Acquired ocular toxoplasmosis in pregnancy.
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Acute Disease↗
Biomedical subjects
J B Weaver
Publications and source records attributed to J B Weaver.
Three-dimensional subzone-based reconstruction algorithm for MR elastography.
Accurate characterization of harmonic tissue motion for realistic tissue geometries and property distributions requires knowledge of the full three-dimensional displacement field because of the asymmetric nature of both the boundaries of the tissue domain and the location of internal mechanical heterogeneities. The implications of this for magnetic resonance elastography (MRE) are twofold. First, for MRE methods which require the measurement of a harmonic displacement field within the tissue region of interest, the presence of 3D motion effects reduces or eliminates the possibility that simpler, lower-dimensional motion field images will capture the true dynamics of the entire stimulated tissue. Second, MRE techniques that exploit model-based elastic property reconstruction methods will not be able to accurately match the observed displacements unless they are capable of accounting for 3D motion effects. These two factors are of key importance for MRE techniques based on linear elasticity models to reconstruct mechanical tissue property distributions in biological samples. This article demonstrates that 3D motion effects are present even in regular, symmetric phantom geometries and presents the development of a 3D reconstruction algorithm capable of discerning elastic property distributions in the presence of such effects. The algorithm allows for the accurate determination of tissue mechanical properties at resolutions equal to that of the MR displacement image in complex, asymmetric biological tissue geometries. Simulation studies in a realistic 3D breast geometry indicate that the process can accurately detect 1-cm diameter hard inclusions with 2.5x elasticity contrast to the surrounding tissue.
Algorithms↗
Magnetic resonance elastography using 3D gradient echo measurements of steady-state motion.
Magnetic resonance elastography (MRE) is an important new method used to measure the elasticity or stiffness of tissues in vivo. While there are many possible applications of MRE, breast cancer detection and classification is currently the most common. Several groups have been developing methods based on MR and ultrasound (US). MR or US is used to estimate the displacements produced by either quasi-static compression or dynamic vibration of the tissue. An important advantage of MRE is the possibility of measuring displacements accurately in all three directions. The central problem in most versions of MRE is recovering elasticity information from the measured displacements. In previous work, we have presented simulation results in two and three dimensions that were promising. In this article, accurate reconstructions of elasticity images from 3D, steady-state experimental data are reported. These results are significant because they demonstrate that the process is truly three-dimensional even for relatively simple geometries and phantoms. Further, they show that the integration of displacement data acquisition and elastic property reconstruction has been successfully achieved in the experimental setting. This process involves acquiring volumetric MR phase images with prescribed phase offsets between the induced mechanical motion and the motion-encoding gradients, converting this information into a corresponding 3D displacement field and estimating the concomitant 3D elastic property distribution through model-based image reconstruction. Fully 3D displacement fields and resulting elasticity images are presented for single and multiple inclusion gel phantoms.
Algorithms↗
The outcome of pregnancy in Kell alloimmunisation.
OBJECTIVE: To assess management and outcome of pregnancies with anti-Kell in the West Midlands in the UK over 13 years. DESIGN: A retrospective review of casenotes. SETTING: A regional referral clinic for red cell alloimmune disease and fetal medicine unit at a university hospital. POPULATION: Sixty-five pregnancies were identified in 52 Kell-sensitised women with Kell positive partners from the records of the Birmingham Blood Transfusion Centre. METHODS: Information from the casenotes was entered on a database and comparisons were made using the SPSS for Windows statistics package. MAIN OUTCOME MEASURES: Mode of sensitisation, degree of fetal or neonatal anaemia, need for transfusion, gestation at delivery, birthweight and pregnancy outcome. RESULTS: Alloimmunisation was transfusion-related in 29 pregnancies and pregnancy-induced in 33. The cause could not be identified in three cases. There were 22 proven Kell positive fetuses, of which 18 were affected, in which alloimmunisation was pregnancy-related in 12 cases and transfusion-related in five. Antibody titres and amniotic fluid OD450 were not helpful in management. Severe or very severe disease occurred in 50% of the affected pregnancies (9/18). There was no difference in pregnancy outcome between transfusion or pregnancy induced sensitisation. CONCLUSIONS: Anti-Kell alloimmunisation is an uncommon cause of serious anaemia in a significant proportion of affected pregnancies. There appears to be no difference between that caused by pregnancy or transfusion. Estimation of fetal haemoglobin concentration by cordocentesis is recommended, as antibody titres and amniocentesis are not helpful.
