The long blood circulating time and the progressive macrophage uptake in inflammatory tissues of ultrasmall superparamagnetic iron oxide (USPIO) particles are 2 properties of major importance for magnetic resonance imaging (MRI) pathologic tissue characterization. This article reviews the proof of principle of applications such as imaging of carotid atherosclerotic plaque, stroke, brain tumor characterization, or multiple sclerosis. In the human carotid artery, USPIO accumulation in activated macrophages induced a focal drop in signal intensity compared with preinfusion MRI. The USPIO signal alterations observed in ischemic areas of stroke patients is probably related to the visualization of inflammatory macrophage recruitment into human brain infarction since animal experiments in such models demonstrated the internalization of USPIO into the macrophages localized in these areas. In brain tumors, USPIO particles which do not pass the ruptured blood-brain barrier at early times postinjection can be used to assess tumoral microvascular heterogeneity. Twenty-four hours after injection, when the cellular phase of USPIO takes place, the USPIO tumoral contrast enhancement was higher in high-grade than in low-grade tumors. Several experimental studies and a pilot multiple sclerosis clinical trial in 10 patients have shown that USPIO contrast agents can reveal the presence of inflammatory multiple sclerosis lesions. The enhancement with USPIO does not completely overlap with the gadolinium chelate enhancement. While the proof of concept that USPIO can visualize macrophage infiltrations has been confirmed in animals and patients in several applications (carotid atherosclerotic lesions, stroke, brain tumors and multiple sclerosis), larger prospective clinical studies are needed to demonstrate the clinical benefit of using USPIO as an MRI in vivo surrogate marker for brain inflammatory diseases.
Patients with intracranial tumors (gliomas) were examined by means of localized water-suppressed 1H NMR single volume spectroscopy and spectroscopic imaging. The 1H NMR spectra of the tumors exhibit signal intensities of the N-acetyl aspartate, choline compounds, and creatine plus phosphocreatine resonance lines that are different from the corresponding intensities observed on normal brain tissue. Also, for 6 out of the 10 patients examined so far, lactate resonance lines were detected in the tumor spectra. For one patient, abnormal 1H NMR spectra were obtained of a hemisphere which appeared normal with 1H NMR imaging. Metabolic heterogeneity of the tumorous regions could be demonstrated with 1H NMR spectroscopic imaging, using a spatial resolution in the order of 1 cm. These results suggest a spectrum of metabolic observations that may ultimately provide an important means for characterizing brain tumors.
BACKGROUND AND PURPOSE:This study aimed to investigate brain maturation along gestational age with diffusion tensor imaging in healthy preterm and term neonates. Therefore, a voxel-based study of fractional anisotropy (FA) and mean diffusivity (D av ) was performed to reveal the brain regions experiencing microstructural changes with age. With tractography, the authors intended to identify which fiber tracts were included in these significant voxels.
Between January 1984 and December 1990. 65 intramedullary spinal cord tumors were diagnosed and operated on. In this series, all patients underwent magnetic resonance imaging investigations and were operated on with the Cavitron ultrasonic surgical aspirator whenever necessary. Major surgical difficulties have been found in patients previously treated by radiotherapy with or without biopsy. We found magnetic resonance imaging to be a highly sensitive imaging procedure and the method of choice for visualizing tumors within the spinal cord. Nevertheless, accurate diagnosis may only be suggested by magnetic resonance imaging, rather than made definitively. Surgery is necessary in every case in order to obtain a definite diagnosis. Radical surgery can be performed when a plane exists between the tumor and the normal spinal cord: biopsy or debulking with the Cavitron ultrasonic surgical aspirator should be performed when the tumor is infiltrative. We have performed 33 so-called total resections, 22 partial resections, and 10 biopsies, among which 5 were performed on lipomas. Surgical results were assessed at 3 months after surgery, showing 35 improvements (53%), 24 stabilizations (37%), and 6 deteriorations (10%).
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