[show abstract][hide abstract] ABSTRACT: We automatically quantify patterns of normal cortical folding in the developing fetus from in utero MR images (N=80) over a wide gestational age (GA) range (21.7 to 38.9 weeks). This work on data from healthy subjects represents a first step towards characterising abnormal folding that may be related to pathology, facilitating earlier diagnosis and intervention. The cortical boundary was delineated by automatically segmenting the brain MR image into a number of key structures. This utilised a spatio-temporal atlas as tissue priors in an expectation-maximization approach with second order Markov random field (MRF) regularization to improve the accuracy of the cortical boundary estimate. An implicit high resolution surface was then used to compute cortical folding measures. We validated the automated segmentations with manual delineations and the average surface discrepancy was of the order of 1mm. Eight curvature-based folding measures were computed for each fetal cortex and used to give summary shape descriptors. These were strongly correlated with GA (R(2)=0.99) confirming the close link between neurological development and cortical convolution. This allowed an age-dependent non-linear model to be accurately fitted to the folding measures. The model supports visual observations that, after a slow initial start, cortical folding increases rapidly between 25 and 30 weeks and subsequently slows near birth. The model allows the accurate prediction of fetal age from an observed folding measure with a smaller error where growth is fastest. We also analysed regional patterns in folding by parcellating each fetal cortex using a nine-region anatomical atlas and found that Gompertz models fitted the change in lobar regions. Regional differences in growth rate were detected, with the parietal and posterior temporal lobe exhibiting the fastest growth, while the cingulate, frontal and medial temporal lobe developed more slowly.
[show abstract][hide abstract] ABSTRACT: RATIONAL AND OBJECTIVE: Dynamic contrast enhanced (DCE)-MRI has great potential to provide quantitative measure of inflammatory activity in rheumatoid arthritis. There is no current benchmark to establish the stability of signal in the joints of healthy subjects when imaged with DCE-MRI longitudinally, which is crucial so as to differentiate changes induced by treatment from the inherent variability of perfusion measures. The objective of this study was to test a pixel-by-pixel parametric map based approach for analysis of DCE-MRI (Dynamika) and to investigate the variability in signal characteristics over time in healthy controls using longitudinally acquired images. MATERIALS AND METHODS: 10 healthy volunteers enrolled, dominant wrists were imaged with contrast enhanced 3T MRI at baseline, week 12, 24 and 52 and scored with RAMRIS, DCE-MRI was analysed using a novel quantification parametric map based approach. Radiographs were obtained at baseline and week 52 and scored using modified Sharp van der Heidje method. RAMRIS scores and dynamic MRI measures were correlated. RESULTS: No erosions were seen on radiographs, whereas MRI showed erosion-like changes, low grade bone marrow oedema and low-moderate synovial enhancement. The DCE-MRI parameters were stable (baseline scores, variability) (mean±st.dev); in whole wrist analysis, MEmean (1.3±0.07, -0.08±0.1 at week 24) and IREmean (0.008±0.004, -0.002±0.005 at week 12 and 24). In the rough wrist ROI, MEmean (1.2±0.07, 0.04±0.02 at week 52) and IREmean (0.001±0.0008, 0.0006±0.0009 at week 52) and precise wrist ROI, MEmean (1.2±0.09, 0.04±0.04 at week 52) and IREmean (0.001±0.0008, 0.0008±0.001 at week 24 and 52). The Dynamic parameters obtained using fully automated analysis demonstrated strong, statistically significant correlations with RAMRIS synovitis scores. CONCLUSION: The study demonstrated that contrast enhancement does occur in healthy volunteers but the inherent variability of perfusion measures obtained with quantitative DCE-MRI method is low and stable, suggesting its suitability for longitudinal studies of inflammatory arthritis. These results also provide important information regarding potential cut-off levels for imaging remission goals in patients with RA using both RAMRIS and DCE-MRI extracted parametric parameters.
