1,721,108 research outputs found
Arterial Spin-Labeled MR Perfusion Imaging Techniques
No full textArterial spin labeling (ASL) is a relatively new technique for MR perfusion assessment that is particularly useful in brain tissues. From a technical point of view, ASL-MRI is essentially a classic tracer experiment where the injected blood-borne tracer has been replaced by a procedure whereby water protons in the blood have been “labeled” on their way to the organ of interest. This labeling is achieved remotely by the application of radio-frequency (RF) waves that effect an inversion of the magnetization of the blood–water in the region where the RF is applied. This is achieved either for all blood within a region (pulsed ASL) or for blood flowing through a plane (continuous ASL), and for brain perfusion, it is usually performed in the neck. Conventional MR imaging can be used to capture this inverted blood signal once it has arrived in the organ, allowing time for it to arrive. However, the image will also contain contribution from the normal soft tissue in the image, which is much larger in magnitude than is the perfusion signal. Hence, the basic ASL experiment contains two images, one with labeling of blood–water and a second without: the subtraction of the two revealing the perfusion. The reliance on an endogenous tracer means that the ASL technique is noninvasive and, for most variants, readily available on existing hardware. However, the small signal magnitude relative to noise in the images and the relatively short “half-life” of the labeled water mean that careful and optimal acquisition and quantification are required. The primary goal of this chapter is to provide a complete overview of ASL from the technical issues, such as acquisition and quantification, to the clinical application in the brain including neuro-oncology, neurodegeneration, psychiatry, vascular and inflammatory disease, and epilepsy. The final section is focused on common pitfalls in ASL that should be avoided in diagnosis and a procedure to assess quality. A white paper1 regarding technical aspects of ASL has recently been published, from which technical recommendations in this chapter are drawn
Studio mediante imaging del tensore di diffusione del principale fascio di connessione interemisferica nel cervello normale e nelle sezioni parziali e totali del corpo calloso
No full textL’attività di ricerca da me svolta durante il triennio di Dottorato in
Neuroscienze e che ha caratterizzato il mio percorso formativo precedente
(certificato di ricerca presso l’Università Johns Hopkins di Baltimore per
fellowship durante il periodo Ottobre 2001 -Aprile 2002 –Ceritificate of
Research fellowship in Radiology and Radiological Science - e certificato di
completamento del corso in ricerca umana – Certificate of Completion of
Course in Human Subjects Research-) si è principalmente espletata nello
studio del Tensore di Diffusione e delle sue applicazioni di ricerca e
cliniche.
In particolare la mia tesi di dottorato presenterà i seguenti argomenti di
ricerca nell’ambito delle Neuroscienze:
- struttura e funzione dei collegamenti interemisferici residui in soggetti
con lesioni callosali (collaborazione con l’Università ed il Policlinico
Umberto I di Ancona): l’applicazione dell’Imaging del Tensore di
Diffusione (DTI) definisce la topografia dei collegamenti callosali
residui in casi di interruzione parziale e/o dei collegamenti
extracallosali in casi di sezione totale. La correlazione tra i risultati
DTI, la clinica e la valutazione con test neuropsicologici –es.
presentazione visiva lateralizzata-, permette la valutazione del ruolo
dei collegamenti interemisferici residui in Pazienti con sezione totale
o parziale del corpo calloso. Lo studio di Tensore di Diffusione può
avere importanza per la valutazione della degradazione mielinica ed
assonale a lunga distanza di tempo dopo lesione.
- rivisitazione della topografia del corpo calloso in volontari sani,
analisi dei valori di diffusione delle diverse fibre callosali e variabilità
intersessuale.
- confronto tra diverse tecniche di analisi dei dati DTI e collaborazione
alla programmazione di un nuovo software di post-processing DTI.Non disponibil
Standards for European training requirements in interventional neuroradiology : Guidelines by the Division of Neuroradiology/Section of Radiology European Union of Medical Specialists (UEMS), in cooperation with the Division of Interventional Radiology/UEMS, the European Society of Neuroradiology (ESNR), and the European Society of Minimally Invasive Neurological Therapy (ESMINT).
