Angela Oatridge

Imperial College London, Londinium, England, United Kingdom

Are you Angela Oatridge?

Claim your profile

Publications (57)289.91 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: A cohort of patients with first-episode schizophrenia was dichotomised into two age- and sex-matched groups of clinical syndromes, the active and withdrawn, and underwent high-resolution three-dimensional magnetic resonance imaging at baseline and 8 months later. A cohort of age- and sex-matched normal controls was also imaged at the same time intervals. The application of subvoxel registration and semiautomated quantification techniques demonstrated a significantly different outcome in ventricular changes between the two groups of patients. Compared with the controls, the withdrawn patients showed progressive ventricular enlargement, with an increase in ventricle-to-brain volume ratio, whereas the active group showed a reduction in ventricle-to-brain volume ratio, with a change opposite in sign and smaller in magnitude. These findings lend further support for the aetiological validity of this syndromal model of schizophrenia and are likely to be of importance in furthering our understanding of its pathogenesis and in the development of suitable therapeutic strategies.
    International Journal of Clinical Practice 05/2005; 59(4):399-402. · 2.54 Impact Factor
  • Source
    Gut 04/2005; 54(3):438. · 13.32 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Magnetic resonance imaging (MRI) coregistration techniques can be used to track changes in brain volume. We aimed to determine whether treatment in chronic liver disease altered brain size. The study group comprised nine patients with cirrhosis (7 Child's grade B and 2 Child's grade C). Six had minimal and three had overt hepatic encephalopathy on clinical, psychometric, and electrophysiological testing. Cerebral MRI was performed in seven patients before and 6 weeks after starting lactulose. A further two patients underwent transjugular intrahepatic portosystemic stent shunting with MRI performed before and 24 h afterwards. One patient had a further scan 3 months after TIPSS. Brain size was measured using a semiautomated contour/thresholding technique. Measurable changes were found after treatment intervention, but there was no correlation with severity of encephalopathy (West Haven criteria) or liver dysfunction (Child's score). Three patients improved on lactulose, the brain size decreased with an increase in ventricular volume. Two patients deteriorated; the brain size increased with a concomitant decrease in ventricular volume. Two stable patients had small changes, one with an increase in brain size and a decrease in ventricular volume and the other showing the converse. Following TIPSS, there was an increase in brain size in both patients, evident within 24 h in one patient and at 3 months in the other. Coregistered MRI demonstrates easily detectable changes in brain size following treatment intervention. Our results support the hypothesis that low-grade brain swelling is present, even in minimal hepatic encephalopathy.
    Metabolic Brain Disease 01/2005; 19(3-4):431-45. · 2.40 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Fatigue is the commonest symptom in primary biliary cirrhosis (PBC), affecting individuals at all stages of disease. The pathogenesis of fatigue in PBC is unknown although rat models suggest a central nervous system (CNS) cause. We examined the hypothesis that a CNS abnormality related to cholestasis, rather than cirrhosis per se, underlies this symptom. Fourteen patients with precirrhotic PBC (stage I-II disease), four patients with stage III-IV PBC, and 11 healthy women were studied using cerebral magnetisation contrast imaging and proton magnetic resonance spectroscopy (MRS). The globus pallidus magnetisation transfer ratio (MTR), a quantifiable tissue characteristic that may be abnormal in the presence of normal magnetic resonance imaging, was significantly reduced in precirrhotic PBC patients compared with healthy controls. These measurements correlated with blood manganese levels and were more abnormal in the more fatigued subjects. There were no differences in MRS measurements between the three study groups, suggesting that the abnormal MTR was not related to hepatic encephalopathy. This study suggests that impairments in liver function in PBC may adversely affect the brain long before the development of cirrhosis and hepatic encephalopathy, possibly as a result of altered manganese homeostasis within the CNS.
