ABSTRACT
OBJECTIVE: This article shows that functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) are very useful in the in vivo description of the visual pathways using today's most advanced techniques and allowing fusion between fMRI and tractography. Two complementary techniques were combined: (1) DTI coupled with the tractography and (2) fMRI. MATERIALS AND METHODS: A group of 205 cases, normal and pathological, children and adults, were studied for tractographic reconstitution of visual pathways. In addition, 11 patients underwent an acquisition in fMRI (BOLD effect), with a stimulation of a black-and-white flickering checkerboard. Acquisition was carried out on a 3.0 Tesla GEHC MRI unit. Activated arrays of fMRI are overlaid with those of neurotractography (neural tractography) having like results a functional neurotractography. RESULTS AND DISCUSSION: The main components of the visual pathways were successfully reconstructed in tractography: the optic nerves, optic chiasm, optic tracts, and optic radiations. It was also possible to visualize fiber decussation within the chiasma (possible direct pathways to the hypothalamus and thalamus were also identified). CONCLUSIONS: The tensor of diffusion is increasingly used and is a promising technology to improve the diagnosis of neurological diseases. Sophisticated algorithms contribute a new vision of the anatomy, with the possibility of isolating distinct anatomical entities. With the software used, the charts of fMRI activation are overlaid on the anisotropy charts. The tractograms that link two regions of the same functional network thus provide information on subjacent structural connectivity. Consequently, one speaks about functional neurotractography.
Subject(s)
Diffusion Magnetic Resonance Imaging , Diffusion Tensor Imaging , Visual Pathways/anatomy & histology , Adolescent , Adult , Aged , Aged, 80 and over , Child , Child, Preschool , Female , Humans , Infant , Male , Middle Aged , Young AdultABSTRACT
After 13 years of glaucoma exploration using MRI at 1.5 and 3 Tesla, we have deduced that there is no specific characteristic between the different forms of this disease, which is manifested by a slowly progressing degenerative optical neuropathy, predominant from front to back (with volume of the optic nerve head always greater than the distal portions of the 2nd neurone, chiasma, and optic tract), interspersed with clinical flare-ups that are recognized by an intense localized hypersignal (frequently from the apex progressing along the canal). Visual tract involvement is always bilateral, even in cases where symptoms are exclusively unilateral (asymmetry can be observed in these cases). The discordance between (i) the severity of axon reduction and (ii) the signs of injury already present at the time when MRI is performed and the relative preservation of visual function argues for encephalic disease with visual involvement. Its delayed discovery makes treatment, even with neuroprotectors, less effective and points toward the need for implementing directed genetic prevention studies, as a first step to more effectively assessing the therapies available.
Subject(s)
Glaucoma/diagnosis , Magnetic Resonance Imaging , HumansSubject(s)
Anemia, Sickle Cell/complications , Craniofacial Abnormalities/diagnosis , Moyamoya Disease/diagnosis , Adolescent , Circle of Willis , Craniofacial Abnormalities/complications , Craniofacial Abnormalities/diagnostic imaging , Humans , Magnetic Resonance Angiography , Magnetic Resonance Imaging , Male , Moyamoya Disease/complications , Moyamoya Disease/diagnostic imaging , Tomography, X-Ray ComputedABSTRACT
The purpose of this study was to determine the optimal tube current setting and scanning mode for hominid fossil skull scanning, using multi-detector row computed tomography (CT). Four fossil skulls (La Ferrassie 1, Abri Pataud 1, CroMagnon 2 and Cro-Magnon 3) were examined by using the CT scanner LightSpeed 16 (General Electric Medical Systems) with varying dose per section (160, 250, and 300 mAs) and scanning mode (helical and conventional). Image quality of two-dimensional (2D) multiplanar reconstructions, three-dimensional (3D) reconstructions and native images was assessed by four reviewers using a four-point grading scale. An ANOVA (analysis of variance) model was used to compare the mean score for each sequence and the overall mean score according to the levels of the scanning parameters. Compared with helical CT (mean score=12.03), the conventional technique showed sustained poor image quality (mean score=4.17). With the helical mode, we observed a better image quality at 300 mAs than at 160 in the 3D sequences (P=0.03). Whereas in native images, a reduction in the effective tube current induced no degradation in image quality (P=0.05). Our study suggests a standardized protocol for fossil scanning with a 16 x 0.625 detector configuration, a 10 mm beam collimation, a 0.562:1 acquisition mode, a 0.625/0.4 mm slice thickness/reconstruction interval, a pitch of 5.62, 120 kV and 300 mAs especially when a 3D study is required.
