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The increase in regulatory challenges on medical technology developed and deployed in the UK is having a negative impact on innovation. In this paper we show how the limited capacity of Approved and Notified Bodies is one more barrier in the innovation pipeline, that could push more teams to consider applying for FDA approval instead of UKCA marking, potentially limiting how much our patients benefit from the world-leading research undertaken in UK universities.

Medical ultrasound (US) is of increasing importance in medical diagnosis and intraoperative assistance and possesses great potential advantages when integrated with robotics. However, some concerns, including the operation efficiency, operation safety, image quality, and comfort of patients, remain after introducing robotics into medical ultrasound. In this article, an ultrasound robot integrating a force control mechanism, force/torque measurement mechanism, and online adjustment method is proposed to overcome the current limitations. The ultrasound robot can measure operating forces and torques, provide adjustable constant operating forces, eliminate great operating forces introduced by accidental operations, and achieve various scanning depths based on clinical requirements. The proposed ultrasound robot would potentially facilitate sonographers to find the targets quickly, improve operation safety and efficiency, and decrease patients’ discomfort. Simulations and experiments were carried out to evaluate the performance of the ultrasound robot. Experimental results show that the proposed ultrasound robot is able to detect operating force in the $z$ -direction and torques around the $x$ - and $y$ -directions with errors of 3.53%, 6.68%, and 6.11% F.S., maintain the constant operating force with errors of less than 0.57 N, and achieve various scanning depths for target searching and imaging. This proposed ultrasound robot has good performance and would potentially be used in medical ultrasound.

Coherent multitransducer ultrasound (CoMTUS) creates an extended effective aperture through the coherent combination of multiple arrays, which results in images with enhanced resolution, extended field-of-view, and higher sensitivity. The subwavelength localization accuracy of the multiple transducers required to coherently beamform the data is achieved by using the echoes backscattered from targeted points. In this study, CoMTUS is implemented and demonstrated for the first time in 3-D imaging using a pair of 256-element 2-D sparse spiral arrays, which keep the channel count low and limit the amount of data to be processed. The imaging performance of the method was investigated using both simulations and phantom tests. The feasibility of free-hand operation is also experimentally demonstrated. Results show that, in comparison with a single dense array system using the same total number of active elements, the proposed CoMTUS system improves spatial resolution (up to ten times) in the direction where both arrays are aligned, contrast-to-noise ratio (CNR; up to 46%), and generalized CNR (gCNR; up to 15%). Overall, CoMTUS shows a narrower main lobe and higher CNR, which results in an increased dynamic range and better target detectability.

Magnetic resonance imaging of whole fetal body and placenta is limited by different sources of motion affecting the womb. Usual scanning techniques employ single-shot multi-slice sequences where anatomical information in different slices may be subject to different deformations, contrast variations or artifacts. Volumetric reconstruction formulations have been proposed to correct for these factors, but they must accommodate a non-homogeneous and non-isotropic sampling, so regularization becomes necessary. Thus, in this paper we propose a deep generative prior for robust volumetric reconstructions integrated with a diffeomorphic volume to slice registration method. Experiments are performed to validate our contributions and compare with ifdefined tmiformat R2.5a state of the art method methods in the literature in a cohort of 72 fetal datasets in the range of 20-36 weeks gestational age. Results suggest improved image resolution Quantitative as well as radiological assessment suggest improved image quality and more accurate prediction of gestational age at scan is obtained when comparing to a state of the art reconstruction method methods. In addition, gestational age prediction results from our volumetric reconstructions compare favourably are competitive with existing brain-based approaches, with boosted accuracy when integrating information of organs other than the brain. Namely, a mean absolute error of ${0}.{618}$ weeks ( ${R}^{{2}}={0}.{958}$ ) is achieved when combining fetal brain and trunk information.

