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J.S. Thornton

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4 papers

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YNICL Journal 2021 Journal Article

FLAIR-only joint volumetric analysis of brain lesions and atrophy in clinically isolated syndrome (CIS) suggestive of multiple sclerosis

O. Goodkin
F. Prados
S.B. Vos
H. Pemberton
S. Collorone
M.H.J. Hagens
M.J. Cardoso
T.A. Yousry

BACKGROUND: MRI assessment in multiple sclerosis (MS) focuses on the presence of typical white matter (WM) lesions. Neurodegeneration characterised by brain atrophy is recognised in the research field as an important prognostic factor. It is not routinely reported clinically, in part due to difficulty in achieving reproducible measurements. Automated MRI quantification of WM lesions and brain volume could provide important clinical monitoring data. In general, lesion quantification relies on both T1 and FLAIR input images, while tissue volumetry relies on T1. However, T1-weighted scans are not routinely included in the clinical MS protocol, limiting the utility of automated quantification. OBJECTIVES: We address an aspect of this important translational challenge by assessing the performance of FLAIR-only lesion and brain segmentation, against a conventional approach requiring multi-contrast acquisition. We explore whether FLAIR-only grey matter (GM) segmentation yields more variability in performance compared with two-channel segmentation; whether this is related to field strength; and whether the results meet a level of clinical acceptability demonstrated by the ability to reproduce established biological associations. METHODS: We used a multicentre dataset of subjects with a CIS suggestive of MS scanned at 1.5T and 3T in the same week. WM lesions were manually segmented by two raters, 'manual 1' guided by consensus reading of CIS-specific lesions and 'manual 2' by any WM hyperintensity. An existing brain segmentation method was adapted for FLAIR-only input. Automated segmentation of WM hyperintensity and brain volumes were performed with conventional (T1/T1 + FLAIR) and FLAIR-only methods. RESULTS: = 0.998, SE = 0.006). Age-associated change in cortical GM volume was a significant covariate in both T1 (p = 0.001) and FLAIR-only (p = 0.005) methods, confirming the expected relationship between age and GM volume for FLAIR-only segmentations. CONCLUSIONS: FLAIR-only automated segmentation of WM lesions and brain volumes were consistent with results obtained through conventional methods and had the ability to demonstrate biological effects in our study population. Imaging protocol harmonisation and validation with other MS phenotypes could facilitate the integration of automated WM lesion volume and brain atrophy analysis as clinical tools in radiological MS reporting.

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YNIMG Journal 2012 Journal Article

High resolution MR anatomy of the subthalamic nucleus: Imaging at 9.4T with histological validation

L.A. Massey
M.A. Miranda
L. Zrinzo
O. Al-Helli
H.G. Parkes
J.S. Thornton
P.-W. So
M.J. White

Using conventional MRI the subthalamic nucleus (STN) is not clearly defined. Our objective was to define the anatomy of the STN using 9. 4T MRI of post mortem tissue with histological validation. Spin-echo (SE) and 3D gradient-echo (GE) images were obtained at 9. 4T in 8 post mortem tissue blocks and compared directly with corresponding histological slides prepared with Luxol Fast Blue/Cresyl Violet (LFB/CV) in 4 cases and Perl stain in 3. The variability of the STN anatomy was studied using internal reference points. The anatomy of the STN and surrounding structures was demonstrated in all three anatomical planes using 9. 4T MR images in concordance with LFB/CV stained histological sections. Signal hypointensity was seen in 6/8 cases in the anterior and medial STN that corresponded with regions of more intense Perl staining. There was significant variability in the volume, shape and location of the borders of the STN. Using 9. 4T MRI, the internal signal characteristics and borders of the STN are clearly defined and significant anatomical variability is apparent. Direct visualisation of the STN is possible using high field MRI and this is particularly relevant, given its anatomical variability, for planning deep brain stimulation.

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YNIMG Journal 2012 Journal Article

Simultaneous intracranial EEG–fMRI in humans: Protocol considerations and data quality

D.W. Carmichael
S. Vulliemoz
R. Rodionov
J.S. Thornton
A.W. McEvoy
L. Lemieux

We have recently performed simultaneous intracranial EEG and fMRI recordings (icEEG–fMRI) in patients with epilepsy. In this technical note, we examine limited thermometric data for potential electrode heating during our protocol and found that heating was ≤0. 1°C in-vitro at least 10 fold less than in-vivo limits. We quantify EEG quality, which can be degraded by MRI scanner-induced artefacts, and fMRI image (gradient echo echo-planar imaging: GE-EPI) signal quality around the electrodes, which can be degraded by electrode interactions with B1 (radiofrequency) and B0 (static) magnetic fields. We recorded EEG outside and within the MRI scanner with and without scanning. EEG quality was largely preserved during scanning and in particular heartbeat-related artefacts were small compared to epileptic events. To assess the GE-EPI signal reduction around the electrodes, we compared image signal intensity along paths into the brain normal to its surface originating from the individual platinum–iridium electrode contacts. GE-EPI images were obtained at 1. 5T with an echo time (TE) of 40ms and repetition time (TR) of 3000ms and a slice thickness of 2. 5mm. We found that GE-EPI signal intensity reduction was confined to a 10mm radius and that it was reduced on average by less than 50% at 5mm from the electrode contacts. The GE-EPI image signal reduction also varied with electrode orientation relative to the MRI scanner axes; in particular, cortical grid contacts with a normal along the scanner's main magnetic field (B0) axis have higher artefact levels relative to those with a normal perpendicular to the z-axis. This suggests that the artefacts were predominantly susceptibility-related rather than due to B1 interactions. This information can be used to guide interpretation of results of icEEG–fMRI experiments proximal to the electrodes, and to optimise artefact reduction strategies.

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YNIMG Journal 2009 Journal Article

Short-term adaptation to a simple motor task: A physiological process preserved in multiple sclerosis

L. Mancini
O. Ciccarelli
F. Manfredonia
J.S. Thornton
F. Agosta
F. Barkhof
C. Beckmann
N. De Stefano

Short-term adaptation indicates the attenuation of the functional MRI (fMRI) response during repeated task execution. It is considered to be a physiological process, but it is unknown whether short-term adaptation changes significantly in patients with brain disorders, such as multiple sclerosis (MS). In order to investigate short-term adaptation during a repeated right-hand tapping task in both controls and in patients with MS, we analyzed the fMRI data collected in a large cohort of controls and MS patients who were recruited into a multi-centre European fMRI study. Four fMRI runs were acquired for each of the 55 controls and 56 MS patients at baseline and 33 controls and 26 MS patients at 1-year follow-up. The externally cued (1 Hz) right hand tapping movement was limited to 3 cm amplitude by using at all sites (7 at baseline and 6 at follow-up) identically manufactured wooden frames. No significant differences in cerebral activation were found between sites. Furthermore, our results showed linear response adaptation (i. e. reduced activation) from run 1 to run 4 (over a 25 minute period) in the primary motor area (contralateral more than ipsilateral), in the supplementary motor area and in the primary sensory cortex, sensory–motor cortex and cerebellum, bilaterally. This linear activation decay was the same in both control and patient groups, did not change between baseline and 1-year follow-up and was not influenced by the modest disease progression observed over 1 year. These findings confirm that the short-term adaptation to a simple motor task is a physiological process which is preserved in MS.

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