    Gut 05/2004; 53(4):587-92. · 13.32 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To assess the Achilles tendon in patients with chronic tendonopathy using magnetic resonance (MR) magic angle imaging, and to compare the appearances and uptake of contrast medium in abnormal tendons with those in normal tendons. Eight patients with chronic Achilles tendonopathy and five normal controls were examined with the long axis of the tendon placed at 55 degrees and at 0 degrees to the main magnetic field. Conventional two-dimensional (2D) multi-slice images were obtained and T1 values were calculated before, and for up to 1h after the administration of intravenous gadodiamide. Both the unenhanced appearance and the pattern of enhancement in the tendon were compared. In the patients with tendonopathy, high signal intensity areas were evident on the short T1 inversion recovery (STIR) images obtained at 55 degrees in all tendons. Contrast medium enhancement was seen in six tendons and was most obvious on the images obtained at the magic angle. This was initially focal and then spread more diffusely within the tendon. After contrast medium administration, T1 values were significantly reduced in the tendonopathy group compared with normal controls (p<0.01). On the late post-contrast medium images obtained at 55 degrees, enhancement was evident in most of the tendon and correlated well with high signal intensity seen on STIR images. The use of magic angle MR imaging improved the demonstration of signal changes in the Achilles tendon in chronic tendonopathy. The STIR images obtained at the magic angle showed more obvious signal change than those obtained at 0 degrees. The changes due to enhancement were much more evident on images obtained at 55 degrees than at 0 degrees. The uptake of contrast medium was greater in the patients than in normal controls.
    Clinical Radiology 05/2003; 58(5):384-8. · 1.66 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To implement a multislice two-dimensional (2D) T2-weighted sequence suitable for subvoxel image registration and to assess its usefulness in detecting change in high-grade intracranial gliomas. Twenty patients with high-grade gliomas were studied on two or more occasions. T2-weighted multislice pulse sequences with a Gaussian slice profile, 50% overlapping slices and nearly isotropic voxels were acquired. The images were registered and subtraction images were produced. The images were compared with three-dimensional (3D) T1-weighted registered images and conventional unregistered T2-weighted images. All images were scored for changes in the lesions and ventricular system. The 2D and 3D registered subtraction images were the most sensitive for detecting changes in both the lesions and other regions in the brain. The mean rank scores were significantly higher for the lesions (chi2=86.742; df=5, n=38, P<0.0001) and for the ventricles (chi2=63.837; df=5, n=35, P<0.0001) compared with the unregistered and registered anatomical images. The subtraction images were also most sensitive for detecting signal intensity changes irrespective of the direction of change. Rigid body subvoxel registration can be successfully performed with both multislice 2D and 3D imaging. In principle, virtually all forms of clinical MR images of the brain can be accurately registered and subtracted.
    Clinical Radiology 12/2002; 57(12):1098-108. · 1.66 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This study describes magnetic resonance imaging findings in women presenting with neurological complications associated with preeclampsia and eclampsia. One eclamptic and two preeclamptic women were studied after presenting with postpartum neurological events. In two women the brain increased in size on the initial follow-up images, following the same pattern seen in normal pregnancy. In the other woman, the brain was decreased in size at 13 days postpartum but increased in size at six weeks postpartum. This initial reduction in brain size may reflect the resolution of cerebral oedema resulting from underlying pathological processes.
    International Journal of Obstetric Anesthesia 11/2002; 11(4):255-9. · 1.83 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Although neuropsychological symptoms and signs are common in thyroid disease, their organic substrate is unknown. We performed brain MR imaging in patients with hyperthyroidism or hypothyroidism before and after treatment and correlated the results with hormonal markers. Eight patients with hyperthyroid disease and three with hypothyroid disease underwent imaging within 1-2 days of a thyroid hormone testing. Images were registered, and brain and ventricular sizes were measured by using a semiautomated contour and thresholding technique. Changes in brain and ventricular volume were correlated with serum levels of total thyroxine (T(4)), unbound triiodothyronine (free T(3)), and thyroid-stimulating hormone (TSH) before and after treatment. With treatment, brain size decreased by 6,329-31,183 mm(3) in the hyperthyroid group and increased by 2,599-48,825 mm(3) in the hypothyroid group. Conversely, with treatment, ventricular size increased by 325-6,279 mm(3) in the hyperthyroid group and decreased by 760-2,376 mm(3) in the hypothyroid group. There was a highly significant correlation between reduction in brain size and reduction in T(4), as well as between the increase in ventricular size and reduction in T(4). There was a significant correlation between reduction in ventricular size and reduction in free T(3). There were highly significant correlations between reduced levels of TSH and increase in brain size, as well as between increased levels of TSH and increase in ventricular size. In thyroid disease, the size of the brain and ventricles significantly change after treatment, and these changes are correlated with T(4), free T(3), and TSH levels. The mechanism of these changes is uncertain, but it may involve osmolyte regulation, the sodium and water balance, and alterations in cerebral hemodynamics.
