Kuberan Pushparajah

Magnetic Resonance Imaging Changes in Idiopathic Intracranial Hypertension in Children

To evaluate the usefulness of neuroimaging in children with idiopathic intracranial hypertension, brain magnetic resonance imaging (MRI) scans of children with idiopathic intracranial hypertension and age-matched controls were reviewed. Compared with controls, patients with idiopathic intracranial hypertension had flattening of the posterior sclera in 61% versus 40% of cases, distension of perioptic subarachnoid space in 65% versus 35%, intraocular protrusion of pre-laminar optic nerve in 17% versus 0%, tortuosity of optic nerve in 30% versus 5%, and an empty sella in 26% versus 5% of cases. The presence of 3 or more of the MRI features is 95% specific in predicting idiopathic intracranial hypertension. The observed general anesthetic effect on these neuroimaging features are also minimized when multiple features are taken into account. Magnetic resonance imaging features can assist in suspecting the diagnosis of idiopathic intracranial hypertension in children, provided caution is applied when interpreting imaging performed under a general anesthesia.

3D echocardiography of the atrial septum: anatomical features and landmarks for the echocardiographer.

A detailed understanding of the anatomy of the atrial septum ([1][1]) is increasingly important for the echocardiographer. This relates to the need to assess suitability for device closure of atrial septal defects (ASDs), echocardiographically guided transeptal puncture, and surgical planning for

A sensitivity analysis on 3D velocity reconstruction from multiple registered echo Doppler views

We present a new method for reconstructing a 3D+t velocity field from multiple 3D+t colour Doppler images. Our technique reconstructs 3D velocity vectors from registered multiple standard 3D colour Doppler views, each of which contains a 1D projection of the blood velocity. Reconstruction is based on a scalable patch-wise Least Mean Squares approach, and a continuous velocity field is achieved by using a B-spline grid. We carry out a sensitivity analysis of clinically relevant parameters which affect the accuracy of the reconstruction, including the impact of noise, view angles and registration errors, using simulated data. A realistic simulation framework is achieved by a novel noise model to represent variations in colour Doppler images based on multiscale additive Gaussian noise. Simulations show that, if the Target Registration Error <2.5mm, view angles are >20° and the standard deviation of noise in the input data is <10 cm/s, the reconstructed velocity field presents visually plausible flow patterns and mean error in flow rate is approximately 10% compared to 2D+t Flow MRI. These results are verified by reconstructing 3D velocity on three healthy volunteers. The technique is applied to reconstruct 3D flow on three paediatric patients showing promising results for clinical application.

A Systematic Three-Dimensional Echocardiographic Approach to Assist Surgical Planning in Double Outlet Right Ventricle

Double outlet right ventricle (RV) describes a range of pathology where both great arteries arise, either entirely or in greater part from the morphologic RV. Accurate prediction of the optimal surgical approach is challenging. Ideally, assuming that the ventricles are balanced with respect to their size, a biventricular repair is normally attempted. The feasibility of the different surgical options for repair depends on morphologic features including the location and size of the ventricular septal defect, and the relationship of the great arteries. Anderson et al. recommend the term interventricular communication, in preference to ventricular septal defect, when describing the defect between the 2 ventricles in double outlet RV. The outlet muscular septum that forms the upper boundary of the true ventricular septal defect in double outlet RV is often sited in a position above the right ventricular cavity. Any closure of the true ventricular septal defect beginning at the crest of the septum would involve crossing into the right ventricular space. The remaining defect between the 2 ventricles is therefore best described as the interventricular communication. The term interventricular communication has been used in the text for the purpose of consistency. The position of this interventricular communication in relation to the great vessels is variable. These are described as being subaortic, subpulmonary, or noncommitted, where the interventricular communication lies remote to either great vessel’s origin. In rare cases, there is fibrous continuity between the 2 arterial valves and the interventricular communication that lies beneath these is described as being doubly committed. Two-dimensional echocardiography has traditionally been used to plan surgical intervention, utilizing multiple separate sonographic views and “sweeps.” Three-dimensional (3D) echocardiography has the advantage of incorporating a depth of field to the sonographic images so that the atrioventricular valves, ventricular septal defect, and great arteries can be visualized within a single sonographic projection, obtained by cropping of a 3D echocardiographic volume. This has the potential to enhance understanding of the relationship of the anatomic structures needed for surgical planning. We describe a systematic 3D echocardiographic approach, which we have adopted to assist decision making for the surgical management of this group of lesions. This approach addresses the anatomic concerns with respect to biventricular repair and whether a RV to pulmonary artery conduit will be required. Biventricular repair options include closure of the interventricular communication with or without an arterial switch procedure. Complex interventricular baffles can necessitate enlargement of the interventricular communication and there may be a need to relieve subpulmonary or subaortic stenosis. Straddling atrioventricular valves may preclude septation and single ventricle palliation is sometimes pursued. The echocardiographic approach is described below using clinical examples. Address for correspondence and reprint requests: John M. Simpson, M.D., F.R.C.P., F.E.S.C., 6th Floor Sky Offices, Evelina Childrens Hospital, Westminster Bridge Road, London SE1 7EH, UK. Fax: +44-207-188-4556; E-mail: john.simpson@gstt.nhs.uk

Towards a fast and efficient approach for modelling the patient-specific ventricular haemodynamics

