| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Callaghan, Martina F, et al.
(författare)
-
Example dataset for the hMRI toolbox
- 2019
-
Ingår i: Data in Brief. - : Elsevier BV. - 2352-3409.
-
Tidskriftsartikel (refereegranskat)abstract
- The hMRI toolbox is an open-source toolbox for the calculation of quantitative MRI parameter maps from a series of weighted imaging data, and optionally additional calibration data. The multi-parameter mapping (MPM) protocol, incorporating calibration data to correct for spatial variation in the scanner’s transmit and receive fields, is the most complete protocol that can be handled by the toolbox. Here we present a dataset acquired with such a full MPM protocol, which is made freely available to be used as a tutorial by following instructions provided on the associated toolbox wiki pages, which can be found at http://hMRI.info, and following the theory described in: hMRI – A toolbox for quantitative MRI in neuroscience and clinical research.
|
|
| 5. |
|
|
| 6. |
- Helms, Gunther, et al.
(författare)
-
Correction of FLASH-based MT saturation in human brain for residual bias of B1-inhomogeneity at 3T
- 2021
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Background: Magnetization transfer (MT) saturation reflects the additional saturation of the MRI signal imposed by an MT pulse and is largely driven by the saturation of the bound pool. This reduction of the bound polarization by the MT pulse is less efficient than predicted by the differential B1-square law of absorption. Thus, B1 inhomogeneities lead to a residual bias in the MT saturation maps. We derive a heuristic correction to reduce this bias for a widely used multi-parameter mapping protocol at 3T. Methods: The amplitude of the MT pulse was varied via the nominal flip angle to mimic variations in B1. The MT saturation's dependence on the actual flip angle features a linear correction term, which was determined separately for gray and white matter. Results: The deviation of MT saturation from differential B1-square law is well described by a linear decrease with the actual flip angle of the MT pulse. This decrease showed no significant differences between gray and white matter. Thus, the post hoc correction does not need to take different tissue types into account. Bias-corrected MT saturation maps appeared more symmetric and highlighted highly myelinated tracts. Discussion:Our correction involves a calibration that is specific for the MT pulse. While it can also be used to rescale nominal flip angles, different MT pulses and/or protocols will require individual calibration. Conclusion: The suggested B1 correction of the MT maps can be applied post hoc using an independently acquired flip angle map.
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
- Lorio, Sara, et al.
(författare)
-
Neurobiological origin of spurious brain morphological changes: A quantitative MRI study
- 2016
-
Ingår i: Human Brain Mapping. - : Wiley. - 1065-9471. ; 37:5, s. 1801-1815
-
Tidskriftsartikel (refereegranskat)abstract
- AbstractThe high gray-white matter contrast and spatial resolution provided by T1-weighted magnetic resonance imaging (MRI) has made it a widely used imaging protocol for computational anatomy studies of the brain. While the image intensity in T1-weighted images is predominantly driven by T1, other MRI parameters affect the image contrast, and hence brain morphological measures derived from the data. Because MRI parameters are correlates of different histological properties of brain tissue, this mixed contribution hampers the neurobiological interpretation of morphometry findings, an issue which remains largely ignored in the community. We acquired quantitative maps of the MRI parameters that determine signal intensities in T1-weighted images (R1 (=1/T1), R2 *, and PD) in a large cohort of healthy subjects (n = 120, aged 18-87 years). Synthetic T1-weighted images were calculated from these quantitative maps and used to extract morphometry features-gray matter volume and cortical thickness. We observed significant variations in morphometry measures obtained from synthetic images derived from different subsets of MRI parameters. We also detected a modulation of these variations by age. Our findings highlight the impact of microstructural properties of brain tissue-myelination, iron, and water content-on automated measures of brain morphology and show that microstructural tissue changes might lead to the detection of spurious morphological changes in computational anatomy studies. They motivate a review of previous morphological results obtained from standard anatomical MRI images and highlight the value of quantitative MRI data for the inference of microscopic tissue changes in the healthy and diseased brain. Hum Brain Mapp, 2016. © 2016 The Authors. Human Brain Mapping Published by Wiley Periodicals, Inc.
|
|
| 10. |
|
|