Adolescent↗
Elasticity reconstruction from experimental MR displacement data: initial experience with an overlapping subzone finite element inversion process.
The determination of the elastic property distribution in heterogeneous gel samples with a finite element based reconstruction scheme is considered. The algorithm operates on small overlapping subzones of the total field to allow for a high degree of spatial discretization while maintaining computational tractability. By including a Maxwellian-type viscoelastic property in the model physics and optimizing the spatial distribution of this property in the same manner as elasticity, a Young's modulus image is obtained which reasonably reflects the true distribution within the gel. However, the image lacks the clarity and accuracy expected based on simulation experience. Preliminary investigations suggest that transient effects in the data are the cause of a significant mismatch between the inversion model, which assumes steady-state conditions, and the actual displacements as measured by a phase contrast MR technique.
Algorithms↗
Brain activation during working memory 1 month after mild traumatic brain injury: a functional MRI study.
OBJECTIVE: To assess patterns of regional brain activation in response to varying working memory loads shortly after mild traumatic brain injury (MTBI). BACKGROUND: Many individuals complain of memory difficulty shortly after MTBI. Memory performance in these individuals can be normal despite these complaints. METHODS: Brain activation patterns in response to a working memory task (auditory n-back) were assessed with functional MRI in 12 MTBI patients within 1 month of their injury and in 11 healthy control subjects. RESULTS: Brain activation patterns differed between MTBI patients and control subjects in response to increasing working memory processing loads. Maximum intensity projections of statistical parametric maps in control subjects showed bifrontal and biparietal activation in response to a low processing load, with little additional increase in activation associated with the high load task. MTBI patients showed some activation during the low processing load task but significantly increased activation during the high load condition, particularly in the right parietal and right dorsolateral frontal regions. Task performance did not differ significantly between groups. CONCLUSION: MTBI patients differed from control subjects in activation pattern of working memory circuitry in response to different processing loads, despite similar task performance. This suggests that injury-related changes in ability to activate or to modulate working memory processing resources may underlie some of the memory complaints after MTBI.
Adult↗
Prenatal diagnosis of tuberous sclerosis with intracerebral signs at 14 weeks' gestation.
We report the ultrasound detection of cranial abnormalities at 14 weeks' gestation in a fetus subsequently confirmed as having tuberous sclerosis using DNA linkage analysis within the affected family. The presence of asymmetrical ventricular enlargement persisted antenatally. Magnetic resonance imaging at 26 weeks indicated the possibility of poor gyral formation consistent with a neuronal migration disorder. Cardiac rhabdomyomata were not visualized on ultrasound scan until 30 weeks' gestation. Postnatal cranial ultrasound confirmed the significant neuropathology which was manifested by severe developmental delay and intractable fits in the child. The potential benefits of earlier diagnosis of tuberous sclerosis by cranial imaging are discussed, although in this patient the routine booking scan resulted in a path of prenatal diagnosis being undertaken which had originally been declined. A mechanism is proposed to explain the variable expression of tuberous sclerosis within this family based on altered TSC2 activity affecting neuronal migration.
Adult↗
An overlapping subzone technique for MR-based elastic property reconstruction.
A finite element-based nonlinear inversion scheme for magnetic resonance (MR) elastography is detailed. The algorithm operates on small overlapping subzones of the total region of interest, processed in a hierarchical order as determined by progressive error minimization. This zoned approach allows for a high degree of spatial discretization, taking advantage of the data-rich environment afforded by the MR. The inversion technique is tested in simulation under high-noise conditions (15% random noise applied to the displacement data) with both complicated user-defined stiffness distributions and realistic tissue geometries obtained by thresholding MR image slices. In both cases the process has proved successful and has been capable of discerning small inclusions near 4 mm in diameter. Magn Reson Med 42:779-786, 1999.
Algorithms↗
Neuroanatomic substrates of semantic memory impairment in Alzheimer's disease: patterns of functional MRI activation.