Two-dimensional (2D) ultrasound echocardiography is the primary technique used to diagnose congenital heart disease before birth. There is, however, a longstanding need for a reliable form of secondary imaging, particularly in cases when more detailed three-dimensional (3D) vascular imaging is required, or when ultrasound windows are of poor diagnostic quality. Fetal MRI, which is well established for other organ systems, is highly susceptible to fetal movement, particularly for 3D imaging. The objective of this study was to investigate the combination of prenatal MRI with novel, motion-corrected 3D image registration software, as an adjunct to fetal echocardiography in the diagnosis of congenital heart disease.

ObjectivesNeurodevelopmental impairment has become the most important comorbidity in infants with congenital heart disease (CHD). We aimed to (1) investigate the burden of brain lesions in infants with CHD prior to surgery and (2) explore clinical factors associated with injury.Study designProspective observational study.SettingSingle centre UK tertiary neonatal intensive care unit.Patients70 newborn infants with critical or serious CHD underwent brain MRI prior to surgery.Main outcome measuresPrevalence of cerebral injury including arterial ischaemic strokes (AIS), white matter injury (WMI) and intracranial haemorrhage.ResultsBrain lesions were observed in 39% of subjects (95% CI 28% to 50%). WMI was identified in 33% (95% CI 23% to 45%), subdural haemorrhage without mass effect in 33% (95% CI 23% to 45%), cerebellar haemorrhage in 9% (95% CI 4% to 18%) and AIS in 4% (95% CI 1.5% to 12%). WMI was distributed widely throughout the brain, particularly involving the frontal white matter, optic radiations and corona radiata. WMI exhibited restricted diffusion in 48% of cases. AIS was only observed in infants with transposition of the great arteries (TGA) who had previously undergone balloon atrial septostomy (BAS). AIS was identified in 23% (95% CI 8% to 50%) of infants with TGA who underwent BAS, compared with 0% (95% CI 0% to 20%) who did not.ConclusionsCerebral injury in newborns with CHD prior to surgery is common.

A 20-minute low-field-strength 0.55-T fetal MRI examination performed with a commercial scanner allowed for robust assessment of fetal growth and placental function while increasing patient comfort and decreasing the need for specialist centers.

The echocardiographic assessment of circulatory function in sick newborn infants has the potential to improve patient care. However, measurements are prone to error and have not been sufficiently validated. Phase-contrast magnetic resonance imaging (MRI) provides highly validated measures of blood flow and has recently been applied to the newborn population. The aim of this study was to validate measures of left ventricular output and superior vena caval flow volume in newborn infants.

We describe a new light transport model, which was applied to three-dimensional lifetime imaging of Förster resonance energy transfer in mice in vivo. The model is an approximation to the radiative transfer equation and combines light diffusion and ray optics. This approximation is well adopted to wide-field time-gated intensity-based data acquisition. Reconstructed image data are presented and compared with results obtained by using the telegraph equation approximation. The new approach provides improved recovery of absorption and scattering parameters while returning similar values for the fluorescence parameters.

A generalized parallel imaging method has been developed that uses coil profiles to generate missing k-space lines. The proposed method is an extension of SMASH, which uses linear combinations of coil sensitivity profiles to synthesize spatial harmonics. In the generalized SMASH approach described here, coil sensitivity profiles are represented directly in the Fourier domain to provide a general description of the spatial properties of the coils. This removes restrictions imposed by conventional SMASH, so that the choice and position of the receiver coils can be made on the basis of sensitivity to the volume of interest rather than suitability for constructing spatial harmonics. Generalized SMASH also intrinsically allows the freedom to accommodate acquisitions with uniform or nonuniform k-space sampling. The proposed method places SMASH on an equal footing with other parallel imaging techniques (SENSE and SPACE-RIP), while combining strengths from each. The method was tested on phantom and human data and provides a robust method of data recovery. Magn Reson Med 47:160–170, 2002. © 2002 Wiley-Liss, Inc.

