Neuroradiology

European Society of Neuroradiology (ESNR)

Subtraction CT angiography in the follow-up of treated cerebral aneurysms

Application of MR morphologic, diffusion tensor, and perfusion imaging in the classification of brain tumors using machine learning scheme Abstract Purpose While MRI is the modality of choice for the assessment of patients with brain tumors, differentiation between various tumors based on their imaging characteristics might be challenging due to overlapping imaging features. The purpose of this study was to apply a machine learning scheme using basic and advanced MR sequences for distinguishing different types of brain tumors. Methods The study cohort included 141 patients (41 glioblastoma, 38 metastasis, 50 meningioma, and 12 primary central nervous system lymphoma). A computer-assisted classification scheme, combining morphologic MRI, perfusion MRI, and DTI metrics, was developed and used for tumor classification. The proposed multistep scheme consists of pre-processing, ROI definition, features extraction, feature selection, and classification. Feature subset selection was performed using support vector machines (SVMs). Classification performance was assessed by leave-one-out cross-validation. Given an ROI, the entire classification process was done automatically via computer and without any human intervention. Results A binary hierarchical classification tree was chosen. In the first step, selected features were chosen for distinguishing glioblastoma from the remaining three classes, followed by separation of meningioma from metastasis and PCNSL, and then to discriminate PCNSL from metastasis. The binary SVM classification accuracy, sensitivity and specificity for glioblastoma, metastasis, meningiomas, and primary central nervous system lymphoma were 95.7, 81.6, and 91.2%; 92.7, 95.1, and 93.6%; 97, 90.8, and 58.3%; and 91.5, 90, and 96.9%, respectively. Conclusion A machine learning scheme using data from anatomical and advanced MRI sequences resulted in high-performance automatic tumor classification algorithm. Such a scheme can be integrated into clinical decision support systems to optimize tumor classification.

Endovascular recanalization for symptomatic subacute and chronic intracranial large artery occlusion of the anterior circulation: initial experience and technical considerations Abstract Purpose This study aimed to report the clinical findings and initial clinical experience of endovascular recanalization for symptomatic subacute/chronic intracranial large artery occlusion (ILAO) of the anterior circulation. Methods From October 2015 to December 2017, 13 patients with symptomatic subacute/chronic ILAO of the anterior circulation were enrolled in this study and underwent endovascular recanalization. We collected the initial procedural results, including the rate of successful recanalization and periprocedural complications, and data pertaining to angiographic and clinical follow-up. Results Recanalization was successful in 11 of 13 patients (84.6%). Intraoperative complications occurred in four cases, including symptomatic distal embolism in three cases; one of which was simultaneously complicated with artery dissection. Intracerebral hemorrhage occurred in one case. Eleven patients underwent angiographic follow-up, and 12 patients underwent clinical follow-up. The results of the angiography follow-up (mean 6 ± 3.29 months) showed that in-stent restenosis occurred in one of the 11 successfully recanalized patients. However, the artery was occluded again in the patient who achieved thrombolysis in cerebral infarction (TICI) grade of 2a after treatment. Clinical follow-up (mean 5.8 ± 2.25 months) showed no recurrence of transient ischemic attack (TIA) or stroke in ten successfully recanalized cases. However, the patient who developed in-stent stenosis suffered TIA. Conclusions Endovascular recanalization for symptomatic subacute/chronic ILAO of anterior circulation is feasible, relatively safe, and efficacious in highly selected cases, improving patients' symptoms in the short-term. However, further larger scale pilot studies are needed to determine the efficacy and long-term outcome associated with this treatment.

Dependency of the blood oxygen level dependent-response to hyperoxic challenges on the order of gas administration in intracranial malignancies Abstract Purpose Literature reports contradicting results on the response of brain tumors to vascular stimuli measured in T2*-weighted MRI. Here, we analyzed the potential dependency of the MRI-response to (hypercapnic) hyperoxia on the order of the gas administration. Methods T2* values were quantified at 3 Tesla in eight consenting patients at rest and during inhalation of hyperoxic/hypercapnic gas mixtures. Patients were randomly divided into two groups undergoing different gas administration protocols (group A: medical air-pure oxygen–carbogen; group B: medical air–carbogen-pure oxygen). Mann-Whitney U test and Wilcoxon signed rank test have been used to proof differences in T2* regarding respiratory challenge or different groups, respectively. Results T2* values at rest for gray and white matter were 50.3 ± 2.6 ms and 46.1 ± 2.0 ms, respectively, and slightly increased during challenge. In tumor areas, T2* at rest were: necrosis = 74.1 ± 10.1 ms; edema = 60.3 ± 17.6 ms; contrast-enhancing lesions = 48.6 ± 20.7 ms; and solid T2-hyperintense lesions = 45.0 ± 3.0 ms. Contrast-enhancing lesions strongly responded to oxygen (+ 20.7%) regardless on the gas protocol (p = 0.482). However, the response to carbogen significantly depended on the order of gas administration (group A, + 18.6%; group B, − 6.4%, p = 0.042). In edemas, a different trend between group was found when breathing oxygen (group A, − 9.9%; group B, + 19.5%, p = 0.057). Conclusion Preliminary results show a dependency of the T2* response of contrast-enhancing brain tumor lesions on the order of the gas administration. The gas administration protocol is an important factor in the interpretation of the T2*-response in areas of abnormal vascular growth.

