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The aim of this study was to evaluate the usefulness of periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER)-based diffusion tensor fiber tractography (DTT) at 3T to visualize infratentorial small fiber structures that cannot be visualized adequately using a conventional single shot echo planar imaging (ssEPI)-based pulse sequence.Four healthy male volunteers were examined in this study. Diffusion tensor images were acquired on a 3T clinical magnetic resonance scanner using PROPELLER and echo planar imaging sequences in six motion-probing gradient orientations. Fiber tracking results for the trigeminal and auditory nerves were compared quantitatively.The trigeminal nerve tract was successfully reconstructed using both acquisition methods (100%). Among these reconstructed tracts, 62.5% of the tracts on PROPELLER-DTT and 25% on ssEPI-DTT were followed to branches beyond the trigeminal ganglion. The reconstructed auditory nerve tract could be identified on PROPELER-DTT (62.5%), whereas no tract or only a short tract was obtained on ssEPI-DTT (37.5%).3T PROPELLER-DTT is useful for visualizing infratentorial small neurofiber structures.

The aim of this study was to develop ex vivo diffusion tensor (DT) flexible phantoms.Materials were bundles of textile threads of cotton, monofilament nylon, rayon, and polyester bunched with spiral wrapping bands and immersed in water. DT images were acquired on a 1.5-Tesla clinical magnetic resonance scanner using echo planar imaging sequences with 15 motion probing gradient directions. DT tractography with seeding and a line-tracking method was carried out by software originally developed on a PC-based workstation.We observed relatively high fractional anisotropy on the polyester phantom and were able to reconstruct tractography. Straight tracts along the bundle were displayed when it was arranged linearly. It was easy to bend arcuately or bifurcate at one end; and tracts followed the course of the bundle, whether it was curved or branched and had good agreement with direct visual observation. Tractography with the other fibers was unsuccessful.The polyester phantom revealed a diffusion anisotropic structure according to its shape and would be utilizable repeatedly under the same conditions, differently from living central neuronal system. It would be useful to validate DT sequences and to optimize an algorithm or parameters of DT tractography software. Additionally, the flexibility of the phantom would enable us to model human axonal projections.

Diffusion tensor imaging can evaluate the cerebral white matter quantitatively using fractional anisotropy (FA) and also can extract a certain tract by tractography, but these two have been used separately and not combined. The purpose of this study was to assess the clinical feasibility of ROI analysis using diffusion tensor tractography (DTT) in patients with amyotrophic lateral sclerosis (ALS).Sixteen patients with ALS (9 limb-onset type, 7 bulbar-onset type) and nine age-matched volunteers were studied. DTT of the corticobulbar tract (DTT-CBT) and corticospinal tract (DTT-CST) were visualized by free software (dTV/VOLUME-ONE). Regions-of-interest (ROIs) were semi-automatically placed on the tracts defined by DTT methods, and FA values within the ROIs were measured.Mean FA values of ALS patients in the ROIs along the DTT-CST (bulbar-onset: 0.574, limb-onset: 0.594) were significantly lower than those of controls (DTT-CST: 0.629) (p0.05). The mean FA of DTT-CBT of the bulbar-onset type (0.509) was significantly lower than that of the limb-onset type (0.558) and that of volunteers (0.561).DTT could segmentate certain white matter tracts and evaluate them quantitatively. It could depict the subtle changes between subtypes of ALS as well as the changes between the patients and volunteers.

Array spatial sensitivity encoding techniques (ASSET) were employed to improve the temporal resolution of two-dimensional (2D) thick-slice contrast-enhanced magnetic resonance digital subtraction angiography (MRDSA).2D MRDSA using ASSET was performed in 28 patients via fast spoiled gradient-echo sequence (TR/TE 5.4/1.5 ms; FA 60; FOV 24x24 cm; matrix size 256x256; slicethickness 50-70 mm), followed by a bolus injection of gadolinium chelate and subsequent saline flush, for 40 seconds on a sagittal plane. Images were evaluated for visualization of normal intracranial vessels and brain lesions utilizing a three-point scale; additionally, in 10 of the 28 patients, results were compared with those of conventional 2D MRDSA.2D MRDSA using ASSET, which improved temporal resolution from 1.45 to 0.77 seconds, displayed image quality comparable to that of conventional 2D MRDSA. Moreover, this technique afforded superior detectability with respect to early venous filling in patients with arteriovenous malformations (AVMs).ASSET improves the temporal resolution of 2D MRDSA without compromising spatial resolution.