European journal of radiology 04/2013; · 2.65 Impact Factor
[show abstract][hide abstract] ABSTRACT: Cerebral white-matter injury is common in preterm-born infants and is associated with neurocognitive impairments. Identifying the pattern of connectivity changes in the brain following premature birth may provide a more comprehensive understanding of the neurobiology underlying these impairments. Here, we characterize whole-brain, macrostructural connectivity following preterm delivery and explore the influence of age and prematurity using a data-driven, nonsubjective analysis of diffusion magnetic resonance imaging data. T1- and T2-weighted and -diffusion MRI were obtained between 11 and 31 months postconceptional age in 49 infants, born between 25 and 35 weeks postconception. An optimized processing pipeline, combining anatomical, and tissue segmentations with probabilistic diffusion tractography, was used to map mean tract anisotropy. White-matter tracts where connection strength was related to age of delivery or imaging were identified using sparse-penalized regression and stability selection. Older children had stronger connections in tracts predominantly involving frontal lobe structures. Increasing prematurity at birth was related to widespread reductions in connection strength in tracts involving all cortical lobes and several subcortical structures. This nonsubjective approach to mapping whole-brain connectivity detected hypothesized changes in the strength of intracerebral connections during development and widespread reductions in connectivity strength associated with premature birth.
[show abstract][hide abstract] ABSTRACT: Mild cerebral ventricular enlargement is associated with schizophrenia, autism, epilepsy, and attention-deficit/hyperactivity disorder. Fetal ventriculomegaly is the most common central nervous system (CNS) abnormality affecting 1% of fetuses and is associated with cognitive, language, and behavioral impairments in childhood. Neurodevelopmental outcome is partially predictable by the 2-dimensional size of the ventricles in the absence of other abnormalities. We hypothesized that isolated fetal ventriculomegaly is a marker of altered brain development characterized by relative overgrowth and aimed to quantify brain growth using volumetric magnetic resonance imaging (MRI) in fetuses with isolated ventriculomegaly. Fetal brain MRI (1.5 T) was performed in 60 normal fetuses and 65 with isolated ventriculomegaly, across a gestational age range of 22-38 weeks. Volumetric analysis of the ventricles and supratentorial brain structures was performed on 3-dimensional reconstructed datasets. Fetuses with isolated ventriculomegaly had increased brain parenchyma volumes when compared with the control cohort (9.6%, P < 0.0001) with enlargement restricted to the cortical gray matter (17.2%, P = 0.002). The extracerebral cerebrospinal fluid and third and fourth ventricles were also enlarged. White matter, basal ganglia, and thalamic volumes were not significantly different between cohorts. The presence of relative cortical overgrowth in fetuses with ventriculomegaly may represent the neurobiological substrate for cognitive, language, and behavioral deficits in these children.
[show abstract][hide abstract] ABSTRACT: Fetal and neonatal MR imaging is increasingly used as a complementary diagnostic tool to sonography. MR imaging is an ideal technique for imaging fetuses and neonates because of the absence of ionizing radiation, the superior contrast of soft tissues compared with sonography, the availability of different contrast options, and the increased FOV. Motion in the normally mobile fetus and the unsettled, sleeping, or sedated neonate during a long acquisition will decrease image quality in the form of motion artifacts, hamper image interpretation, and often necessitate a repeat MR imaging to establish a diagnosis. This article reviews current techniques of motion compensation in fetal and neonatal MR imaging, including the following: 1) motion-prevention strategies (such as adequate patient preparation, patient coaching, and sedation, when required), 2) motion-artifacts minimization methods (such as fast imaging protocols, data undersampling, and motion-resistant sequences), and 3) motion-detection/correction schemes (such as navigators and self-navigated sequences, external motion-tracking devices, and postprocessing approaches) and their application in fetal and neonatal brain MR imaging. Additionally some background on the repertoire of motion of the fetal and neonatal patient and the resulting artifacts will be presented, as well as insights into future developments and emerging techniques of motion compensation.
American Journal of Neuroradiology 05/2012; · 3.17 Impact Factor
[show abstract][hide abstract] ABSTRACT: Background: Echo is unable to quantify volume of patent ductus arteriosus(PDA) shunt and has limited repeatability for assessing systemic perfusion. Phase Contrast MR(PCMR) can reliably assess left ventricular output(LVO) and systemic perfusion(superior vena cava(SVC), descending aorta(DAo))1. Our aim was to use PCMR to assess LVO and total systemic flow (TSF)(as SVC+DAo-Azygous flow) to infer PDA shunt volume.
