White-gray matter differentiation in computed tomography

Evaluation of the quantitative performance of non-enhanced dual-energy CT X-map in detecting acute ischemic brain stroke: A model observer study using computer simulation

PURPOSE

A simulation study was performed to evaluate the quantitative performance of X-map images-derived from non-enhanced (NE) dual-energy computed tomography (DECT)-in detecting acute ischemic stroke (AIS) compared with that of NE-DECT mixed images.

METHODS

A virtual phantom, 150 mm in diameter, filled with tissues comprising various gray- and white-matter proportions was used to generate pairs of NE-head images at 80 kV and Sn150 kV at three dose levels (20, 40, and 60 mGy). The phantom included an inserted low-contrast object, 15 mm in diameter, with four densities (0%, 5%, 10%, and 15%) mimicking ischemic edema. Mixed and X-map images were generated from these sets of images and compared in terms of detectability of ischemic edema using a channelized Hotelling observer (CHO). The area under the curve (AUC) of the receiver operating characteristic that generated CHO for each condition was used as a figure of merit.

RESULTS

The AUCs of X-map images were always significantly higher than those of mixed images (P < 0.001). The improvement in AUC for X-map images compared with that for mixed images at edema densities was 9.2%-12.6% at 20 mGy, 10.1%-17.7% at 40 mGy, and 14.0%-19.4% at 60 mGy. At any edema density, X-map images at 20 mGy resulted in higher AUCs than mixed images acquired at any other dose level (P < 0.001), which corresponded to a 66% dose reduction on X-map images.

CONCLUSIONS

The simulation study confirmed that NE-DECT X-map images have superior capability of detecting AIS than NE-DECT mixed images.

Pharmacology of Kappa Opioid Receptors: Novel Assays and Ligands

The present study investigated the in vitro pharmacology of the human kappa opioid receptor using multiple assays, including calcium mobilization in cells expressing chimeric G proteins, the dynamic mass redistribution (DMR) label-free assay, and a bioluminescence resonance energy transfer (BRET) assay that allows measurement of receptor interaction with G protein and β-arrestin 2. In all assays, dynorphin A, U-69,593, and [D-Pro10]dyn(1-11)-NH2 behaved as full agonists with the following rank order of potency [D-Pro10]dyn(1-11)-NH2 &gt; dynorphin A ≥ U-69,593. [Dmt1,Tic2]dyn(1-11)-NH2 behaved as a moderate potency pure antagonist in the kappa-β-arrestin 2 interaction assay and as low efficacy partial agonist in the other assays. Norbinaltorphimine acted as a highly potent and pure antagonist in all assays except kappa-G protein interaction, where it displayed efficacy as an inverse agonist. The pharmacological actions of novel kappa ligands, namely the dynorphin A tetrameric derivative PWT2-Dyn A and the palmitoylated derivative Dyn A-palmitic, were also investigated. PWT2-Dyn A and Dyn A-palmitic mimicked dynorphin A effects in all assays showing similar maximal effects but 3–10 fold lower potency. In conclusion, in the present study, multiple in vitro assays for the kappa receptor have been set up and pharmacologically validated. In addition, PWT2-Dyn A and Dyn A-palmitic were characterized as potent full agonists; these compounds are worthy of further investigation in vivo for those conditions in which the activation of the kappa opioid receptor elicits beneficial effects e.g. pain and pruritus.

Computed tomography provides enhanced techniques for longitudinal monitoring of progressive intracranial volume loss associated with regional neurodegeneration in ovine neuronal ceroid lipofuscinoses

INTRODUCTION

The neuronal ceroid lipofuscinoses (NCLs; Batten disease) are a group of fatal neurodegenerative lysosomal storage diseases of children caused by various mutations in a range of genes. Forms associated with mutations in two of these, CLN5 and CLN6, are being investigated in well-established sheep models. Brain atrophy leading to psychomotor degeneration is among the defining features, as is regional progressive ossification of the inner cranium. Ongoing viral-mediated gene therapy trials in these sheep are yielding encouraging results. In vivo assessment of brain atrophy is integral to the longitudinal monitoring of individual animals and provides robust data for translation to treatments for humans.