    American Journal of Neuroradiology 11/2002; 23(9):1539-44. · 3.68 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: OBJECTIVE: The objective of this study was to image the Achilles tendon with MR imaging at the magic angle (the long axis of the tendon at 55 degrees relative to the direction of the main static magnetic field [B(0)]) to detect signal from the tendon, to measure the T1 of the tendon, and to determine patterns of contrast enhancement in control subjects and patients. CONCLUSION: Mean T1 values of 311 +/- 30 msec (at 1.0 T) were found in six volunteers. In six control volunteers, slow uptake of contrast material that dispersed over 40 min-1.5 hr was shown without focal change, with elimination in most cases occurring within 18-24 hr. Small rapidly enhancing focal areas of enhancement were seen next to the insertion of the tendon and centrally within 5-10 min in two control volunteers. The focal areas were located at the sites of the blood supply. A patient with chronic tendinopathy showed early local contrast enhancement that extended widely within the tendon over several hours. Two patients with a partially ruptured or repaired tendon showed marked rapid contrast enhancement. The enhancement was obvious with the tendon at the magic angle but was not evident with the tendon in the usual orientation for MR examinations parallel to B(0).
    American Journal of Roentgenology 08/2002; 179(1):187-92. · 2.74 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Qualitative decreases in maternal brain size have been observed late in pregnancy. The aim of this study was to quantitatively evaluate changes to the maternal brain during and after healthy pregnancy and to compare these changes with those observed in cases of preeclampsia. Three-dimensional T1-weighted MR volume images were obtained in nine healthy participants before and after delivery. Additional images were obtained in some of these participants before pregnancy, during pregnancy, and within 52 weeks after delivery. Five women with preeclampsia were examined before delivery and 6 weeks after delivery. Three of these patients were examined within 52 weeks after delivery. Images were registered, and both brain and ventricular volumes were calculated by using a semiautomated computer program. Both the healthy and preeclamptic groups had a reduction in brain size during pregnancy that was maximal at term and that reversed by 6 months after delivery. The ventricular size showed a corresponding increase in size during pregnancy and a decrease in size after delivery. In the preeclamptic patients, brain size was significantly smaller (P =.05) than in healthy participants, both before and after delivery. The brain decreases in size during pregnancy and increases in size after delivery. The changes follow a consistent time course in each woman. The mechanism and physiologic importance of these findings are speculative at the present time.
    American Journal of Neuroradiology 02/2002; 23(1):19-26. · 3.68 Impact Factor
  • 01/2002;
  • [Show abstract] [Hide abstract]
    ABSTRACT: Tendons do not normally produce detectable signals with conventional magnetic-resonance techniques and are recognised as dark signal voids. However, if tendons are examined at 55 degrees to the static magnetic field (the "magic angle"), signals become detectable and the tendons can become the brightest structure on the image. We have used this approach to establish tendon relaxation times and magnetisation transfer ratios and to show contrast enhancement. We have also shown more detail of acute and chronic tendon rupture by this method compared with images made with the tendon parallel to the static magnetic field.
    The Lancet 12/2001; 358(9293):1610-1. · 39.21 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: High-signal artifacts produced by cerebrospinal fluid (CSF) flow can adversely affect fluid-attenuated inversion recovery (FLAIR) imaging of the brain and spinal cord. This study explores the use of a nonslice-selective inversion pulse to eliminate CSF flow artifacts together with a technique called "K-space Reordered by Inversion-time for each Slice Position" (KRISP) to achieve constant contrast in a multislice acquisition. Theory shows that with this method the CSF point spread function (PSF) has a minimum at the center and attenuated side lobes, providing CSF suppression, but residual edge signals remain. The PSF for brain is only mildly attenuated and signals for extended regions are not attenuated. KRISP FLAIR sequences were assessed in 15 patients (10 brain and five spinal cord cases). The images showed reduced CSF and blood flow artifacts and higher conspicuity of the cortex, meninges, ventricular system, brainstem, and cerebellum when compared with conventional FLAIR sequences.