A generalized parallel imaging method has been developed that uses coil profiles to generate missing k‐space lines. The proposed method is an extension of SMASH, which uses linear combinations of coil sensitivity profiles to synthesize spatial harmonics. In the generalized SMASH approach described here, coil sensitivity profiles are represented directly in the Fourier domain to provide a general description of the spatial properties of the coils. This removes restrictions imposed by conventional SMASH, so that the choice and position of the receiver coils can be made on the basis of sensitivity to the volume of interest rather than suitability for constructing spatial harmonics. Generalized SMASH also intrinsically allows the freedom to accommodate acquisitions with uniform or nonuniform k‐space sampling. The proposed method places SMASH on an equal footing with other parallel imaging techniques (SENSE and SPACE‐RIP), while combining strengths from each. The method was tested on phantom and human data and provides a robust method of data recovery. Magn Reson Med 47:160–170, 2002. © 2002 Wiley‐Liss, Inc.

A 6-month randomized, placebo-controlled pilot study of the ethyl-ester of eicosapentaenoic acid (ethyl-EPA) was carried out in seven in-patients with advanced (stage III) Huntington's disease (three on ethyl-EPA, four on placebo; no significant difference in age or sex between the groups). After 6 months all the patients treated with ethyl-EPA improved on the orofacial component of the Unified Huntington's Disease Rating Scale while all the patients on placebo deteriorated on this scale (p<0.03). Following subvoxel registration of follow-up 3D MRI brain scans with baseline scans, subtraction images showed that while the placebo was associated with progressive cerebral atrophy, the ethyl-EPA was associated with a reverse process. We conclude that treatment with ethyl-EPA is associated with beneficial motor and MRI changes.

Gadolinium‐enhanced dynamic magnetic resonance (MR) imaging is playing an increasingly important diagnostic role in patients with breast cancer. Because of the multi‐focal nature of the disease, it is mandatory to cover all of both breasts, not only in the initial scan, but also at subsequent follow‐up. This requires volume acquisitions with a temporal resolution limited to 60–80 seconds, which is insufficient to clearly discriminate malignant from benign rates of contrast uptake. In this work, we performed sensitivity‐encoded imaging using a commercially available four‐channel breast coil (MRI Devices Corporation) on a commercial 0.5‐T scanner with moderate gradient performance to give increased temporal resolution in these dynamic contrast‐enhanced scans. A two‐fold increase in temporal resolution was readily achievable with this coil. Image reconstruction was robust and image quality was assessed qualitatively to be good. We also investigated higher speed‐up factors using two directions of sensitivity‐encoded reduction and discussed some of the potential artifacts associated with such imaging. J. Magn. Reson. Imaging 2001;14:329–335. © 2001 Wiley‐Liss, Inc.

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. Magn Reson Med 46:354–364, 2001. © 2001 Wiley‐Liss, Inc.

As part of a large, randomized placebo-controlled trial of inpatients with multiple sclerosis (MS), a subsample of 15 underwent cerebral MRI at baseline and 6-months (eight on lofepramine and l-phenylalanine; seven on placebo). Unlike the placebo group, the active group showed a significant reduction in lesion number visible on T1-weighted scans (p< 0.05). The lateral ventricular volume increased, on average, by 1020 mm3in the untreated group and 600 mm3in the treated group. In the treated patients the ventricular size change correlated with both change in Gulick MS-related symptoms scale scores (rs0.71, p0.07) and Gulick MS-related activities of daily living scale scores (rs−0.83, p0.02). It is concluded that treatment with lofepramine and l-phenylalanine is associated with significant MRI changes.

AIM: 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. MATERIALS AND METHODS: 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. RESULTS: 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 T1weighted spin echo sequence. CONCLUSION: 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

Increased acquisition efficiency has been achieved by exciting several slices simultaneously. The mixed data were unfolded to produce separate slices using the spatial encoding information inherent in a multicoil receiver system. Each coil yields a linear combination of signals from all excited slices weighted by the sensitivity of each coil. A matrix inversion provides a solution to unfold these images. J. Magn. Reson. Imaging 2001;13:313–317. © 2001 Wiley‐Liss, Inc.

