Rapid CNN-based needle localization for automatic slice alignment in MR-guided interventions using 3D undersampled radial white-marker imaging.

Background: In MR-guided in-bore percutaneous needle interventions, typically 2D interactive real-time imaging is used for navigating the needle into the target. Misaligned 2D imaging planes can result in losing visibility of the needle in the 2D images, which impedes successful targeting. Necessary iterative manual slice adjustment can prolong interventional workflows.

Assessment of Sodium MRI at 7 Tesla as Predictor of Therapy Response and Survival in Glioblastoma Patients.

The purpose of this work was to prospectively investigate sodium (Na) MRI at 7 Tesla (T) as predictor of therapy response and survival in patients with glioblastoma (GBM). Thus, 20 GBM patients underwent Na MRI at 7T before, immediately after and 6 weeks after chemoradiotherapy (CRT). The median tissue sodium concentration (TSC) inside the whole tumor excluding necrosis was determined.

Multiparametric MRI for Characterization of the Basal Ganglia and the Midbrain.

To characterize subcortical nuclei by multi-parametric quantitative magnetic resonance imaging. The following quantitative multiparametric MR data of five healthy volunteers were acquired on a 7T MRI system: 3D gradient echo (GRE) data for the calculation of quantitative susceptibility maps (QSM), GRE sequences with and without off-resonant magnetic transfer pulse for magnetization transfer ratio (MTR) calculation, a magnetization-prepared 2 rapid acquisition gradient echo sequence for T mapping, and (after a coil change) a density-adapted 3D radial pulse sequence for Na imaging. First, all data were co-registered to the GRE data, volumes of interest (VOIs) for 21 subcortical structures were drawn manually for each volunteer, and a combined voxel-wise analysis of the four MR contrasts (QSM, MTR, T, Na) in each structure was conducted to assess the quantitative, MR value-based differentiability of structures.

Ultra-high-field sodium MRI as biomarker for tumor extent, grade and IDH mutation status in glioma patients.

Purpose: This prospective clinical trial investigated sodium (Na) MRI at 7 Tesla (T) field strength as biomarker for tumor extent, isocitrate dehydrogenase (IDH) mutation and O6-methylguanine DNA methyltransferase (MGMT) promotor methylation in glioma patients.

Methods: 28 glioma patients underwent Na MRI on a 7T scanner (Siemens Healthcare, Erlangen, Germany) parallel to standard 3T MRI before chemoradiation. Areas of Gadolinium-contrast enhancement (gdce), non-enhancing T2-hyperintensity (regarded as edema), necrosis, and normal-appearing white matter (nawm) were segmented on 3T MRI imaging and were co-registered with the Na images.

Towards accelerated quantitative sodium MRI at 7 T in the skeletal muscle: Comparison of anisotropic acquisition- and compressed sensing techniques.

Purpose: To compare three anisotropic acquisition schemes and three compressed sensing (CS) approaches for accelerated tissue sodium concentration (TSC) quantification using Na MRI at 7 T.

Materials And Methods: Three anisotropic 3D-radial acquisition sequences were evaluated using simulations, phantom- and in vivo TSC measurements: An anisotropic density-adapted 3D-radial sequence (3DPR-C), a 3D acquisition-weighted density-adapted stack-of-stars sampling scheme (SOS) and a SOS approach with golden-ratio rotation (SOS-GR). Eight healthy volunteers were examined at a 7 Tesla MRI system.

Sodium relaxometry using Na MR fingerprinting: A proof of concept.

Purpose: To evaluate the feasibility of Na MR fingerprinting (MRF) for simultaneous quantification of T , , , in addition to ΔB .

Methods: A framework for sodium relaxometry using MRF at 7T was developed, allowing simultaneous measurement of relaxation times and inhomogeneities in the static field. The technique distinguishes between bi- and monoexponential transverse relaxation and was validated in simulations with respect to the ground truth.

Correction to: Accelerated quantification of tissue sodium concentration in skeletal muscle tissue: quantitative capability of dictionary learning compressed sensing.

The original version of this article unfortunately contained a mistake. Title was incorrect.

