Multi-site harmonization of 7 tesla MRI neuroimaging protocols.

Increasing numbers of 7 T (7 T) magnetic resonance imaging (MRI) scanners are in research and clinical use. 7 T MRI can increase the scanning speed, spatial resolution and contrast-to-noise-ratio of many neuroimaging protocols, but technical challenges in implementation have been addressed in a variety of ways across sites. In order to facilitate multi-centre studies and ensure consistency of findings across sites, it is desirable that 7 T MRI sites implement common high-quality neuroimaging protocols that can accommodate different scanner models and software versions. With the installation of several new 7 T MRI scanners in the United Kingdom, the UK7T Network was established with an aim to create a set of harmonized structural and functional neuroimaging sequences and protocols. The Network currently includes five sites, which use three different scanner platforms, provided by two different vendors. Here we describe the harmonization of functional and anatomical imaging protocols across the three different scanner models, detailing the necessary changes to pulse sequences and reconstruction methods. The harmonized sequences are fully described, along with implementation details. Example datasets acquired from the same subject on all Network scanners are made available. Based on these data, an evaluation of the harmonization is provided. In addition, the implementation and validation of a common system calibration process is described.

A case of a chlorine inhalation injury in an Ebola treatment unit.

We present a 26-year-old male British military nurse, deployed to Sierra Leone to treat patients with Ebola virus disease at the military-run Kerry Town Ebola Treatment Unit. Following exposure to chlorine gas during routine maintenance procedures, the patient had an episode of respiratory distress and briefly lost consciousness after exiting the facility. Diagnoses of reactive airways disease, secondary to the chlorine exposure and a hypocapnic syncopal episode were made. The patient was resuscitated with minimal intervention and complete recovery occurred in less than 1 week. This case highlights the issues of using high-strength chlorine solution to disinfect the red zone. Although this patient had a good outcome, this was fortunate. Ensuring Ebola treatment centres are optimally designed and that appropriate management systems are formulated with extraction scenarios rehearsed are important to mitigate the chlorine-associated risk.

Detection of physiological noise in resting state fMRI using machine learning.

We present a technique for predicting cardiac and respiratory phase on a time point by time point basis, from fMRI image data. These predictions have utility in attempts to detrend effects of the physiological cycles from fMRI image data. We demonstrate the technique both in the case where it can be trained on a subject's own data, and when it cannot. The prediction scheme uses a multiclass support vector machine algorithm. Predictions are demonstrated to have a close fit to recorded physiological phase, with median Pearson correlation scores between recorded and predicted values of 0.99 for the best case scenario (cardiac cycle trained on a subject's own data) down to 0.83 for the worst case scenario (respiratory predictions trained on group data), as compared to random chance correlation score of 0.70. When predictions were used with RETROICOR--a popular physiological noise removal tool--the effects are compared to using recorded phase values. Using Fourier transforms and seed based correlation analysis, RETROICOR is shown to produce similar effects whether recorded physiological phase values are used, or they are predicted using this technique. This was seen by similar levels of noise reduction noise in the same regions of the Fourier spectra, and changes in seed based correlation scores in similar regions of the brain. This technique has a use in situations where data from direct monitoring of the cardiac and respiratory cycles are incomplete or absent, but researchers still wish to reduce this source of noise in the image data.

The long-term safety and efficacy of bilateral transplantation of human fetal striatal tissue in patients with mild to moderate Huntington's disease.

