Whole-Brain Myelin Imaging Using 3D Double-Echo Sliding Inversion Recovery Ultrashort Echo Time (DESIRE UTE) MRI

Abstract

Background: Signal contamination from long T2 water is a major challenge in direct imaging of myelin with MRI. Nulling of the unwanted long T2 signals can be achieved with an inversion recovery (IR) preparation pulse to null long T2 white matter within the brain. The remaining ultrashort T2 signal from myelin can be detected with an ultrashort echo time (UTE) sequence.Purpose: To develop patient-specific whole-brain myelin imaging with a three-dimensional double-echo sliding inversion recovery (DESIRE) UTE sequence. Materials and Methods:The DESIRE UTE sequence generates a series of IR images with different inversion times during a single scan. The optimal inversion time for nulling long T2 signal is determined by finding minimal signal on the second echo. Myelin images are generated by subtracting the second echo image from the first UTE image. To validate this method, a prospective study was performed in phantoms, cadaveric brain specimens, healthy volunteers, and patients with multiple sclerosis (MS). A total of 20 healthy volunteers (mean age, 40 years 6 13 [standard deviation], 10 women) and 20 patients with MS (mean age, 58 years 6 8; 15 women) who underwent MRI between November 2017 and February 2019 were prospectively included. Analysis of variance was performed to evaluate the signal difference between MS lesions and normal-appearing white matter in patients with MS.Results: High signal intensity and corresponding T2* and T1 of the extracted myelin vesicles provided evidence for direct imaging of ultrashort-T2 myelin protons using the UTE sequence. Gadobenate dimeglumine phantoms with a wide range of T1 values were selectively suppressed with DESIRE UTE. In the ex vivo brain study of MS lesions, signal loss was observed in MS lesions and was conformed with histologic analysis. In the human study, there was a significant reduction in normalized signal intensity in MS lesions compared with that in normal-appearing white matter (0.19 6 0.10 vs 0.76 6 0.11, respectively; P , .001). Conclusion:The double-echo sliding inversion recovery ultrashort echo time sequence can generate whole-brain myelin images specifically with a clinical 3-T scanner.

Volumetric imaging of myelin in vivo using 3D inversion recovery‐prepared ultrashort echo time cones magnetic resonance imaging

“…3D UTE images show high signal from the intact myelin vesicles with a short T 1 of 367 ± 4 ms and T 2 * of 225 ± 7 μs on a clinical 3 T scanner. 44 The T 2 * of intact myelin vesicles is quite similar to those of myelin lipid powder and myelin-D 2 O paste. 27 It is currently unknown what (if any) changes in the MRI signal result from the ultrastructure, perhaps through interactions between the lamella.…”

Point-of-care lung ultrasound imaging in pediatric COVID-19

“…Since the first reports on COVID-19 pneumonia, emphasis has been given to the role and impact of thoracic imaging for accurate assessment of lung compromise and timely detection of complications. Chest CT has gained an important role in this setting, because chest radiograph is of limited value for COVID-19 diagnosis, with a reported sensitivity of only 69% [95% CI 56–80%] [ 20 ]. Lung US has an already established accuracy and reliability in diagnosing many lung pathologies, but up to now, only few studies have been published on its applicability in COVID-19.…”

Fast T1 measurement of cortical bone using 3D UTE actual flip angle imaging and single‐TR acquisition (3D UTE‐AFI‐STR)

“…The matrix sizes of UTE‐AFI acquisitions can potentially be reduced to improve the scan efficiency of the UTE‐AFI‐STR method. Together with our recently developed combined parallel imaging and compressed‐sensing reconstruction for fast 3D UTE imaging, 19 it is potentially possible to generate a cortical bone T 1 measurement protocol with a clinically acceptable scan time of about 5 minutes. We will work on this protocol and report the results in a future study.…”