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
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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)