Refined modelling of the short-T2 signal component and ensuing detection of glutamate and glutamine in short-TE, localised, (1) H MR spectra of human glioma measured at 3 T.

Short-TE (1) H MRS has great potential for brain cancer diagnostics. A major difficulty in the analysis of the spectra is the contribution from short-T2 signal components, mainly coming from mobile lipids. This complicates the accurate estimation of the spectral parameters of the resonance lines from metabolites, so that a qualitative to semi-quantitative interpretation of the spectra dominates in practice.

Technical Note: Clinical translation of the Rapid-Steady-State-T1 MRI method for direct cerebral blood volume quantification.

Purpose: In preclinical studies, the Rapid-Steady-State-T1 (RSST1) MRI method has advantages over conventional MRI methods for blood volume fraction (BVf) mapping, since after contrast agent administration, the BVf is directly quantifiable from the signal amplitude corresponding to the vascular equilibrium magnetization. This study focuses on its clinical implementation and feasibility.

Methods: Following sequence implementation on clinical Philips Achieva scanners, the RSST1-method is assessed at 1.

Surgical implantation of STN-DBS leads using intraoperative MRI guidance: technique, accuracy, and clinical benefit at 1-year follow-up.

Background: Improvement of surgical accuracy during DBS-lead implantation has been described recently, leading to "frameless" or "MRI-verified" techniques. However, combining a high-quality definition of the STN using intraoperative 1.5 MRI with the possibility to reduce errors due to co-registration and to monitor lead progression during surgical insertion while checking the absence of surgical complication is an appealing method.

Disentangling the Role of Cortico-Basal Ganglia Loops in Top-Down and Bottom-Up Visual Attention: An Investigation of Attention Deficits in Parkinson Disease.

It is solidly established that top-down (goal-driven) and bottom-up (stimulus-driven) attention mechanisms depend on distributed cortical networks, including prefrontal and frontoparietal regions. On the other hand, it is less clear whether the BG also contribute to one or the other of these mechanisms, or to both. The current study was principally undertaken to clarify this issue.

Ongoing egocentric spatial processing during learning of non-spatial information results in temporal-parietal activity during retrieval.

Deficits in amnesic patients suggest that spatial cognition and episodic memory are intimately related. Among the different types of spatial processing, the allocentric, relying on the hippocampal formation, and the egocentric-updated, relying on parieto-temporal connections have both been considered to functionally underlie episodic memory encoding and retrieval. We explore the cerebral correlates underlying the episodic retrieval of words previously learnt outside the magnet while performing different spatial processes, allocentric and egocentric-updated.

Retinotopic and lateralized processing of spatial frequencies in human visual cortex during scene categorization.

Using large natural scenes filtered in spatial frequencies, we aimed to demonstrate that spatial frequency processing could not only be retinotopically mapped but could also be lateralized in both hemispheres. For this purpose, participants performed a categorization task using large black and white photographs of natural scenes (indoors vs. outdoors, with a visual angle of 24° × 18°) filtered in low spatial frequencies (LSF), high spatial frequencies (HSF), and nonfiltered scenes, in block-designed fMRI recording sessions.

Assessment of white matter injury and outcome in severe brain trauma: a prospective multicenter cohort.

Background: Existing methods to predict recovery after severe traumatic brain injury lack accuracy. The aim of this study is to determine the prognostic value of quantitative diffusion tensor imaging (DTI).

Methods: In a multicenter study, the authors prospectively enrolled 105 patients who remained comatose at least 7 days after traumatic brain injury.

Pre-orthographic character string processing and parietal cortex: a role for visual attention in reading?

The visual front-end of reading is most often associated with orthographic processing. The left ventral occipito-temporal cortex seems to be preferentially tuned for letter string and word processing. In contrast, little is known of the mechanisms responsible for pre-orthographic processing: the processing of character strings regardless of character type.

Perfusion magnetic resonance imaging: comparison of semiologic characteristics in first-pass perfusion of brain tumors at 1.5 and 3 Tesla.

Objectives: To investigate whether using 3 Tesla (T) instead of 1.5T modifies the data obtained from first-pass perfusion in relation to the quantitative values of cerebral blood volume (CBV) and estimation of micro-vascular leakage (MVL). To describe the differences in data in the setting of neuro-oncology cases and propose explanations based on the discrepancies.

Impaired fMRI activation in patients with primary brain tumors.

To characterize peritumoral BOLD contrast disorders, 25 patients referred for resection of primary frontal or parietal neoplasms (low-grade glioma (LGG) (n=8); high-grade glioma (HGG) (n=7); meningioma (n=10)) without macroscopic tumoral infiltration of the primary sensorimotor cortex (SM1) were examined preoperatively using BOLD fMRI during simple motor tasks. Overall cerebral BOLD signal was estimated using vasoreactivity to carbogen inhalation. Using bolus of gadolinium, cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) were estimated.

