The field of diagnostic neuroradiology has advanced considerably from its incipient use of skull radiography and, later, other important X-ray-based techniques, 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.
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