Huntington's disease (HD) is a fatal autosomal dominant neurodegenerative disease involving progressive motor, cognitive and behavioural decline, leading to death approximately 20 years after motor onset. The disease is characterised pathologically by an early and progressive striatal neuronal cell loss and atrophy, which has provided the rationale for first clinical trials of neural repair using fetal striatal cell transplantation. Between 2000 and 2003, the 'NEST-UK' consortium carried out bilateral striatal transplants of human fetal striatal tissue in five HD patients. This paper describes the long-term follow up over a 3-10-year postoperative period of the patients, grafted and non-grafted, recruited to this cohort using the 'Core assessment program for intracerebral transplantations-HD' assessment protocol. No significant differences were found over time between the patients, grafted and non-grafted, on any subscore of the Unified Huntington's Disease Rating Scale, nor on the Mini Mental State Examination. There was a trend towards a slowing of progression on some timed motor tasks in four of the five patients with transplants, but overall, the trial showed no significant benefit of striatal allografts in comparison with a reference cohort of patients without grafts. Importantly, no significant adverse or placebo effects were seen. Notably, the raclopride positron emission tomography (PET) signal in individuals with transplants, indicated that there was no obvious surviving striatal graft tissue. This study concludes that fetal striatal allografting in HD is safe. While no sustained functional benefit was seen, we conclude that this may relate to the small amount of tissue that was grafted in this safety study compared with other reports of more successful transplants in patients with HD.

Targeting patient recovery priorities in degenerative cervical myelopathy: design and rationale for the RECEDE-Myelopathy trial-study protocol.

INTRODUCTION: Degenerative cervical myelopathy (DCM) is a common and disabling condition of symptomatic cervical spinal cord compression secondary to degenerative changes in spinal structures leading to a mechanical stress injury of the spinal cord. RECEDE-Myelopathy aims to test the disease-modulating activity of the phosphodiesterase 3/phosphodiesterase 4 inhibitor Ibudilast as an adjuvant to surgical decompression in DCM. METHODS AND ANALYSIS: RECEDE-Myelopathy is a multicentre, double-blind, randomised, placebo-controlled trial. Participants will be randomised to receive either 60-100 mg Ibudilast or placebo starting within 10 weeks prior to surgery and continuing for 24 weeks after surgery for a maximum of 34 weeks. Adults with DCM, who have a modified Japanese Orthopaedic Association (mJOA) score 8-14 inclusive and are scheduled for their first decompressive surgery are eligible for inclusion. The coprimary endpoints are pain measured on a visual analogue scale and physical function measured by the mJOA score at 6 months after surgery. Clinical assessments will be undertaken preoperatively, postoperatively and 3, 6 and 12 months after surgery. We hypothesise that adjuvant therapy with Ibudilast leads to a meaningful and additional improvement in either pain or function, as compared with standard routine care. STUDY DESIGN: Clinical trial protocol V.2.2 October 2020. ETHICS AND DISSEMINATION: Ethical approval has been obtained from HRA-Wales.The results will be presented at an international and national scientific conferences and in a peer-reviewed journals. TRIAL REGISTRATION NUMBER: ISRCTN Number: ISRCTN16682024.

Proton magnetic resonance spectroscopy in frontotemporal lobar degeneration-related syndromes.

There is an urgent need for a better understanding of the pathophysiology of cognitive impairment in syndromes associated with frontotemporal lobar degeneration. Here, we used magnetic resonance spectroscopy to quantify metabolite deficits in sixty patients with a clinical syndrome associated with frontotemporal lobar degeneration (behavioral variant frontotemporal dementia n = 11, progressive supranuclear palsy n = 26, corticobasal syndrome n = 11, primary progressive aphasias n = 12), and 38 age- and sex-matched healthy controls. We measured nine metabolites in the right inferior frontal gyrus, superior temporal gyrus and right primary visual cortex. Metabolite concentrations were corrected for age, sex, and partial volume then compared with cognitive and behavioral measures using canonical correlation analysis. Metabolite concentrations varied significantly by brain region and diagnosis (region x metabolite x diagnosis interaction F(64) = 1.73, p < 0.001, corrected for age, sex, and atrophy within the voxel). N-acetyl aspartate and glutamate concentrations were reduced in the right prefrontal cortex in behavioral variant frontotemporal dementia and progressive supranuclear palsy, even after partial volume correction. The reduction of these metabolites was associated with executive dysfunction and behavioral impairment (canonical correlation analysis R = 0.85, p < 0.001).

Split gradient coils for simultaneous PET-MRI.

