24 to 51 years,with an average age of 32.59±7.18 years,were divided in two groups.The first group: 34 asymptomatic male pilots,ranging in age from 25 to 51 years,with an average age of 33.47±7.29 years,had no history of stopping flight or stopping training.The second,control group:35 asymptomatic health volunteers,ranging in age from 24 to 48 years,with an average age of 31.74±6.99 years,had no history of strenuous exercise.All 69 volunteers were divided into three groups according to age,<30 years,30~40 years,?40 years.All pilots were subdivided into three groups according to flight time,<2000 hours,2000~3000 hours,?3000 hours.Inclusion criteria in all subjects as following:(1)no contraindication of MRI examination,(2)no back pain,(3)no scoliosis or spondylolisthesis,(4)no spine trauma or prior back surgery,(5)no metabolic diseases or autoimmune diseases.Both sagittal routine T2-and T1?-weigted images of all lumbar discs were acquired at every examination,and then uploaded the source date to the AW 4.5 workstation.The sagittal T1? maps were reformatted for each of the discs using FUNCTOOL T2-map software.Mean T1? values of the central disc nucleus pulposus were measured.The degenerative grade of each lumbar disc was assessed from T2-weighted images according to Pfirrmann degenerative grade.Bivariate correlation analysis was performed comparing T1? values to the pilots' s degenerative grade,disc space level,age and flight time.The differences between the pilots and the control group in terms of degenerative grade and in T1? values of Pfirrmann grade,age group and the level of discs were analyzed.Results:(1)Pilots group1)Pseudocolor imaging of T1?-map of normal Lumbar intervertebral discs:the central nucleus pulposus was orange red or yellow,and to the surrounding gradually became blue.The annulus fibrosus was homogeneous blue.There was a clear boundary between the nucleus pulposus and the annulus fibrous.The nucleus pulposus which degenerated seriously(Pfirrmann ?,?)was homogeneous blue and had no clear boundary.2)There was a significant difference in T1? values between Pfirrmann grade ?-?(F=277.892,P < 0.01),but no difference between ? and ?.T1 ? values negatively correlated with Pfirrmann grade ?-?(r=-0.901,P<0.01).T1?values of grade ?-? were 161.73±17.14 ms,128.18±12.65 ms,98.66±13.61 ms and 61.05±11.01 ms respectively.3)ROC analysis indicated that T1? cut-off values between ?-?,?-? and ?-? were 143.96 ms,110.7ms and 80.42 ms respectively with perfect sensitivity,specificity,and accuracy.Corresponding areas under the curve(AUC)were 0.975,0.930 and 0.988 respectively.4)There was no significant difference in the T1? values between every level(Welch=0.0849,P>0.05).T1? values of all level were: 105.45±19.85 ms,106.46±27.47 ms,112.46±37.75 ms,107.33±44.6ms and 96.51±35.17 ms respectively.5)The difference in T1? values between all the age groups was significant(Welch=77.406,P<0.01).T1?values of age groups were: 130.51±31.15 ms,93.24±19.8ms and 73.62±16.6ms respectively.6)T1? values were significantly different between each flight time group(Welch=41.641,P<0.01).T1?values of flight time groups were: 121.77±34.2ms,91.58±19.05 ms and 79.65±19.52 ms respectively.(2)Differences between pilots and control group1)The mean T1? value of pilots was significantly lower than that of the control group(t=-3.154,P<0.01).2)The differences between the pilots and the control group in terms of degenerative grade was significant(Z=-4.04,P<0.01).The degenerative grade of pilots mainly are grade ? and ?,but control group are grade ? and ?.3)Evaluation between groups showed no difference in T1? values between each Pfirrmann grade(t=1.504?0.809?0.692?0.248,P>0.05).4)There were significant differences in T1? values at each age group between pilots and control group(t=-4.438,-4.646,P < 0.01),but except for < 30 years group(t=0.583,P>0.05).5)T1? values of nucleus pulposus from L2-3 to L5-S1 discs had a significant decreasing trend in both groups,and T1? values of pilots' s discs were lower than that of control group at each level.But there was no significant difference between the groups(t=0.435,-1.667,-1.74,-1.667,-1.884,-3.154,P>0.05).Conclusion:T1? values of Lumbar intervertebral discs in pilots had significantly negative correlations with degenerative grade,age and flight time,except for disk space levels.Disc degeneration increased with age and flight time.Disc degeneration occurred on pilots was more seriously and the process of degeneration was more quickly.Overload on spine column of pilots maybe was the important reason in degeneration and which accelerates thedegeneration process.T1? can be potentially used as a valid clinical tool in quantitative diagnosis of early intervertebral disc degeneration in asymptomatic Pilots,and it can reflect the process of degeneration with age and overload. |
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