Biomedical subjects
Publications and source records attributed to P Mansfield.
The echo planar imaging (EPI) method and related variants of this technique can produce complete two-dimensional images from the data collected in a single experiment lasting a fraction of a second. EPI methods are used at 0.5 T to produce snapshot images of the human head with a spatial resolution of less than 2 mm.
Three infants were studied by echo planar imaging after repair of congenital diaphragmatic hernias. Total lung volume and individual lung volumes were estimated using echo planar imaging. In the two patients with left sided hernias, the right lung was more than twice as large as the left. The patient with a right sided hernia had developed emphysema on the right side, and the right lung was twice as large as the left when estimated by echo planar imaging. Echo planar imaging studies took less than five minutes to perform and no sedation was required.
Following the Industrial Revolution technology has led to the identification and employment of a vast variety of chemicals. This has affected both agriculture and nutrition. The body's capacity to cope with chemicals is limited. Many, obviously, are toxic. What is safe is what is serviceable. Children, long before immune defences have been properly organised, are particularly vulnerable. Body changes are apt to result--food intolerance and asthma are becoming increasingly common and behaviour has been shown to be affected. Means of dealing with the results are discussed.
New variants of the ultra-high-speed echo-planar imaging technique have been used to obtain snap-shot images of adult patients and volunteers at 0.1 T. Modified pulsed-gradient sequences together with non-linear signal sampling and activity screened gradients have greatly improved the image quality obtainable by single-shot methods. A particular variant, modulus blipped echo-planar single-pulse technique (MBEST), although slightly slower than the blipped echo-planar single-pulse technique (BEST), is experimentally more robust and incorporates intrinsic T2 weighting. An account of these improvements together with some experimental results is presented.
Explore the source record for details and available documents.
Using a 1-m-bore superconductive magnet at 0.1 T, whole-body transverse images through adult humans have been obtained at repetition times of 57 ms. The techniques used were minor variations of echo-planar imaging (EPI) employing large pulsed gradients to provide complete coverage of the plane in phase space, and low-angle RF excitation sequences allowing rapid repetition of the experiment. In addition active magnetic screening of the gradient coils was implemented to protect the surrounding magnet from the eddy currents induced by the necessarily fast switching of the large gradient fields.
The hybrid technique of projection-reconstruction echo-planar (PREP) imaging for obtaining chemical-shift images is demonstrated experimentally using a fluorine sample. The technique which is a variation on echo-planar imaging (EPI) relies on a multipass procedure. It is nevertheless quite efficient and consequently chemical-shift images may be produced in a few minutes. The method produces images in 64 chemical-shift regions, each region mapped spatially by 64 X 64 pixels. The imaging time was just over 4 min. These 64 chemical-shifted images can be straightforwardly added together to form an undistorted image of the complete object. In addition the chemical-shift spectrum can be extracted and the various chemical-shift images can be unambiguously assigned to the spectral peaks.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Echo planar imaging (EPI) is that form of magnetic resonance imaging which provides very short image acquisition times. EPI also provides very rapid sequential imaging. The EPI method is ideal for imaging the heart and thoracic content because images are devoid of cardio-respiratory motion artefact. Previously an analysis of transectional images has been presented. This paper is concerned with the study of the heart by the use of EPI constructions in the sagittal and coronal planes. Defining connections between ventricle and great artery is of cardinal importance in paediatric cardiology. EPI constructions in the normal heart, transposition, truncus arteriosus and right heart hypoplasia are presented and discussed.
Echo planar imaging is that form of magnetic resonance imaging which gives very short image acquisition times. The method has been used to produce images of the infant heart which are free of cardiorespiratory motion artefact, despite tachypnoea and tachycardia. EPI transections of the normal heart are compared with transections in truncus arteriosus, tetralogy of Fallot, right heart hypoplasia and transposition of the great arteries. The diagnosis of the cause of cyanosis in these infants was established by the noninvasive EPI method and validation of the findings may be found in transectional postmortem analyses reported in the literature.
The high-speed echo-planar imaging (EPI) technique is used to obtain rapid T1 and spin density measurements by a two-point method. It is shown that neglect of edge effects in the slice selection procedure leads to significant systematic errors in T1. T1 maps for two young patients, obtained at 4.0 MHz, are presented. The T1 and spin density values obtained are used to produce computer-generated images in inversion recovery simulations. These results demonstrate marked improvement in image contrast without paying the time penalty incurred in real experiments, thereby greatly increasing patient throughput potential.
The echo-planar shift mapping (EPSM) technique, a variant of echo-planar imaging (EPI), is evaluated with theoretical studies using computer simulations and with experimental studies using fluorine resonances in phantoms. In situations where the signal-to-noise ratio permits, it is shown that EPSM can produce in a few seconds chemical-shift spectra at all points in a specified spin-density image corresponding to a selected slice. Applications of this technique are likely to be for proton and fluorine chemical-shift measurements and rapid studies of magnetic field inhomogeneities produced by magnet non-alignment and field shifts around magnetic materials.
In many biological systems, nuclear magnetic resonance chemical-shift studies of 31P, 13C, and 1H can be of great value as a means of studying metabolic processes in vivo. This information is likely to be of great clinical value in the diagnosis of disease and in the study and monitoring of the effect of drug treatment. This paper discusses two new techniques, based on the echo-planar imaging (EPI) method. One is the echo-planar shift mapping (EPSM) technique and the other is a hybrid projection reconstruction-echo-planar (PREP) method. Both methods may be used to obtain complete chemical-shift spectra at each point of a specified grid in a chosen plane through the subject. A major attraction of the EPSM method is the very high speed at which this information is obtained. The major attraction of the PREP hybrid method is its simplicity. Both techniques have the advantage of speed and efficiency over both the point-by-point topical magnetic resonance (TMR) and 3D Fourier transform approaches. The new mapping techniques may also be used to measure magnetic field spatial inhomogeneities, caused by either the presence of magnetic material or simply nonalignment of the magnet.
Explore the source record for details and available documents.
Echo-planar imaging (EPI), a distinctive variant of nuclear magnetic resonance, needs only a fraction of a second for an image to be acquired and so is free from movement artifacts caused by respiration or heart beat. Clinical findings in the lungs, heart, and mediastinum of three children with high respiratory and heart rates who were examined by EPI are described.