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Peripheral gating and first-order flow compensation were compared for their ability to improve the quality of second-echo (echo time = 80 msec) brain images obtained with a T2-weighted spin-echo sequence. The contrast-to-noise ratios (C/Ns) for interfaces between brain and cerebrospinal fluid, gray and white matter, and lesion and white matter were measured; the C/N was highest for the combination of gating and flow compensation. This combination of motion compensation also reduced motion artifacts more than did either technique alone. Further improvement in C/N was sought by using a variable-bandwidth pulse sequence, which was compared to a conventional spin-echo sequence. The variable-bandwidth technique increased the C/N of the second-echo image by 27%. The combined use of gating, flow compensation, and the variable-bandwidth option produced high-resolution brain images with a single excitation and retained flexibility in number of sections, number of echoes, and echo times.

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Experimental allergic encephalomyelitis, a demyelinating disease with marked similarity to multiple sclerosis, was produced in two of 12 dogs. All dogs were studied with serial MR imaging. T1- and T2-weighted MR images were obtained both before and after IV Gd-DTPA. Multiple, new periventricular white matter demyelinating lesions were observed after each clinical episode of the disease. Like multiple sclerosis, the acute lesions of experimental allergic encephalomyelitis on T2-weighted MR images were indistinguishable from the older, more chronic lesions. However, after Gd-DTPA, there was bright paramagnetic enhancement of the acute lesions and, in one animal, no enhancement of the chronic lesions on T1-weighted MR images. At necropsy, the differences in the MR paramagnetic enhancement correlated well with the relative histologic age of the demyelinating lesions. Our results suggest that MR with Gd-DTPA may be used to differentiate acute, active demyelinating lesions from the more chronic, inactive lesions in this animal model.

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Evidence from computerized tomography (CT) suggests that schizophrenic patients may have smaller brains than normal subjects. Magnetic resonance imaging (MRI), which produces more clearly defined images than CT, was used to measure T1 and brain size of 24 schizophrenic and 24 normal subjects matched for age and sex but not for education. Two transverse images were obtained: slice 1 at the foramina of Monro and slice 2 at the widest part of the lateral ventricles. Adequate T1 instrumental reliability could not be demonstrated. Schizophrenic subjects had smaller right hemispheres (slice 1) and smaller frontal areas (slice 2) than normal subjects. However, when education was taken into account, only the left frontal area (slice 2) was smaller in schizophrenic than in normal subjects. Larger brain areas were associated with better cognitive test scores and fewer neurological signs. Cranial and body size were similar in both diagnostic groups.

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The subclavian vein is a commonly used venous access route. Percutaneous cannulation is associated with complications and malpositioning of the catheter. We studied the potential effect of various body positions on subclavian vein catheterization using gross anatomic dissection and magnetic resonance imaging. Findings show that traditional recommendations for patient positioning with the shoulders retracted and the head turned away can act to distort the subclavian vein anatomy and make successful cannulation more difficult. Positioning the patient flat with the head and shoulders in a neutral position is suggested.

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Computed tomography (CT) has provided a imaging modality by which the central pulmonary arteries can be studied noninvasively. CT provides cross-sectional images which accurately depict the pulmonary arteries and adjacent structures. Magnetic resonance (MR) imaging with its ability to image vessels without contrast media provides a potential truly noninvasive means of examining the pulmonary arteries. These modalities are well suited to evaluate pathology involving the central pulmonary arteries. Normal CT and MR anatomy is illustrated and discussed. The clinical presentation and appearance of pathological processes involving the pulmonary arteries are described.

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Magnetic resonance imaging of the temporomandibular joint (TMJ) was performed on two normal volunteer subjects and two symptomatic subjects using a 0.15 T resistive magnet. A spin echo pulse sequence with a TE of 38 ms and a TR of 500 ms was employed. The TMJ meniscus is a low signal structure, and the bilaminar zone behind it is a relatively high signal structure. In normal closed mouths, the demarcation between meniscus and bilaminar zone is located at the vertex position above the mandibular condyle. When the condyle translates, the posterior portion of the meniscus bulges into the joint space. Dislocated meniscus can be identified by a gray mass anterior to the condylar head. The joint space is filled with the higher signal of the bilaminar zone. In non-reducible dislocations, the meniscus remains anterior to the condylar head with opening of the mouth. Reduced dislocations appear similar to normal joints in the open mouth.

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Seven patients with angiographically proved cerebral venous angiomas were imaged by magnetic resonance. The venous angioma was identified in all cases. The most characteristic feature was an enlarged transcerebral draining vein (86%), followed by increased signal on T2-weighted images (57%) and decreased signal on T1-weighted images (40%) in adjacent parenchyma. Mass effect was absent in all cases. T2 imaging was more successful in showing the lesions than was T1 imaging.

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