Asymptomatic subjects present with a variety of abnormalities, providing valuable information on disease prevalence in a presumed healthy population. A small percentage of these findings require urgent medical attention and/or additional studies.

In patients with NF2 and spinal tumors, extramedullary tumors (predominantly NSTs) were present in higher numbers and were associated with more surgery than were intramedullary tumors. Our data suggest that the association between nonsense and frameshift mutations and severe NF2 may extend to specific categories of spinal tumors.

Double-inversion fast spin-echo (FSE) pulse sequences can be designed to provide excellent suppression of blood signal in black-blood MRI. However, because a nonselective inversion is used, these sequences typically have been highly inefficient. In this work it is demonstrated that the efficiency of double-inversion sequences can be greatly improved by a form of interleaving in which all of the slices to be imaged in a single pass are reinverted each time a signal is obtained from any single slice. Visualization of disease in the cervical carotid bifurcation has been improved by optimized "black-blood" techniques which suppress the signal from flowing blood and enhance the intensity of tissue, vessel wall, and plaque components. The quality of black-blood techniques depends on the extent to which the signal from blood is suppressed and does not contribute confounding signal to the vessel wall images. Blood suppression in black-blood imaging was improved with the introduction of selective preinversion pulses (1-3). In selective preinversion, the spins outside of the imaged slice are inverted while the spins within the slice are unaffected. This selective inversion is usually accomplished by a nonselective inversion of the entire volume, followed by a selective inversion of the imaged slice. The time between inversion and image acquisition is selected based on the time required to null the signal from blood. All blood that flows into the imaged slice produces no MR signal, and the contrast between stationary tissue and flowing blood is very high. Although initially applied to fast gradient-echo sequences (such as turbo fast imaging with steady precession (turboFISP)), the technique has also been applied successfully to fast spin-echo (FSE) sequences (4).Although the double-inversion technique provides excellent suppression of blood signal, and excellent contrast between the vessel wall and the lumen, the requirement of a nonselective inversion results in the limitation that slices can only be acquired sequentially. An improvement in efficiency was demonstrated recently by Song et al. (5), in which two widely separated slices are reinverted and imaged at each repetition time (TR). Although this technique doubles the efficiency of double-inversion FSE acquisition, only one of the slices imaged will have the appropriate inversion time to null the signal from blood.In this work, we present a modification of the efficient carotid imaging technique of Song et al. (5). In our modification two or more slices are selectively reinverted with each inversion time, but data is acquired from only one slice. The acquired slice is alternated between the selected slices such that the TR of each slice is maximized. The technique is described and results are given below. METHODS SubjectsTwo subjects (48 and 80 years old) with minor carotid artery disease were imaged. Both have flow patterns which lead to consistent lesion-mimicking blood signal in normal double-inversion FSE imaging techniques. The technique was also tested on at le...

Review of MEG-localized epileptiform areas on high-spatial-resolution MR images enables detection of epileptogenic neocortical lesions, some of which are occult on conventional MR images.

Purpose: To demonstrate that the time delay between phase and frequency encoding and the presence of pulsatile blood flow in high-resolution time-of-flight (TOF) imaging of the intracranial arteries (especially near the circle of Willis) can distort the appearance of blood vessels and result in a cross-hatch-appearing artifact in surrounding tissue. Materials and Methods:Two techniques to reduce the artifact, tri-directional flow compensation (3DFC) and elliptical-centric (EC) phase-encoding order, are investigated in five volunteer studies.Results: 3DFC eliminates the pulsation-related artifacts and the vessel distortion. A residual amplitude variation artifact is observed. EC phase encoding nearly eliminates the pulsatile motion-related artifact, but it does not eliminate vessel distortion. Conclusion:The combination of 3DFC and EC phase encoding appears to provide the greatest artifact reduction in the five volunteer studies performed.