Postmortem Magnetic Resonance Imaging Scans Research Articles

Visualisation of fetal meconium on post-mortem magnetic resonance imaging scans: a retrospective observational study.

BackgroundLess invasive techniques for fetal post-mortems are increasingly used to correlate with parental wishes. With the use of post-mortem magnetic resonance imaging (MRI), normal appearance of the organs must be established.PurposeTo investigate the after death appearance of the fetal meconium throughout gestation using the hyperintense appearance of meconium on T1 weighted MRI.Material and MethodsThis was a retrospective study that took place in a tertiary referral centre radiology department. Sixty-two fetal body post-mortem MRI scans (January 2014 to May 2018) between 12 and 41 weeks gestation were reviewed. Signal intensity of meconium at the rectum, sigmoid colon, splenic flexure and hepatic flexure was evaluated and correlated with gestational age. Interrater reliability was calculated.ResultsMeconium did not consistently have high signal intensity on T1 scans and was not always obvious. Rectal meconium had the highest intensity, and the more proximal the bowel the lower the intensity. The meconium had higher intensity at earlier gestations. Interrater reliability for rectal meconium gradings was excellent.ConclusionThis study provides the first published primary research on the appearance of fetal meconium on post-mortem MRI. Overall, results were variable and suggest an alteration of bowel contents after death, but further investigation is needed to effectively inform practice.

Histology-derived volumetric annotation of the human hippocampal subfields in postmortem MRI

Recently, there has been a growing effort to analyze the morphometry of hippocampal subfields using both in vivo and postmortem magnetic resonance imaging (MRI). However, given that boundaries between subregions of the hippocampal formation (HF) are conventionally defined on the basis of microscopic features that often lack discernible signature in MRI, subfield delineation in MRI literature has largely relied on heuristic geometric rules, the validity of which with respect to the underlying anatomy is largely unknown. The development and evaluation of such rules are challenged by the limited availability of data linking MRI appearance to microscopic hippocampal anatomy, particularly in three dimensions (3D). The present paper, for the first time, demonstrates the feasibility of labeling hippocampal subfields in a high resolution volumetric MRI dataset based directly on microscopic features extracted from histology. It uses a combination of computational techniques and manual post-processing to map subfield boundaries from a stack of histology images (obtained with 200μm spacing and 5μm slice thickness; stained using the Kluver–Barrera method) onto a postmortem 9.4Tesla MRI scan of the intact, whole hippocampal formation acquired with 160μm isotropic resolution. The histology reconstruction procedure consists of sequential application of a graph-theoretic slice stacking algorithm that mitigates the effects of distorted slices, followed by iterative affine and diffeomorphic co-registration to postmortem MRI scans of approximately 1cm-thick tissue sub-blocks acquired with 200μm isotropic resolution. These 1cm blocks are subsequently co-registered to the MRI of the whole HF. Reconstruction accuracy is evaluated as the average displacement error between boundaries manually delineated in both the histology and MRI following the sequential stages of reconstruction. The methods presented and evaluated in this single-subject study can potentially be applied to multiple hippocampal tissue samples in order to construct a histologically informed MRI atlas of the hippocampal formation.

Cerebral white matter disease is associated with Alzheimer pathology in a prospective cohort.

Although magnetic resonance imaging (MRI)-detected white matter disease has been correlated with cognitive decline in the elderly individuals, it is unclear whether white matter disease is primarily responsible for the cognitive deterioration or whether another process is common to both white matter disease and dementia. We examined the relationship between Alzheimer-type brain pathology at autopsy and MRI-detected cerebral white matter disease in 50 participants from the Baltimore Longitudinal Study of Aging Autopsy Program, a prospective study of aging that includes detailed cognitive assessments. White matter disease was quantitated in pre- and postmortem MRI scans using the Cardiovascular Health Study (CHS) criteria in a blinded manner. We found that several measures of Alzheimer's disease (AD) pathology, including the Consortium to Establish a Registry for Alzheimer's Disease score, Braak score, and a composite AD pathology score, along with hypertension, were significantly associated with CHS white matter score using univariate and multivariate ordinal regression. In contrast, amyloid angiopathy was not independently associated with CHS score. Although a clinical diagnosis of dementia was associated with CHS score in univariate analysis, the association disappeared after accounting for AD pathology. AD pathology at autopsy is associated with MRI-detected cerebral white matter disease. This relationship may explain, in part, the association between cerebral white matter disease and cognitive decline in the elderly individuals.