METHODS

Computed tomography (CT)-based three-dimensional reconstruction of the intracranial volume (ICV) over time reflects the progression of cortical brain atrophy, verifying the use of ICV measurements as a surrogate measure for brain size in ovine NCL.

RESULTS

ICVs of NCL-affected sheep increase for the first few months, but then decline progressively between 5 and 13 months in CLN5^-/- sheep and 11-15 months in CLN6^-/- sheep. Cerebral ventricular volumes are also increased in affected animals. To facilitate ICV measures, the radiodensities of ovine brain tissue and cerebrospinal fluid were identified. Ovine brain tissue exhibited a Hounsfield unit (HU) range of (24; 56) and cerebrospinal fluid a HU range of (-12; 23).

CONCLUSIONS

Computed tomography scanning and reconstruction verify that brain atrophy ovine CLN5 NCL originates in the occipital lobes with subsequent propagation throughout the whole cortex and these regional differences are reflected in the ICV loss.

The effect of skull volume and density on differentiating gray and white matter on routine computed tomography scans of the head

Increased volume and density of the skull makes computed tomography differentiation of gray and white matter (GM and WM, respectively) more difficult. The purpose of this investigation was to study the effects of skull volume and bone density on GM and WM differentiation. A total of 21 patients with thick skulls and 22 controls were included in this study. Three consecutive slices from the computed tomography scan were analyzed. The basal ganglia had to be visualized on at least 1 slice. Calvarial volume measurement, mean pixel value in each slice, and Hounsfield unit difference between WM and GM, were compared between the thick-skulled and control groups. The mean bone volume of each slice in the thick-skulled group was 55.7, 54.3, and 56 mL, whereas the mean volume of each slice in the normal group was 39.3, 38.5, and 39.9 mL (P < 0.001). In our series, patients with thick skulls had 41% more bone volume than the normal group. The mean skull pixel value in each slice was 935.9 in patients with thick skulls and 987 in patients in the normal group. There was no difference between right and left sides of the same group of patients. Patients with larger volumes of skull have significant decrease in the Hounsfield unit of the GM and WM compared with the control group. As a result, diagnosing any low-contrast brain abnormality including early/subtle infarction in subjects with a thicker calvarium may be more difficult.

Diagnostic evaluation of stroke

Diagnostic testing in patients with ischemic stroke serves many purposes, including confirmation of the diagnosis and providing clues as to possible causes. Evaluation of the cerebral vasculature, the heart, the blood coagulation system, and selected other diagnostic tests may point to a mechanism of stroke which helps determine treatment and prognosis. With the recent advent of acute interventions for ischemic stroke, diagnostic testing is now an important component in the emergency management of stroke. In this article, the authors will review the standard approach to diagnostic testing for patients with ischemic stroke or transient ischemic attack, and new developments in neuro-imaging and their use in acute stroke assessment.

Imaging of acute cerebral ischemia

Until recently, there was no efficacious treatment for acute cerebral ischemia. As a result, the role of neuroimaging and the radiologist was peripheral in the diagnosis and management of this disease. The demonstration of efficacy using thrombolysis has redefined this role, with the success of intervention becoming increasingly dependent on timely imaging and accurate interpretation. The potential benefits of intervention have only begun to be realized. In this State-of-the-Art review of imaging of acute stroke, the role of imaging in the current and future management of stroke is presented. The role of computed tomography is emphasized in that it is currently the most utilized technique, and its value has been demonstrated in prospective clinical trials. Magnetic resonance techniques are equally emphasized in that they have the potential to provide a single modality evaluation of tissue viability and vessel patency in an increasingly rapid evaluation.

