Spatial distortion in MRI with application to stereotactic neurosurgery

The aim of this work was to implement a thorough method for quantifying the errors introduced to frame-based neurosurgical stereotactic procedures by the use of MRI. Chang & Fitzpatrick's reversed gradient distortion correction method was used, in combination with a phantom, to measure these errors. Spatial distortion in MR images of between 1 mm and 2 mm was measured. Further analysis showed that this typically introduced an additional error in the coordinate of the actual treatment point of 0.7 mm. The implications of this are discussed. The main source of distortion in the MR images used for stereotaxis was found to be the head ring. A comparison between imaging sequences and MR scanners revealed that the spatial distortion depends mainly on the bandwidth per pixel of the sequence rather than other differences in the imaging sequences. By comparison with a phase map distortion correction technique, the imaging parameters required to allow successful distortion correction with the reversed gradient method were identified. The most important was the use of full Fourier spin echo acquisitions. The reversed gradient correction method was applied to two contemporary EPI techniques. Considerable improvement was seen in the production of ADC maps after the images had been corrected for distortion. The method also was shown to be valid in application to BOLD fMRI data

Spatial distortion in MRI with application to stereotactic neurosurgery

The aim of this work was to implement a thorough method for quantifying the errors introduced to frame-based neurosurgical stereotactic procedures by the use of MRI. Chang & Fitzpatrick's reversed gradient distortion correction method was used, in combination with a phantom, to measure these errors. Spatial distortion in MR images of between 1 mm and 2 mm was measured. Further analysis showed that this typically introduced an additional error in the coordinate of the actual treatment point of 0.7 mm. The implications of this are discussed. The main source of distortion in the MR images used for stereotaxis was found to be the head ring. A comparison between imaging sequences and MR scanners revealed that the spatial distortion depends mainly on the bandwidth per pixel of the sequence rather than other differences in the imaging sequences. By comparison with a phase map distortion correction technique, the imaging parameters required to allow successful distortion correction with the reversed gradient method were identified. The most important was the use of full Fourier spin echo acquisitions. The reversed gradient correction method was applied to two contemporary EPI techniques. Considerable improvement was seen in the production of ADC maps after the images had been corrected for distortion. The method also was shown to be valid in application to BOLD fMRI data

Optimizing a magnetic resonance care pathway : a strategy for radiography managers

This study reports the optimization of a local MR care pathway. A search of the literature did not result in any studies regarding the optimization of MRI care pathways through a formal research process. Discussions with international MR radiographers indicated that such development is often carried out using informal methods that are highly dependent on local conditions, that are rarely reported in the public domain and the validities of which are therefore not open to scrutiny; in addition, care pathways need to be specific to local healthcare needs and culture. In this study, the authors propose a formal documented methodology for developing a local MRI care pathway based on the well-established nominal group technique.peer-reviewe

Premonitory urges are associated with decreased grey matter thickness within the insula and sensorimotor cortex in young people with Tourette syndrome

Tourette syndrome (TS) is a neurological disorder characterized by vocal and motor tics and is associated with cortical–striatal–thalamic–cortical circuit (CSTC) dysfunction and hyperexcitability of cortical limbic and motor regions, which are thought to lead to the occurrence of tics. Importantly, individuals with TS often report that their tics are preceded by ‘premonitory sensory phenomena’ (PSP) that are described as uncomfortable cognitive or bodily sensations that precede the execution of a tic, and are experienced as a strong urge for motor discharge. While the precise role played by PSP in the occurrence of tics is controversial, PSP are nonetheless of considerable theoretical and clinical importance in TS, not least because they form the core component in many of the behavioural therapies that are currently used in the treatment of tic disorders. In this study, we investigated the brain structure correlates of PSP. Specifically, we conducted a whole-brain analysis of cortical (grey matter) thickness in 29 children and young adults with TS and investigated the association between grey matter thickness and PSP. We demonstrate for the first time that PSP are inversely associated with grey matter thickness measurements within the insula and sensori-motor cortex. We also demonstrate that grey matter thickness is significantly reduced in these areas in individuals with TS relative to a closely age- and gender-matched group of typically developing individuals and that PSP ratings are significantly correlated with tic severity

Real-World Performance of Autonomously Reporting Normal Chest Radiographs in NHS Trusts Using a Deep-Learning Algorithm on the GP Pathway