    Magnetic Resonance in Medicine 09/2001; 46(2):354-64. · 3.40 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Our purpose was to test a new variant of the fluid-attenuated inversion-recovery (FLAIR) sequence that was designed to reduce CSF and blood flow artifacts by use of a non-slice-selective inversion pulse and k-space reordered by inversion time at each slice position (KRISP). With the KRISP FLAIR sequence, the slice order was cycled so that each inversion time (TI) was associated with a region of k-space rather than a particular slice, and the effective inversion time (TI(eff)) was chosen to null the signal from CSF. Scans were obtained with both conventional and KRISP FLAIR sequences. Studies were performed in 20 adult patients with a variety of brain diseases. Images were evaluated for artifacts from patient motion, CSF, and blood flow, and scored on a four-point scale. The conspicuity of the cortex, meninges, ventricular system, brain stem, and cerebellum was evaluated, as was lesion number and conspicuity. The KRISP FLAIR sequence showed more patient motion artifacts but had a pronounced advantage over the conventional sequence in control of CSF artifacts around the foramen of Munro, in the third ventricle, aqueduct, and fourth ventricle, as well as in the basal cisterns and around the brain stem and cerebellum. Blood flow artifacts from the internal carotid, basilar, and vertebral arteries were also much better controlled. Spurious high signal in the sylvian branches of the middle cerebral artery was eliminated. The meninges, cortex, ventricular system, brain stem, and cerebellum were better seen due to improved artifact suppression and an edge enhancement effect. The KRISP FLAIR sequence can suppress CSF and blood flow artifacts and improve the conspicuity of the meninges, cortex, brain stem, and cerebellum. Its major disadvantage is its duration, which may be reducible with a fast spin-echo version.
    American Journal of Neuroradiology 06/2001; 22(5):896-904. · 3.68 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study was to compare the performance of three fluid attenuated inversion recovery (FLAIR) pulse sequences for control of cerebrospinal fluid (CSF) and blood flow artifacts in imaging of the brain. The first of these sequences had an initial sinc inversion pulse which was followed by conventional k-space mapping. The second had an initial sinc inversion pulse followed by k-space re-ordered by inversion time at each slice position (KRISP) and the third had an adiabatic initial inversion pulse followed by KRISP. Ten patients with established disease were studied with all three pulse sequences. Seven were also studied with the adiabatic KRISP sequence after contrast enhancement. Their images were evaluated for patient motion artifact, CSF and blood flow artifact as well as conspicuity of the cortex, meninges, ventricular system, brainstem and cerebellum. The conspicuity of lesions and the degree of enhancement were also evaluated. Both the sinc and adiabatic KRISP FLAIR sequences showed better control of CSF and blood flow artifacts than the conventional FLAIR sequence. In addition the adiabatic KRISP FLAIR sequence showed better control of CSF artifact at the inferior aspect of the posterior fossa. The lesion conspicuity was similar for each of the FLAIR sequences as was the degree of contrast enhancement to that shown with a T(1)weighted spin echo sequence. The KRISP FLAIR sequence controls high signal artifacts from CSF flow and blood flow and the adiabatic pulse controls high signal artifacts due to inadequate inversion of the CSF magnetization at the periphery of the head transmitter coil. The KRISP FLAIR sequence also improves cortical and meningeal definition as a result of an edge enhancement effect. The effects are synergistic and can be usefully combined in a single pulse sequence. Curati, W. L.et al. (2001)Clinical Radiology56, 375-384
    Clinical Radiology 06/2001; 56(5):375-84. · 1.66 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Lateral ventricular enlargement is the most consistently replicated brain abnormality found in schizophrenia. This article reports a first episode, longitudinal study of ventricular volume using high-resolution serial magnetic resonance imaging (MRI) and recently developed techniques for image registration and quantitation. Baseline and follow-up (on average 8 months later) MRI scans were carried out on 24 patients and 12 controls. Accurate subvoxel registration was performed and subtraction images were produced to reveal areas of regional brain change. Whereas there were no differences between patients and controls with respect to the mean change in ventricular volume, the patients were much more variable in this respect and showed larger increases and decreases. The percentage increase in ventricular size was greater than one standard deviation of control values for 14 patients and the percentage decrease exceeded one standard deviation in eight patients. Although the finding of progressive ventricular enlargement in a proportion of patients supports other studies indicating an ongoing neuropathological process in the early stages of schizophrenia, the reduction of ventricular size in the remaining patients is more difficult to explain. It is suggested that this may reflect improvement in nutrition and hydration following treatment.