Accelerated quantification of tissue sodium concentration in skeletal muscle tissue: quantitative capability of dictionary learning compressed sensing.

Objective: To accelerate tissue sodium concentration (TSC) quantification of skeletal muscle using Na MRI and 3D dictionary-learning compressed sensing (3D-DLCS).

Materials And Methods: Simulations and in vivo Na MRI examinations of calf muscle were performed with a nominal spatial resolution of [Formula: see text]. Fully sampled and three undersampled Na MRI data sets (undersampling factors (USF) = 3, 4.

High-resolution FLAIR MRI at 7 Tesla for treatment planning in glioblastoma patients.

Ultra-high field MRI is an emerging technique promising high-resolution images for radiotherapy planning. We compared a 7 Tesla FLAIR sequence with clinical FLAIR imaging at 3 Tesla in glioblastoma patients before radiotherapy. High-resolution 7 Tesla FLAIR imaging may enhance the depiction of organs at risk and possibly modify target volumes.

Probing the microscopic environment of Na ions in brain tissue by MRI: On the accuracy of different sampling schemes for the determination of rapid, biexponential T2* decay at low signal-to-noise ratio.

Purpose: To investigate and to reduce influences on the determination of the short and long apparent transverse relaxation times ( T2,s*, T2,l*) of Na in vivo with respect to signal sampling.

Methods: The accuracy of T2* determination was analyzed in simulations for five different sampling schemes. The influence of noise in the parameter fit was investigated for three different models.

Reproducibility of CMRO determination using dynamic O MRI.

Purpose: To assess the reproducibility of O MRI-based determination of the cerebral metabolic rate of oxygen consumption (CMRO ) in healthy volunteers. To assess the influence of image acquisition and reconstruction parameters on dynamic quantification of functional parameters such as CMRO .

Methods: Dynamic O MRI data were simulated and used to investigate influences of temporal resolution (Δt) and partial volume correction (PVC) on the determination of CMRO .

Iterative reconstruction of radially-sampled P bSSFP data using prior information from H MRI.

The purpose of this study is to improve direct phosphorus (P) MR imaging. Therefore, 3D density-adapted radially-sampled balanced steady-state free precession (bSSFP) sequences were developed and an iterative approach exploiting additional anatomical information from hydrogen (H) data was evaluated. Three healthy volunteers were examined at B=7T in order to obtain the spatial distribution of the phosphocreatine (PCr) intensities in the human calf muscle with a nominal isotropic resolution of 10mm in an acquisition time of 10min.

Amide proton transfer of carnosine in aqueous solution studied in vitro by WEX and CEST experiments.

Amide protons of peptide bonds induce an important chemical exchange saturation transfer (CEST) contrast in vivo. As a simple in vitro model for a peptide amide proton CEST effect, we suggest herein the dipeptide carnosine. We show that the metabolite carnosine creates a CEST effect and we study the properties of the exchange of the amide proton (-NH) of the carnosine peptide bond (NHCPB) in model solutions for a pH range from 6 to 8.

Three-dimensional dictionary-learning reconstruction of (23)Na MRI data.

Purpose: To reduce noise and artifacts in (23)Na MRI with a Compressed Sensing reconstruction and a learned dictionary as sparsifying transform.

Methods: A three-dimensional dictionary-learning compressed sensing reconstruction algorithm (3D-DLCS) for the reconstruction of undersampled 3D radial (23)Na data is presented. The dictionary used as the sparsifying transform is learned with a K-singular-value-decomposition (K-SVD) algorithm.

Iterative 3D projection reconstruction of (23) Na data with an (1) H MRI constraint.

Purpose: To increase the signal-to-noise ratio (SNR) and to reduce artifacts in non-proton magnetic resonance imaging (MRI) by incorporation of a priori information from (1) H MR data in an iterative reconstruction.

Methods: An iterative reconstruction algorithm for 3D projection reconstruction (3DPR) is presented that combines prior anatomical knowledge and image sparsity under a total variation (TV) constraint. A binary mask (BM) is used as an anatomical constraint to penalize non-zero signal intensities outside the object.