Specific absorption rate (SAR) due to a butterfly surface coil in a realistic model of the leg was calculated for frequencies 64 ≤ ν ≤ 213 MHz. The resulting temperature distribution and temperature changes (ΔT) were found using the bioheat transfer equation. To compare results at different frequencies, the minimum B‐field within the coil's footprint in the plane parallel to the coil but displaced 50 mm from it was kept constant. To achieve the same minimum B‐field as that associated with operation at 64 MHz that was compliant with safety guidelines (peak SAR in 1 cm3of tissue of 2.3 W/kg), it was predicted that SAR would exceed recommended levels when ν ≥ 149 MHz. The corresponding maximum ΔT at 64, 128, and 213 MHz were 0.3, 1.3, and 5.0°C, respectively. J. Magn. Reson. Imaging 2000;12:68–74. © 2000 Wiley‐Liss, Inc.

Specific absorption rate (SAR) due to a butterfly surface coil in a realistic model of the leg was calculated for frequencies 64 ≤ ν ≤ 213 MHz. The resulting temperature distribution and temperature changes (ΔT) were found using the bioheat transfer equation. To compare results at different frequencies, the minimum B-field within the coil's footprint in the plane parallel to the coil but displaced 50 mm from it was kept constant. To achieve the same minimum B-field as that associated with operation at 64 MHz that was compliant with safety guidelines (peak SAR in 1 cm3of tissue of 2.3 W/kg), it was predicted that SAR would exceed recommended levels when ν ≥ 149 MHz. The corresponding maximum ΔT at 64, 128, and 213 MHz were 0.3, 1.3, and 5.0°C, respectively. J. Magn. Reson. Imaging 2000;12:68–74. © 2000 Wiley-Liss, Inc.

The potential for using pre‐polarized liquids as contrast agents in vivois investigated and the feasibility of the method demonstrated. In this study we show the enhancement obtained following intravenous delivery of pre‐polarized saline into the antecubital vein of a volunteer. This form of contrast agent provides signal gain on time scales commensurate with its T1and allows repeated doses to be administered, thus making alternate acquisitions of data with and without enhancement practicable. Copyright © 1999 John Wiley & Sons, Ltd.

The potential for using pre-polarized liquids as contrast agents in vivo is investigated and the feasibility of the method demonstrated. In this study we show the enhancement obtained following intravenous delivery of pre-polarized saline into the antecubital vein of a volunteer. This form of contrast agent provides signal gain on time scales commensurate with its T1 and allows repeated doses to be administered, thus making alternate acquisitions of data with and without enhancement practicable. Copyright © 1999 John Wiley & Sons, Ltd.

MR temperature measurements made by the chemical‐shift‐of‐water technique in peripheral muscle of volunteers have produced larger‐than‐expected coefficients of change and shown significant hysteresis effects as the temperature was cycled, although these effects were not reproduced in the present study. Previous work has suggested that susceptibility effects could be a contributor to the behavior of the chemical shift data. Here, we use proton spectroscopy of muscle in conjunction with temperature cycling to evaluate the relative shifts of the water peak and those of creatine, choline, and lipids. These latter are considered not to have significant temperature coefficients of chemical shift. The results show that these lines remain very stable as the temperature is cycled, suggesting that susceptibility effects are not present in this study. The method offers the possibility that the lines can be used as frequency references if there are any questions about the stability of other moieties.

Inversion recovery (IR) sequences with an inversion time (TI) designed to markedly reduce or null the signal from CSF (TI of ∼2,100 ms at 1.0 T) and a very long echo time (TE) of 240 ms were used to image the brain of two normal adult volunteers, one 34-year-old man with an intrinsic tumor, and one 3-month-old infant with an infarct. Using these very heavily T2-weighted pulse sequences, adult gray and white matter showed similar signal intensity in may areas of the brain, but normal white matter in regions of the centrum semiovale, posterior internal capsule, parietopontile tract, occipitothalamic radiation, and brain stem showed a much higher signal intensity than surrounding gray or white matter. The infant displayed a low signal intensity in myelinated regions in the internal capsule and occipitothalamic radiation and a high signal in unmyelinated white matter. In many of the images there were strong similarities to the distribution of high signal within white matter seen with pulsed gradient spin echo sequences (TE 130 ms) designed to demonstrate effects due to anisotropic diffusion. Arguments are advanced to support the view that the high signal intensity in white matter tracts is due to one or more long T2 components that may be associated with unmyelinated or sparsely myelinated fibres within white matter. The resemblance to diffusion weighted images may reflect the fact that both employ long TEs and both produce a low signal from CSF. If myelin possessed a different susceptibility from axoplasm so that magnetic field gradients were generated around nerve fibres when their orientation was not parallel to B0, diffusion of water might then produce the observed dependence on fibre direction. The high signal regions in white matter are a potential source of confusion in image interpretation, and measurements of T2 in white matter need to be made with these regional variations in mind. The concept of normal appearing white matter also needs to be applied with a knowledge of these differences. The IR sequences used in this study provide a very high T2 dependence with a low signal from CSF and may be useful for detecting disease in the CNS of adults and children.