Combining positron emission tomography (PET) and MRI necessarily involves an engineering tradeoff as the equipment needed for the two modalities vies for the space closest to the region where the signals originate. In one recently described scanner configuration for simultaneous positron emission tomography-MRI, the positron emission tomography detection scintillating crystals reside in an 80-mm gap between the 2 halves of a 1-T split-magnet cryostat. A novel set of gradient and shim coils has been specially designed for this split MRI scanner to include an 110-mm gap from which wires are excluded so as not to interfere with positron detection. An inverse boundary element method was necessarily employed to design the three orthogonal, shielded gradient coils and shielded Z0 shim coil. The coils have been constructed and tested in the hybrid positron emission tomography-MRI system and successfully used in simultaneous positron emission tomography-MRI experiments.

Mechanism-based MRI classification of traumatic brainstem injury and its relationship to outcome.

While computed tomography (CT) is the appropriate technique for the urgent detection of hematomas and contusions in the cerebral hemispheres, it is much less effective at documenting diffuse injury and posterior fossa lesions, and is therefore only partially predictive of outcome. More recently, magnetic resonance imaging (MRI) has been used, particularly to examine posterior fossa structures, but the relationship between brainstem injury and outcome is unclear and the types of brainstem injury are poorly understood. The aim of this study was to use acute MRI to examine the types of brainstem injury following severe traumatic brain injury (TBI) and their relationship to supratentorial injury. We also aimed to correlate these findings with outcome at 6 months (Glasgow Outcome Scale [GOS] score). Forty-six patients (mean age, 34 years, range, 16-70 years; 76% male) admitted to a regional neurocritical care unit with TBI requiring ventilation underwent CT and MRI (T2, FLAIR, gradient echo) scanning within 3 days (median, 1 day) of injury. GOS was ascertained by outpatient interview. Brainstem lesions were detected in 13 patients by MRI, only two of which were detected by CT. Eleven out of 13 patients with brainstem injury had an unfavorable outcome (death, vegetative state, or severe disability), of whom five died. Of the 33 patients without brainstem lesions, 18 had an unfavorable outcome, of whom four died. The direct relationship between brainstem lesions and unfavorable outcome was statistically significant (p < 0.05, chi-squared test). With regard to supratentorial injury, all but two brainstem lesions were seen either in the context of severe diffuse axonal injury or a significant mass lesion, and all of these patients had a poor outcome. However, the two patients with brainstem injury and good outcome had relatively few supratentorial abnormalities. From these observations, we have devised a simple classification system that is useful clinically and has potential associations with outcome. Poor prognosis is common following major TBI but is more common in those with brainstem injury. However, brainstem injury is not an absolute indicator of poor outcome. Understanding the anatomy and extent of brainstem injury, as well as its relationship to supratentorial abnormalities, will facilitate a more accurate use of early MRI as a prognostic tool and assist in the counseling of families.

Magnetic Resonance Imaging of the Codman Microsensor Transducer Used for Intraspinal Pressure Monitoring: Findings From the Injured Spinal Cord Pressure Evaluation Study.

STUDY DESIGN: Laboratory and human study. OBJECTIVE: To test the Codman Microsensor Transducer (CMT) in a cervical gel phantom. To test the CMT inserted to monitor intraspinal pressure in a patient with spinal cord injury. SUMMARY OF BACKGROUND DATA: We recently introduced the technique of intraspinal pressure monitoring using the CMT to guide management of traumatic spinal cord injury [Werndle et al. Crit Care Med 2014;42:646]. This is analogous to intracranial pressure monitoring to guide management of patients with traumatic brain injury. It is unclear whether magnetic resonance imaging (MRI) of patients with spinal cord injury is safe with the intraspinal pressure CMT in situ. METHODS: We measured the heating produced by the CMT placed in a gel phantom in various configurations. A 3-T MRI system was used with the body transmit coil and the spine array receive coil. A CMT was then inserted subdurally at the injury site in a patient who had traumatic spinal cord injury and MRI was performed at 1.5 T. RESULTS: In the gel phantom, heating of up to 5°C occurred with the transducer wire placed straight through the magnet bore. The heating was abolished when the CMT wire was coiled and passed away from the bore. We then tested the CMT in a patient with an American Spinal Injuries Association grade C cervical cord injury. The CMT wire was placed in the configuration that abolished heating in the gel phantom. Good-quality T1 and T2 images of the cord were obtained without neurological deterioration. The transducer remained functional after the MRI. CONCLUSION: Our data suggest that the CMT is MR conditional when used in the spinal configuration in humans. Data from a large patient group are required to confirm these findings. LEVEL OF EVIDENCE: N/A.

