Neuroradiology Review Series Cover Essay

Neurosurgery, Sep 2016

Saindane, Amit M.

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Neuroradiology Review Series Cover Essay

Neuroradiology Review Series Cover Essay Amit M. Saindane 0 0 Department of Radiology and Imaging Sciences Emory University School of Medicine Atlanta , Georgia - Tuse of skull radiography and, later, other important X-ray-based techniques, he field of diagnostic neuroradiology has advanced considerably from its incipient including pneumoencephalography, contrast myelography, and arteriography to diagnose patients with neurological disorders and plan for neurosurgical intervention. The advent of X-ray computed tomography (CT) in the 1970s revolutionized the ability to non-invasively diagnose neurosurgical emergencies, such as intracranial hemorrhage, and to assess mass lesions pre-operatively with greater specificity and confidence. Despite the tremendous progress in the practice of diagnostic neuroradiology due to CT imaging, it was not until the arrival of magnetic resonance imaging (MRI) in the early 1980s that the greatest advances in non-invasive imaging were realized. Early MRI scanners took inordinately long by today’s standards to generate each axial image, yet simply the ability to characterize normal and abnormal tissues by their T1 and T2 properties vastly improved our understanding of numerous clinical diagnoses. The past 3 decades have brought rapid improvements in both the hardware and pulse sequences used for generating images using MRI. Scanner systems have evolved from the early low-magnetic field systems to higher main magnetic field strength (1.5T and 3.0T) superconducting units with greater signal-to-noise and field homogeneity. Scanner gradient systems impact performance capabilities of spatial resolution and imaging speed and have become faster and stronger facilitating new imaging techniques. Radiofrequency systems have improved profoundly with increases in the number and density of channels for receiving signal, allowing for greater signal-to-noise. As importantly, numerous advances in the technology of image acquisition and image processing with novel pulse-sequence programming strategies have revolutionized the generation of MR images. All of these advances have driven greater spatial resolution, faster temporal resolution for dynamic evaluations, and the ability to probe various facets of physiology non-invasively using MRI. Brain perfusion, water diffusion, blood flow, cerebrospinal fluid (CSF) dynamics, and indirect measures of neuronal activation can all now be routinely evaluated using clinical MRI techniques. While the imaging technologies used clinically have evolved over the decades, robust communication and a high level of interaction between neurosurgeons and neuroradiologists remain a constant in the delivery of effective patient care using neuroimaging. It is through these interactions that the neuroradiologist achieves an understanding of what is truly important for the neurosurgeon, and how the neurosurgeon best utilizes the neuroradiologist to develop optimal strategies for imaging specific diagnoses based on the merits and limitations of various techniques, improving diagnostic accuracy and aiding in pre-surgical planning. It is in this spirit of delivering to the neurosurgical community what current clinical imaging can accomplish for common and important neurosurgical diagnoses that this series, Neuroradiology Reviews, was conceived. This series highlights approaches to relevant diagnoses, clinically useful imaging techniques, and recommended diagnostic imaging workups. While some advanced techniques will be covered, the focus is not on esoteric diagnoses or experimental modalities, but rather what will be most useful for the neurosurgeon to understand in clinical practice. This issue’s cover highlights some of the imaging techniques in use today that provide noninvasive information for the care of neurosurgical patients. The central image is diffusion tensor imaging (DTI) tractography, based on the diffusion of water molecules and their interaction with white matter fiber tracts; the fundamentals of the technique are found in diffusion weighted imaging (DWI), which revolutionized stroke imaging. DTI fiber tractography currently in use for pre-surgical planning affords the ability to assess the position of major fiber tracts relative to a lesion. The image on the upper right is a perfusion map from a CT perfusion examination and demonstrates an area of diminished perfusion in the right middle cerebral artery distribution in a patient with acute left hemiparesis and a large territorial infarction. CT- and MRI-based perfusion techniques offer routine characterization of the hemodynamic properties of ischemic and mass lesions. On the lower left is a maximum intensity projection (MIP) of the circle of Willis from a 3D time-of-flight non-contrast MR angiogram. Advances in MRI technology have pushed the spatial resolution of this technique to facilitate detection of small aneurysms and demonstration of other pathology without the need for ionizing radiation or int (...truncated)


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Saindane, Amit M.. Neuroradiology Review Series Cover Essay, Neurosurgery, 2016, pp. 313-314, Volume 79, Issue 3, DOI: 10.1227/NEU.0000000000001337