Impairment in semantic processing occurs early in Alzheimer's disease (AD) and differential impact on subtypes of semantic relations have been reported, yet there is little data on the neuroanatomic basis of these deficits. Patients with mild AD and healthy controls underwent 3 functional MRI auditory stimulation tasks requiring semantic or phonological decisions (match-mismatch) about word pairs (category-exemplar, category-function, pseudoword). Patients showed a significant performance deficit only on the exemplar task. On voxel-based fMRI activation analyses, controls showed a clear activation focus in the left superior temporal gyrus for the phonological task; patients showed additional foci in the left dorsolateral prefrontal and bilateral cingulate areas. On the semantic tasks, predominant activation foci were seen in the inferior and middle frontal gyrus (left greater than right) in both groups but patients showed additional activation suggesting compensatory recruitment of locally expanded foci and remote regions, for example, right frontal activation during the exemplar task. Covariance analyses indicated that exemplar task performance was strongly related to signal increase in bilateral medial prefrontal cortex. The authors conclude that fMRI can reveal similarities and differences in functional neuroanatomical processing of semantic and phonological information in mild AD compared to healthy elderly, and can help to bridge cognitive and neural investigations of the integrity of semantic networks in AD.
Aged↗
Pruritus in pregnancy and obstetric cholestasis.
Pruritus is often considered a common but minor symptom of pregnancy. However, pruritus caused by obstetric cholestasis is increasingly being recognized as a cause of so-called 'unexplained' stillbirths. This article reviews recent literature and outlines possible management strategies with the aim of reducing maternal morbidity and improving perinatal outcome.
Cholagogues and Choleretics↗
Imaging equipment and techniques for optimal intraoperative imaging during endovascular interventions.
Because endovascular procedures represent an ever-increasing portion of many vascular surgery practices, many surgeons are faced with difficult choices. Endovascular procedures often require open surgery, and open surgical techniques increasingly require fluoroscopic imaging. Without good intraoperative imaging, endovascular procedures are difficult and endovascular aneurysm repair is impossible. How does one balance the need for optimal imaging without sacrificing the ability to safely perform open surgical procedures, especially in the early stages of a developing endovascular program? Strategies include the use of a portable c-arm and carbon fiber table in the operating room (OR), adding a fixed imaging platform to an OR, gaining access to an angiography suite that does not meet OR requirements, and modifying it into an interventional suite that does meet operating room standards. Once the optimal equipment and facilities have been chosen, other choices must be considered. Should a radiology technician be hired? Should an interventional radiologist be available to assist or be incorporated as a routine member of the team? How will typical operating room procedures and technique need to be altered in an effort to optimize intraoperative imaging for endovascular procedures? This article gives an overview of the many issues that arise as a vascular surgery practice evolves to incorporate complex endovascular procedures.
Angiography↗
Monotonic noise suppression used to improve the sensitivity of fMRI activation maps.
We have introduced a new method of removing noise from images that identifies significant extrema and forces the pixel intensities between any two extrema to change monotonicly. The method has some similarities to wavelet denoising methods we worked with several years ago but is generally more stable and is effective on images with lower SNR's. In this paper the method of monotonic filtering is used to increase the sensitivity in functional magnetic resonance imaging (fMRI) studies. We have used the increased sensitivity to improve the temporal resolution in fMRI studies by roughly a factor of six. A motor activation study was acquired with single slice 256 x 256 pixel T2* weighted images; six cycles of finger tapping were acquired. Each cycle consisted of five images of rest followed by five images of right hand finger tapping followed by five images of left hand finger tapping. The z-scores were calculated and used as the activation map. The left and right activations were both clearly visible when all six cycles were used in the analysis. However, no definitive activation was seen for any one cycle. When the original 256 x 256 images were averaged down to 64 x 64 pixel images before calculation of the z-scores, the activations were partially identified. When the original images were filtered using the monotonic noise reduction algorithm, the left activation was clearly visible in three of the six cycles and partially visible in two others. The right activation was partially visible in 4 out of 6 cycles. Optimized noise reduction should improve the results significantly. The ability to use a single cycles is very important in fMRI studies because many stimuli are more difficult to maintain over many cycles and because complex processes such as in cognitive or memory activity do not have simple responses.
Brain Mapping↗
Elastic image registration using correlations.