Rapid dynamic CT scanning in primary degenerative dementia and age-matched controls

Dynamic computed tomography (CT) scanning of the brain was performed in 26 patients with primary degenerative dementia (PDD) and in 15 age-matched controls without evidence of a dementing illness. Changes in CT density values over time were obtained for 16 regions of interest (ROIs) that were carefully chosen to avoid overlap with adjacent cerebrospinal fluid (CSF), sulsi, or bone. CT density washout curves were compared between patients and controls to detect regions where blood brain barrier (BBB) permeability might be increased. Although the patients' washout curves declined more gradually than control curves in 11 of the 14 ROIs with a functioning BBB, in no case did the difference reach statistical significance. Intrarater correlation coefficients indicated good overall reliability in the selection of ROIs.

Late childhood changes in brain morphology observable with MRI

Quantitative studies of brain morphology in groups of normal children aged eight to 10 years and of young adults aged 25 to 39 years revealed continuing maturation of the brain over this age-range. There was some evidence of slightly increasing brain volume, but the most striking changes occurred in the gray matter to white matter ratio, and especially in the cortical mantle, which becomes substantially thinner on MRI between the age of eight and adulthood. An increase in the volume of the cerebral ventricles occurred in close association with the decrease in cortical gray matter. Analyses of the morphology of the cerebellar vermis suggest that significant increases occur in the neocerebellar vermal area over this age-range, and that the ratio of neocerebellar to paleocerebellar vermal areas may also increase.

Correlation between cranial computed tomographic scans at diagnosis in children with acute lymphoblastic leukaemia and central nervous system relapse

145 children with acute lymphoblastic leukaemia (ALL) were evaluated over a period of 3 years in a multicentre study in which serial cranial computed tomographic (CT) scans of the brain were done. All patients were symptom-free. CT scans were graded as normal, borderline (slight or moderate cerebral atrophy), or pathological (severe cerebral atrophy). 62% (90/145) of children had CT scan abnormalities at diagnosis. After a median follow-up of 24 months (range 6-36) 12 of 108 evaluable patients had central nervous system (CNS) relapses (6 isolated relapses and 6 combined with relapse at another site). All patients with CNS relapse had an abnormal CT scan at diagnosis (8 pathological and 4 borderline). No relapses were observed among the 42 patients with a normal cranial CT scan at diagnosis. A significantly higher proportion of severe cerebral atrophy, both following CNS prophylaxis and after the discontinuation of treatment, was found among patients with a borderline CT scan at diagnosis than among patients with a normal CT scan at diagnosis. Thus an abnormal cranial CT scan at diagnosis in children with ALL seems to have prognostic significance.

The CT (Hounsfield unit) number of brain tissue in healthy infants. A new reliable method for detection of possible degenerative disease

It is difficult to correlate CT Hounsfield unit (H. U.) numbers from one CT investigation to another and from one CT scanner to another, especially when dealing with small changes in the brain substance, as in degenerative brain diseases in children. By subtracting the mean value of cerebrospinal fluid (CSF) from the mean value of grey and white matter, it is possible to remove most of the errors due, for example, to maladjustments, short and long-term drift, X-ray fan, and detector asymmetry. Measurements of white and grey matter using these methods showed CT H. U. numbers changing from 15 H. U. to 22 H. U. in white matter and 23 H. U. to 30 H. U. in grey matter in 86 healthy infants aged 0-5 years. In all measurements, the difference between grey and white matter was exactly 8 H. U. The method has proven to be highly accurate and reproducible.

CT and MRI in late-onset metachromatic leukodystrophy

A 23-year-old patient suffering from mental deterioration was referred for CT study following her first epileptic fit. The study disclosed generalized atrophy and diffuse symmetric white matter hypodensities. Similar findings were found in her 13-year-old retarded sister. The diagnosis of metachromatic leukodystrophy (MLD) was confirmed by the finding of low arylsulfatase A (ASA) levels in cultured fibroblasts in both sisters. MRI study revealed widespread high intensity signals of T2 nature in the periventricular regions indicating changes in white matter composition.