Neuroanatomy of the Subadult and Fetal Brain of the Atlantic White‐sided Dolphin (Lagenorhynchus acutus) from in Situ Magnetic Resonance Images

This article provides the first anatomically labeled, magnetic resonance imaging (MRI) -based atlas of the subadult and fetal Atlantic white-sided dolphin (Lagenorhynchus acutus) brain. It differs from previous MRI-based atlases of cetaceans in that it was created from images of fresh, postmortem brains in situ rather than extracted, formalin-fixed brains. The in situ images displayed the classic hallmarks of odontocete brains: fore-shortened orbital lobes and pronounced temporal width. Olfactory structures were absent and auditory regions (e.g., temporal lobes and inferior colliculi) were enlarged. In the subadult and fetal postmortem MRI scans, the hippocampus was identifiable, despite the relatively small size of this structure in cetaceans. The white matter tracts of the fetal hindbrain and cerebellum were pronounced, but in the telencephalon, the white matter tracts were much less distinct, consistent with less myelin. The white matter tracts of the auditory pathways in the fetal brains were myelinated, as shown by the T2 hypointensity signals for the inferior colliculus, cochlear nuclei, and trapezoid bodies. This finding is consistent with hearing and auditory processing regions maturing in utero in L. acutus, as has been observed for most mammals. In situ MRI scanning of fresh, postmortem specimens can be used not only to study the evolution and developmental patterns of cetacean brains but also to investigate the impacts of natural toxins (such as domoic acid), anthropogenic chemicals (such as polychlorinated biphenyls, polybrominated diphenyl ethers, and their hydroxylated metabolites), biological agents (parasites), and noise on the central nervous system of marine mammal species.

Correlation of Postmortem 9.4 Tesla Magnetic Resonance Imaging and Immunohistopathology of the Human Thoracic Spinal Cord 7 Months after Traumatic Cervical Spine Injury

To correlate high-resolution magnetic resonance imaging (MRI) with immunohistopathology in the injured human spinal cord. Postmortem MRI scans at a field strength of 9.4 T, as well as standard histology and immunohistochemistry, were performed on an excised specimen of human high thoracic spinal cord, obtained 7 months after the initial trauma, several segments below a severe spinal cord lesion (C5). A precise correlation is described between MRI and immunohistochemistry of the long white matter tracts undergoing Wallerian degeneration and of an extension of the cervical lesion into the high thoracic cord. MRI, the only imaging technique that currently provides useful information on the spinal cord parenchyma after trauma, is rapidly evolving. High-field scanners of up to 9.4 T are being clinically tested. The present postmortem investigation of an isolated spinal cord specimen demonstrates the precise correlation that can be achieved between imaging and pathology. In future investigations, this type of technique can lead to a more precise description of spinal cord injuries and their consequences in remote tissue. Translation into the clinical setting will improve diagnosis and follow-up of spinal cord injured patients.

Asymptomatic pontine lesions found by magnetic resonance imaging: Are they central pontine myelinolysis?

Clinicians occasionally receive radiographic reports noting pontine lesions in their patients who have undergone magnetic resonance imaging (MRI) for symptoms not referable to the pons. Based on these relatively isolated lesions, patients may receive the presumptive radiographic diagnosis of central pontine myelinolysis (CPM). Review of our MRI database from the last five years identified twelve such patients with hyperintense pontine lesions on T2-weighted scans which were out of proportion to supratentorial white matter disease processes and unexplained by the remainder of their radiographic studies. In an attempt to further clarify whether these findings were more consistent with CPM or some other process, we reviewed these patients' clinical records with particular attention to electrolyte disturbances, alcoholism, liver disease and hypertension. We also compared the MRI studies from these twelve patients with four MRI scans from patients with clinically diagnosed CPM and with eight post-mortem MRI scans on autopsy-proven asymptomatic CPM. By comparing pre- and post-mortem scans, five of the twelve unknown pontine lesions were felt to be too large to represent asymptomatic CPM. Five were thought to be incompatible with CPM based on shape and/or discohesiveness; one of these came to autopsy and showed cerebral and pontine ischemic rarefaction, not CPM. Only two of these twelve cases were felt to be asymptomatic or mildly symptomatic CPM, but have not come to autopsy. We conclude that pontine lesions found incidentally on MRI scans are a heterogeneous group, many of which are more consistent with pontine ischemic rarefaction than with asymptomatic CPM.

The relationship of quantitative brain magnetic resonance imaging measures to neuropathologic indexes of human immunodeficiency virus infection.

To directly examine the relationship between magnetic resonance imaging (MRI) abnormalities and neuropathologic changes in the brains of patients with the acquired immunodeficiency syndrome. A total of 17 brains from patients with acquired immunodeficiency syndrome for which postmortem MRI scans were available were used in this study. Volumes of cortical gray matter, deep gray matter, and abnormal white matter were estimated from the MRIs of the left hemispheres of the formalin-fixed brains from patients with acquired immunodeficiency syndrome using quantitative morphometric techniques. Quantitative estimates of human immunodeficiency virus, gliosis, and neocortical synaptic and dendritic density were obtained from the corresponding right hemispheres. Quantification of human immunodeficiency virus and gliosis was performed on all 17 specimens, while quantification of synaptic and dendritic density was performed on 10 of the 17 specimens. All specimens were obtained from patients with the acquired immunodeficiency syndrome who underwent autopsy between 1990 and 1992 at the University of California-San Diego Medical Center and the San Diego (Calif) Department of Veterans Affairs Hospital. No association was found between MRI volumes and gliosis, a nonspecific marker of central nervous system damage. Significant and regionally specific relationships were obtained, however, between the severity of central nervous system human immunodeficiency virus infection and the MRI volume estimates of gray matter and abnormal white matter. In addition, a significant association was observed between cortical gray matter volumes and cortical synaptic density. These findings indicate that the quantitative morphometric analysis of MRIs in patients may provide sensitive in vivo markers of neuropathologic changes associated with human immunodeficiency virus infection of the brain.