Changes in cerebral blood flow during cerebrospinal fluid pressure manipulation in patients with normal pressure hydrocephalus: a methodological study.

The combination of cerebral blood flow measurement using (15)O-water positron emission tomography with magnetic resonance coregistration and CSF infusion studies was used to study the global and regional changes in CBF with changes in CSF pressure in 15 patients with normal pressure hydrocephalus. With increases in CSF pressure, there was a variable increase in arterial blood pressure between individuals and global CBF was reduced, including in the cerebellum. Regionally, mean CBF decreased in the thalamus and basal ganglia, as well as in white matter regions. These reductions in CBF were significantly correlated with changes in the CSF pressure and with proximity to the ventricles. A three-dimensional finite-element analysis was used to analyze the effects on ventricular size and the distribution of stress during infusion. To study regional cerebral autoregulation in patients with possible normal pressure hydrocephalus, a sensitive CBF technique is required that provides absolute, not relative normalized, values for regional CBF and an adequate change in cerebral perfusion pressure must be provoked.

Normal pressure hydrocephalus and cerebral blood flow: a PET study of baseline values.

Regional cerebral blood flow (CBF) was studied with O(15)-water positron emission tomography and anatomic region-of-interest analysis on co-registered magnetic resonance in patients with idiopathic (n = 12) and secondary (n = 5) normal pressure hydrocephalus (NPH). Mean CBF was compared with values obtained from healthy volunteers (n = 12) and with clinical parameters. Mean CBF was significantly decreased in the cerebrum and cerebellum of patients with NPH. The regional analysis demonstrated that CBF was reduced in the basal ganglia and the thalamus but not in white matter regions. The results suggest that the role of the basal ganglia and thalamus in NPH may be more prominent than currently appreciated. The implications for theories regarding the pathogenesis of NPH are discussed.

Short term arterial remodelling in the aortae of cholesterol fed New Zealand white rabbits shown in vivo by high-resolution magnetic resonance imaging - implications for human pathology.

High-resolution, non-invasive imaging methods are required to monitor progression and regression of atherosclerotic plaques. We investigated the use of MRI to measure changes in plaque volume and vessel remodelling during progression and regression of atherosclerosis in New Zealand White rabbits. Atherosclerotic lesions were induced in the abdominal aorta by balloon injury and cholesterol feeding. MR images (2D) of the abdominal aorta were acquired with cardiac and respiratory gating using a fast spin echo sequence with and without fat-suppression. In an initial study on rabbits treated for 30 weeks we imaged the aortae with a spatial resolution of 250x250 micrometers with a slice thickness of 2 mm and achieved a close correlation between MRI-derived measurements and those made on perfusion pressure-fixed histological sections (r(1) = 0.83, slope p(1) < 0.01). We subsequently imaged 18 rabbits before and periodically during 12 weeks of cholesterol feeding (progression) followed by 12 weeks on normal diet (regression). Aortic wall (atherosclerotic lesion) volume increased significantly during progression and decreased during regression. In contrast, lumen volume increased during progression and did not change during regression. In conclusion, this study confirms that non-invasive, high-resolution MRI can be used to monitor progression and regression of atherosclerosis, each within 3 months and shows, for the first time in a short-term model, that positive remodelling occurs early during progression and persists through regression of atherosclerotic lesions.

Riociguat reduces infarct size and post-infarct heart failure in mouse hearts: insights from MRI/PET imaging.