Brain MR examinations were performed on one normal and 30 abnormal neonates and infants with a variety of clinical problems using pulsed gradient spin echo (PGSE) sequences sensitized in different directions to detect changes due to anisotropically restricted diffusion of water within the brain. Anisotropically restricted diffusion was demonstrated within white matter, which appeared to be myelinated with T1-weighted inversion recovery or spin echo sequences and within white matter where the presence of myelin was not demonstrated with these sequences. Cysts and fluid collections were recognised by their low signal intensity using PGSE sequences in the subcortical regions, lentiform nuclei, and periventricular regions. An intracerebral hematoma and a subdural hematoma showed a high signal intensity with PGSE sequences consistent with isotropically restricted diffusion. Chronic infarction displayed a low signal intensity consistent with relatively free isotropic diffusion. Patients with leukodystrophy associated with congenital muscular dystrophy showed an anisotropic pattern with different components of the abnormality present on images with sensitization in different directions. The corticospinal tracts failed to show highlighting in three cases where conventional imaging was normal. In several patients with a history of birth asphyxia, asymmetry and a relative reduction in signal intensity were seen in the corticospinal tracts.

The use of MR imaging to image anisotropically restricted diffusion (ARD) of water in the nervous system is described. The theoretical basis for the use of the pulsed gradient spin echo sequences is outlined, including an estimate of the range of cell dimensions that can be studied with this technique. The importance of restricted diffusion across myelinated white matter fibre tracts is emphasised and the capacity of MR imaging to demonstrate fibre pathways as a function of their direction is illustrated. Technical developments that have been implemented include 256 × 256 spatial resolution, a wider range of diffusion times Td, and an increased range of diffusion sensitivity parameters b. Effects of these are illustrated together with the use of gradient moment nulling methods, oblique sensitisation, and a smaller set of gradient coils that enable shorter values of echo time to be used with the same value of b. The anatomical basis for ARD imaging is analysed, and association, commissural, and projection fibre tracts are demonstrated in different planes. The published literature on variations of the apparent diffusion coefficient from normal is reviewed and examples where diffusion weighted images revealed information that was not necessarily apparent with conventional sequences are illustrated. These include cases of multiple sclerosis, chronic head injury, progressive multifocal leucoencephalopathy, cerebrovascular disease, astrocytoma, and probable metastases to the brain. Imaging of ARD affords a fascinating conjunction between the microscopic movement of water, the properties of myelinated white matter fibres, gross anatomy of the brain, and changes of the diffusion of water in disease.