Computed tomography in affective disorders. Part II. Brain density

The attenuation values of brain density were investigated in 53 patients with affective disorder and 53 individually age- and sex-matched controls by computed tomography (CT). Asymmetry of density distribution, with higher values in most regions of the left hemisphere, was found in patients as well as in controls. Patients tended to display higher attenuation values than controls. In patients, an association between higher density of the parenchyma and smaller ventricular size was observed, but not in controls. Corresponding greater density in patients, compared to controls, was found in those subgroups (women, nonpsychotics, and bipolars) that did not differ in ventricle size from controls. Comparisons within subgroups of patients revealed lower attenuation values in psychotic than in nonpsychotic subjects, lower values in men than in women, lower values in lithium-treated than in non-lithium-treated patients, and lower values in unipolar than in bipolar patients. No differences were observed between older and younger patients or Dexamethasone Suppression Test (DST) normal versus DST-abnormal patients. No correlations between age and density were obtained in patients and controls.

A comprehensive study of chronic schizophrenic patients. II: Biological, neuropsychological, and clinical correlates of CT abnormality

There are numerous reports of lateral cerebral ventricle enlargement on computed tomography (CT) in schizophrenics, but the significance and its relationship to traditional notions of organicity remain unclear. Therefore we studied a subgroup of chronic schizophrenics who had lateral ventriculomegaly (and also cortical hyperdensity) on a battery of relevant biological, neuro-psychological, and clinical parameters such as electroencephalogram (EEG), platelet monoamine oxidase (MAO) and serum dopamine-beta-hydroxylase (DBH) activity, the Halstead Reitan Neuropsychological Battery (HRB), premorbid personality adjustment, drug response, positive and negative symptoms, employment history, and family history. Our findings support the notion that there is an "organic" subgroup of schizophrenia that has 1) CT structural abnormalities such as lateral ventricle enlargement and cortical hyperdensity; and cerebral dysfunction or deficits as evidenced by 2) an increased incidence of abnormal EEGs and also 3) greater impairment on neuropsychological tests. The biochemical measures, platelet MAO and serum DBH activity, nor any of the clinical measures could differentiate between the subgroups. The implications of these findings for the subtyping of schizophrenia are discussed.

Long-term neuropsychologic sequelae of childhood leukemia: correlation with CT brain scan abnormalities

Previous studies have failed to establish a direct relationship between behavioral disorders and organic pathology in long-term survivors of childhood acute lymphoblastic leukemia. We evaluated 23 long-term survivors who received central nervous system preventive therapy with cranial irradiation and intrathecal chemotherapy, using neuropsychologic tests and computed tomographic brain scans. The patients were in continuous first remission for 7 to 11 years, and none were receiving chemotherapy. On the basis of their CT scan findings, they were divided into three groups: 10 with normal CT findings, five with intracerebral calcifications, and eight with cortical atrophy. Neuropsychologic test results allowed prediction of CT scan findings with an 87% accuracy (P less than 0.001), indicating a strong correlation between the presence and type of CT scan abnormality and neuropsychologic functioning. Tests that measured verbal memory, attention, and functions correlated with frontal lobe integrity were most powerful in discriminating between groups.

Computer-assisted categorization of brain computerized tomography pixels into cerebrospinal fluid, white matter, and gray matter

A computer-assisted method was employed to estimate the amounts of cerebrospinal fluid (CSF), white matter, and gray matter in individual computerized tomography (CT) scans of brains. By means of an image processing procedure (DMORPH), the means +/- SD CT numbers of "pure" CSF, white matter, and gray matter were determined in each scan and stored. A CATSEG program used these means to define ranges for CT numbers for each of the three tissues on each scan, and to assign each pixel in a scan to one of the three categories. Summing over seven serial scans provided volumetric estimates of CSF, white matter, and gray matter in a brain segment. For 10 subjects aged 21 to 43 years, CSF volume equaled 1.4 to 4.7% of the total segment volume, white matter equaled 37.5 to 48.2%, and gray matter equaled 50.2 to 58.9%. Image processing hardware and software which allow standardized sampling from CT images for the evaluation of surface areas and CT numbers are described. These procedures, as applied to CT scans of the human brain, can be used to estimate the volumes of CSF, white matter, and gray matter in a selected intracranial segment.

