Separation and quantification of perfusion and BOLD effects by simultaneous acquisition of functional I(0)- and T2(*)-parameter maps.

The nature of the coupling between neuronal activity and the hemodynamic response is the subject of intensive research. As a means to simultaneously measure parametric changes of T2(*), initial intensity (I(0)) and perfusion with high temporal resolution, a multi-image EPI technique with slice-selective inversion recovery (ssIR) for arterial spin labeling was developed and implemented. Comparative measurements with and without the preceding slice-selective inversion pulse were performed. I(0) and R2(*) changes induced by primary visual stimulation were separated. For ssIR-multi-image EPI the average change of I(0) over all 12 subjects was 3.4%, corresponding to a perfusion change of 40 ml/min/100 g, whereas only minor I(0) changes were observed without inversion. On average, the R2(*) of the activated pixels changed by -0.62 sec(-1) without inversion, while a significantly reduced average R2(*) change of -0.46 sec(-1) was calculated for ssIR-multi-image EPI due to a decreased BOLD effect contribution of the intravascular compartment.

Quiet imaging with interleaved spiral read-out.

The acoustic noise generated during an MRI sequence can be effectively reduced with the help of soft gradient pulses using sinusoidal ramps. The long slope duration, however, leads to long acquisition times. The use of interleaved spiral trajectories, calculated with long gradient slopes, is proposed to reduce the acquisition time while maintaining low acoustic noise levels. The practicality of this approach is demonstrated on phantom and volunteer images.

Benefits and pitfalls of keyhole imaging, especially in first-pass perfusion studies.

A comparison of dynamic results of a multi-echo contrast-enhanced perfusion study obtained from a keyhole imaging experiment and the results from low-resolution updates is presented. If, for each dynamic state, a separate reference image exists, high spatial resolution in the dynamic results can be preserved through keyhole imaging. If only one reference image can be used, the dynamic key-hole results still offer high spatial frequency content due to spatial phase discontinuities in the images. These often exist at the outline of organs and result from the fat in connective tissues. If the basic assumption of keyhole imaging, namely, that the relevant information is centered in k-space, is violated, as in T2*-weighted gradient-echo images, keyhole imaging can lead to erroneous results even though the update images themselves seem to be free of any artifacts.

Spiral reconstruction by regridding to a large rectilinear matrix: a practical solution for routine systems.

Spiral trajectories offer a number of attractive features for fast imaging. A practical problem for the implementation on routine magnetic resonance scanners is the lack of appropriate and efficient reconstruction algorithms in the available scanner software. In this paper, a simple way to implement a spiral reconstruction algorithm is described that avoids the data interpolation required by gridding approaches commonly used. Using the optimized fast Fourier transform built into each scanner, it offers image reconstruction times of less than 1 second and thus allows the introduction of spiral imaging to routine scanners.

Improvement of spatial resolution of keyhole effect images.

An algorithm is proposed which improves the spatial resolution of difference or effect images acquired with a keyhole sampling strategy. This new reconstruction algorithm uses a priori information about sharp structures in the observed signal changes from a high resolution reference scan. The potential of this algorithm even being able to deal with noisy effect images is illustrated by application to functional MRI data.

Implementation of a fast gradient-echo SVD encoding technique for dynamic imaging.

In the paper, the results of a fast gradient-echo implementation of the singular value decomposition (SVD) encoding technique for dynamic imaging are presented. The method used is an adaptation with several critical modifications of a keyholetype approach previously proposed but not implemented. The method was tested by imaging the events following injection of a contrast agent into a phantom, producing a series of dynamic image updates. It is demonstrated that, for this type of application, the SVD encoding technique adequately follows dynamic changes with even a small number of encodes. The result is compared qualitatively to that obtained by standard Fourier-based keyhole imaging and is shown to provide improved spatial resolution of dynamic events when updating with the same number of encodes.

Exercise induced esotropia.

A case of unusual intermittent esotropia and diplopia is reported. A 13-year-old boy experienced diplopia during vigorous exercise that resolved within 30 minutes after stopping the exercise. The symptoms had been present unchanged since age 6. Examination revealed orthophoria. After vigorous exercise an esotropia of 14 prism diopters in the distance developed, which gradually resolved over 30 minutes. Neurologic evaluation, CT scan, and magnetic resonance imaging scan have been normal. The symptoms have continued unchanged for 11 years. To my knowledge, no other similar case of exercise induced esotropia has been reported.

Traumatic retinoschisis in battered babies.

Five infants who were victims of physical abuse had extensive bilateral retinal hemorrhages on initial evaluation and subsequently developed signs of permanent retinal damage. None showed external evidence of trauma to the eyes. Vitreous hemorrhage developed after a delay of several days or more in three cases that were followed closely from the time of the traumatic incident. In several eyes, apparent intraretinal blood-filled cavities were seen acutely in the macular region and elsewhere. Late scarring of the macula typically had a cystic or crater-like configuration. Electroretinography showed loss or reduction of the positive B-wave with preservation of the negative A-wave in every case. We propose that splitting of the retina resulting from the direct mechanical effects of violent shaking was responsible for all of these findings.

Eye bobbing associated with jaw movement.

Two patients were treated for a previously unreported disorder believed to be related to Marcus Gunn jaw-winking. The first, a 9-month-old infant with left congenital blepharoptosis without jaw-winking and with normal ocular motility had an up and down movement of the left globe synchronous with nursing movements of the jaw. The second was a 5-year-old girl with left blepharoptosis, jaw-winking, and left double elevator palsy who had up and down movements of both the left upper lid and the left globe synchronous with chewing. The left globe movements were most prominent in the field of vertical action of the superior rectus muscle and persisted after levator excision and fascia lata sling procedures. The possible etiology of the Marcus Gunn jaw-winking phenomenon is discussed and related to our cases of eye bobbing. The eye bobbing probably is caused by abnormal innervation to the superior rectus muscle produced by jaw movements in a manner analogous to the abnormal stimulation of the levator muscle in jaw-winking. The similar embryologic development and innervation of the levator and superior rectus muscles add credence to this theory.

Endophthalmitis caused by an Erwinia species.

A 14-year-old boy developed exogenous endophthalmitis presumably caused by an Erwinia species. To our knowledge, this is the firs reported case of endophthalmitis caused by an Erwinia species, which has been considered pathogenic for only the last ten years. The endophthalmitis developed after a piece of wood penetrated the patient's sclera. After removal of the foreign body, the patient received intravitreally and subconjunctivally administered gentamicin sulfate, intramuscularly administered cephaloridine, and a short course of orally administered prednisone. The patient had clinical and visual improvement.