Jianwei Liao1, Jin Liu1, Yajun Ma2, Xiaojun Chen1, Wei Li1, Lin Yao1, Long Qian3, Jiang Du2, and Shaolin Li1
1Department of Radiology, The Fifth Affiliated Hospital of Sun Yat-Sen University, Zhuhai, China, 2Department of Radiology, University of California, San Diego, CA, United States, 3MR Research, GE Healthcare, Guangzhou, China
Synopsis
Magnetization
transfer ratio (MTR) has been used for assessment of macromolecules in
biological tissues. Ultrashort echo time technique magnetization
transfer (UTE-MT) can quantify both of short and long T2 tissues, may have
potential to evaluate early disc herniation. The current study aims to assess the
feasibility of UTE-MT quantification of posterior longitudinal ligament and nucleus
pulposus for evaluation of early disc herniation. It was concluded that the UTE-MT
sequence is feasible to quantify posterior longitudinal ligament and nucleus
pulposus in lumbar. Posterior longitudinal ligament and nucleus pulposus UTE-MTR may provide a new
opportunity for early prediction of lumbar disc herniation.
Introduction
Lumbar
discectomy is the most common surgical procedure for patients with back pain in
the United States, with over 300,000 discectomy procedures every year.[1]The degeneration or ossification of
posterior longitudinal ligament and nucleus pulposus may be closely related to
the early disc herniation. However, the T2 of the posterior longitudinal
ligament is relatively short and cannot be effectively imaged in conventional
clinical sequences. Ultrashort echo time magnetization transfer (UTE-MT) sequence
with TEs less than 100 μs can be used for imaging
and quantifying both short and long T2 tissues. The derived index magnetization
transfer ratio (MTR) [2] may be potentially useful for early disc herniation
assessment. In this study, we utilized UTE-MT sequence to investigate the
correlations between UTE-MTR of posterior longitudinal ligament/nucleus pulposus
and lumbar disc herniation.Methods
A total of 50 disc herniation patients (age
47 ± 16 years, age range 34-75 years) were recruited and underwent UTE-MT sequence
of lumbar on a 3.0T MRI scanner (Signa, Pioneer, GE Healthcare). A Fermi pulse
was employed to generate the MT contrast in UTE-MT sequence with duration of
8ms and bandwidth of 160Hz. The frequency offset of this MT pulse was 1500 Hz.
The UTE-MT sequence was scanned twice with flip angle of 750° for MT-On and 0°
for MT-Off. Other UTE-MT sequence parameters were as follows: TR = 100 ms, TE =
0.032 ms, excitation flip angle = 5°, number of spokes per-TR = 5, FOV = 28cm ×
28cm, matrix = 140 × 140, slice thickness = 3.6mm, and slice number = 16, oversampling
factor = 1.2, and scan time = 3min. The ROI of the posterior longitudinal ligament
and nucleus pulposus was manually delineated by a radiologist with 10 years of experience. The grade of disc herniation was divided into disc herniation
and non disc herniation by a radiologist with 15 years of experience. Then, according
to Michigan State University (MSU) classification of lumbar disc herniation[3],
lumbar disc herniation was divided into grade 1, grade 2 and grade 3, and
no herniated disc was defined as grade 0. Pearson correlation
analysis was performed to calculate the correlations between posterior longitudinal
ligament/nucleus pulposus UTE-MTR value and two kinds of classification of disc
herniation. A one way ANOVA test was used to compare posterior longitudinal ligament
and nucleus pulposus UTE-MTR between different grades of disc herniation. A
value of P < 0.05 was considered as a statistically significant.Results
Figure
1 shows the representative lumbar UTE-MT images acquired from a 63-year-old male
disc herniation volunteer. The posterior longitudinal ligament and nucleus pulposus
UTE-MTR showed a positive correlation with disc herniation (r2= 0.333,
P < 0.001; r2= 0.504, P < 0.001, respectively) (Figure 2). The
posterior longitudinal ligament and nucleus pulposus UTE-MTR showed a positive
correlation with MSU classification of disc herniation (r2= 0.382, P <
0.001; r2= 0.516, P < 0.001, respectively) (Figure 3).Discussion and Conclusion
To
our best knowledge, this is the first prospective study of applying UTE-MT in posterior
longitudinal ligament and nucleus pulposus to assess lumbar disc herniation. Our
findings suggested that the high UTE-MTR of posterior longitudinal ligament and nucleus
pulposus associate with more severe lumbar disc herniation in patients. In conclusion,
the UTE-MTR of posterior longitudinal ligament and nucleus pulposus may be a promising
biomarker to predict early disc herniation in lumbar spine.Acknowledgements
No acknowledgement found.References
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