Computed tomography of the brain following prophylactic treatment with irradiation therapy and intraspinal methotrexate in children with acute lymphoblastic leukemia

In 28 children with acute lymphoblastic leukemia (ALL) computed tomography (CT) was performed in order to demonstrate possible cerebral changes following treatment with prophylactic irradiation and intraspinal methotrexate (MTX). The time of CT-scan examination varied from 1 year and 1 month to 10 years and 1 month after diagnosis of ALL. The age of the children ranged from 3 years and 11 months to 14 years and 5 months. Six children had normal CT scans, 12 children had slight atrophy-like changes, and nine had severe cerebral atrophy. Two patients in the latter group presented an enlarged ventricular system as well. In one patient intracerebral calcification was the only pathologic finding. The severe changes were seen in children of all age groups, but predominantly in children with a short duration of their disease, severe symptoms, and frequent marrow relapse. Changes induced by steroid therapy may be reversible. No satisfactory explanation of the demonstrated cerebral pathologic findings can be given, except that they are the consequences of the combination of total therapy and severity of disease in the individual patient. Measurement of attenuation coefficients in grey and white matter shows increasing values with age during childhood. A combination of decreasing attenuation coefficients, especially in the white matter, and the finding of severe atrophy seems to be a bad prognostic sign.

Computed tomography in late-onset metachromatic leucodystrophy

In late-onset metachromatic leucodystrophy (MLD), early clinical diagnosis is difficult since initial symptoms frequently consist of misleading nonspecific psychopathological alterations. On cranial computed tomography (CT), however, symmetrical attenuation decrease of the white matter and mild cerebral atrophy can already be found in an early stage of the disease, and may even precede clinical symptoms. On the basis of observations in four patients with late-onset MLD who were followed between 1 and 5 years, characteristic CT appearances in different stages of the disease are outlined and compared with the literature.

The impact of future technology on oncologic diagnosis: oncologic imaging and diagnosis

Over the past few years, the discipline of medical imaging has entered an evolutionary period that reflects primarily the introduction of computers and digital technology into the imaging process. Clinical applications of this evolution realized to date (e.g., transmission computed tomography, ultrasound and quantitative nuclear medicine) are only indicative of future developments that promise to increase the contributions of medical imaging in a very substantial manner. This increase in the area of oncologic diagnosis is one of the more exciting possibilities existing in medicine today.

Cerebellar morphology in chronic schizophrenic patients: a controlled computed tomography study

Simple, objective, linear, and density measures were used to evaluate by computed tomography (CT) the cerebellum-fourth ventricular region of 23 chronic schizophrenic patients and 23 normal controls. Our data suggest that a subgroup of chronic schizophrenic patients have cerebellar atrophy associated with a strong but nonsignificant trend toward increased cerebellar density. The implications of these findings are discussed in view of previous CT and neuropathological studies.

CT response of brain parenchyma to intravenous contrast injections

Pre- and postcontrast scans of the same normal brain tissue layer were compared in 20 patients in order to evaluate postcontrast density response. The original purpose of this investigation was to explain a paradoxical phenomenon of density decrease, which has been regularly observed in our patients. Control phantom measurements revealed that the decrease of density values is a function of the time interval between the analysed and the previous scan. Prolonged interscan interval--due to contrast injection--enables a change in the sensitivity of CT detectors to be registered. It is probable that any study of cerebral blood volume could be unfavourably influenced by this phenomenon. Comparison between the postcontrast brain scan density decrease and density decrease of a phantom showed substantially no difference, so that we estimate the contrast response of the brain parenchyma in toto as insignificant. Further, a comparative analysis between contrast response of the white and gray matter has been made. The gray-white matter difference increased from precontrast 4.56 H to postcontrast 7.82 H. The relatively high difference of 3.26 H between the white and gray matter enhancement compared with negligible enhancement of the brain slice as a whole leads us to the hypothesis, that an absolute decrease of white matter density, as a biological reaction to the injected contrast solution, has to be presumed.

