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Daniel Birchall

Publications and source records attributed to Daniel Birchall.

10 recordsLinked to original sources
PubMed2006

Analysis of haemodynamic disturbance in the atherosclerotic carotid artery using computational fluid dynamics.

Computational fluid dynamics (CFD) provides a means for the quantitative analysis of haemodynamic disturbances in vivo, but most work has used phantoms or idealised geometry. Our purpose was to use CFD to analyse flow in carotid atherosclerosis using patient-specific geometry and flow data. Eight atherosclerotic carotid arteries and one healthy control artery were imaged with magnetic resonance angiography (MRA) and duplex ultrasound, and the data used to construct patient-specific computational models used for CFD and wall shear stress (WSS) analysis. There is a progressive change in three-dimensional (3-D) velocity profile and WSS profile with increasing severity of stenosis, characterised by increasing restriction of areas of low WSS, change in oscillation patterns, and progressive rise in WSS within stenoses and downstream jets. Areas of turbulent, retrograde flow and of low WSS are demonstrated in the lee of the stenoses. This study presents the largest CFD analysis of abnormal haemodynamics at the atheromatous carotid bifurcation using patient-specific data and provides the basis for further investigation of causal links between haemodynamic variables and atherogenesis and formation of unstable plaque. We propose that this provides a means for the prospective assessment of relative stroke risk in patients with carotid atherosclerosis.

Aged↗
PubMed2005

Weights and measures: a new look at bisection behaviour in neglect.

Horizontal line bisection is a ubiquitous task in the investigation of visual neglect. Patients with left neglect typically make rightward errors that increase with line length and for lines at more leftward positions. For short lines, or for lines presented in right space, these errors may 'cross over' to become leftward. We have taken a new approach to these phenomena by employing a different set of dependent and independent variables for their description. Rather than recording bisection error, we record the lateral position of the response within the workspace. We have studied how this varies when the locations of the left and right endpoints are manipulated independently. Across 30 patients with left neglect, we have observed a characteristic asymmetry between the 'weightings' accorded to the two endpoints, such that responses are less affected by changes in the location of the left endpoint than by changes in the location of the right. We show that a simple endpoint weightings analysis accounts readily for the effects of line length and spatial position, including cross-over effects, and leads to an index of neglect that is more sensitive than the standard measure. We argue that this novel approach is more parsimonious than the standard model and yields fresh insights into the nature of neglect impairment.

Aged↗
PubMed2005

Subclinical semitendinosus and obturator externus involvement defines an autosomal dominant myopathy with early respiratory failure.

We recently described a dominant limb myopathy characterised by early respiratory failure whilst affected individuals were still ambulant (autosomal dominant myopathy with early respiratory failure). Early diagnosis and exclusion of this disorder is difficult because of the insidious onset in late adult life and the highly selective muscle involvement, both clinically and pathologically. We performed muscle magnetic resonance imaging on seven cases of autosomal dominant myopathy with early respiratory failure (age range 37-66 years, 4 male) and show selective early involvement of semitendinosus and obturator externus on magnetic resonance imaging that cannot be detected clinically, with different rates of progression in closely related muscles. These findings are specific to autosomal dominant myopathy with early respiratory failure and enable early non-invasive diagnosis for individuals at risk.

Female↗
PubMed2005

Imaging of metastatic orbital leiomyosarcoma.

A 74-year-old man with a previous history of lower leg soft tissues leiomyosarcoma and multiple metastasis presented with a progressive painless proptosis of the left eye. Orbital ultrasound, CT, and MRI revealed a large mass in the left medial orbit. The mass was surgically removed and pathologic examination confirmed the diagnosis of a metastatic orbital leiomyosarcoma. The imaging characteristics of this rare tumor are comprehensively detailed, using complementary ultrasound, CT, and MRI, the combination of which allowed planning of total excision of the lesion.

Aged↗
PubMed2004

Muscle MRI findings in patients with limb girdle muscular dystrophy with calpain 3 deficiency (LGMD2A) and early contractures.

