Hyperecho-turbo spin-echo sequences at 3T: clinical application in neuroradiology.

BACKGROUND AND PURPOSE: Hyperecho-turbo spin-echo (hyperTSE) sequences were developed to reduce the specific absorption rate (SAR), especially at high fields such as 3T and above. The purpose of this study was to quantitatively and qualitatively assess the detection of neuroradiologic pathologies by hyperTSE in comparison with standard turbo spin-echo (TSE180 degrees) sequences. MATERIALS AND METHODS: TSE180 degrees and hyperTSE images with parameters adapted for equal T2 contrast were acquired on a 3T whole-body system in 51 patients with 54 cerebral pathologies. Region-of-interest analysis was performed of signal intensities of pathologies, normal white and gray matter, CSF, and the SD of noise. Signal intensity-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) for healthy tissues and pathologies were determined. A qualitative rating concerning artifacts, lesion conspicuity, and image quality was performed by 2 experienced neuroradiologists. RESULTS: HyperTSE sequences were equivalent to standard TSE180 degrees sequences for the CNR of pathologies and of the contrast between gray and white matter. The SNR of gray and white matter and CSF were also the same. The CNRs of the pathologies in hyperTSE and TSE180 degrees images were strongly correlated with each other (r = 0.93, P = .001). The visual rating of images revealed no significant differences between hyperTSE and TSE180 degrees. CONCLUSION: HyperTSE sequences proved to be qualitatively and quantitatively equivalent to TSE180 degrees sequences in the detection of high- and low-signal-intensity lesions. They provide equal CNR of pathologies and of gray minus white matter and reduce the imaging restrictions of conventional TSE180 degrees imposed by SAR limitations at 3T.

Possible genotype-phenotype correlations in children with mild clinical course of Canavan disease.

Canavan disease is characterised as a rare, neurodegenerative disease that usually causes death in early childhood. It is an autosomal recessive disorder due to an aspartoacylase (ASPA) deficiency. The causative gene has been mapped to chromosome 17 pter-p13. Here we describe three affected children from two Greek families with an unusually mild course of Canavan disease. All children presented with muscular hypotonia and macrocephaly. Diagnosis was based on elevated N-acetylaspartate in urine, reduced aspartoacylase activity in fibroblasts, and marked white matter changes on cerebral imaging. All three affected individuals exhibited continuous psychomotor development without any regression. Genetic analyses revealed compound heterozygous mutations (Y288 C; F295 S) in two individuals. The Y288 C variant was previously described in a child with macrocephaly, mild developmental delay, increased signal intensity in the basal ganglia, partial cortical blindness and retinitis pigmentosa, and slightly elevated N-acetylaspartate in the urine. Demonstration of the same variant in two unusually mildly affected Canavan disease patients and absence of this variant in 154 control chromosomes suggest a possible pathogenic role in mild Canavan disease. In the third individual, two homozygous sequence variants were identified, which comprise the known G274R mutation and a novel K213E variant.

FDG-PET and MRI in potassium channel antibody-associated non-paraneoplastic limbic encephalitis: correlation with clinical course and neuropsychology.

OBJECTIVES: We report a patient with potassium channel antibody-associated non-paraneoplastic limbic encephalitis (NPLE) in whom repeated fluorodeoxyglucose-positron emission tomography (FDG-PET) and magnetic resonance imaging (MRI) are correlated with epileptic activity and memory performance during the course of disease. CASE SUMMARY: A 32-year-old woman suffered from prolonged global amnesia after two generalized tonic-clonic seizures due to NPLE. Initially, MRI showed swelling of the left hippocampus. In FDG-PET, however, bitemporomesial hypermetabolism was seen corresponding to frequent bitemporal independent seizure patterns. Also neuropsychological impairments pointed to a bitemporal involvement at this early stage. In parallel with improved control of electrographic seizure patterns, improvement was seen in FDG-PET and in memory performance. During the whole course, MRI showed only left-sided abnormalities, which correlated with a permanent verbal memory impairment. CONCLUSION: FDG-PET was more sensitive in showing the initial bitemporal involvement and correlated well with EEG findings and neuropsychological impairment in the acute phase of disease. In contrast, structural MRI better reflected persistent neuropsychological deficits.

Dynamic 3D MR angiography of intra- and extracranial vascular malformations at 3T: a technical note.

Time-resolved, contrast-enhanced 3D MR angiography combined with parallel imaging at 3T was applied to an intracranial arteriovenous malformation, a dural arteriovenous fistula, and an extracranial facial arteriovenous malformation. The temporal resolution was one image every 1.5 seconds. Arterial feeders were depicted in all three cases. Early venous drainage was observed in the intracerebral arteriovenous malformation and the dural arteriovenous fistula, but not in the facial arteriovenous malformation. All findings were concordant with conventional angiography.

