Jay V Gonyea1, Richard Watts1, Angela Applebee2, Trevor Andrews1,3, Scott Hipko1, Joshua P Nickerson1, Lindsay Thornton4, and Christopher G Filippi5
1Radiology-MRI Center for Biomedical Imaging, University of Vermont College of Medicine, Burlington, VT, United States, 2Neurological Sciences, University of Vermont College of Medicine, Burlington, VT, United States, 3Philips Health Tech, Cleveland, OH, United States, 4Radiology, University of Florida, Gainesville, FL, United States, 5Radiology, North Shore University Hospital-Long Island Jewish, New York, NY, United States
Synopsis
Quantitative MRI measures such as T2 are
limited in their ability of staging MS progression. T1ρ may be
sensitive to low-frequency chemical exchange between proteins and extracellular
water. A 3D TSE with whole-brain coverage, spin-lock times of 0, 20, 40, 60,
80, and 100 ms spin-lock times was acquired at 500 Hz. We found that T1ρ provides
better contrast-to-noise-ratio (CNR) than T2.Purpose
To determine if whole-brain 3D T
1rho (T
1ρ)
provides improved MS lesion conspicuity than T
2(1).
Methods
This prospective, IRB-approved study of 23
MS patients (17 female, age 43± 9 yrs, 10 with clinically isolated syndrome and
13 relapsing remitting) compared quantitative T
1ρ and T
2 contrast
of MS lesions against background tissue. Whole-brain axial T
1ρ and T
2 weighted MR imaging was performed
at 3.0T, using a 3D Turbo Spin Echo (TSE) sequence with fluid suppression (1.8 x 1.8 x 1.8 mm3), TR/TE = 4800/24ms,
TI 1650ms, FOV 250mm and spin lock frequencies of 500Hz (T
1ρ) and 0Hz (T
2), with spin-lock
times of 0, 20, 40, 60, 80, and 100ms. For
lesion detection and segmentation 3D T
1 turbo field echo (TFE), 3D
FLAIR, and 3D double inversion recovery (DIR) were acquired. Regions-of-interest
(ROIs) were defined over GM and WM lesions by a CAQ-certified neuroradiologist
using MRIcron.(2) Mean T
1ρ
and T
2 values of lesions were compared to the surrounding normal appearing
WM and GM. Lesion conspicuity was defined
as:, where μLesion is the mean T
1ρ
(or T
2) value of the
lesion, and μTissue and σTissue
represent the mean standard
deviation of the corresponding normal appearing tissue (WM or GM, depending on
the location of the lesion).(3)
Results
T
1ρ
and T
2 values for WM lesions were highly correlated (Figure 1, r2=0.83),
but T
1ρ demonstrated 25% higher lesion CNR than T
2. We
found 233/260 (89%, p<0.001) white matter lesions and 20/26 (77%, p=0.001)
of gray matter lesions were more conspicuous on T
1ρ than T
2
maps. Despite this high correlation,
some lesions showed moderate to large discrepancies between their visualization
on the T
1ρ and T
2 maps (Figure 2).
Discussion
Despite strong correlation between T
1ρ and T
2, lesions were more conspicuous on T
1ρ. T
1ρ MR imaging
may be a useful tool for measuring focal changes in cortical and white matter lesions
and may provide improved sensitivity to low-frequency chemical exchange that is
not possible with other quantitative techniques, such as T
2.
Conclusion
T
1ρ provides superior CNR and lesion conspicuity
to T
2 in patients with multiple sclerosis.
Acknowledgements
The authors
thank Aida Arapovic and Jane Low for their diligent administrative efforts
related to this project. We also thank the MS patients who participated in the
study.References
1. Watts R, Hipko S, Gonyea J, Filippi C. In vivo Whole-Brain T1-rho mapping across adulthood - Normative values and age dependence Journal of Magnetic Resonance Imaging 2013;Manuscript # JMRI-13-0297.R2(TBA).
2. Rorden C, Brett M. Stereotaxic display of brain lesions. Behavioural neurology 2000;12(4):191-200.
3. Filippi M, Baratti C, Yousry T, et al. Quantitative assessment of MRI lesion load in multiple sclerosis A comparison of conventional spin-echo with fast fluid attenuated inversion recovery. Brain 1996;119(4):1349-1355.