Postpartum CT examination of the heads of full term infants

Intracranial hemorrhage and decreased density of the cerebral parenchyma were the major findings on CT of 150 full term newborns in the first week of life. Clinically silent hemorrhage was rare. All neonates with severe intracranial bleeding had neurological abnormalities. A correlation was not found between hemorrhage and the mode of delivery. The site of hemorrhage and the mode of delivery. The site of hemorrhage has an important bearing on brain development. Periventricular hypodensity is an ambiguous finding which should be interpreted in conjunction with the clinical findings.

Computed tomography in neuronal ceroid lipofuscinosis

The computed tomography (CT) findings in a verified case of neuronal ceroid lipofuscinosis (NCL) are presented. CT revealed diffuse and severe cerebral atrophy, reflected by generalized subarachnoid space enlargement and symmetric ventricular dilatation. There was no evidence of abnormalities of the white matter. The CT features in our case of NCL correspond perfectly with the neuropathologic changes of the disease mentioned in the literature. Furthermore, CT is of considerable help in differentiating between those inherited metabolic brain diseases characterized primarily by white matter involvement and those presenting predominantly with changes of grey matter.

Hypothalamic-pituitary dysfunction following CNS prophylaxis in acute lymphocytic leukemia: correlation with CT scan abnormalities

In an attempt to identify possible adverse effects of CNS prophylaxis (cranial radiation and intrathecal chemotherapy), we examined hypothalamic-pituitary function in 23 patients with acute lymphocytic leukemia (ALL). Of 18 patients who had received both cranial radiation and intrathecal chemotherapy, nine had abnormally low growth hormone responses to insulin-induced hypoglycemia (less than 7.0 ng/ml). Seven of the nine patients with abnormally low growth hormone responses also manifested ventricular dilatation on computed tomography (CT) brain scans, whereas only one of the nine patients with normal growth hormone responses demonstrated this CT scan finding (P = 0.015). The remaining patients, who had not received cranial radiation, had normal growth hormone responses and normal CT scans. There is significant correlation between ventricular dilatation on CT and abnormally low peak growth hormone responses following CNS prophylaxis in ALL.

Abnormal CT scans of the brain in asymptomatic children with acute lymphocytic leukemia after prophylactic treatment of the central nervous system with radiation and intrathecal chemotherapy

Thirty-two asymptomatic patients with acute lymphocytic leukemia, who had received prophylactic cranial radiation (2400 rads) and either intrathecal methotrexate or cytosine arabinoside were studied by computed tomography of the brain 19 to 67 months after initiation of prophylaxis. Seventeen of 32 (53 per cent) had one or more abnormal findings. Dilatation of the ventricles (eight patients) and widening of the subarachnoid spaces (nine patients) were equally distributed among patients in both intrathecal-chemotherapy groups. Areas of decreased attenuation coefficient (hypodense, abnormally radiolucent regions) (four patients) and intracerebral calcification (one patient)--lesions previously described in methotrexate leukoencephalopathy--were found only in those who had received intrathecal methotrexate. Mild central-nervous-system dysfunction was detected in seven patients but did not correlate with the presence of tomographic abnormalities. Nevertheless, these tomographic findings may represent preclinical lesions. The unexpectedly high prevalence of such abnormalities contrasts with the essentially normal tomographic findings in a control group with acute lymphocytic leukemia who received no central-nervous-system prophylaxis. These results suggest that alternative approaches to such prophylaxis be considered.

Leukoencephalopathy following high-dose intravenous methotrexate chemotherapy: quantitative assessment of white matter attenuation using computed tomography

A clinical or subclinical leukoencephalopathy occurs in some children after treatment of acute lymphatic leukemia with prophylactic cranial radiation therapy and parenteral or intrathecal methotrexate. We have observed a similar clinical leukoencephalopathy in patients with bone tumors treated with intravenous high-dose methotrexate and citrovorum factor without cranial irradiation. CT scans of such patients may indicate decreased white matter attenuation, but visual appraisal of this phenomenon is occasionally misleading. A computerized method for analyzing white matter hypodensity by determining the mean attenuation coefficient for one or several contiguous CT slices has therefore been developed. Serial comparisons of this mean attenuation coefficient appear to be more reliable than simple visual appraisal.