Vessel size imaging in humans.

The relation of contrast-enhanced transverse relaxation rates R2* and R2 provides in vivo mapping of the mean caliber of cerebral vessels. This technique is referred to as vessel size imaging (VSI). Here a quantitative assessment of the vessel caliber in brain tumor patients is presented. The obtained mean vessel size shows sensitivity to the tumor type. A theoretical analysis is given to elucidate the morphological information content of VSI in the context of vessel architecture. The simplification of the theory underlying the data processing results in a systematic overestimation of the vessel caliber. An increase in the magnetic susceptibility of the contrast agent allows for quantitatively more accurate measurements. Quantitative VSI must include measurements of the regional diffusion coefficient and absolute determination of the regional cerebral blood volume.

Parkes Weber or Klippel-Trenaunay syndrome? Non-invasive diagnosis with MR projection angiography.

Klippel-Trenaunay and Parkes Weber (Klippel-Trenaunay-Weber) syndromes consist of vascular malformations of the capillary, venous and lymphatic systems combined with soft tissue and bone hypertrophy of the affected extremity. Klippel-Trenaunay syndrome is a pure low-flow condition, while Parkes Weber syndrome is characterized by significant arteriovenous fistulas. The distinction of both entities is relevant, since the prognosis and therapeutic strategies differ significantly. Our purpose is to demonstrate that thick-slice dynamic magnetic resonance projection angiography (MRPA) is a non-invasive tool to detect arteriovenous shunting in Parkes Weber syndrome. Four patients underwent MR imaging and MRPA. MRPA demonstrated arteriovenous shunting in three patients. Arteriovenous shunting was characterized by early appearing draining veins. The time of arrival between normal arteries and pathological veins varied between less than 0.5 and 1.0 s. Therefore, the diagnosis in these cases could be specified as Parkes Weber syndrome. In all these cases, arteriovenous shunting was confirmed by intraarterial digital subtraction angiography. One patient showed normal results in MRPA and could be diagnosed as having Klippel-Trenaunay syndrome.

Automated detection of gray matter malformations using optimized voxel-based morphometry: a systematic approach.

Malformations of cortical development (MCD) are a recognized cause of epilepsy. Their special significance lies in the fact that, once detected and delineated, they are amenable to surgical removal. However, diagnosis from high-resolution MRI is still difficult, time-consuming, and highly dependent on individual expertise. We have recently proposed a simple procedure to detect cortical dysplasias, using automated procedures available within SPM99 (Wellcome Department, University College London, UK). Here, we aimed to systematically determine the best combination of processing parameters, using an optimized voxel-based morphometry approach. We included 20 patients with a known MCD and compared them to a normal database of 53 healthy, age- and gender-matched controls. The approaches taken during spatial normalization and a number of other parameters were systematically altered in order to find the best combination of parameters. Overall, 99 different approaches were evaluated in different ways. As far as possible, automatic processing and evaluation steps were used. With the number of candidate regions for MCD limited to five per patient, the best approaches resulted in the correct identification of up to 16 of 20 malformations. However, a number of approaches failed to perform well. The reasons for these failures and the implications this has for other studies are discussed. We conclude that voxel-based morphometry is able to detect cortical malformations with a high degree of accuracy. However, specific problems seem to arise when using an optimized protocol for voxel-based morphometry, indicating that this protocol may not be optimal for all voxel-based studies on brain morphology. Our approach, involving systematic alterations of parameters and evaluation, may be useful for other studies.

Head and neck vascular malformations: time-resolved MR projection angiography.

Extracranial vascular anomalies can be divided into haemangiomas and vascular malformations. The latter can be subdivided on the basis of the predominant type of vascular channels. Separation of high- and low-flow vascular malformations is of clinical importance. We report preliminary observations on time-resolved magnetic resonance projection angiography (MRPA) of vascular malformations of the head and neck. We examined eight patients with vascular anomalies of the head and neck. On MRPA the time between the early arterial phase and enhancement of the malformation could be used to distinguish high- and low-flow lesions. High-flow arteriovenous malformations showed early, intense enhancement. Venous malformations were either not visible on MRPA or showed late enhancement of veins. One patient was examined after embolisation of an arteriovenous fistula of the mandible. Normal MRPA was taken to indicate absence of a residual lesion.

Determination of hemisphere dominance for language: comparison of frontal and temporal fMRI activation with intracarotid amytal testing.

