Dataset Information

Whole-brain vessel wall MRI: A parameter tune-up solution to improve the scan efficiency of three-dimensional variable flip-angle turbo spin-echo.

ABSTRACT: To propose and evaluate a parameter tune-up solution to expedite a three-dimensional (3D) variable-flip-angle turbo spin-echo (TSE) sequence for whole-brain intracranial vessel wall (IVW) imaging.Elliptical k-space sampling and prolonged echo train length (ETL), were used to expedite a 3D variable-flip-angle TSE-based sequence. To compensate for the potential loss in vessel wall signal, optimal combination of prescribed T2 and ETL was experimentally investigated on 22 healthy volunteers at 3 Tesla. The optimized protocol (7-8?min) was then compared with a previous protocol (reference protocol, 11-12?min) in terms of signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), vessel wall sharpness, and wall delineation quality on a 4-point scale (0:poor; 3:excellent) in 10 healthy volunteers. A pilot study of five patients was performed and lesion delineation score was used to demonstrate the diagnostic quality.A protocol with ETL?=?52 and prescribed T2 ?=?170 ms was deemed an optimized one, which, compared with the reference protocol, provided significantly improved wall SNR (12.0?±?1.3 versus 10.0?±?1.1; P?=?0.002), wall-lumen CNR (9.7?±?1.2 versus 8.0?±?0.9; P?=?0.002), wall-CSF CNR (2.8?±?1.0 versus 1.7?±?1.0; P?=?0.026), similar vessel wall sharpness at both inner (1.59?±?0.18 versus 1.58?±?0.14, P?=?0.87) and outer (1.71?±?0.25 versus 1.83?±?0.30; P?=?0.18) boundaries, and comparable vessel wall delineation score for individual segments (1.95-3; P?>?0.06). In all patients, atherosclerotic plaques (10) or wall dissection (5) were identified with a delineation score of 3 or 2.A parameter tune-up solution can accelerate 3D variable-flip-angle TSE acquisitions, particularly allowed for expedited whole-brain IVW imaging with preserved wall delineation quality.2. Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:751-757.

SUBMITTER: Yang Q

PROVIDER: S-EPMC5519453 | biostudies-other | 2017 Sep

REPOSITORIES: biostudies-other

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Whole-brain vessel wall MRI: A parameter tune-up solution to improve the scan efficiency of three-dimensional variable flip-angle turbo spin-echo.

Yang Qi Q Deng Zixin Z Bi Xiaoming X Song Shlee S SS Schlick Konrad H KH Gonzalez Nestor R NR Li Debiao D Fan Zhaoyang Z

Journal of magnetic resonance imaging : JMRI 20170120 3

<h4>Purpose</h4>To propose and evaluate a parameter tune-up solution to expedite a three-dimensional (3D) variable-flip-angle turbo spin-echo (TSE) sequence for whole-brain intracranial vessel wall (IVW) imaging.<h4>Materials and methods</h4>Elliptical k-space sampling and prolonged echo train length (ETL), were used to expedite a 3D variable-flip-angle TSE-based sequence. To compensate for the potential loss in vessel wall signal, optimal combination of prescribed T<sub>2</sub> and ETL was expe ...[more]

PMID: 28106936

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Project description:Quantitative proton density (PD) maps measure the amount of free water, which is important for non-invasive tissue characterization in pathology and across lifespan. PD mapping requires the estimation and subsequent removal of factors influencing the signal intensity other than PD. These factors include the T1, T2* relaxation effects, transmit field inhomogeneities, receiver coil sensitivity profile (RP) and the spatially invariant factor that is required to scale the data. While the transmit field can be reliably measured, the RP estimation is usually based on image post-processing techniques due to limitations of its measurement at magnetic fields higher than 1.5 T. The post-processing methods are based on unified bias-field/tissue segmentation, fitting the sensitivity profile from images obtained with different coils, or on the linear relationship between T1 and PD. The scaling factor is derived from the signal within a specific tissue compartment or reference object. However, these approaches for calculating the RP and scaling factor have limitations particularly in severe pathology or over a wide age range, restricting their application. We propose a new approach for PD mapping based on a multi-contrast variable flip angle acquisition protocol and a data-driven estimation method for the RP correction and map scaling. By combining all the multi-contrast data acquired at different echo times, we are able to fully correct the MRI signal for T2* relaxation effects and to decrease the variance and the entropy of PD values within tissue class of the final map. The RP is determined from the corrected data applying a non-parametric bias estimation, and the scaling factor is based on the median intensity of an external calibration object. Finally, we compare the signal intensity and homogeneity of the multi-contrast PD map with the well-established effective PD (PD*) mapping, for which the RP is based on concurrent bias field estimation and tissue classification, and the scaling factor is estimated from the mean white matter signal. The multi-contrast PD values homogeneity and accuracy within the cerebrospinal fluid (CSF) and deep brain structures are increased beyond that obtained using PD* maps. We demonstrate that the multi-contrast RP approach is insensitive to anatomical or a priori tissue information by applying it in a patient with extensive brain abnormalities and for whole body PD mapping in post-mortem foetal imaging.

Dataset Information

Whole-brain vessel wall MRI: A parameter tune-up solution to improve the scan efficiency of three-dimensional variable flip-angle turbo spin-echo.

Publications

Whole-brain vessel wall MRI: A parameter tune-up solution to improve the scan efficiency of three-dimensional variable flip-angle turbo spin-echo.

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