Conventional T1-weighted spin echo (T1WSE) and T1-weighted magnetization transfer (MT) images were obtained in 26 patients with biopsy-proven cirrhosis (nine Child's grade A, 10 Child's grade B and seven Child's grade C). Four subjects showed no evidence of neuropsychiatric impairment on clinical, psychometric and electrophysiological testing, seven showed evidence of subclinical hepatic encephalopathy and 15 were classified as having overt hepatic encephalopathy. Signal intensities of basal ganglia nuclei (head of caudate, putamen, globus pallidus and thalamus) and adjacent brain parenchyma were measured and contrast calculated. On T1WSE imaging, contrast measurements of the globus pallidus were significantly greater in patients with neuropsychiatric dysfunction than in those who were unimpaired (p<0.05). This was not observed in the other basal ganglia nuclei. Patients with subclinical and overt hepatic encephalopathy could not be distinguished on the basis of contrast measurements of the globus pallidus or of any other nucleus. T1WSE contrast measurements of the globus pallidus were increased with elevations in blood ammonia levels (p<0.05) and with the severity of liver dysfunction, when graded according to the Pugh's score (p<0.05). Those patients with the worst liver injury (Child's grade C) had significantly greater T1WSE pallidal contrast measurements (p<0.05) than those patients with minimal liver injury (Child's grade A). The patients with intermediate liver damage (Child's grade B) could not be distinguished from the other two groups. While MT imaging highlighted the basal ganglia and showed a correlation between globus pallidus contrast and blood ammonia levels (p<0.05), no other relationship between MT contrast measurements and either the degree of hepatic encephalopathy or the severity of liver dysfunction was found.

The transfer of magnetization between a free and a bound pool of spins is described in terms of the respective longitudinal relaxation times and the life times of spins in each pool. The effect of an off resonance radiofrequency (RF) pulse in producing saturation in the bound pool and a consequent decrease in both the available longitudinal magnetization and the T1 of spins in the free pool is described. The effects of increasing duration of the saturating RF pulse on image pixel signal intensity were used to determine values for the decrease in both T1 and the available magnetization in gray and white matter of the brain as well as in muscle, fat and CSF At 0.15 T the available magnetization of muscle was reduced by 60 and its T1 was decreased from 350 to 150 ms. The available magnetization of white and gray matter was reduced by 40 and their values of T1 were reduced by 80–110 ms. The reduction in available magnetization was used to increase contrast on proton density weighted or T2-weighted SE pulse sequences. These changes were also used to design inversion recovery (IR) pulse sequences with particular contrast properties. A short inversion time (TI) magnetization transfer (MT) IR (MT-STIR) pulse sequence was used to reduce the signal from normal muscle to zero to produce an angiographic effect in the leg. Increased tissue contrast was observed with a T2-weighted (MT-SE) sequence in a patient with bilateral cerebral infarction and with an MT-IR pulse sequence in a patient who had an intracranial hematoma. Three patients with cerebral tumors showed high lesion contrast with MT-STIR sequences. Components within two tumors were changed to different degrees by MT and in one case change in the brain attributable to recent radiotherapy treatment was only identified with an MT-STIR sequence. Magnetization transfer can be used to manipulate both the available longitudinal magnetization and the T1 of normal and abnormal tissues. The changes in tissue contrast produced by this can be very substantial and are likely to be of importance in clinical imaging.

A pulsed magnetic field gradient spin echo technique was used to study the brain of two volunteers and eight patients. The pulsed gradients were applied both perpendicular and parallel to the image slice. Striking changes in signal intensity were demonstrated in white matter depending on the direction in which pulsed gradients were applied. These effects enabled specific white matter tracts to be identified depending on the direction of their fibres. Abnormalities were also demonstrated in these tracts in patients with a variety of diseases, including cases where only minor abnormalities were seen with conventional, highly T2-weighted sequences. The effects were attributed to anisotropically restricted diffusion within white matter. The technique may have application in a wide range of neurological disease and result in better localisation of lesions and improved detection of disease.

An automated procedure has been developed to isolate the brain in single/multislice or whole-volume MR images obtained from various sequences.

The aim of this study was to examine the potential of accurate image registration for detecting subtle changes in the brain.

Methods for automatically registering and reslicing MR images using an interpolation function that matches the structure of the image data are described.

Fluid attenuated inversion recovery pulse sequences with a long echo time (TE) have been used to image the brain in one volunteer and four patients. The long inversion time used with this sequence suppresses the signal from CSF and the long TE produces very heavy T2 weighting. The marked reduction in flow artefact from CSF and the high T2 weighting enabled anatomical detail to be seen within the brain stem and produced high lesion contrast in areas close to CSF. Lesions were demonstrated with greater conspicuity than with conventional T2-weighted sequences in patients with cerebral infarction, low grade astrocytoma, and diplegia.