Limb girdle muscular dystrophy 2A is a common variant secondary to mutations in the calpain 3 gene. A proportion of patients has early and severe contractures, which can cause diagnostic difficulties with other conditions. We report clinical and muscle magnetic resonance imaging findings in seven limb girdle muscular dystrophy 2A patients (four sporadic and three familial) who had prominent and early contractures. All patients showed a striking involvement of the posterior thigh muscles. The involvement of the other thigh muscles was variable and was related to clinical severity. Young patients with minimal functional motor impairment showed a predominant involvement of the adductors and semimembranosus muscles while patients with restricted ambulation had a more diffuse involvement of the posterolateral muscles of the thigh and of the vastus intermedius with relative sparing of the vastus lateralis, sartorius and gracilis. At calf level all patients showed involvement of the soleus muscle and of the medial head of the gastrocnemius with relative sparing of the lateral head. MRI findings were correlated to those found in two patients with the phenotype of limb girdle muscular dystrophy 2A without early contractures and the pattern observed was quite similar. However, the pattern observed in limb girdle muscular dystrophy 2A is different from that reported in other muscle diseases such as Emery-Dreifuss muscular dystrophy and Bethlem myopathy which have a significant clinical overlap with limb girdle muscular dystrophy 2A once early contractures are present. Our results suggest that muscle MRI may help in recognising patients with limb girdle muscular dystrophy 2A even when the clinical presentation overlaps with other conditions, and may therefore, be used as an additional investigation to target the appropriate biochemical and genetic tests.

Adolescent↗
PubMed2004

Demonstration of vertebral and disc mechanical torsion in adolescent idiopathic scoliosis using three-dimensional MR imaging.

This study was designed to demonstrate and measure mechanical torsion in patients with adolescent idiopathic scoliosis using three-dimensional magnetic resonance (MR) imaging. Ten patients with adolescent idiopathic scoliosis were imaged with three-dimensional MR imaging, and the data post-processed through multiplanar reconstruction to produce images angled through individual endplates. Transverse rotation was measured at each endplate and these measurements used to calculate the amount of vertebral and disc mechanical torsion present. A test object was imaged in order to validate the measurement technique. Mechanical torsion was demonstrated within the vertebral bodies and discs of the imaged subjects, with vertebral mechanical torsion contributing on average 45% of the overall transverse plane deformity. It is concluded that deformation occurs in the transverse plane within the vertebrae and discs of subjects with idiopathic scoliosis, and a significant proportion of the rotation present in the scoliotic spine occurs as a result of plastic deformation within the vertebrae themselves. We believe that this is the first systematic demonstration of mechanical torsion in idiopathic scoliosis.

Adolescent↗
PubMed2004

Genetics in reverse.

Explore the source record for details and available documents.

Fragile X Messenger Ribonucleoprotein 1↗
PubMed2004

Widespread capillary malformation associated with global developmental delay and megalencephaly.

Although port wine stains are seen in 0.3% births, widespread cutaneous capillary malformations are unusual and an association with static gliosis has not been previously reported. This is a report of a 3-year-old boy with a fixed widespread capillary naevus (port wine stain), megalencephaly and global developmental, and features of gliosis on brain magnetic resonance imaging (MRI).

Abnormalities, Multiple↗
PubMed2002

Computed tomography angiography for the evaluation of carotid atherosclerotic plaque: correlation with histopathology of endarterectomy specimens.

BACKGROUND AND PURPOSE: The goal of this study was to determine the efficacy of CT angiography for the characterization of plaque morphology and composition in carotid atherosclerotic disease. METHODS: Fifty-five patients undergoing carotid endarterectomy were imaged preoperatively with single-slice spiral CT angiography. One hundred sixty-five endarterectomy sections were examined histologically at selected levels through the distal common and proximal internal carotid arteries. Plaque density was measured (in Hounsfield units) on axial CT sections, and the presence or absence of ulceration was noted. These observations were compared with the histological findings at corresponding levels. Data were analyzed with 2-sample t tests and 1-way analysis of variance (ANOVA). RESULTS: ANOVA testing showed a statistically significant decrease in CT attenuation values with increasing plaque lipid but with a very high standard deviation of values. No other histological factor showed a statistically significant link with CT attenuation. Plaque ulceration was detected by CT with a sensitivity of 60% and a specificity of 74%. CONCLUSIONS: Analysis of plaque attenuation with single-slice spiral CT does not give useful information concerning plaque composition. The predictive value of CT for the detection of plaque ulceration was moderate. Single-slice CT angiography is insufficiently robust to be a useful tool for the characterization of carotid plaque composition and morphology.

Analysis of Variance↗