Brain Parcellation Repeatability and Reproducibility Using Conventional and Quantitative 3D MR Imaging.

Background And Purpose: Automatic brain parcellation is typically performed on dedicated MR imaging sequences, which require valuable examination time. In this study, a 3D MR imaging quantification sequence to retrieve R and R relaxation rates and proton density maps was used to synthesize a T1-weighted image stack for brain volume measurement, thereby combining image data for multiple purposes. The repeatability and reproducibility of using the conventional and synthetic input data were evaluated.

Quantitative MRI using relaxometry in malignant gliomas detects contrast enhancement in peritumoral oedema.

Malignant gliomas are primary brain tumours with an infiltrative growth pattern, often with contrast enhancement on magnetic resonance imaging (MRI). However, it is well known that tumour infiltration extends beyond the visible contrast enhancement. The aim of this study was to investigate if there is contrast enhancement not detected visually in the peritumoral oedema of malignant gliomas by using relaxometry with synthetic MRI.

Synthetic MRI of the Knee: Phantom Validation and Comparison with Conventional MRI.

Purpose To test the hypothesis that synthetic MRI of the knee generates accurate and repeatable quantitative maps and produces morphologic MR images with similar quality and detection rates of structural abnormalities than does conventional MRI. Materials and Methods Data were collected prospectively between January 2017 and April 2018 and were retrospectively analyzed. An International Society for Magnetic Resonance in Medicine-National Institute of Standards and Technology phantom was used to determine the accuracy of T1, T2, and proton density (PD) quantification.

Improved Precision of Automatic Brain Volume Measurements in Patients with Clinically Isolated Syndrome and Multiple Sclerosis Using Edema Correction.

Background And Purpose: The presence of edema will result in increased brain volume, which may obscure progressing brain atrophy. Similarly, treatment-induced edema reduction may appear as accelerated brain tissue loss (pseudoatrophy). The purpose of this study was to correlate brain tissue properties to brain volume, to investigate the possibilities for edema correction and the resulting improvement of the precision of automated brain volume measurements.

Quantitative MRI for analysis of peritumoral edema in malignant gliomas.

Background And Purpose: Damage to the blood-brain barrier with subsequent contrast enhancement is a hallmark of glioblastoma. Non-enhancing tumor invasion into the peritumoral edema is, however, not usually visible on conventional magnetic resonance imaging. New quantitative techniques using relaxometry offer additional information about tissue properties.

Myelin Detection Using Rapid Quantitative MR Imaging Correlated to Macroscopically Registered Luxol Fast Blue-Stained Brain Specimens.

Background And Purpose: Myelin detection is of great value in monitoring diseases such as multiple sclerosis and dementia. However, most MR imaging methods to measure myelin are challenging for routine clinical use. Recently, a novel method was published, in which the presence of myelin is inferred by using its effect on the intra- and extracellular water relaxation rates and proton density, observable by rapid quantitative MR imaging.

Multi-parametric representation of voxel-based quantitative magnetic resonance imaging.

The aim of the study was to explore the possibilities of multi-parametric representations of voxel-wise quantitative MRI data to objectively discriminate pathological cerebral tissue in patients with brain disorders. For this purpose, we recruited 19 patients with Multiple Sclerosis (MS) as benchmark samples and 19 age and gender matched healthy subjects as a reference group. The subjects were examined using quantitative Magnetic Resonance Imaging (MRI) measuring the tissue structure parameters: relaxation rates, R(1) and R(2), and proton density.

Effects of gadolinium contrast agent administration on automatic brain tissue classification of patients with multiple sclerosis.

Background And Purpose: The administration of gadolinium contrast agent is a common part of MR imaging examinations in patients with MS. The presence of gadolinium may affect the outcome of automated tissue classification. The purpose of this study was to investigate the effects of the presence of gadolinium on the automatic segmentation in patients with MS by using the synthetic tissue-mapping method.

Application of quantitative MRI for brain tissue segmentation at 1.5 T and 3.0 T field strengths.

Background: Brain tissue segmentation of white matter (WM), grey matter (GM), and cerebrospinal fluid (CSF) are important in neuroradiological applications. Quantitative Mri (qMRI) allows segmentation based on physical tissue properties, and the dependencies on MR scanner settings are removed. Brain tissue groups into clusters in the three dimensional space formed by the qMRI parameters R1, R2 and PD, and partial volume voxels are intermediate in this space.

Brain characterization using normalized quantitative magnetic resonance imaging.

