Cerebral venous thrombosis: direct thrombus imaging with sub-millimeter isotropic resolution dark-blood CMR
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KeywordsCerebral Venous Thrombosis Arachnoid Granulation Vessel Wall Imaging Grappa Factor Sinus Lumen
Cerebral venous thrombosis (CVT) is a disorder potentially leading to devastating disability and even death if not timely diagnosed and treated. While TOF MR venography is most commonly used for diagnosis, the accuracy can be compromised by the flow voids caused by a slow or complex flow pattern and in-plane flow saturation. Several other MR techniques, relying on characteristic image contrast of CVT, may also under- or over-estimate the thrombus due to the signals from venous flow and other structures. High-spatial resolution dark-blood CMR could address the above issues, but, to our knowledge, has not been attempted. In this work, a fast dark-blood CMR technique was developed and validated in CVT patients.
Sequence SPACE (variable-flip-angle 3D TSE) has increasingly been applied in vessel wall imaging at various arterial vascular beds due to its inherent dark-blood effect and fast imaging speed. However, suppressing slower venous blood flow remains a challenge for SPACE. To better detect CVT, particularly in the subacute stage, we combined T1-w SPACE with (a) a nonselective saturation pulse to exclude the T2-weighting that resides in the longitudinal magnetization at the end of the long echo train and (b) a DANTE preparation to suppress slow flow signals while introducing less T2-weighting. Imaging Using a 3T system and 32-ch coil, the sequence was first optimized for blood suppression on 5 healthy subjects (2F 3M). Six scans with different DANTE RF pulse train lengths (0, 50, 100, 150, 200, 250) were conducted with other DANTE parameters held fixed (FA 12o, RF gap 1ms, gradient strength 20mT/m). Imaging parameters for SPACE included: sagittal orientation, isotropic 0.78mm resolution, TR/TE 600/8.8ms, 37 echoes, GRAPPA factor 2, scan time 5min38sec. Contrast-to-noise ratio (CNR) analysis for the residual blood region vs. dark lumen and white matter vs. dark lumen were performed to determine the optimal DANTE pulse train length. The optimized sequence was prospectively tested on 4 patients (3F 1M) who were suspected of CVT.
This work, for the first time, investigated the feasibility of dark-blood CMR for CVT imaging. The T1-w DANTE-prepared SPACE technique eliminates the flow artifact in the sinus and permits direct visualization of intrasinus thrombus and surrounding structures. A large clinical study is underway to validate the clinical value of the technique for different CVT stages.
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