Magnetic resonance angioplasty for prepharyngoplasty assessment in velocardiofacial syndrome.

OBJECTIVE: The assessment of the posterior pharyngeal vasculature in velocardiofacial syndrome has been traditionally based on endoscopic visualization of pulsations or conventional angiography. This case report describes the utility of presurgical imaging with magnetic resonance angiography (MRA) prior to performing pharyngoplasty. CONCLUSION: The use of the MRA data presurgically is an effective way to prevent bleeding complications during pharyngoplasty.

MR compatibility of Guglielmi detachable coils.

Guglielmi detachable endovascular coils were evaluated for magnetic resonance (MR) compatability at 1.5 T. Tests to determine magnetic field attraction (deflection angle and Petri-dish displacement methods), heating (infrared thermometry), and artifact production (beef phantom) were performed. Adverse event data were reviewed for MR imaging in 142 patients in whom the coils were implanted to treat intracranial aneurysms. There was no magnetic field attraction, the temperature increased 0.2 degrees C, and only a mild signal void relative to the size and shape of the coil was produced. All patients underwent MR imaging without incident. The Guglielmi coils are compatible with MR imaging at static magnetic field strengths of 1.5 T or less.

Nuclear magnetic resonance imaging and spectroscopy in experimental brain edema in a rat model.

Many aspects of the use of high-resolution nuclear magnetic resonance (NMR) imaging in the examination of brain edema have not been fully explored. These include the quantitation of edema fluid, the ability to distinguish between various types of edema, and the extent to which tissue changes other than a change in water content can affect NMR relaxation times. The authors have compared NMR relaxation times obtained by both in vivo magnetic resonance imaging (MRI) and in vitro NMR spectroscopy of brain-tissue samples from young adult rats with cold lesions, fluid-percussion injury, hypoxic-ischemic injury, bacterial cerebritis, and cerebral tumor. Changes in relaxation times were compared with changes in brain water content, cerebral blood volume, and the results of histological examination. In general, both in vivo and in vitro longitudinal relaxation times (T1) and transverse relaxation times (T2) were prolonged in the injured hemispheres of all experimental groups. Water content of tissue from the injured hemispheres was increased in all groups. A linear correlation between T2 (but not T1) and water content was found. Changes in the values of T1 and T2 could be used to distinguish tumor from cold-injured tissue. Cerebral blood volume was reduced in the injured hemispheres and correlated inversely with prolongation of T1 and T2. The results of this study suggest that, in a clinical setting, prolongation of T2 is a better indicator of increased water content than prolongation of T1, yet quantitation of cerebral edema based solely upon prolongation of in vivo or in vitro T1 and T2 should be undertaken with caution.

Nuclear magnetic resonance imaging. Applications in the diagnosis of cerebrospinal diseases.

The applications of the important new diagnostic modality, nuclear magnetic resonance (NMR) imaging (or MRI), to the diagnosis of diseases of the central nervous system (CNS) are discussed. Specific examples of NMR imaging of cerebral and spinal tumours, infarction, demyelination and subdural haematomas are illustrated and compared with corresponding CT scans. The greater sensitivity of NMR, together with its ability to image in axial, coronal and sagittal planes, suggests that NMR will replace CT for many diagnostic investigations of the CNS.

Nuclear magnetic resonance imaging. Basic principles.

The physical principles underlying nuclear magnetic resonance (NMR) imaging (also known as MRI) are described. NMR is an important new non-invasive imaging modality, which does not use ionizing radiation. Its ability to map hydrogen ion distribution, and to detect two intrinsic parameters ("relaxation times") which are indicative of the immediate chemical environment of the hydrogen nuclei, results in images of superior spatial detail in the brain and spinal cord. The potential of this technique for quantitating blood flow and for the exact identification of tissues is discussed.