The reliability of frontal and temporal fMRI activations for the determination of hemisphere language dominance was evaluated in comparison with intracarotid amytal testing (IAT). Twenty-two patients were studied by IAT (bilateral in 13, unilateral in 9 patients) and fMRI using a paradigm requiring semantic decisions. Global and regional (frontal and temporoparietal) lateralisation indices (LI) were calculated from the number of activated (r>0.4) voxels in both hemispheres. Frontolateral activations associated with the language task were seen in all patients, temporoparietal activations in 20 of 22. Regional LI corresponded better with IAT results than global LI. Frontolateral LI were consistent with IAT in all patients with bilateral IAT (including three patients with right dominant and one patient with bilateral language representation) and were not conflicting in any of the patients with unilateral IAT. Temporoparietal LI were discordant with IAT in two patients with atypical language representation. In the determination of hemisphere dominance for language, regional analysis of fMRI activation is superior to global analysis. In cases with clear-cut fMRI lateralisation, i.e. consistent lateralised activation of frontal and temporoparietal language zones, IAT may be unnecessary. FMRI should be performed prior to IAT in all patients going to be operated in brain regions potentially involved in language.

MRI-visible pericochlear lesions in osteogenesis imperfecta type I.

Osteogenesis imperfecta (OI) is an inherited generalized disorder of type-I collagen synthesis often associated with hearing loss. We present a case of OI type I in which hearing loss led to examination of the temporal bone with MRI. In the osseous otic capsule MRI demonstrated pericochlear lesions with soft tissue signal intensity and contrast enhancement. Changes similar to otosclerosis have been described in the temporal bone of OI patients when applying CT, but reports on MRI findings do not yet exist.

The influence of gliomas and nonglial space-occupying lesions on blood-oxygen-level-dependent contrast enhancement.

BACKGROUND AND PURPOSE: Functional MR (fMR) imaging with blood-oxygen-level-dependent (BOLD) contrast enhancement is increasingly used as a noninvasive tool for presurgical mapping in patients with intracranial tumors. Most physiologic studies of task-related BOLD contrast enhancement have involved healthy volunteers. Therefore, it is not known whether BOLD contrast is evoked in the same way in or adjacent to tumor tissue. The purpose of this study was to study the influence of different intracranial tumors on BOLD contrast enhancement. METHODS: fMR mapping of the sensorimotor cortex was successfully performed in 15 of 21 patients with intracranial space-occupying lesions by using a bimanual motor task. Tumors were located either within the sensorimotor area itself or in adjacent brain areas, inducing changes of signal intensity on T2-weighted images along the pre- or postcentral gyrus. Space-occupying lesions were divided into a group comprising gliomas (seven cases) and a group comprising nonglial space-occupying lesions (three metastases, two cavernomas, one abscess, one arteriovenous malformation, one meningioma). A hemispheric activation index was calculated using the volume of activation on the affected and on the contralateral hemisphere. Hemispheric activation indices of gliomas and nonglial lesions were compared statistically. RESULTS: The activated volume in the hemispheres ipsilateral to the nonglial lesions was 14% larger than in the contralateral hemisphere, whereas in the hemispheres ipsilateral to gliomas, the activated volume decreased by 36% in comparison with the contralateral hemisphere. The difference between nonglial lesions and gliomas was significant (P < .05). CONCLUSION: The generation of BOLD contrast enhancement is reduced near gliomas but is not affected by nonglial tumors.

MRI of active otosclerosis.

Our aim was to determine whether MRI reliably shows pathology in patients with active otosclerosis (otospongiosis). We studied five patients with clinical and audiometric signs of this disorder and positive findings on high-resolution CT and tympanocochlear scintigraphy. Contrast enhancement of otospongiotic lesions was found in all affected ears, and could be topographically related to demineralised otospongiotic foci on CT. In lesions in the lateral wall of the labyrinth MRI sometimes showed the pathology better than CT, where partial-volume effects could be troublesome.

[Inversion recovery RARE: clinical use of a T2-weighted CSF-suppressed rapid sequence]. / Inversion-Recovery-RARE: Klinische Anwendung einer T2-gewichteten, liquorunterdrückten Schnellsequenz.

Inversion-Recovery RARE is a strongly T2-weighted fast sequence in which the CSF appears dark. This sequence was used in more than 100 patients. Retrospective analysis of 80 patients with cerebrovascular and inflammatory disease was carried out. The IR-RARE sequence proved to be particularly suitable for identifying small lesions in the neighbourhood of the subarachnoid space. We illustrate the typical contrast provided by this sequence, and describe its characteristics, exemplifying the advantages it offers for the diagnosis of multiple sclerosis, cerebral microangiopathy and brain infarction.

Bone marrow cytological storage phenomena in lipidoses.

The bone marrow cytological storage phenomena in generalized lysosomal lipid storage disorders (Gaucher disease, Niemann-Pick disease, GM1-gangliosidosis, cholesterol ester storage diseases) are reviewed. The value of bone marrow cytology as a pre-screening method in the diagnostic strategy for the different diseases depends on the disease type suspected and the availability of biochemical screening methods. While cytological screening is not necessary in certain patients with typical clinical pictures, it may prove undispensable in others.