Full text linkThis document sets out standards for training in Interventional Neuroradiology (INR) in Europe. These standards have been developed by a working group of the European Society of Neuroradiology (ESNR) and the European Society of Minimally Invasive Neurological Therapy (ESMINT) on the initiative and under the umbrella of the Division of Neuroradiology/Section of Radiology of the European Union of Medical Specialists (UEMS)
Non-invasive brain stimulation in dementia: a complex network story
No full textNon-invasive brain stimulation (NIBS) is emerging as a promising rehabilitation tool for a number of neurodegenerative diseases. However, the therapeutic mechanisms of NIBS are not completely understood. In this review, we will summarize NIBS results in the context of brain imaging studies of functional connectivity and metabolites to gain insight into the possible mechanisms underlying recovery. We will briefly discuss how the clinical manifestations of common neurodegenerative disorders may be related with aberrant connectivity within large-scale neural networks. We will then focus on recent studies combining resting-state functional magnetic resonance imaging with NIBS to delineate how stimulation of different brain regions induce complex network modifications, both at the local and distal level. Moreover, we will review studies combining magnetic resonance spectroscopy and NIBS to investigate how microscale changes are related to modifications of large-scale networks. Finally, we will re-examine previous NIBS studies in dementia in light of this network perspective. A better understanding of NIBS impact on the functionality of large-scale brain networks may be useful to design beneficial treatments for neurodegenerative disorders
MRI performed after intratympanic gadolinium administration in patients with Ménière's disease: correlation with symptoms and signs.
No full textThe objective of the study was to compare the outcomes of a series of diagnostic parameters in Ménière's disease (MD) patients with the extent of endolymphatic hydrops (EH) as shown by magnetic resonance imaging (MRI) performed after intra-tympanic gadolinium administration using 18 patients (13 males and 5 females, age 25-78 years, median age 54.3 years) with definite MD. A 0.6-ml solution of Gadobutrol (1 mmol/ml) diluted 1:7 in saline was injected through the inferior-posterior quadrant of the tympanic membrane, using a 22-gauge spinal needle. The patient was kept with the head rotated 45° contralaterally for 30 min after the injection. Twenty-four hours later, three-dimensional fluid-attenuated inversion recovery MRI, using a 3-Tesla unit, was performed. Prevalence and extension of EH in MD patients was evaluated and correlated with age, duration and stage of the disease, frequency of attacks, time interval from the last attack, functional level scale, tinnitus, aural fullness, caloric stimulation, electrocochleography, and vestibular evoked myogenic potentials. All patients showed impaired enhancement of the inner ear of variable degree with the vestibular portion of the labyrinth more frequently involved than the cochlea. Abnormal vestibular evoked myogenic potentials, duration, and stage of the disease were significantly correlated to the number of inner ear sites involved. Modern imaging makes possible the identification of the endolymphatic hydrops in MD patients, improving diagnostic accuracy. The role of hydrops in the clinical manifestations and its correlation with most of the diagnostic parameters remain, however, not completely clear
Functional Sensitivity of Dual-Echo ASL in Localizing Active and Imagery Hand Movements
No full textDual-echo arterial spin labeling (DE-ASL) techniques have been recently proposed for thesimultaneous acquisition of ASL and blood-oxygenation-level-dependent (BOLD) functionalmagnetic resonance imaging (fMRI) data (Woolrich et al., 2006). The images acquired at the firstecho time are perfusion weighted (ASL), while the images from the second echo are primarilyT2* weighted, thus sensitive to the BOLD signal (Leontiev and Buxton, 2007). The sequence isuseful when the simultaneous estimation of blood flow and BOLD signal are targeted. Thepurpose of this study was to assess the sensitivity of the DE-ASL sequence in comparison to theconventional one (BOLD-fMRI) in detecting brain activations elicited by active and motor imageryhand movements
Neuroradiology training in EU: international survey of 31 countries within UEMS frame
No full textTo assess the current framework of interventional and diagnostic neuroradiology in Europe METHODS: The UEMS (European Union of Medical Specialists) Section of Radiology and the subspecialty UEMS Division of Neuroradiology collected by e-mail a survey on the situation of diagnostic and Interventional Neuroradiology' training and practice in Europe. The questionnaire was sent to the national delegates from 31 UEMS member countries, belonging to the European Union, the European Economic Area and the Council of Europe. In case of uncertain or discordant replies, the survey envisaged the involvement of neuroradiology scientific societies' experts for providing a decisive answer
A dehiscent superior semicircular canal may be plugged and resurfaced via the transmastoid route.
