Dopamine transporter genotype predicts behavioural and neural measures of response inhibition.

The ability to inhibit unwanted actions is a heritable executive function that may confer risk to disorders such as attention deficit hyperactivity disorder (ADHD). Converging evidence from pharmacology and cognitive neuroscience suggests that response inhibition is instantiated within frontostriatal circuits of the brain with patterns of activity that are modulated by the catecholamines dopamine and noradrenaline. A total of 405 healthy adult participants performed the stop-signal task, a paradigmatic measure of response inhibition that yields an index of the latency of inhibition, termed the stop-signal reaction time (SSRT). Using this phenotype, we tested for genetic association, performing high-density single-nucleotide polymorphism mapping across the full range of autosomal catecholamine genes. Fifty participants also underwent functional magnetic resonance imaging to establish the impact of associated alleles on brain and behaviour. Allelic variation in polymorphisms of the dopamine transporter gene (SLC6A3: rs37020; rs460000) predicted individual differences in SSRT, after corrections for multiple comparisons. Furthermore, activity in frontal regions (anterior frontal, superior frontal and superior medial gyri) and caudate varied additively with the T-allele of rs37020. The influence of genetic variation in SLC6A3 on the development of frontostriatal inhibition networks may represent a key risk mechanism for disorders of behavioural inhibition.

Multimodality imaging review for suspected ovarian torsion cases in children.

OBJECTIVES: Ovarian torsion (OT), although rare, can be described as a complete or partial twist of the ovary with impairment of blood flow. Although occurring at any age, it is more common in children and during pregnancy. Presenting symptoms are non-specific but include either persistent or intermittent acute abdominal pain, making early diagnosis difficult. Delayed diagnosis is associated with an increased need for oophorectomy. The aim of this literature review is to establish the safest and most efficacious imaging strategy for OT by comparing and contrasting evidence for current imaging modalities found in the literature. KEY FINDINGS: Characteristically, OT can be identified through a combination of findings some of which includes an enlarged ovary, multiple follicles at the periphery and a "whirlpool" sign. Currently, ultrasound is the preferred primary imaging modality; although computed tomography (CT) and magnetic resonance imaging (MRI) may also be used when findings are equivocal; with MRI being the safer option. CONCLUSION: Ultimately, while it is true that ovarian torsion is not a common cause of acute abdominal pain in children, it should always be considered in the differential diagnosis. Prior to selecting an imaging modality; the clinical presentation, age group, possible radiation dose and availability of the modality needs to be considered to ensure the appropriate imaging strategy. IMPLICATIONS FOR PRACTICE: With new tools such as scoring systems, B-flow imaging (BFI), diffusion-weighted imaging (DWI) and susceptibility-weighted imaging (SWI) currently being explored for possible use in the future, early diagnosis of OT may be attainable. Thus, reducing the likelihood of adverse complications and consequently the need for oophorectomy.

Diffusion indices on magnetic resonance imaging and neuropsychological performance in amnestic mild cognitive impairment.

BACKGROUND: Magnetic resonance diffusion tensor imaging (DTI) shows promise in the early detection of microstructural pathophysiological changes in the brain. OBJECTIVES: To measure microstructural differences in the brains of participants with amnestic mild cognitive impairment (MCI) compared with an age-matched control group using an optimised DTI technique with fully automated image analysis tools and to investigate the correlation between diffusivity measurements and neuropsychological performance scores across groups. METHODS: 34 participants (17 participants with MCI, 17 healthy elderly adults) underwent magnetic resonance imaging (MRI)-based DTI. To control for the effects of anatomical variation, diffusion images of all participants were registered to standard anatomical space. Significant statistical differences in diffusivity measurements between the two groups were determined on a pixel-by-pixel basis using gaussian random field theory. RESULTS: Significantly raised mean diffusivity measurements (p<0.001) were observed in the left and right entorhinal cortices (BA28), posterior occipital-parietal cortex (BA18 and BA19), right parietal supramarginal gyrus (BA40) and right frontal precentral gyri (BA4 and BA6) in participants with MCI. With respect to fractional anisotropy, participants with MCI had significantly reduced measurements (p<0.001) in the limbic parahippocampal subgyral white matter, right thalamus and left posterior cingulate. Pearson's correlation coefficients calculated across all participants showed significant correlations between neuropsychological assessment scores and regional measurements of mean diffusivity and fractional anisotropy. CONCLUSIONS: DTI-based diffusivity measures may offer a sensitive method of detecting subtle microstructural brain changes associated with preclinical Alzheimer's disease.

