Book Review: Neuroimaging Clinics: Advanced Imaging in Ischemic and Hemorrhagic Stroke
Gemmete JJ, Wilseck ZM, guest ed. Mukherji SK, consulting ed. Neuroimaging Clinics: Advanced Imaging in Ischemic and Hemorrhagic Stroke. Theclinics.com; 2024;34(2): i–292; Online and print yearly $413.00
With the constantly changing protocols in imaging and treatment of cerebral ischemia, it is valuable to recognize and understand the newest concepts and their relevance to the evaluation of ischemic and hemorrhagic stroke. This issue of Neuroimaging Clinics (May 2024) fulfills that need.
Edited by Dr. Joseph Gemmete and Dr. Zachary Wilseck, who are both faculty members at the University of Michigan, this 292-page volume contains 10 chapters and has contributions from 36 authors from a number of different institutions in the US.
The first chapter, “CT Imaging/CT Angiography/CT Perfusion,” provides a review of these techniques primarily for stroke and is a good starting point for appreciation of material presented in following chapters. This 13-page chapter contains a concise summary of key items in the evaluation of stroke and presents the reader with proper imaging and definitions of terms used in the chapter. For CTA, protocols, image evaluation, and pitfalls are discussed. For CTP, protocols for obtaining high-quality perfusion studies along with postprocessing methods and a listing and explanation of 6 current software programs, among them RapidAI and Viz.ai, are included. From this explanation one clearly understands what is in use today. Most of the concepts in CTP are generally well known by neuroimagers, but it would have been worthwhile to have included some accepted numbers/ratios such as what is currently considered a favorable mismatch ratio or what is a good hyperperfusion index.
After a chapter on transcranial ultrasound in a neuro ICU (material here would be of most interest to neurointerventionalists), this issue then returns to acute ischemic stroke (AIS) and delayed cerebral ischemia (DCI) in the chapter on MR imaging techniques for AIS and DCI following SAH.
The next 2 chapters deal first with biomarkers in cerebral hemorrhagic stroke, with a discussion of secondary brain injury primarily thought to be due to increased tissue iron, and second with MR imaging of the wall of cerebral aneurysms and the assessment for potential rupture. While in most institutions these techniques for aneurysm wall characterization are not commonly used, the chapter does give the reader an insight into where this field may be headed and, importantly, what neuroimagers may be asked by their neurosurgical colleagues to look for in incidentally detected aneurysms and in clinically presenting aneurysms. The images are striking and point to the future. One minor criticism is that the references noted in the major table on histologic correlates (Table 1) do not all match the listed references in the bibliography.
The ensuing chapter on dual-energy CT deals with the physical principles in DECT, how images are generated, and examples of how this technique is used in a number of potentially confusing situations, such as distinguishing subarachnoid or intraparenchymal blood from retained contrast material using an iodine subtraction technique. The physics involved in 80 versus 140 kVp using either 1 or 2 tubes along with 2 detection layers of different sensitivity is explained.
Although infrequently used, the techniques for vessel wall imaging (Chapter 7) can be employed when one is looking at either atherosclerosis or inflammatory changes seen in vasculitis. The examples shown are adequate, but the window settings on a number of cases result in images that are dark, which detracts from the presentation. Protocol for this type of imaging is described, but it would have been preferable to have this information displayed in tabular form with all the technical factors included. Pitfalls and mimics are included at the end of the chapter. This chapter fits in nicely with the final chapter, which describes vessel wall characterization with a more quantitative approach to MR imaging. Here the advantages of the black-blood technique, relaxation methods on T1 and T2 sequences, DCE, and wall stress show the important advances that have been made in vascular imaging. This final chapter should be read in conjunction with Chapter 7 mentioned above.
To gain insight into advances in intraoperative imaging in vascular neurosurgery, one can read through the material in this next informative chapter. Among other items, descriptions of indocyanine green (ICG) angiography will be new information for most neuroimagers. Here, after exposure of the surgical field, ICG is utilized to detect fluorescence of small vessels that may be involved in a vascular malformation and allow follow-up ICG to show the pre- versus postocclusion of vessels. The images (which incidentally are quite remarkable) show just one aspect of the evolving techniques and advances in vascular neurosurgery.
While metabolic imaging is rarely used in the evaluation of acute ischemic stroke, the chapter on metabolic imaging in this disorder does convey the multiple molecular derangements that can be assessed by a number of techniques, including PET, hydrogen spectroscopy, sodium imaging, pH imaging, and oxygen imaging. Aside from describing what these techniques can theoretically accomplish, this material does give insight into the intraparenchymal chemical alterations in stroke.
Taken as a whole, this issue of Neuroimaging Clinics not only describes the state of the art in assessing stroke but also opens new vistas and ideas, some of which will or have recently become part of overall patient evaluation. Because stroke evaluation by imaging is one of the key parts of neuroimaging, this volume is to be considered an important addition to the radiology literature.