AIM To analyse the performance of a deep-learning (DL) algorithm currently deployed as diagnostic decision support software in two NHS Trusts used to identify normal chest x-rays in active clinical pathways. MATERIALS AND METHODS A DL algorithm has been deployed in Somerset NHS Foundation Trust (SFT) since December 2022, and at Calderdale & Huddersfield NHS Foundation Trust (CHFT) since March 2023. The algorithm was developed and trained prior to deployment, and is used to assign abnormality scores to each GP-requested chest x-ray (CXR). The algorithm classifies a subset of examinations with the lowest abnormality scores as High Confidence Normal (HCN), and displays this result to the Trust. This two-site study includes 4,654 CXR continuous examinations processed by the algorithm over a six-week period. RESULTS When classifying 20.0% of assessed examinations (930) as HCN, the model classified exams with a negative predictive value (NPV) of 0.96. There were 0.77% of examinations (36) classified incorrectly as HCN, with none of the abnormalities considered clinically significant by auditing radiologists. The DL software maintained fast levels of service to clinicians, with results returned to Trusts in a mean time of 7.1 seconds. CONCLUSION The DL algorithm performs with a low rate of error and is highly effective as an automated diagnostic decision support tool, used to autonomously report a subset of CXRs as normal with high confidence. Removing 20% of all CXRs reduces workload for reporters and allows radiology departments to focus resources elsewhere.Comment: 7 pages, 5 figures, 2 tables. Submitted to Clinical Radiolog

Mutational Analysis of the Active Site and Antibody Epitopes of the Complement-inhibitory Glycoprotein, CD59

The Ly-6 superfamily of cell surface molecules includes CD59, a potent regulator of the complement system that protects host cells from the cytolytic action of the membrane attack complex (MAC). Although its mechanism of action is not well understood, CD59 is thought to prevent assembly of the MAC by binding to the C8 and/or C9 proteins of the nascent complex. Here a systematic, structure-based mutational approach has been used to determine the region(s) of CD59 required for its protective activity. Analysis of 16 CD59 mutants with single, highly nonconservative substitutions suggests that CD59 has a single active site that includes Trp-40, Arg-53, and Glu-56 of the glycosylated, membrane-distal face of the disk-like extracellular domain and, possibly, Asp-24 positioned at the edge of the domain. The putative active site includes residues conserved across species, consistent with the lack of strict homologous restriction previously observed in studies of CD59 function. Competition and mutational analyses of the epitopes of eight CD59-blocking and non-blocking monoclonal antibodies confirmed the location of the active site. Additional experiments showed that the expression and function of CD59 are both glycosylation independent

Radiocephalic and brachiocephalic arteriovenous fistula outcomes in the elderly

BackgroundA recent meta-analysis has suggested that patients aged >65 have worse outcomes with radiocephalic arteriovenous fistulas (RCAVFs) compared with brachiocephalic arteriovenous fistulas (BCAVFs). We hypothesized that outcomes in patients aged ≥80—a rapidly expanding cohort within this elderly group—might be skewing the results, and that age >65 may not be a contraindication to RCAVF formation. This study examined the effect of age group (<65, 65 to 79, ≥80) on functional outcomes (use; primary and secondary functional patency) in RCVAFs and BCAVFs.MethodsWe identified the outcomes of all patients undergoing a first surgical access procedure for a RCAVF or BCVAF between January 1, 2000, and December 31, 2005. We examined the effect of age and other factors including sex, diabetes mellitus, hypertension, late referral (<3 months before dialysis), dialysis before surgical access, preoperative duplex ultrasound imaging, and ethnicity on non-AVF use and primary and secondary functional AVF patency. Logistic regression and Cox proportional hazards regression models were used.ResultsFrom a total of 658 patients, 361 had a RCAVF, and 297 had a BCAVF. Their median age was 68.5 years (interquartile range [IQR], 54.4 to 76.5 years), and 288 (43.8%) were aged <65 years, 274 (41.6%) were 65 to 79, and 96 (14.6%) were ≥80. Age did not influence the site of the first surgical access (P = .874). Only 85.7% of patients actually progressed to hemodialysis, and the RCAVF or BCAVF in 45.7% of those was never used for dialysis. Female sex (hazard ratio [HR], 2.24; 95% confidence interval [CI] 1.387 to 3.643; P = .001) was the only factor associated with an increase risk of RCAVF nonuse, whereas diabetes (HR, 2.095; 95% CI, 1.261 to 3.482; P = .004) was the only factor associated with an increase risk of BCAVF nonuse. The respective primary patency rates at 1 and 2 years for RCAVFs were 46.0% and 27.1% for patients <65, 47.0% and 36.0% for those 65 to 79, and 45.7% and 38.1% for those ≥80. Only female sex (HR, 1.679; 95% CI, 1.261 to 2.236; P = .001) and prior hemodialysis (HR, 1.363; 95% CI, 1.0.29 to 1.804; P = .031) were associated with loss of patency of RCAVFs. The primary functional patency rates for BCAVFs at 1 and 2 years were 39.3% and 31.0% for those <65 years; 53.30% and 37.5% for those 65 to 79, and 46.3% and 42.6% for those ≥80. No factors analyzed were associated with loss of primary functional patency of BCAVFs.ConclusionsAge did not affect usability, primary or secondary patency of either RCAVFs or BCAVFs. Although patient selection is important, even patients ≥80 years who are considered suitable for surgical placement of access should not be denied a RCAVF solely because of age

