Amide proton transfer (APT) imaging of brain tumors at 7 T: The role of tissue water T -Relaxation properties.

Purpose: To provide insight into the effect of water T relaxation (T ) on amide proton transfer (APT) contrast in tumors. Three different metrics of APT contrast-magnetization transfer ratio (MTR ), relaxation-compensated MTR (AREX), and traditional asymmetry (MTR )-were compared in normal and tumor tissues in a variety of intracranial tumors at 7 Tesla (T).

Methods: Six consented intracranial tumor patients were scanned using a low-power, three-dimensional (3D) APT imaging sequence.

Re-distribution of brachytherapy dose using a differential dose prescription adapted to risk of local failure in low-risk prostate cancer patients.

Background And Purpose: We investigated the application of a differential target- and dose prescription concept for low-dose-rate prostate brachytherapy (LDR-BT), involving a re-distribution of dose according to risk of local failure and treatment-related morbidity.

Material And Methods: Our study included 15 patients. Multi-parametric MRI was acquired prior to LDR-BT for gross tumor volume (GTV) delineation.

Local specific absorption rate in brain tumors at 7 tesla.

Purpose: MR safety at 7 Tesla relies on accurate numerical simulations of transmit electromagnetic fields to fully assess local specific absorption rate (SAR) safety. Numerical simulations for SAR safety are currently performed using models of healthy patients. These simulations might not be useful for estimating SAR in patients who have large lesions with potentially abnormal dielectric properties, e.

Establishing implantation uncertainties for focal brachytherapy with I-125 seeds for the treatment of localized prostate cancer.

Background: The efficacy of focal continuous low dose-rate brachytherapy (CLDR-BT) for prostate cancer requires that appropriate margins are applied to ensure robust target coverage. In this study we propose a method to establish such margins by emulating a focal treatment in patients treated with CLDR-BT to the entire gland.

Material And Methods: In 15 patients with localized prostate cancer, prostate volumes and dominant intra-prostatic lesions were delineated on pre-treatment magnetic resonance imaging (MRI).

Multimodal tract-based analysis in ALS patients at 7T: a specific white matter profile?

Our objective was to explore the value of additional MR contrasts in elucidating the decrease in fractional anisotropy (FA) as has been observed in the corticospinal tracts (CST) of patients with amyotrophic lateral sclerosis (ALS). Eleven patients and nine healthy control subjects were scanned at 3T and 7T MRI. Whole brain and tract specific comparison was performed of both diffusion weighted (3T), quantitative T1 (qT1), magnetization transfer ratio (MTR) and amide proton transfer weighted (APTw) imaging (7T).

Chemical Exchange Saturation Transfer MR Imaging: Potential Clinical Applications.

Chemical exchange saturation transfer (CEST) measurements hold great promise as the next step in magnetization transfer imaging and possibly allow for in vivo quantification of many clinically relevant parameters, including pH, temperature, and amide concentration. Therefore, it is a valuable method to add to the MR imaging toolbox. The aim of this article was to review the methods for the acquisition of CEST data and necessary postprocessing.

Uncertainty estimations for quantitative in vivo MRI T1 mapping.

Mapping the longitudinal relaxation time (T(1)) of brain tissue is of great interest for both clinical research and MRI sequence development. For an unambiguous interpretation of in vivo variations in T(1) images, it is important to understand the degree of variability that is associated with the quantitative T(1) parameter. This paper presents a general framework for estimating the uncertainty in quantitative T(1) mapping by combining a slice-shifted multi-slice inversion recovery EPI technique with the statistical wild-bootstrap approach.

In vivo three-dimensional whole-brain pulsed steady-state chemical exchange saturation transfer at 7 T.

Chemical exchange saturation transfer (CEST) is a technique to indirectly detect pools of exchangeable protons through the water signal. To increase its applicability to human studies, it is needed to develop sensitive pulse sequences for rapidly acquiring whole-organ images while adhering to stringent amplifier duty cycle limitations and specific absorption rate restrictions. In addition, the interfering effects of direct water saturation and conventional magnetization transfer contrast complicate CEST quantification and need to be reduced as much as possible.

Signal to noise ratio and uncertainty in diffusion tensor imaging at 1.5, 3.0, and 7.0 Tesla.

Purpose: To compare diffusion tensor imaging (DTI) measurements at ultra high field strength (7 Tesla [T]) in human volunteers with DTI measurements performed at 1.5 and 3 Tesla.

Materials And Methods: The signal to noise ratio (SNR) and the uncertainty in fitted DTI parameters fractional anisotropy and primary eigenvector are assessed with tractography based regions of interest, measured in nine volunteers at 1.

Diffusion-weighted MR neurography of the sacral plexus with unidirectional motion probing gradients.

Background: This technical note introduces diffusion-weighted (DW) MR neurography (MRN) of the sacral plexus with unidirectional motion probing gradients (MPGs).

Methods: This is compared with DW MRN with three-directional and six-directional MPGs.

Results And Conclusion: This paper indicates that DW MRN of the sacral plexus should be performed with unidirectional MPGs.

A novel improved method for analysis of 2D diffusion-relaxation data--2D PARAFAC-Laplace decomposition.

This paper demonstrates how the multi-linear PARAFAC model can with advantage be used to decompose 2D diffusion-relaxation correlation NMR spectra prior to 2D-Laplace inversion to the T(2)-D domain. The decomposition is advantageous for better interpretation of the complex correlation maps as well as for the quantification of extracted T(2)-D components. To demonstrate the new method seventeen mixtures of wheat flour, starch, gluten, oil and water were prepared and measured with a 300 MHz nuclear magnetic resonance (NMR) spectrometer using a pulsed gradient stimulated echo (PGSTE) pulse sequence followed by a Carr-Purcell-Meiboom-Gill (CPMG) pulse echo train.