Micro-computed tomography: a new diagnostic tool in postmortem assessment of brain anatomy in small fetuses Abstract Purpose The aim of our study was to evaluate the postmortem micro-CT anatomy of early fetal human fetal brains, either in situ or isolated. Methods We studied 12 ex vivo specimens, 9 whole human fetuses (9–18 GW), and 3 isolated samples (16–26 GW). Specimens were fixed in formalin, then immersed in Lugol solution. Images were evaluated by two neuroradiologists. The depiction of CNS structures was defined based on the comparison between micro-CT images and a reference histologic anatomical Atlas of human brain development. Results Micro-CT provided informative high-resolution brain images in all cases, with the exception of one case (9 weeks) due to advanced maceration. All major CNS structures (i.e., brain hemispheres, layering, ventricles, germinal neuroepithelium, basal ganglia, corpus callosum, major cranial nerves, and structures of the head and neck) were recognizable. Conclusions Micro-CT imaging of the early fetal brain is feasible and provides high-quality images that correlate with the histological Atlas of the human brain, offering multiplanar and volumetric images that can be stored and shared for clinical, teaching, and research purposes.

Dynamic cerebellar herniation in Chiari patients during the cardiac cycle evaluated by dynamic magnetic resonance imaging Abstract Purpose Cerebellar herniation in Chiari patients can be dynamic, following the cerebrospinal fluid pulsatility during the cardiac cycle. We present a voxel intensity distribution method (VIDM) to automatically extract the pulsatility-dependent herniation in time-resolved MRI (CINE MRI) and compare it to the simple linear measurements. The degree of herniation is furthermore compared on CINE and static sequences, and the cerebellar movement is correlated to the presence of hydrocephalus and syringomyelia. Methods The cerebellar movement in 27 Chiari patients is analyzed with VIDM and the results were compared to linear measurements on an image viewer (visual inspection, VI) using a paired t test. Second, an ANOVA test is applied to compare the degree of herniation on static 3D MRI and CINE. Finally, the Pearson's correlation coefficient is calculated for the correlation between cerebellar movement and the presence of hydrocephalus and syringomyelia. Results VIDM showed significant movement in 85% of our patients. Assuming that movement < 1 mm cannot be detected reliably on an image viewer, VI identified movement in 29.6% of the patients (p = 0.002). The herniation was greater on static sequences than on CINE in most cases, but this was not statistically significant. The cerebellar movement was not correlated with hydrocephalus or syringomyelia (Pearson's coefficient < 0.3). Conclusions VIDM is a sensitive method to detect tissue movement on CINE MRI and could be used for Chiari patients, but also for the evaluation of cyst membranes, ventriculostomies, etc. The cerebellar movement appears not to correlate with hydrocephalus and syringomyelia in Chiari patients.