Objectives: To present a method for generating reference maps of typical brain characteristics of groups of subjects using a novel combination of rapid quantitative Magnetic Resonance Imaging (qMRI) and brain normalization. The reference maps can be used to detect significant tissue differences in patients, both locally and globally.

Materials And Methods: A rapid qMRI method was used to obtain the longitudinal relaxation rate (R1), the transverse relaxation rate (R2) and the proton density (PD).

Increased concentrations of glutamate and glutamine in normal-appearing white matter of patients with multiple sclerosis and normal MR imaging brain scans.

In Multiple Sclerosis (MS) the relationship between disease process in normal-appearing white matter (NAWM) and the development of white matter lesions is not well understood. In this study we used single voxel proton 'Quantitative Magnetic Resonance Spectroscopy' (qMRS) to characterize the NAWM and thalamus both in atypical 'Clinically Definite MS' (CDMS) patients, MRI(neg) (N = 15) with very few lesions (two or fewer lesions), and in typical CDMS patients, MRI(pos) (N = 20) with lesions, in comparison with healthy control subjects (N = 20). In addition, the metabolite concentrations were also correlated with extent of brain atrophy measured using Brain Parenchymal Fraction (BPF) and severity of the disease measured using 'Multiple Sclerosis Severity Score' (MSSS).

Procedure for quantitative (1)H magnetic resonance spectroscopy and tissue characterization of human brain tissue based on the use of quantitative magnetic resonance imaging.

Purpose: Existing methods for quantitative magnetic resonance spectroscopy are not widely used for magnetic resonance spectroscopy examinations in clinical practice due to the lengthy and difficult workflow. In this report, we aimed to investigate whether metabolite concentrations show co-variation with relaxation parameters (R1,H2O,R2,H2O), water concentration (ĈH2O), and age, using a quantitative magnetic resonance spectroscopy method, which is suitable for a clinical setting.

Methods: We performed 166 single voxel magnetic resonance spectroscopy measurements in the white matter and thalamus in 47 healthy subjects, aged 18-72 years.

Synthetic MRI of the brain in a clinical setting.

Background: Conventional magnetic resonance imaging (MRI) has relatively long scan times for routine examinations, and the signal intensity of the images is related to the specific MR scanner settings. Due to scanner imperfections and automatic optimizations, it is impossible to compare images in terms of absolute image intensity. Synthetic MRI, a method to generate conventional images based on MR quantification, potentially both decreases examination time and enables quantitative measurements.

Automated determination of brain parenchymal fraction in multiple sclerosis.

Background And Purpose: Brain atrophy is a manifestation of tissue damage in MS. Reduction in brain parenchymal fraction is an accepted marker of brain atrophy. In this study, the approach of synthetic tissue mapping was applied, in which brain parenchymal fraction was automatically calculated based on absolute quantification of the tissue relaxation rates R1 and R2 and the proton attenuation.

Novel whole brain segmentation and volume estimation using quantitative MRI.

Objectives: Brain segmentation and volume estimation of grey matter (GM), white matter (WM) and cerebro-spinal fluid (CSF) are important for many neurological applications. Volumetric changes are observed in multiple sclerosis (MS), Alzheimer's disease and dementia, and in normal aging. A novel method is presented to segment brain tissue based on quantitative magnetic resonance imaging (qMRI) of the longitudinal relaxation rate R(1), the transverse relaxation rate R(2) and the proton density, PD.

Rapid magnetic resonance quantification on the brain: Optimization for clinical usage.

A method is presented for rapid simultaneous quantification of the longitudinal T(1) relaxation, the transverse T(2) relaxation, the proton density (PD), and the amplitude of the local radio frequency B(1) field. All four parameters are measured in one single scan by means of a multislice, multiecho, and multidelay acquisition. It is based on a previously reported method, which was substantially improved for routine clinical usage.

Atomic spectral detection of tunable extreme ultraviolet pulses.

A novel method of detecting the spectral width and wavelength of extreme ultraviolet (XUV) pulses with a minimum number of experimental tools is demonstrated. The method relies on the photoionization probability of an atom as a function of the electric field. A tunable laser source in the XUV is used that is based on higher-harmonic generation of the frequency-doubled output of a 50-fs Ti:sapphire laser.

Novel method for rapid, simultaneous T1, T2*, and proton density quantification.

An imaging method called "quantification of relaxation times and proton density by twin-echo saturation-recovery turbo-field echo" (QRAPTEST) is presented as a means of quickly determining the longitudinal T(1) and transverse T(2) (*) relaxation time and proton density (PD) within a single sequence. The method also includes an estimation of the B(1) field inhomogeneity. High-resolution images covering large volumes can be achieved within clinically acceptable times of 5-10 min.