[show abstract][hide abstract] ABSTRACT: Background: Episodes of intestinal ischaemia are likely to be central to the pathogenesis of necrotising enterocolitis. Echocardiographic techniques can estimate volume of superior mesenteric artery(SMA) flow1, however these measures have not yet been validated. Phase Contrast Magnetic resonance(PCMR) techniques have been shown to provide repeatable quantifications of cardiac output and systemic perfusion in newborn infants2. The aim of this study was to assess the feasibility of performing PCMR assessments of abdominal visceral blood flow in newborn preterm infants.
[show abstract][hide abstract] ABSTRACT: This observational cohort study addressed the hypothesis that after preterm delivery brain growth between 24 and 44 weeks postmenstrual age (PMA) is related to global neurocognitive ability in later childhood.
Growth rates for cerebral volume and cortical surface area were estimated in 82 infants without focal brain lesions born before 30 weeks PMA by using 217 magnetic resonance images obtained between 24 and 44 weeks PMA. Abilities were assessed at 2 years using the Griffiths Mental Development Scale and at 6 years using the Wechsler Preschool and Primary Scale of Intelligence-Revised (WPPSI-R), the Developmental Neuropsychological Assessment (NEPSY), and the Movement Assessment Battery for Children (MABC). Analysis was by generalized least-squares regression.
Mean test scores approximated population averages. Cortical growth was directly related to the Griffiths Developmental Quotient (DQ), the WPPSI-R full-scale IQ, and a NEPSY summary score but not the MABC score and in exploration of subtests to attention, planning, memory, language, and numeric and conceptual abilities but not motor skills. The mean (95% confidence interval) estimated reduction in cortical surface area at term corrected age associated with a 1 SD fall in test score was as follows: DQ 7.0 (5.8-8.5); IQ 6.0 (4.9-7.3); and NEPSY 9.1 (7.5-11.0) % · SD(-1). Total brain volume growth was not correlated with any test score.
The rate of cerebral cortical growth between 24 and 44 weeks PMA predicts global ability in later childhood, particularly complex cognitive functions but not motor functions.
[show abstract][hide abstract] ABSTRACT: Background
Fetal MRI is increasingly used in clinical settings. Ongoing vigilance regarding safety is essential. Medicines and Healthcare Products Regulatory Agency (MHRA) 2007 limits whole body specific absorption rate (SAR) to 2W/Kg (normal mode) during MRI. Estimated fetal temperature must not exceed 38°C, assuming fetal-maternal temperature gradient ∼0.5°C. Temperature rise depends on the specific sequences used and length of image acquisition.AimTo audit maternal temperature during fetal MR scans in accordance with recommended safety guidance.MethodsA prospective study of 100 women undergoing clinical and research fetal MR scan. Our typical protocol includes standard T2-weighted single-shot images (SAR 2 W/kg). Tympanic temperatures were measured within 5 min of the start and end of scanning and length of time in the scanner was documented.ResultsMean pre and post-scan temperatures were 36.6°C (35.4–37.3°C) and 37°C (36–37.9°C) respectively. The mean temperature increase was 0.4°C (0–1.3°C). While an increase exceeding 1°C occurred in 3/100, none resulted in post-scan temperatures over 37.5°C. Six participants had a post-scan temperature above 37.5°C; of these 4 temperatures were above 37°C at the start of the scan. Mean length of time in the scanner was 59 min (25–110 min) of which approximately 75% involves image acquisition, according to our typical protocol.Conclusions
Mean temperature rises during long MR examinations are acceptable. Screening maternal temperature pre-scan identifies women in whom fetal temperature is most likely to exceed 38°C. Women with pre-scan temperatures over 37°C should be imaged cautiously, with intervals between acquisitions to avoid heat absorption.
Archives of Disease in Childhood-fetal and Neonatal Edition - ARCH DIS CHILD-FETAL NEONATAL. 01/2011; 96(1).