Altered brain diffusion tensor imaging indices in adolescents with the Fontan palliation Abstract Purpose Single ventricle heart disease (SVHD) patients show injury in brain sites that regulate autonomic, mood, and cognitive functions. However, the nature (acute or chronic changes) and extent of brain injury in SVHD are unclear. Our aim was to examine regional brain tissue damage in SVHD over controls using DTI-based mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD), and fractional anisotropy (FA) procedures. Methods We collected two DTI series (3.0-T MRI), mood and cognitive data, from 27 SVHD and 35 control adolescents. Whole-brain MD, AD, RD, and FA maps were calculated from each series, realigned and averaged, normalized to a common space, smoothed, and compared between groups using ANCOVA (covariates, age and sex; false discovery rate, p < 0.05). Region-of-interest analyses were performed to calculate MD, AD, RD, and FA values for magnitude assessment between groups. Results SVHD patients showed impaired mood and cognitive functions over healthy adolescents. Multiple brain sites in SVHD showed increased MD values, including the insula, caudate, cingulate, hypothalamus, thalamus, medial prefrontal and frontal cortices, parahippocampal gyrus, hippocampus, precentral gyrus, amygdala, cerebellum, corpus callosum, basal forebrain, mammillary bodies, internal capsule, midbrain, fornix, and occipital, parietal, and temporal cortices, indicating chronic tissue changes. Similar areas showed either increased AD or RD values, with RD changes more enhanced over AD in SVHD compared to controls. Few brain regions emerged with increased or decreased FA values in SVHD patients over controls. Conclusion SVHD adolescents, more than a decade from their last surgical procedure, show widespread brain abnormalities in autonomic, mood, and cognitive regulatory areas. These findings indicate that brain injury is in a chronic stage in SVHD with predominantly myelin changes that may result from previous hypoxia/ischemia- or developmental-induced processes.

Meningeal enhancement depicted by magnetic resonance imaging in tumor patients: neoplastic meningitis or therapy-related enhancement? Abstract Purpose To assess the prevalence of false-positive meningeal contrast enhancement in patients with solid tumors who were undergoing chemotherapy. Methods A total of 2572 magnetic resonance imaging (MRI) examinations of the brain were retrospectively evaluated by two readers for the presence of pathological meningeal contrast enhancement conspicuous for neoplastic meningitis. These patients either had malignant melanoma, breast or lung cancer, or lymphoma. The reference standards were cerebrospinal fluid cytology results and follow-up MRI. In cases with pathological contrast enhancement that decreased upon follow-up and non-malignant cytology, the enhancement pattern was further described as pial or dural, local or diffuse, or supra- or infra-tentorial. Moreover, the underlying therapy regimes were assessed. Results The final study cohort included 78 patients (51 females, median age 57 years), of which 11 patients (14.1%) had a repeated non-malignant cytology ('pseudomeningeosis'). In one case, this finding, a granular pleocytosis, was attributed to previous radiotherapy. Of the remaining patients, seven were receiving multimodal, immunotherapy-based therapy regimens. Patients with unsuspicious cytology had a predominantly supratentorial distribution pattern in comparison to patients with neoplastic meningitis. Conclusions The overall prevalence of the presence of false-positive meningeal contrast enhancement is low (< 1%) and not associated with specific imaging patterns. We hypothesize that there is a possible relationship between immunotherapy and 'pseudomeningeosis'. Therefore, in all cases with suspected neoplastic meningitis, the cerebrospinal fluid should be analyzed to confirm the diagnosis, especially in patients undergoing immunotherapy.

Dual-energy CT angiography-derived virtual non-contrast images for follow-up of patients with surgically clipped aneurysms: a retrospective study Abstract Purpose To evaluate the diagnostic performance, image quality, artifacts, and radiation doses of virtual non-contrast (VNC) images, relative to true non-contrast (TNC) images, in patients with surgically clipped aneurysms. Methods Seventy-six patients who underwent unenhanced computed tomography (CT) and dual-energy (DE)-CT angiography after surgical clipping of 85 intracranial aneurysms were included in the study. Diagnostic performances of VNC and TNC images were compared with respect to sensitivity, specificity, and positive and negative predictive values. The results of quantitative and qualitative analyses were compared between VNC and TNC images. Radiation doses were also compared between VNC and TNC images. Results Diagnostic performance of VNC images was lower than that of TNC images; however, addition of contrast-enhanced images improved diagnostic performance. Image noise and mean attenuation of VNC images were significantly higher than those of TNC images in the centrum semiovale, cerebellum, and pons. The quality of VNC images was excellent or sufficient (85.5% for observer 1, 85.5% for observer 2), and complete acceptance of VNC images was achieved in 64.5% for observer 1 and in 71.0% for observer 2; however, the addition of contrast-enhanced images increased the level of acceptance (92.0% for observer 1, 90.9% for observer 2). Clip artifacts were significantly lower in VNC images than in TNC images. CT dose index, dose-length product, and effective dose were significantly lower without TNC images. Conclusion VNC images showed lower diagnostic performance and image quality, and higher image noise than TNC images; however, VNC images could reduce clip artifacts and radiation doses.

Alexandros Sfakianakis
Anapafseos 5 . Agios Nikolaos
Crete.Greece.72100
2841026182

6948891480

alsfakia@gmail.com