Perfusion CT to quantify the cerebral vasospasm following subarachnoid hemorrhage.

Background And Purpose: After subarachnoid hemorrhage (SAH), vasospasm is frequent and increases the risk of stroke and poor clinical outcome. The purpose of this study was to identify the best perfusion parameters in perfusion-CT (PCT) able to predict vasospasm diagnosed by angiography after SAH.

Methods: Seventy-six patients with SAH were investigated by PCT and cerebral angiography.

Predicting cognitive dysfunctioning in nondemented patients early after stroke.

Background: Cognitive dysfunctioning (CDF) is an important issue in stroke, interfering with recovery and social dysfunctioning. We aimed to investigate the clinical and imaging correlates of CDF in patients with a first-ever subacute ischemic stroke and no dementia.

Methods: We evaluated CDF 15 days after stroke in a prospective cohort of consecutive patients with a Mini Mental State Examination score > or =23 using a comprehensive neuropsychological battery.

Effects of magnetic resonance imaging in patients with implanted deep brain stimulation systems.

Object: The aim of this study was to study the effects of MR imaging on the electrical settings of deep brain stimulation (DBS) systems and their clinical consequences.

Methods: The authors studied the effects of 1.5-T MR imaging on the electrical settings of implanted DBS systems, including 1 or more monopolar or quadripolar leads, extension leads, and single- or dual-channel implantable pulse generators (IPGs).

Bilateral pallidal deep brain stimulation for the treatment of patients with dystonia-choreoathetosis cerebral palsy: a prospective pilot study.

Background: Cerebral palsy (CP) with dystonia-choreoathetosis is a common cause of disability in children and in adults, and responds poorly to medical treatment. Bilateral pallidal deep brain stimulation (BP-DBS) of the globus pallidus internus (GPi) is an effective treatment for primary dystonia, but the effect of this reversible surgical procedure on dystonia-choreoathetosis CP, which is a subtype of secondary dystonia, is unknown. Our aim was to test the effectiveness of BP-DBS in adults with dystonia-choreoathetosis CP.

Hidden dysfunctioning in subacute stroke.

Background And Purpose: Determining cognitive dysfunctioning (CDF) after stroke is an important issue because it influences choices for management in terms of return to previous activities. Because previous research in subacute stroke has shown important variations in CDF rates, we aimed to describe the frequency and neuropsychological profile of CDF in subacute stroke outside dementia. We used a large battery of tests to screen any potentially hidden CDF.

Pretargeting for the implantation of stimulation electrodes into the subthalamic nucleus: a comparative study of magnetic resonance imaging and ventriculography.

Objective: The optimal imaging modality for preoperative targeting of the subthalamic nucleus (STN) for high-frequency stimulation is controversially discussed. Commonly used methods were stereotactic magnetic resonance imaging (MRI), stereotactic ventriculography, and fusion between MRI and stereotactic computer tomography. All of these techniques not only have their own advantages but also specific limitations and drawbacks.

Cerebral blood volume quantification in a C6 tumor model using gadolinium per (3,6-anhydro) alpha-cyclodextrin as a new magnetic resonance imaging preclinical contrast agent.

In magnetic resonance imaging (MRI), cerebral blood volume (CBV) quantification is dependent on the MRI sequence and on the properties of the contrast agents (CAs). By using the rapid steady-state T(1) method, we show the potential of gadolinium per (3,6-anhydro) alpha-cyclodextrin (Gd-ACX), a new MRI paramagnetic CA (inclusion complex of Gd(3+) with per (3,6-anhydro)-alpha-cyclodextrin), for the CBV quantification in the presence of blood-brain barrier lesions. After biocompatibility and relaxivity experiments, in vivo experiments on rats were performed on a C6 tumor model with 0.

Perfusion-sensitive MRI of pilocytic astrocytomas: initial results.

Purpose: To present the imaging and perfusion data obtained in nine patients with pilocytic astrocytomas (PA) and to discuss the original functional issues of this technique.

Method: Nine patients with pathologically proven PA underwent conventional and perfusion MR imaging. Various areas of relative cerebral blood volume (rCBV) within the tumors were obtained.

Functional MRI approach for assessing hemispheric predominance of regions activated by a phonological and a semantic task.

This fMRI study performed in healthy subjects aimed at using a statistical approach in order to determine significant functional differences between hemispheres and to assess specialized regions activated during a phonological and during a semantic task. This approach ("flip" method and subsequent statistical analyses of the parameter estimates extracted from regions of interest) allows identifying: (a) hemispheric specialized regions for each language task [semantic (living categorization) and phonological (rhyme detection)] and (b) condition-specific regions with respect to paradigm conditions (task and control). Our results showed that the rhyme-specific task regions were the inferior frontal (sub-region of BA 44, 45) and left inferior parietal (BA 40, 39) lobules.