AIM: Stimulation of the nitric oxide (NO)--soluble guanylate (sGC)--protein kinase G (PKG) pathway confers protection against acute ischaemia/reperfusion injury, but more chronic effects in reducing post-myocardial infarction (MI) heart failure are less defined. The aim of this study was to not only determine whether the sGC stimulator riociguat reduces infarct size but also whether it protects against the development of post-MI heart failure. METHODS AND RESULTS: Mice were subjected to 30 min ischaemia via ligation of the left main coronary artery to induce MI and either placebo or riociguat (1.2 µmol/l) were given as a bolus 5 min before and 5 min after onset of reperfusion. After 24 hours, both, late gadolinium-enhanced magnetic resonance imaging (LGE-MRI) and (18)F-FDG-positron emission tomography (PET) were performed to determine infarct size. In the riociguat-treated mice, the resulting infarct size was smaller (8.5 ± 2.5% of total LV mass vs. 21.8% ± 1.7%. in controls, p = 0.005) and LV systolic function analysed by MRI was better preserved (60.1% ± 3.4% of preischaemic vs. 44.2% ± 3.1% in controls, p = 0.005). After 28 days, LV systolic function by echocardiography treated group was still better preserved (63.5% ± 3.2% vs. 48.2% ± 2.2% in control, p = 0.004). CONCLUSION: Taken together, mice treated acutely at the onset of reperfusion with the sGC stimulator riociguat have smaller infarct size and better long-term preservation of LV systolic function. These findings suggest that sGC stimulation during reperfusion therapy may be a powerful therapeutic treatment strategy for preventing post-MI heart failure.

Early metabolic characteristics of lesion and nonlesion tissue after head injury.

We defined lesion and structurally normal regions using magnetic resonance imaging at follow-up in patients recovering from head injury. Early metabolic characteristics in these regions of interest (ROIs) were compared with physiology in healthy volunteers. Fourteen patients with severe head injury had positron emission tomography within 72 h, and magnetic resonance imaging at 3 to 18 months after injury. Cerebral blood flow (CBF), oxygen utilization (CMRO(2)), and oxygen extraction fraction (OEF) were all lower in lesion ROIs, compared with nonlesion and control ROIs (P<0.001); however, there was substantial overlap in physiology. Control ROIs showed close coupling among CBF, blood volume (CBV), and CMRO(2), whereas relationships within lesion and nonlesion ROIs were abnormal. The relationship between CBF and CMRO(2) generally remained coupled but the slope was reduced; that for CBF and OEF was variable; whereas that between CBF and CBV was highly variable. There was considerable heterogeneity between and within patients. Although irreversibly damaged tissue is characterized by marked derangements in physiology, a more detailed analysis shows acute changes in physiology and physiologic relationships within regions of the brain that appear structurally normal at follow-up. Such pathophysiological derangements may result in selective neuronal loss and impact on functional outcome.

The relationship between motor deficit and hemisphere activation balance after stroke: A 3T fMRI study.

Functional imaging during movement of the hand affected by a stroke has shown excess activation of the contralesional motor network, implying less physiological hemisphere activation balance. Although this may be adaptive, the relationship between the severity of motor deficit and the hemisphere activation balance for the four major cortical motor areas has not been systematically studied. We prospectively studied 19 right-handed patients with first-ever stroke (age range 61+/-10 years) in the stable phase of recovery (>3 months after onset), using auditory-paced index-thumb (IT) tapping of the affected hand at 1.25 Hz as the fMRI paradigm. The hemisphere activation balance for the primary motor (M1), primary somatosensory (S1), supplementary motor (SMA) and dorsal premotor (PMd) areas was measured by a modified weighted laterality index (wLI), and correlations with motor performance (assessed by the affected/unaffected ratio of maximum IT taps in 15 s, termed IT-R) were computed. There were statistically significant negative correlations between IT-R and the wLI for M1 and S1, such that the more the hemispheric balance shifted contralesionally, the worse the performance. Furthermore, worse performance was related to a greater amount of contralesional, but not ipsilesional, activation. No significant correlation between IT-R and the wLI was obtained for the SMA and PMd, which functionally have stronger bilateral organization. These findings suggest that the degree of recovery of fine finger motion after stroke is determined by the extent to which activation balance in the primary sensory motor areas--where most corticospinal fibers originate--departs from normality. This observation may have implications for therapy.