    Psychiatry Research 05/2001; 106(2):141-50. · 2.68 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to investigate the possibility that some artifactual high signals produced in CSF with fluid-attenuated inversion-recovery MR sequences could be due to inhomogeneity in the amplitude of the initial inversion pulse, and that this problem could be reduced or eliminated by the use of adiabatic inversion pulses. Studies with four volunteers showed dependence of high CSF signals in the posterior fossa on radiofrequency pulse amplitudes and that these signals could be eliminated by the use of adiabatic inversion pulses. Two illustrative clinical cases are included.
    American Journal of Neuroradiology 03/2001; 22(2):317-22. · 3.68 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The objective of this study was to compare conventional and KRISP (k-space reordered by inversion time at each slice position) fluid-attenuated inversion recovery (FLAIR) sequences in high grade gliomas for artifact control, conspicuity of intracranial structures, and lesions as well as sensitivity to contrast enhancement. Artifacts were lower with the KRISP FLAIR sequence, and the conspicuity of all assessed structures and lesions was better. The degree of contrast enhancement was similar with T1-weighted and KRISP FLAIR sequences.
    Journal of Computer Assisted Tomography 01/2001; 25(2):251-6. · 1.60 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Cerebral intracellular energy production (cerebral bioenergetics) via oxidative phosphorylation and the production of adenosine triphosphate (ATP) is critical to cerebral function. To test the hypothesis that patients with chronic stable hypoxia also generate neuronal ATP via an anaerobic metabolism, we studied the changes in cerebral (31)P magnetic resonance spectra ((31)P MRS) in patients with stable chronic obstructive pulmonary disease (COPD), and compared the results with MR spectra from similar areas of the brain in control subjects. Ten patients with stable COPD (age: 65 +/- 9 yr [mean +/- SD]; Pa(O(2)): 8.8 +/- 1.2 kPa; Pa(CO(2)): 6.1 +/- 0.8 kPa; pH 7.42 +/- 0.03, and FEV(1): 41 +/- 20% predicted) and five healthy volunteers underwent cerebral (31)P MRS (TR-5,000 ms) at 1.5 T. When COPD patients were compared with controls, the percentage MR signal with respect to total MR-detectable phosphorus-containing metabolites was increased from inorganic phosphate (Pi) (7.1 +/- 1. 3% versus 3.9 +/- 0.7%, p = 0.0001) and phosphomonoesters (PMEs) (9. 4 +/- 1.2% versus 6.9 +/- 0.3%, p = 0.0001), whereas the signal from phosphodiesters was reduced (34.8 +/- 3.2 versus 40.4 +/- 3.3%, p = 0.015). The ratios of Pi to betaATP (0.8 +/- 0.2 versus 0.4 +/- 0.1, p = 0.001) and of PME to betaATP (1.0 +/- 0.2 versus 0.7 +/- 0.1, p = 0.015) were increased, but the phosphocreatine-to-Pi ratio (2.1 +/- 0.6 versus 3.2 +/- 0.6, p = 0.01) was reduced in patients as compared with controls. This alteration in phosphorus-containing metabolites within cerebral cells provides evidence of extensive use of anaerobic metabolism in hypoxic COPD patients.
    American Journal of Respiratory and Critical Care Medicine 01/2000; 160(6):1994-9. · 11.99 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Lateral ventricular volume asymmetries in schizophrenia were studied using high resolution 3D magnetic resonance imaging in conjunction with segmentation and quantitation techniques. Comparisons were made between two clinical syndromes that have been associated with opposite patterns of functional hemispheric activation, namely an active and a withdrawn syndrome. Ratios of both left to right ventricular volume and left to right ventricle-to-brain ratios differed significantly between the two groups. These results primarily reflected differences in the left ventricular volume, in keeping with previous reports which have usually implicated left hemispheric structural abnormalities in schizophrenia. It is suggested that a syndromal approach might help to resolve some of the inconsistencies in the existing literature on lateralised neuroanatomical differences in schizophrenia.
    International Journal of Psychophysiology 12/1999; 34(3):207-11. · 2.65 Impact Factor

Publication Stats

2k Citations
289.91 Total Impact Points

Institutions

  • 2002–2005
    • Imperial College London
      • • Department of Imaging Sciences
      • • Faculty of Medicine
      Londinium, England, United Kingdom
  • 1999–2005
    • MRC Clinical Sciences Centre
      London Borough of Harrow, England, United Kingdom