Automatic segmentation of the glenohumeral cartilages from magnetic resonance images.

PURPOSE: Magnetic resonance (MR) imaging plays a key role in investigating early degenerative disorders and traumatic injuries of the glenohumeral cartilages. Subtle morphometric and biochemical changes of potential relevance to clinical diagnosis, treatment planning, and evaluation can be assessed from measurements derived from in vivo MR segmentation of the cartilages. However, segmentation of the glenohumeral cartilages, using approaches spanning manual to automated methods, is technically challenging, due to their thin, curved structure and overlapping intensities of surrounding tissues. Automatic segmentation of the glenohumeral cartilages from MR imaging is not at the same level compared to the weight-bearing knee and hip joint cartilages despite the potential applications with respect to clinical investigation of shoulder disorders. In this work, the authors present a fully automated segmentation method for the glenohumeral cartilages using MR images of healthy shoulders. METHODS: The method involves automated segmentation of the humerus and scapula bones using 3D active shape models, the extraction of the expected bone-cartilage interface, and cartilage segmentation using a graph-based method. The cartilage segmentation uses localization, patient specific tissue estimation, and a model of the cartilage thickness variation. The accuracy of this method was experimentally validated using a leave-one-out scheme on a database of MR images acquired from 44 asymptomatic subjects with a true fast imaging with steady state precession sequence on a 3 T scanner (Siemens Trio) using a dedicated shoulder coil. The automated results were compared to manual segmentations from two experts (an experienced radiographer and an experienced musculoskeletal anatomist) using the Dice similarity coefficient (DSC) and mean absolute surface distance (MASD) metrics. RESULTS: Accurate and precise bone segmentations were achieved with mean DSC of 0.98 and 0.93 for the humeral head and glenoid fossa, respectively. Mean DSC scores of 0.74 and 0.72 were obtained for the humeral and glenoid cartilage volumes, respectively. The manual interobserver reliability evaluated by DSC was 0.80 ± 0.03 and 0.76 ± 0.04 for the two cartilages, implying that the automated results were within an acceptable 10% difference. The MASD between the automatic and the corresponding manual cartilage segmentations was less than 0.4 mm (previous studies reported mean cartilage thickness of 1.3 mm). CONCLUSIONS: This work shows the feasibility of volumetric segmentation and separation of the glenohumeral cartilages from MR images. To their knowledge, this is the first fully automated algorithm for volumetric segmentation of the individual glenohumeral cartilages from MR images. The approach was validated against manual segmentations from experienced analysts. In future work, the approach will be validated on imaging datasets acquired with various MR contrasts in patients.

The effect of a 12-month exercise trial on balance, strength, and falls in older women: a randomized controlled trial.

OBJECTIVE: To determine whether a 12-month program of regular exercise can improve balance, reaction time, neuromuscular control, and muscle strength and reduce the rate of falling in older women. DESIGN: A randomized, controlled trial of 12 months duration. SETTING: Conducted as part of the Randwick Falls and Fractures Study in Sydney, Australia. PARTICIPANTS: One hundred ninety-seven women aged 60 to 85 years (mean age 71.6, SD = 5.4) who were randomly recruited from the community. OUTCOME MEASURES: Accidental falls, postural sway, reaction time, neuromuscular control, and lower limb muscle strength. MAIN RESULTS: Exercise and control subjects were tested before, midway through, and at the end of the trial. At initial testing, exercisers and controls performed similarly in all tests and were well matched in relevant health and lifestyle factors. The mean number of classes attended for the 75 exercise subjects who completed the program was 60.0 (range 26-82). At the end of the trial, the exercise subjects showed improved performance in all five strength measures, in reaction time, neuromuscular control, body sway on a firm surface with the eyes open, and body sway on a compliant surface with the eyes open and closed. In contrast, there were no significant improvements in any of the test measures in the controls. In one test measure, hip flexion strength, the exercisers showed continued improvement throughout the study year. There was no significant difference in the proportion of fallers between the exercise and control subjects. Interesting trends were evident, however, between falls frequency and adherence to the exercise program. CONCLUSIONS: These findings show that exercise can produce long-term benefits with regard to improving sensorimotor function in older persons. The findings also suggest that high compliance to an exercise program may reduce falls frequency, although further studies are required to conclusively demonstrate that exercise offers an effective means of preventing falls.