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Editorial |
1 From the Department of Radiology, Division of Neuroradiology, University of Pennsylvania School of Medicine, Hospital of the University of Pennsylvania, 3400 Spruce St, Philadelphia, PA 19104. Received August 11, 2006; accepted August 14. Address correspondence to the author (e-mail: laurie.loevner{at}uphs.upenn.edu).
It was just a little over a decade ago that I completed my training in neuroradiology. In just 10 years, the subspecialty has reinvented itself, and there is no end in sight. Advances in technology, informatics, and, most important, the basic and clinical sciences emerge at a rate that is difficult to fathom. It was just about 6 years ago that I was sitting in front of an alternator, with my "pedal-to-the-metal," watching hung films roll by while I dictated into a system where the radiologic verbiage would later be transcribed into a written report that would be available in 24–48 hours. Today, we use voice recognition software as we read images from a sophisticated PACS (picture archiving and communication system) in "film-less" imaging departments. Computer networking allows thousands of images to be transmitted in seconds and an instant review of images side by side with older images when they exist. There are no issues of inadequate windowing or of critical anatomy or abnormalities being "cropped" off the images. And I definitely do not miss those painful "paper cuts" that were a part of daily life when we were hanging films. As we look at almost real-time computed tomographic (CT) and magnetic resonance (MR) images, we dictate into a voice recognition system by using talk technology that we sometimes jokingly refer to as "type tech." But all joking aside, this technology has substantially affected patient care and throughput, because it allows our important finalized radiologic reports to be available to our referring clinical colleagues in minutes to hours, rather than days. In addition, our filmless imaging departments are in the process of becoming "paperless," as the procedure requisitions are scanned into the hospital information system for electronic posterity.
Ten years ago, 1.5-T MR imaging systems were becoming routine (so was the use of gadolinium-based contrast material), and a brain study took approximately 45 minutes to perform. Today, at some institutions, much of the brain imaging is performed on 3.0-T systems, and a standard study can be performed in 25 minutes. Ten years ago, there was no such thing as fluid-attenuated inversion recovery (FLAIR), a pulse sequence that is now routine and allows instant detection of brain lesions previously difficult to detect, especially those along brain–cerebral spinal fluid interfaces, where this sequence makes lesion discrimination from adjacent cerebral spinal fluid effortless. There was no diffusion-weighted imaging, a technique that has revolutionized our understanding of and ability to accurately determine the age of strokes, resulting in better and more expedient medical and interventional management. These techniques are just a few of numerous pulse sequences that have been developed and are now a part of our daily practice. I remember tedious hours (sometimes it felt like days) performing conventional diagnostic angiography to look for atherosclerotic disease in the carotid arteries, vascular injuries in the head and neck, or unruptured intracranial aneurysms. Today, we review two- and three-dimensional MR and CT angiograms produced noninvasively and in minutes with computer-assisted reconstruction algorithms that create images that are almost like looking at the "real thing." In the majority of cases, conventional angiography is used only before an interventional procedure, whether it be "coiling" an aneurysm, embolizing an arteriovenous malformation, or placing a stent. Myelography has been replaced with high-resolution noninvasive spine MR imaging in most cases, with myelography reserved for special circumstances, such as in patients with contraindications to MR imaging.
With the invaluable assistance of RadioGraphics panelists and reviewers from all over the world, we have selected articles for this monograph that illustrate just a few of the clinical (and research) applications of emerging technologies in neuroradiology. The authors come from numerous continents and represent a cross section of academic and private practice neuroradiology groups all over the world. The articles are divided into four major groups: vascular imaging, spine imaging and interventions, head and neck imaging, and state-of-the-art imaging of the central nervous system. The emphasis on noninvasive vascular imaging is timely, given the rapid explosion of CT and MR vascular imaging techniques applied to every organ system. These articles represent the cutting edge of neuroradiology as it is practiced today and give us a small taste of what is coming tomorrow. Topics addressed range from applications of CT angiography and MR angiography to assess cerebral venous thrombosis and stroke, to imaging vascular conditions of the artery of Adamkiewicz. Diffusion-weighted MR imaging is discussed in detail, including clinical applications, scalar diffusion-weighted imaging, diffusion-tensor imaging, and beyond. Applications of multi-detector CT are addressed, from examining the patient with orthopedic spinal hardware to exploring the role of 64-detector and three-dimensional CT in the evaluation of temporal bone anatomy and disease. Other articles explore use of advanced imaging techniques to look at clinical conditions that affect difficult anatomic regions such as the brachial plexus or to evaluate the more intricate details of brain tumors.