In this study we assessed different magnetic resonance imaging (MRI) scanning regimes and examined some of the assumptions commonly made for measuring body fat content by MRI. Whole body MRI was used to quantify and study different body fat depots in 67 women. The whole body MRI results showed that there was a significant variation in the percentage of total internal, as well as visceral, adipose tissue across a range of adiposity, which could not be predicted from total body fat and/or subcutaneous fat. Furthermore, variation in the amount of total, subcutaneous, and visceral adipose tissue was not related to standard anthropometric measurements such as skinfold measurements, body mass index, and waist-to-hip ratio. Finally, we show for the first time subjects with a percent body fat close to the theoretical maximum (68%). This study demonstrates that the large variation in individual internal fat content cannot be predicted from either indirect methods or direct imaging techniques, such as MRI or computed tomography, on the basis of a single-slice sampling strategy.

1The main purpose of this study was to evaluate non‐invasively with magnetic resonance spectroscopy (1H‐MRS) changes in the concentrations of intracellular (IT) and extracellular (between muscle fibres) triglycerides (ET) in skeletal muscles of trained males (age range: 24–38 years) during two standard exercise protocols of alternating velocities.2Protocol 1 consisted of locomotion in a shuttle manner between two lines 30 m apart at four different velocities (1, 2, 3 and 4 m s−1) which were alternated every minute in a standard routine for 90 min, whereas Protocol 2 included locomotion between two lines 20 m apart at only three velocities (2, 2.7 and 4 m s−1) until volitional exhaustion. The heart rate during both protocols fluctuated between 140 and 200 beats min−1.3Using pre‐exercise muscle water to quantify individual total creatine (TCr) that was utilized as an internal standard and assuming that TCr does not change during exercise, subjects’ mean IT and ET concentrations in soleus (Sol) muscle before Protocol 1 (n= 8) were 45.8 ± 4.8 mmol (kg dry weight)−1(mean ± s.e.m.) and 93.1 ± 14.1 mmol (kg dry weight)−1, respectively. After the exercise, the concentrations of IT and ET were not significantly different from the values at rest. Before Protocol 2 (n= 4), IT concentrations in Sol, gastrocnemius (Gast) and tibialis (Tib) muscles were 46.4 ± 13.6, 35.0 ± 12.1 and 23.1 ± 4.8 mmol (kg dry weight)−1, respectively, and were not affected by the exhaustive exercise. The ET concentrations in Sol, Gast and Tib were 136.4 ± 38.1, 175.3 ± 86.5 and 79.3 ± 20.0 mmol (kg dry weight)−1, respectively, and they did not change significantly after exhaustion.4The study showed that levels of IT and ET were not affected by alternating intensity exercise to fatigue. This suggests that IT and ET in human Sol, Gast and Tib muscles do not contribute significantly to the energy turnover during this type of exercise. Energy for this type of muscle contraction may arise primarily from muscle phosphocreatine (PCr) and glycogen breakdown, circulating glucose and fatty acids from triglycerides other than those encountered within and between muscle cells.

Precise measurement of T1 is needed for its use in temperature monitoring in vivo. Movement of tissue relative to fixed regions of interest can result in large variations in apparent T1, with consequent substantial errors in the measured temperature. This paper evaluates methods of tracking regions of interest as tissue moves during a study in an effort to minimize errors from this cause. Tracking techniques evaluated are based on maintaining constant gray scale levels, locating nearby edges and maintaining position relative to them, and global image registration.

We report a three-dimensional time-resolved tomographic imaging technique for localizing protein-protein interaction and protein conformational changes in turbid media based on Förster resonant energy-transfer read out using fluorescence lifetime. This application of “tomoFRET” employs an inverse scattering algorithm utilizing the diffusion approximation to the radiative-transfer equation applied to a large tomographic data set of time-gated images. The approach is demonstrated by imaging a highly scattering cylindrical phantom within which are two thin wells containing cytosol preparations of HEK293 cells expressing TN-L15, a cytosolic genetically encoded calcium Förster resonant energy-transfer sensor. A 10 mM calcium chloride solution was added to one of the wells, inducing a protein conformation change upon binding to TN-L15, resulting in Förster resonant energy transfer and a corresponding decrease in the donor fluorescence lifetime. We successfully reconstruct spatially resolved maps of the resulting fluorescence lifetime distribution as well as of the quantum efficiency, absorption, and scattering coefficients.