[show abstract][hide abstract] ABSTRACT: This study describes the initial results from novel quantitative and qualitative explorations of specific central nervous system structures. The development of cerebral deep grey matter structures was the focus, and normal development was contrasted against fetuses diagnosed with ventricular dilatation or with fetal growth restriction. No significant differences were found in the basal ganglia volume between the volumetric development of the normal and ventriculomegaly cohorts, despite the cohort containing ventricular volumes up to 6 times larger than the normal fetuses. This was unexpected since there did not appear to be a concurrent increase in total brain volume for these fetuses, suggesting that there may be volumetric reductions in other brain tissues.These findings are not consistent with previous studies which show relative preservation of thalamic volume in fetal growth restriction. This may be due to the difference in methodology between the present study and prior ones, which have not been able to compensate for motion-artifacted brain images.This is the first study of volumetric quantification of deep grey matter structures that has used the SVR method to generate consistent 3D volumetric datasets of the fetal brain in order to correct for fetal motion and so increase the accuracy of quantitative measures. Future work could further investigate the shape of these brain structures in normal and pathological conditions in order to enhance our understanding of the morphological development of the CNS. Also, gender comparisons can be made as well as left versus right asymmetries.
Archives of Disease in Childhood-fetal and Neonatal Edition - ARCH DIS CHILD-FETAL NEONATAL. 01/2011; 96(1).
[show abstract][hide abstract] ABSTRACT: The assessment of motor function is an essential component of neurologic examinations, which imaging studies have extended to the fetus. US assessment is hampered by a limited FOV, whereas MR imaging has the potential to be an alternative. Our objectives were to optimize a cine MR imaging sequence for capturing fetal movements and to perform a pilot analysis of the relationship between the frequency of movements and uterine spatial constrictions in healthy fetuses.
Initially, a bSSFP cine sequence was selected for optimization, and various compromises were explored in all acquisition parameters to achieve an effective balance between anatomic coverage of the fetus and the temporal resolution of cine data, with the aim of maximizing both. Subsequently, cross-sectional qualitative and quantitative analyses of fetal movements were performed prospectively by using a cohort of 37 healthy fetuses (median GA, 29 weeks; range, 20-37 weeks) with the optimized cine protocol. Two smaller subgroups were selected for representative sampling of overall behavior patterns by using cine data of longer duration and for volumetric quantification of free intrauterine space.
The optimized cine sequence, with TR/TE of 3.21/1.59 ms, coupled with parallel imaging and partial-Fourier imaging, resulted in a section-acquisition time of 0.303 seconds. Anatomic coverage was enhanced by using a combination of thick sagittal sections (30-40 mm) and multisection acquisitions to display movements in all fetal limbs, head, and trunk simultaneously. All expected motor patterns were observed throughout this gestational period, and a significant decreasing trend in overall movement frequency with age was demonstrated (r = -0.514, P = .0011). Also a significant negative correlation was found between overall movement frequency and the total intrauterine free space (r = -0.703, P = .0001). Furthermore, a significant decrease in the frequency of leg movements was shown in fetuses older then 30 weeks' GA compared with those younger than that (P = .015).
Cine MR imaging is effective for observing fetal movements from midgestation with near full-body coverage. Also, reductions in free space with increasing GA appear to be a factor in the gradual reductions in overall levels of fetal activity as well as in restrictions in movement within specific regions of the fetal anatomy.
American Journal of Neuroradiology 11/2010; 32(2):331-8. · 3.17 Impact Factor
[show abstract][hide abstract] ABSTRACT: Brain structural volumes can be used for automatically classifying subjects into categories like controls and patients. We aimed to automatically separate patients with temporal lobe epilepsy (TLE) with and without hippocampal atrophy on MRI, pTLE and nTLE, from controls, and determine the epileptogenic side. In the proposed framework 83 brain structure volumes are identified using multi-atlas segmentation. We then use structure selection using a divergence measure and classification based on structural volumes, as well as morphological similarities using SVM. A spectral analysis step is used to convert the pairwise measures of similarity between subjects into per-subject features. Up to 96% of pTLE patients were correctly separated from controls using 14 structural brain volumes. The classification method based on spectral analysis was 91% accurate at separating nTLE patients from controls. Right and left hippocampus were sufficient for the lateralization of the seizure focus in the pTLE group and achieved 100% accuracy.
