Synopsis
DTI can noninvasive
evaluate the injury and prognosis of spinal cord, and NRG-1 has the function of
protecting and repairing of injury spinal cord in rats.Objective
To investigate
the value of DTI and DTT in evaluating the protective effect of neuregulin-1 on
spinal cord transection models of Sprague–Dawley (SD) rats.
methods
30 SD rats were randomly
divided into three groups: normal saline (NS) group (10 rats), NRG-1 group (10
rats), health control group (HC) group (10 rats). T9/10 level spinal cord
transection model was performed on NS group and NRG-1 group, and NS and NRG-1
were injected respectively after operation, once a day for three days; nothing
treated was on HC group. MRI and DTI examinations were performed in three
groups using 3.0T Philips MR scanner a week later. The date was transferred to
Philips workstation to calculate the DTI indices. ROIs were placed in the
spinal cord within 1 centimeter of the level of T9/10. The parameters: ADC
values, FA values, Fiber density coefficient (FDi) and Fiber Length were
acquired, and then taking those averages of multiple measurements as the final
results.
Conventional MRI and DTI scans were conducted on 3.0T MR scanner (Philips Achieva
TX, Best, The Netherlands) with wrist coil. The SD rats were mounted in supine
position within the scanner. Conventional MRI scan, including T1-weighted and
T2-weighted sagittal images, was completed with the SE sequence. DTI images
were acquired with the parameters as follows: single shot spin-echo planar
imaging(EPI) sequence, TR 3034ms, TE 66ms, max b-factor 800s/mm2, EPI
factor 25, slice thickness 0.8mm, slice gap 0, acquisition matrix 64×68, FOV 106mm×106mm×16mm, total scan duration was 4 minutes
8 seconds.
I
After image acquisition,
the date was transferred to Philips workstation to calculate the DTI indices. For
accurate positioning, DTI images confused with the sagittal T2-weighted images,
ROIs were placed in the spinal cord within 1 centimeter of the level of T9/10.
The parameters: ADC values, FA values, Fiber density
coefficient (FDi), Fiber Length, were acquired, and then taking those
averages of multiple measurements as the final results. The DTT of the spinal
cord was generated with the parameters:
anisotropy 0.2, angular 25°.
Fig.1 Confused DTI
images with T2-weighted sagittal images, placing the ROI on the axial map (Purple
region) within 1 centimeter of the level T9/10. The ADC, FA, FDi, Length values
were acquired.
Data were
expressed as mean± SD, and were analyzed using SPSS 19.0. Statistical analysis
using Student’s t-test, P < 0.05 was regarded as statistically significant.
Results
The ADC values, FA values, FDi and Fiber Length of NS group
were（0.86±0.14）×10-3cm2/s,
0.28±0.09,
4.8±1.0
and（13.3±1.3）mm；NRG-1
group were（0.87±0.15）×10-3cm2/s,
0.33±0.04,
7.8±1.1
and（29.7±3.5）mm;
HC group were（0.71±0.08）×10-3cm2/s,
0.67±0.07,
14.3±2.5
and（38.3±5.8）mm
respectively. The ADC values of NS and NRG-1group were significantly decreased
compared with HC group; however, there was no difference between NS and NRG-1.
The FA values, FDi and Fiber Length of NRG-1group were all decreased compared
with HC group, and increased compared with NS group, and the differences were
statistically significant.
Fig.2 The MR Images of HC
group. a. sagittal T2-weighted
images show the spinal cord was intact, there
was no abnormal signal; b. DTT map, demonstrating
the fiber bundle was continuous.Fig.3 The MR Images of
NRG-1 group. a. sagittal T2-weighted
image show abnormal mixed signal at
the level of T9/10(arrow), the swelling of close soft
tissue in the back of the rats was caused by surgery; b. DTT map, demonstrating a part of fiber bundle at the level of
T9/10 (arrow)was fracture.
Conclusion
DTI can noninvasive evaluate the injury and prognosis of spinal
cord, and NRG-1 has the function of protecting and repairing of injury spinal
cord in rats.
Acknowledgements
No acknowledgement found.References
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