Where will we be in 10 years? Perhaps in cyberspace! Functional and spectroscopic imaging will be used for the spinal cord. CT angiography and MR angiography will replace diagnostic catheter angiography for the assessment of spinal vascular disease. I see CT angiography (possibly with 256-detector scanners) as being the mainstay technology for evaluating every blood vessel in the body. Imaging will occupy operating rooms, with much more use of intraoperative imaging, and 50% of the neurosurgical and head and neck procedures will use neuroradiologic guidance. Image fusion, combining data sets from positron emission tomography (PET), CT, conventional MR imaging, functional MR imaging, and diffusion-tensor imaging, will provide such eloquent merging of anatomic and functional information that surgical times will be cut in half and so will be recovery periods and hospital stays. The neuroradiologic information provided to our surgical colleagues will help reduce morbidity and neurologic deficits from surgical procedures. Fusion of PET with MR imaging will significantly contribute to planning for surgery to treat head and neck disorders, especially cancer and skull base disease. Surgical procedures will be modified to further improve speech conservation, reduce cosmetic deformity, and lower operative time. There will be more ultrasound- and CT-guided ablative procedures, especially for but not limited to neoplastic disease including intracranial lesions, and there will be monitoring by high-field-strength open MR imaging systems. In less than 20 years, endovascular MR angiography and intraoperative MR imaging for even more invasive procedures will be well under way. Interventional neuroradiologists will be placing drug-infusing stents. They may be using catheter-guided lasers to "melt" atherosclerotic plaques, instilling materials other than glue to ablate arteriovenous malformations, and injecting aneurysms with a substance rather than packing them with bulky coils. Viral vectors and other therapeutic agents will be delivered directly into the substance of tumors through a catheter placed with imaging guidance. They may also be using radiofrequency ablation to treat brain tumors.
In diagnostic imaging, we will see a shift to higher and higher field strengths, from 3.0 T to 7.0 T and maybe 10-T MR imaging systems, with which we will routinely look at the layers of the cortex and the individual tracts of the central nervous system. PET-MR imaging machines will be in use. We will be merging PET images obtained with a whole new set of radionuclide molecules and ultra high-field-strength MR images such that we can precisely depict tumor hypoxia and vascularity. Optical imaging at such wavelengths as infrared will be used more routinely to image tumor physiology and hypoxia. Molecular imaging will move toward genetic imaging, allowing "personalized" medicine. We will be able to label genes such that a patient’s genetic profile will determine the screening tests needed, based on the genetically predicted risk. Superparamagnetic iron oxide agents will be used as contrast material for MR imaging, and iron oxide particles will be used for in vivo tracking.
With regard to image acquisition, whole-body MR imaging will take just a few minutes to perform, and multiplanar image reconstruction of regions of interest (eg, the brain) will be produced. Massive data sets will be processed rapidly online rather than being transferred to offline workstations as they are now. This will lead to information overload for the poor neuroradiologists and their information technology brethren; however, artificial intelligence will help in the interpretation of these enormous image sets. In 10 years from now, while we may not have cured or prevented very much, we will detect many diseases much earlier, and such preclinical detection may allow cure. What will be the cost of such screening? Well, that is another editorial.
I wish to express my deepest appreciation to Bill Olmsted for his invaluable insight, wisdom, and expert guidance. I am also indebted to the amazing staff of RadioGraphics, whom I am certain had a few sleepless nights and gained more than a few gray hairs while assisting me with pulling this monograph together. There are so many colleagues and friends to thank—you know who you are—and I owe my family "big time" for their support and understanding. Lastly, I would like especially to thank you, the readers of this journal, for your interest, support, and continual quest to understand and apply the advancements in neuroradiology.
Editor’s Note.—This year’s October special issue is the eighth in the series of annual monographs on a subspecialty topic in imaging. The monograph series in RadioGraphics is extremely important to the mission of the Journal: providing quality education for radiologists in all subspecialties of diagnostic imaging. Dr Laurie Loevner, as this year’s guest editor, and her authors, panelists, and reviewers have done a superior job in giving us an overview of neuroradiology, including a review of its state-of-the-art techniques and future directions. These two important aspects of education in radiology remain the major focus of the yearly monograph and the Journal. They are especially apparent in Dr Loevner’s excellent editorial, which covers the history of the past 10 years in neuroradiology and speculates on the not-too-distant future.
Neuroradiology is a rapidly evolving subspecialty that is crucial to patient care and to the specialty of diagnostic imaging. Excellent educational content such as that found in this monograph gives us all an understanding of the status of the subspecialty and its future directions. I am indebted to Dr Loevner for an outstanding job as guest editor and appreciate her perpetual passion for excellence that is very much apparent in this special issue of the Journal.—WILLIAM W. OLMSTED, MD
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