Computer modelling of the heart has emerged over the past decade as a powerful technique to explore the cardiovascular pathophysiology and inform clinical diagnosis. The current state-of-the-art in biophysical modelling requires a wealth of, potentially invasive, clinical data for the parametrisation and validation of the models, a process that is still too long and complex to be compatible with the clinical decision-making time. Therefore, there remains a need for models that can be quickly customised to reconstruct physical processes difficult to measure directly in patients. In this paper, we propose a less resource-intensive approach to modelling, whereby computational fluid-dynamics (CFD) models are constrained exclusively by boundary motion derived from imaging data through a validated wall tracking algorithm. These models are generated and parametrised based solely on ultrasound data, whose acquisition is fast, inexpensive and routine in all patients. To maximise the time and computational efficiency, a semi-automated pipeline is embedded in an image processing workflow to personalise the models. Applying this approach to two patient cases, we demonstrate this tool can be directly used in the clinic to interpret and complement the available clinical data by providing a quantitative indication of clinical markers that cannot be easily derived from imaging, such as pressure gradients and the flow energy.

Magnetic resonance imaging catheter stress haemodynamics post-Fontan in hypoplastic left heart syndrome

AIMS Exercise limitation is common post-Fontan. Hybrid X-ray and magnetic resonance imaging (XMR) catheterization allows haemodynamic assessment by means of measurement of ventricular volumes and flow in major vessels with simultaneous invasive pressures. We aim to assess haemodynamic response to stress in patients with hypoplastic left heart syndrome (HLHS) post-Fontan. METHODS AND RESULTS Prospective study of 13 symptomatic children (NHYA 2) with HLHS post-Fontan using XMR catheterization. Three conditions were applied: baseline (Stage 1), dobutamine at 10 µg/kg/min (Stage 2), and dobutamine at 20 µg/kg/min (Stage 3). Seven consecutive patients received inhaled nitric oxide (iNO) at peak stress. Control MRI data were from normal healthy adults. In the HLHS patients, baseline mean pulmonary vascular resistance (PVR) was 1.51 ± 0.59 WU m(2) and aortopulmonary collateral flow was 17.7 ± 13.6% of systemic cardiac output. Mean right ventricular end-diastolic pressure was 6.7 ± 2.5 mmHg which did not rise with stress. Cardiac index (CI) increased at Stage 2 in HLHS (40%) and controls (61%) but continued to increase at Stage 3 only in controls (19%) but not in HLHS. The blunted rise in CI in HLHS was due to a continuing fall in end-diastolic volume throughout stress, with no significant change in PVR or CI at peak stress in response to iNO. CONCLUSION Cardiac output post-Fontan in HLHS at peak stress is blunted due to a limitation in preload which is not responsive to inhaled pulmonary vasodilators in the setting of normal PVR.

4D Blood Flow Reconstruction Over the Entire Ventricle From Wall Motion and Blood Velocity Derived From Ultrasound Data

We demonstrate a new method to recover 4D blood flow over the entire ventricle from partial blood velocity measurements using multiple 3D+t colour Doppler images and ventricular wall motion estimated using 3D+t BMode images. We apply our approach to realistic simulated data to ascertain the ability of the method to deal with incomplete data, as typically happens in clinical practice. Experiments using synthetic data show that the use of wall motion improves velocity reconstruction, shows more accurate flow patterns and improves mean accuracy particularly when coverage of the ventricle is poor. The method was applied to patient data from 6 congenital cases, producing results consistent with the simulations. The use of wall motion produced more plausible flow patterns and reduced the reconstruction error in all patients.

Managed Care Network for the assessment of cardiac problems in children in a district general hospital: a working model.

Aim: To assess a model for cardiology assessments in children with suspected heart disease by a general paediatrician with special expertise in paediatric cardiology (PsePC) in a district general hospital. Methods: A new monthly “screening” clinic was established in May 2004 by the PsePC to reduce the burden of new referrals on outreach tertiary paediatric cardiology services. All patients were to have echocardiograms as part of their referral for cardiac assessment. Over a one year period (May 2004–April 2005), through audit, details of referrers, indications for referral, echocardiography assessments, and subsequent management were recorded. This was compared with the pattern of patients seen in the joint paediatric cardiology outreach clinics over a two year period (May 2003–April 2005). Results: In the “screening” clinic, there were 75 appointments for 65 patients seen in 12 months. Fifty five of these patients had normal echocardiographic studies. Of the 47 referrals with heart murmurs in asymptomatic children, four had structurally abnormal hearts on echocardiographic assessment. Between May–October 2003 and November 2003–April 2004, the number of new patients with normal echocardiographic studies seen in the paediatric cardiology outreach clinic was 33/106 (31%) and 28/110 (25.4%) respectively. Following the introduction of the “screening” clinic, the number decreased to 21/99 (21%) during May–October 2004, and 10/102 (9.8%) during November 2004–April 2005. Conclusion: This model can work effectively in order to identify pathology requiring input of a paediatric cardiologist more appropriately. Paediatricians with specific training in paediatric cardiology are potentially well equipped to provide this basic screening service.

An exploration of the potential utility of fetal cardiovascular MRI as an adjunct to fetal echocardiography

Fetal cardiovascular magnetic resonance imaging (MRI) offers a potential alternative to echocardiography, although in practice, its use has been limited. We sought to explore the need for additional imaging in a tertiary fetal cardiology unit and the usefulness of standard MRI sequences.

Fetal cardiac cine imaging using highly accelerated dynamic MRI with retrospective motion correction and outlier rejection

Development of a MRI acquisition and reconstruction strategy to depict fetal cardiac anatomy in the presence of maternal and fetal motion.