We present a novel fluorescence lifetime tomography system applied to a highly scattering autofluorescent phantom containing live cells expressing the fluorophore enhanced green fluorescent protein (EGFP). The fluorescence signal was excited using a fiber-laser-pumped supercontinuum source and detected using wide-field time gating imaging. To facilitate rapid 3D reconstruction of the fluorescence lifetime distribution, the time-resolved data were Fourier-transformed in time to give complex functions that formed a data set for the Fourier domain reconstruction. Initially the presence of an unspecified background autofluorescence signal impeded reconstruction of the lifetime distribution, but we show that this problem can be addressed using a simple iterative technique.

Foldover artifacts arise when the same imaging frequency occurs both at a desired location within a slice and at another location within the sensitive region of the radiofrequency (RF) coil. Foldover artifacts can be caused by nonlinearity in the gradient system and by inhomogeneity in B0. This study investigates an approach in which an extra RF receiver coil and a postprocessing method are used to identify and remove foldover artifacts. J. Magn. Reson. Imaging 2000;12:795–797. © 2000 Wiley‐Liss, Inc.

Foldover artifacts arise when the same imaging frequency occurs both at a desired location within a slice and at another location within the sensitive region of the radiofrequency (RF) coil. Foldover artifacts can be caused by nonlinearity in the gradient system and by inhomogeneity in B0. This study investigates an approach in which an extra RF receiver coil and a postprocessing method are used to identify and remove foldover artifacts. J. Magn. Reson. Imaging 2000;12:795–797. © 2000 Wiley-Liss, Inc.

An RF coil, made by twisting a conventional wire loop, was tuned to form an extended sensor to provide an effective method of showing the track of a catheter. A twisted‐pair coil can be made small enough in diameter to pass through needles in common clinical use. The coil has a very small field of view and in transmit/receive operation has minimal effect on the magnetization of the surrounding tissue. Magn Reson Med 41:636–638, 1999.  © 1999 Wiley‐Liss, Inc.

An RF coil, made by twisting a conventional wire loop, was tuned to form an extended sensor to provide an effective method of showing the track of a catheter. A twisted-pair coil can be made small enough in diameter to pass through needles in common clinical use. The coil has a very small field of view and in transmit/receive operation has minimal effect on the magnetization of the surrounding tissue. Magn Reson Med 41:636–638, 1999.  © 1999 Wiley-Liss, Inc.

Mechanical forces generated by fetal kicks and movements result in stimulation of the fetal skeleton in the form of stress and strain. This stimulation is known to be critical for prenatal musculoskeletal development; indeed, abnormal or absent movements have been implicated in multiple congenital disorders. However, the mechanical stress and strain experienced by the developing human skeleton in uterohave never before been characterized. Here, we quantify the biomechanics of fetal movements during the second half of gestation by modelling fetal movements captured using novel cine-magnetic resonance imaging technology. By tracking these movements, quantifying fetal kick and muscle forces, and applying them to three-dimensional geometries of the fetal skeleton, we test the hypothesis that stress and strain change over ontogeny. We find that fetal kick force increases significantly from 20 to 30 weeks' gestation, before decreasing towards term. However, stress and strain in the fetal skeleton rises significantly over the latter half of gestation. This increasing trend with gestational age is important because changes in fetal movement patterns in late pregnancy have been linked to poor fetal outcomes and musculoskeletal malformations. This research represents the first quantification of kick force and mechanical stress and strain due to fetal movements in the human skeleton in utero, thus advancing our understanding of the biomechanical environment of the uterus. Further, by revealing a potential link between fetal biomechanics and skeletal malformations, our work will stimulate future research in tissue engineering and mechanobiology.

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° 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.