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A fundamental issue in neuroscience is the relation between structure and function. However, gross landmarks do not correspond well to microstructural borders and cytoarchitecture cannot be visualized in a living brain used for functional studies. Here, we used diffusion-weighted and functional MRI to test structure-function relations directly. Distinct neocortical regions were defined as volumes having similar connectivity profiles and borders identified where connectivity changed. Without using prior information, we found an abrupt profile change where the border between supplementary motor area (SMA) and pre-SMA is expected. Consistent with this anatomical assignment, putative SMA and pre-SMA connected to motor and prefrontal regions, respectively. Excellent spatial correlations were found between volumes defined by using connectivity alone and volumes activated during tasks designed to involve SMA or pre-SMA selectively. This finding demonstrates a strong relationship between structure and function in medial frontal cortex and offers a strategy for testing such correspondences elsewhere in the brain.

As diffusion tractography is increasingly used to generate quantitative measures to address clinical questions, it is important to characterise the inter-session reproducibility and inter-subject variability of these measures. Here, we assess the reproducibility and variability of diffusion tractography measures using diffusion data from 8 subjects scanned 3 times. We used probabilistic tractography to define the cingulum bundle, pyramidal tracts, optic radiations and genu of the corpus callosum in each individual data set using three different methods of seed definition. Measures of mean fractional anisotropy (FA) and mean diffusivity (MD) along the tracts were more reproducible than measures of tract volume. Further, tracts defined using a two region of interest (ROI) approach were more reproducible than those defined using manually placed seed masks alone. For mean FA taken from tracts defined using the two ROI approach, inter-session coefficients of variation (CV) were all below 5% and inter-subject CVs were below 10%; for mean MD inter-session, CVs were all below 3% and inter-subject CVs were below 8%. We use the variability measures found here to calculate the sample sizes required to detect changes in FA, MD or tract volume of a given size, either between groups of subjects or within subjects over time. Finally, we compare tractography results using 60 diffusion encoding directions to those found using a subset of 12 directions; the number of diffusion directions did not have a significant effect on reproducibility, but tracts derived using fewer directions were consistently smaller than those derived using 60 direction data. We suggest that 12 direction data are sufficient for reproducibly defining the core of large bundles but may be less sensitive to smaller pathways.

As well as the long-T2 relaxation components normally detected with conventional imaging techniques, the brain has short-T2 components. We wished to use ultra-short (0.08 ms) echo time (UTE) pulse sequences to assess the feasibility of imaging these in normal subjects and patients. UTE sequences were employed, with or without fat suppression, 90 degree long-T2 suppression pulses, and selective nulling of long-T2 components using an inversion pulse. Subtraction of later echoes from the first was also used to reduce the signal from long-T2 components. We studied dive normal subjects and 15 patients with various diseases. Short-T2 components were demonstrated in grey and white matter. Increased signal from these components was seen in meningeal disease, probable calcification, presumed cavernomas, melanoma metastases and probable gliosis. Reduced signal was seen in some tumours, infarcts, mild multifocal vascular disease and vasogenic oedema. Further development and evaluation of these pulse sequences is warranted.

Functionally significant landmarks in the brain do not necessarily align with local sulcal and gyral architecture in a manner that is consistent across individuals. However, the functional specialisation underlying these landmarks is strongly constrained by the connectional architecture of the region. Here, we explore this relationship in the supplementary motor area (SMA) and pre-SMA in the medial frontal cortex of the human brain. Using diffusion tensor, conventional and functional MR imaging, we find that the location of the functional boundary between SMA and preSMA is more consistent with respect to specific features of the local white matter as it approaches neocortex than with respect to the local gyral and sulcal anatomy in the region.

Doc number: W10

Doc number: W9

Objectives To compare conventional MRI, ultrashort echo time MRI and ultrasound for assessing the extent of tendon abnormalities in spondyloarthritis. Methods 25 patients with spondyloarthritis and Achilles symptoms were studied with MRI and ultrasound. MR images of the Achilles tendon were acquired using T1-weighted spin echo, gradient echo and ultrashort echo time (UTE) sequences with echo times (TE) between 0.07 and 16 ms, before and after intravenous contrast medium. Greyscale and power Doppler ultrasound were also performed. The craniocaudal extent of imaging abnormalities measured by a consultant musculoskeletal radiologist was compared between the different techniques. Results Abnormalities were most extensive on spoiled gradient echo images with TE = 2 ms. Contrast enhancement after intravenous gadolinium was greatest on the UTE images (TE = 0.07 ms). Fewer abnormalities were demonstrated using unenhanced UTE. Abnormalities were more extensive on MRI than ultrasound. Contrast enhancement was more extensive than power Doppler signal. Conclusions 3D spoiled gradient echo images with an echo time of 2 ms demonstrate more extensive tendon abnormalities than the other techniques in spondyloarthritis. Abnormalities of vascularity are best demonstrated on enhanced ultrashort echo time images.