We have developed a multiscale algorithm for elastic registration of images. Rigid registration has many applications but it is often limited by distortions in the images. For example, different views of the same object produce distortions. Common examples of slightly different views producing a distortion can be found in medical imaging, such as matching a current mammogram or chest radiograph with one from a previous year, and in remote sensing, such as matching images taken from different satellite positions. We have developed two methods of elastic registration. Both are multiscale but one used an iterative minimization of the local error and the other uses a windowed correlation. We present preliminary results of the elastic registration method used on windowed correlations.
Algorithms↗
Intravenous immunoglobulin therapy in compromised pregnancies associated with antiphospholipid antibodies and systemic lupus erythematosus.
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Adult↗
Scleroderma in pregnancy.
The case records of four patients with scleroderma who booked for care between 1989 and 1994 at the Birmingham Women's Hospital (formerly the Birmingham Maternity Hospital), a tertiary care obstetric unit, were studied retrospectively. The aim of the study was to look at infertility, early and late pregnancy losses, fetal growth retardation and maternal complications in these four women afflicted with this rare condition. Two patients gave a history of infertility. There were two growth retarded fetuses and one intrauterine fetal death. Worsening Raynaud's phenomenon occurred in three patients. Another patient developed massive haematemesis due to an oesophageal tear resulting from intractable vomiting. Scleroderma may adversely affect pregnancy: obstetrical complications are common and require close monitoring.
Journal Article↗
Multiresolution elastic image registration.
We have developed a multiscale algorithm for elastic (or molded) alignment of images. There is a wide array of medical applications of elastic (as opposed to strictly rigid) alignment: Subtraction of previous images from current ones to identify changes is perhaps the most obvious. We present preliminary results of this molding technique on a variety of images, and conclude with some closing remarks about this and future directions and goals of this work.
Algorithms↗
Brain size, head size, and intelligence quotient in monozygotic twins.
Many studies of monozygotic (MZ) twins have revealed evidence of genetic influences on intellectual functions and their derangement in certain neurologic and psychiatric diseases afflicting the forebrain. Relatively little is known about genetic influences on the size and shape of the human forebrain and its gross morphologic subdivisions. Using MRI and quantitative image analysis techniques, we examined neuroanatomic similarities in MZ twins and their relationship to head size and intelligence quotient (IQ). ANOVA were carried out using each measure as the dependent variable and genotype, birth order, and sex, separately, as between-subject factors. Pairwise correlations between measures were also computed. We found significant effects of genotype but not birth order for the following neuroanatomic measures: forebrain volume (raw, p < or = 0.0001; normalized by body weight, p = 0.0003); cortical surface area (raw, p = 0.002; normalized, p = 0.001); and callosal area (raw, p < or = 0.0001; normalized by forebrain volume, p = 0.02). We also found significant effects of genotype but not birth order for head circumference (raw, p = 0.0002; normalized, p < or = 0.0001) and full-scale IQ (p = 0.001). There were no significant sex effects except for raw head circumference (p = 0.03). Significant correlations were observed among forebrain volume, cortical surface area, and callosal area and between each brain measure and head circumference. There was no significant correlation between IQ and any brain measure or head circumference. These results indicate that: 1) forebrain volume, cortical surface area, and callosal area are similar in MZ twins; and 2) these brain measures are tightly correlated with one another and with head circumference but not with IQ in young, healthy adults.
Adult↗
Exploring the relation between personality and the appreciation of rock music.
Scores on five personality characteristics, extraversion, neuroticism, and psychoticism as well as reactive and proactive rebelliousness, and the appreciation of soft/nonrebellious and hard/rebellious rock-music videotapes were explored. After completing the personality tests, female and male undergraduates were exposed to rock-music videotapes and asked to rate various aspects of their enjoyment of each. Analysis indicated that psychoticism and reactive rebelliousness were associated with enjoyment in a parallel fashion. Specifically, respondents scoring high on psychoticism or high on reactive rebelliousness enjoyed hard/rebellious rock-music videotapes more than did their peers scoring low on psychoticism or low on reactive rebelliousness. The reverse was evident for the enjoyment of soft/nonrebellious rock-music videotapes. In contrast, scores on extraversion, neuroticism, and proactive rebelliousness were not associated with enjoyment. Gender differences emerged, however; women (n = 78) enjoyed soft/nonrebellious rock music more than did men (n = 60); and conversely, men enjoyed hard/rebellious rock music more than did women.
Adolescent↗