Validation of a competence profile for MR radiographers using a formal research process

Owing to the limited time for continuous professional development available and hence the impossibility of covering all the knowledge, skills and competences required for the full range of MR techniques available today, it’s important that competence profiles are context specific. This study sought to develop and validate a context specific competence profile for MR radiographers that would be necessary and sufficient to deliver the MR service portfolio and care pathway in Malta. The study forms part of a wider study on continuous professional development for MR radiographers in Malta.peer-reviewe

Inhibition of the classical pathway of the complement cascade prevents early dendritic and synaptic degeneration in glaucoma

BACKGROUND: Glaucoma is a complex, multifactorial disease characterised by the loss of retinal ganglion cells and their axons leading to a decrease in visual function. The earliest events that damage retinal ganglion cells in glaucoma are currently unknown. Retinal ganglion cell death appears to be compartmentalised, with soma, dendrite and axon changes potentially occurring through different mechanisms. There is mounting evidence from other neurodegenerative diseases suggesting that neuronal dendrites undergo a prolonged period of atrophy, including the pruning of synapses, prior to cell loss. In addition, recent evidence has shown the role of the complement cascade in synaptic pruning in glaucoma and other diseases. RESULTS: Using a genetic (DBA/2J mouse) and an inducible (rat microbead) model of glaucoma we first demonstrate that there is loss of retinal ganglion cell synapses and dendrites at time points that precede axon or soma loss. We next determine the role of complement component 1 (C1) in early synaptic loss and dendritic atrophy during glaucoma. Using a genetic knockout of C1qa (D2.C1qa (-/-) mouse) or pharmacological inhibition of C1 (in the rat bead model) we show that inhibition of C1 is sufficient to preserve dendritic and synaptic architecture. CONCLUSIONS: This study further supports assessing the potential for complement-modulating therapeutics for the prevention of retinal ganglion cell degeneration in glaucoma. Mol Neurodegener 2016 Apr 6; 11(2):2

Complement biomarkers as predictors of disease progression in Alzheimer's disease

There is a critical unmet need for reliable markers of disease and disease course in mild cognitive impairment (MCI) and early Alzheimer’s disease (AD). The growing appreciation of the importance of inflammation in early AD has focused attention on inflammatory biomarkers in cerebrospinal fluid or plasma; however, non-specific inflammation markers have disappointed to date. We have adopted a targeted approach, centered on an inflammatory pathway already implicated in the disease. Complement, a core system in innate immune defense and potent driver of inflammation, has been implicated in pathogenesis of AD based on a confluence of genetic, histochemical, and model data. Numerous studies have suggested that measurement of individual complement proteins or activation products in cerebrospinal fluid or plasma is useful in diagnosis, prediction, or stratification, but few have been replicated. Here we apply a novel multiplex assay to measure five complement proteins and four activation products in plasma from donors with MCI, AD, and controls. Only one complement analyte, clusterin, differed significantly between control and AD plasma (controls, 295 mg/l; AD, 388 mg/l: p < 10- 5). A model combining clusterin with relevant co-variables was highly predictive of disease. Three analytes (clusterin, factor I, terminal complement complex) were significantly different between MCI individuals who had converted to dementia one year later compared to non-converters; a model combining these three analytes with informative co-variables was highly predictive of conversion. The data confirm the relevance of complement biomarkers in MCI and AD and build the case for using multi-parameter models for disease prediction and stratification