No full textTo evaluate the results obtained in treating superior semicircular canal dehiscence by plugging and resurfacing the defect via the transmastoid approach.Six patients (30-70 yr old) who had disabling semicircular canal dehiscence syndrome underwent surgery.After a wide mastoidectomy and skeletonization of the semicircular canals, a shell of bone covering the middle fossa lateral to the superior semicircular canal was removed. The exposed dura was gently retracted and the canal skeletonized. Bone dust mixed with fibrine glue and bone wax were pressed to plug the dehiscent portion of the canal, and a slice of cortical bone was inserted to resurface it.Recovery from vestibular and auditory symptoms was evaluated.No intraoperative or postoperative complications occurred. Patients experienced an immediate relief of symptoms attributable to the dehiscence.A superior semicircular canal dehiscence may be plugged and resurfaced via the transmastoid approach, thus avoiding the more invasive middle fossa craniotomy
Variability in the perilymphatic diffusion of gadolinium does not predict the outcome of intratympanic gentamicin in patients with Ménière's disease.
No full textOBJECTIVES/HYPOTHESIS:
To assess the utility of imaging in planning intratympanic (IT) gentamicin (Gent) treatment in Ménière's disease (MD), we compared the dosage and outcomes of ITGent with the severity and extent of endolymphatic hydrops (EH), as evaluated by three-dimensional fluid-attenuated inversion recovery (3D-FLAIR) sequence in a 3-T magnetic resonance imaging (MRI) unit, after IT gadolinium administration.
STUDY DESIGN:
Retrospective review.
METHODS:
A total of 18 patients (10 males and 8 females; age, 28-78 years; median age, 53.2 years) with definite MD participated in the investigation. The duration of the disease ranged from 8 months to 9 years (median, 2 years), with a prevalence of vertigo spells ranging from 0.8 to 8 per month (median, 2.2), as calculated in the last 6 months. A 3D-FLAIR MRI was performed 24 hours after IT injection of diluted gadobutrol. ITGent injection was performed within a variable period of time, from 1 week to 3 weeks after 3D-FLAIR MRI. The degree and extension of EH as evaluated by 3D-FLAIR MRI were compared with the number of injections necessary to cure vertigo attacks. Vertigo results, functional level scale modifications, variations in caloric excitability, and pure-tone average modifications.
RESULTS:
No statistically significant correlation was observed between severity of EH and outcomes of ITGent administration.
CONCLUSIONS:
The hypothesis of a reduced effect of Gent administered intratympanically in the presence of severe EH, owing to obstacled diffusion along the perilymphatic compartments, has not been confirmed in the present investigation
Magnetic resonance imaging fails to show evidence of reduced endolymphatic hydrops in gentamicin treatment of Ménière's disease.
No full textOBJECTIVE:
To verify the hypothesis that intratympanic (IT) gentamicin (Gent) treatment in Ménière's disease (MD) is capable of reducing endolymphatic hydrops (EH), as evaluated by 3-dimensional fluid-attenuated inversion recovery (3D-FLAIR) sequence in a 3-Tesla magnetic resonance imaging (MRI) unit, after IT gadolinium administration.
PATIENTS:
A total of 8 patients (5 men and 3 women; aged 40-78 yr; median, 60 yr) with definite MD participated in the investigation. The duration of the disease ranged from 1 to 10 years (median, 4 yr), with a prevalence of vertigo spells of 1 to 6 per month (median, 3.1), as calculated in the last 6 months.
INTERVENTION:
A 3D-FLAIR MRI was performed 24 hours after IT injection of diluted gadobutrol. Intratympanic Gent injection was performed in a period variable from 1 to 3 weeks after 3D-FLAIR MRI. A single-shot administration protocol was attempted with additional injections administered on demand in the case of relapsing vertigo spells. MRI was repeated after 3 to 12 months (median, 8 mo) after treatment.
MAIN OUTCOME MEASURE:
The degree and extension of EH as evaluated by 3D-FLAIR MRI was compared from images obtained pre- and post-ITGent administration.
RESULTS:
After ITGent administration, 4 patients did not show any MRI modification, 3 patients showed a worsening of EH in one site, and 1 patient showed a worsening in two sites. No subjects presented reduction of EH.
CONCLUSION:
No evidence of reduced EH following ITGent treatment has been shown in the present imaging investigation
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