Biomedical Imaging: From Nano to Macro, 2010 IEEE International Symposium on; 05/2010
[show abstract][hide abstract] ABSTRACT: Numerical simulations of specific absorption rate (SAR) and temperature changes in a 26-week pregnant woman model within typical birdcage body coils as used in 1.5 T and 3 T MRI scanners are described. Spatial distributions of SAR and the resulting spatial and temporal changes in temperature are determined using a finite difference time domain method and a finite difference bio-heat transfer solver that accounts for discrete vessels. Heat transfer from foetus to placenta via the umbilical vein and arteries as well as that across the foetal skin/amniotic fluid/uterine wall boundaries is modelled. Results suggest that for procedures compliant with IEC normal mode conditions (maternal whole-body averaged SAR(MWB) < or = 2 W kg(-1) (continuous or time-averaged over 6 min)), whole foetal SAR, local foetal SAR(10 g) and average foetal temperature are within international safety limits. For continuous RF exposure at SAR(MWB) = 2 W kg(-1) over periods of 7.5 min or longer, a maximum local foetal temperature >38 degrees C may occur. However, assessment of the risk posed by such maximum temperatures predicted in a static model is difficult because of frequent foetal movement. Results also confirm that when SAR(MWB) = 2 W kg(-1), some local SAR(10g) values in the mother's trunk and extremities exceed recommended limits.
Physics in Medicine and Biology 02/2010; 55(4):913-30. · 2.70 Impact Factor
[show abstract][hide abstract] ABSTRACT: Very low birth weight (VLBW) infants (weight <1500 g) are increasingly cared for without prolonged periods of positive pressure ventilation (PPV).
To develop a system for 3.0 T magnetic resonance (MR) image acquisition from VLBW infants who are not receiving PPV, and to test the clinical stability of a consecutive cohort of such infants.
Seventy VLBW infants whose median weight at image acquisition was 940 g (590-1490) underwent brain MR imaging with the developed care system as participants in research. Twenty infants (29%) received nasal continuous positive airway pressure (nCPAP), 28 (40%) received supplemental oxygen by nasal cannulae, and 22 (31%) breathed spontaneously in air during the MR examination.
There were no significant adverse events. Seventy-six percent had none or transient self-correcting oxygen desaturations. Desaturations that required interruption of the scan for assessment were less common among infants receiving nCPAP (2/20) or breathing spontaneously in air (2/22), compared with those receiving nasal cannulae oxygen (13/28), p=0.003. Sixty-four (91%) infants had an axillary temperature > or =36 degrees C at completion of the scan (lowest 35.7 degrees C), There was no relationship between weight (p=0.167) or use of nCPAP (p=0.453) and axillary temperature <36 degrees C. No infant became hyperthermic.
VLBW infants who do not require ventilation by endotracheal tube can be imaged successfully and safely at 3.0 T, including those receiving nCPAP from a customised system.
Early human development 11/2009; 85(12):779-83. · 2.12 Impact Factor
[show abstract][hide abstract] ABSTRACT: It has been shown that the brain of a preterm infant develops differently from that of a term infant, but little is known about the neonatal cerebrovascular anatomy. Our aims were to establish reference data for the prevalence of the anatomic variations of the neonatal circle of Willis (CoW) and to explore the effect of prematurity, MR imaging abnormality, vascular-related abnormality, laterality, and sex on these findings.
We scanned 103 infants with an optimized MR angiography (MRA) protocol. Images were analyzed for different variations of the CoW, and results were compared for the following: 1) preterm-at-term and term-born infants, 2) infants with normal and abnormal MR imaging, 3) infants with and without a vascular-related abnormality, 4) boys and girls, and 5) left- and right-sided occurrence.
The most common anatomic variation was absence/hypoplasia of the posterior communicating artery. Preterm infants at term had a higher prevalence of a complete CoW and a lower prevalence of anatomic variations compared with term-born infants; this finding was significant for the anterior cerebral artery (P = .02). There was increased prevalence of variations of the major cerebral arteries in those infants with vascular-related abnormalities, statistically significant for the posterior cerebral artery (P = .004). There was no statistically significant difference between boys and girls and left/right variations.
Prematurity is associated with more complete CoWs and fewer anatomic variations. In vascular-related abnormalities, more variations involved major arterial segments, but fewer variations occurred in the communicating arteries. Overall reference values of the variations match those of the general adult population.
American Journal of Neuroradiology 08/2009; 30(10):1955-62. · 3.17 Impact Factor