IntroductionLuminal stenosis is a poor predictor of the risk posed by any given atherosclerotic plaque, therefore current angiographic imaging techniques cannot reliably determine which patients are most likely to suffer future ischaemic events. However, MRI may be able to detect features of atherosclerotic plaque rupture that have been associated with an increased risk of recurrent atherothrombosis.Hypothesis3T MRI of the carotid artery can identify atherosclerotic plaque rupture in patients presenting with TIA or minor stroke.Methods81 patients with carotid artery disease were recruited; 41 presented acutely with TIA or minor stroke and 40 asymptomatic patients acted as the control group. Median time from symptom onset to MRI in the symptomatic group was 2.1 days (range 0.17–7.0). All patients underwent T1, T2 and proton density-weighted turbo spin echo MRI to 10 mm either side of the carotid. As part of a combined scan protocol, study participants then underwent diffusion-weighted imaging (DWI) and Fluid-Attenuated Inversion Recovery (FLAIR) imaging of the brain to assess acute and chronic injury, respectively. If physically able, patients underwent follow-up scanning a minimum of six weeks later. Plaques were graded according to the MRI modified American Heart Association (AHA) system by two independent reviewers blinded to the clinical status of the patient. Statistical analysis was performed using the Wilcoxon sign rank test and Fisher′s exact test to compare plaques, in addition to the Mann Whitney U test to compare cerebral injury.ResultsAHA type VI (ruptured) plaque was seen in 22/41(54%) in the symptomatic group vs 8/41(20%) in the asymptomatic group (p<0.05), either due to intra-plaque haemorrhage (34% vs 18%, p=0.08; Abstract 109 figure 1A), surface rupture (24% vs 5%, p=0.03; Abstract 109 figure 1B), or luminal thrombus (7% vs 0%, p=0.24; Abstract 109 figure 1C). Of particular note, 17/30 (57%) cases of AHA VI (ruptured) plaque were seen to cause <70% stenosis―the current cut-off for surgical treatment. At follow-up scanning a minimum of 6 weeks later, only two cases of AHA VI plaque showed evidence of full healing. Of the 41 patients in the acute group, evidence of cerebral injury on DWI imaging was seen in 32/41 patients; the median number of lesions per patient was 7 and the median total lesion volume was 10.62 ml (range 0–522 ml). No significant associations were noted between AHA plaque type and downstream cerebral injury, however the presence of plaque surface rupture independently predicted a higher number of DWI lesions, a higher total DWI burden at presentation, and higher total cerebral FLAIR signal at follow-up when compared to all other plaque types (p<0.05).Abstract 109 Figure 1ConclusionAcute atherosclerotic plaque rupture can be visualised using 3T MRI. In particular, MRI can provide detailed information on plaque morphology that can predict downstream embolic injury, independent of the degree of luminal stenosis caused.

Rapid innovations in cardiovascular magnetic resonance (CMR) now permit the routine acquisition of quantitative measures of myocardial and blood T1 which are key tissue characteristics. These capabilities introduce a new frontier in cardiology, enabling the practitioner/investigator to quantify biologically important myocardial properties that otherwise can be difficult to ascertain clinically. CMR may be able to track biologically important changes in the myocardium by: a) native T1 that reflects myocardial disease involving the myocyte and interstitium without use of gadolinium based contrast agents (GBCA), or b) the extracellular volume fraction (ECV)–a direct GBCA-based measurement of the size of the extracellular space, reflecting interstitial disease. The latter technique attempts to dichotomize the myocardium into its cellular and interstitial components with estimates expressed as volume fractions. This document provides recommendations for clinical and research T1 and ECV measurement, based on published evidence when available and expert consensus when not. We address site preparation, scan type, scan planning and acquisition, quality control, visualisation and analysis, technical development. We also address controversies in the field. While ECV and native T1 mapping appear destined to affect clinical decision making, they lack multi-centre application and face significant challenges, which demand a community-wide approach among stakeholders. At present, ECV and native T1 mapping appear sufficiently robust for many diseases; yet more research is required before a large-scale application for clinical decision-making can be recommended.

Irritable bowel syndrome is one of several functional bowel disorders. As the data about this common syndrome increase, so does the understanding that it is a disorder with complex pathophysiologic factors. In this article, Drs Morgan and Robson provide the latest information about IBS and its diagnosis and outline a strategy for cost-effective treatment and improved quality of life for patients with this disorder.