Site and Rate of Occlusive Disease in Cervicocerebral Arteries: A CT Angiography Study of 2209 Patients with Acute Ischemic Stroke

Fellows’ Journal Club

The authors used CTA to assess arterial stenosis and occlusion in an ischemic stroke population arriving at a tertiary stroke center within 24 hours of symptom onset to obtain a comprehensive picture of occlusive disease pattern. Extra- and intracranial pathology, defined as stenosis of ≥50% and occlusions, were registered and classified into 21 prespecified segments. In the 50,807 arterial segments available for revision, 1851 (3.6%) abnormal segments were in the ischemic (symptomatic) territory and another 408 (0.8%) were outside it (asymptomatic). In the 1211 patients with ischemic stroke imaged within 6 hours of symptom onset, 40.7% had symptomatic large, proximal occlusions. They conclude that CTA in patients with acute ischemic stroke shows large individual variations of occlusion sites and degrees. Approximately half of patients have no visible occlusive disease, and 40% imaged within 6 hours show large, proximal segment occlusions amenable to endovascular therapy.

A Multiparametric Model for Mapping Cellularity in Glioblastoma Using Radiographically Localized Biopsies

Editor’s Choice

Ninety-one localized biopsies were obtained from 36 patients with glioblastoma. Signal intensities corresponding to these samples were derived from T1-postcontrast subtraction, T2-FLAIR, and ADC sequences by using an automated coregistration algorithm. Cell density was calculated for each specimen by using an automated cell-counting algorithm. T2-FLAIR and ADC sequences were inversely correlated with cell density. T1-postcontrast subtraction was directly correlated with cell density. The authors conclude that the model illustrates a quantitative and significant relationship between MR signal and cell density. Applying this relationship over the entire tumor volume allows mapping of the intratumoral heterogeneity for both enhancing core and nonenhancing margins.

Journal Scan – This Month in Other Journals, May 2017

Wilson JR, Tetreault LA, Kim J, et al. State of the Art in Degenerative Cervical Myelopathy: An Update on Current Clinical Evidence. Neurosurgery. 2017;80(3S):S33-S45. doi:10.1093/neuros/nyw083.

Degenerative cervical myelopathy (DCM) is used to describe myelopathy resulting from degenerative pathology in the cervical spine including spondylosis, degenerative disc disease, ossification of the posterior longitudinal ligament (OPLL), and ossification of the ligamentum flavum. The authors provide a wide-ranging overview of the state of the art in degenerative cervical myelopathy, with a focus on updating the spine surgeon on the current evidence surrounding pathophysiology, natural history, imaging, outcome measures, and outcome prediction tools. They also provide an overview of the evidence for surgical vs. nonoperative management, and a summary of the literature regarding the most commonly used approaches to the cervical spine.

The pathophysiology of DCM includes both static and dynamic factors. Static factors result from congenital stenosis or acquired stenosis secondary to spondylosis and disc degeneration.Dynamic factors relate to exacerbation of spinal cord compression seen with physiological and, in the setting of degenerative subluxation, pathological motion of the cervical spine. In addition to physical compression, there is a reduction in blood supply leading to ischemia within the cord.  Pathological features of DCM include gray and white matter degeneration, anterior horn cell loss, cystic cavitation, and Wallerian degeneration of the posterior columns adjacent to the site of compression.

There is also likely a secondary cascade of neuroinflammation consisting of microglia activation and macrophage recruitment which occurs at the site of mechanical compression within the spinal cord. In the noncompressed nonmyelopathic spinal cord, the blood-spinal cord-barrier is isolated from the peripheral immune system; however, chronic compression renders the cord susceptible to cell infiltration that may be involved in

MR Neuroimaging: Brain, Spine, Peripheral Nerves

Forsting M, Jansen O. MR Neuroimaging: Brain, Spine, Peripheral Nerves. Thieme; 2017; 600 pp; 1399 ill; $224.99

Cover of Forsting and Jansen

MR Neuroimaging: Brain, Spine, Peripheral Nerves by Michael Forsting and Olav Jansen is an English translation of the second German edition of MRT des Zentralnervensystems, which was published in 2014. This 600-page hardcover book intends to serve as a reference manual for neuroimaging interpretation.

As suggested by the title, the book is divided into 3 sections: 1) brain, 2) spinal cord, and 3) peripheral nervous system.

The first 2 sections have an introductory chapter on anatomy. MRI appearance of different structures is the focus, with several illustrations that lay a good foundation for the material to come. The chapters conclude with an abridged description of normal variants, which, if more inclusive, could have further benefitted a practitioner less familiar with neuroimaging.

The chapter on brain anatomy is followed by 9 others covering a broad range of common and unusual conditions. Pediatric neuroimaging is dealt with in a dedicated chapter.

Imaging of the spine is covered in 6 further chapters.

The third section includes a concise discussion of magnetic resonance neurography and neuropathies in the final 8 pages.

Most pathological conditions are described under the subheadings of epidemiology, clinical manifestations and treatment, pathology, MRI findings, and differential diagnosis. This systematic approach, paired with a straightforward index, makes it very easy to navigate the text.

The highlight of this book is the excellent quality of the images it uses to depict the pathology described. Multiple sequences and planes are routinely used to characterize the findings. The annotations are descriptive and easily comprehensible. The authors often discuss the best techniques and ideal sequences for optimal evaluation of imaging findings. Most pages are studded with boxes labeled “Note,” “Tips and Tricks,” or “Pitfall” and highlighted …

Imaging Characteristics of Pediatric Diffuse Midline Gliomas with Histone H3 K27M Mutation

Fellows’ Journal Club

The 2016 WHO Classification of Tumors of the Central Nervous System includes “diffuse midline glioma with histone H3 K27M mutation” as a new diagnostic entity. This study of 33 patients with diffuse midline gliomas found histone H3 K27M mutation was present in 24 patients (72.7%) and absent in 9 (27.3%). The location was the thalamus in 27.3%; the pons in 42.4%; within the vermis/fourth ventricle in 15%; and the spinal cord in 6%. The radiographic features of diffuse midline gliomas with histone H3 K27M mutation were highly variable, ranging from expansile masses without enhancement or necrosis with large areas of surrounding infiltrative growth to peripherally enhancing masses with central necrosis with significant mass effect.

Feasibility of Flat Panel Detector CT in Perfusion Assessment of Brain Arteriovenous Malformations: Initial Clinical Experience

Editor’s Choice

Five patients with brain arteriovenous malformations were studied with flat panel detector CT, DSC-MR imaging, and vessel-encoded pseudocontinuous arterial spin-labeling. Flat panel detector CT, which was originally thought to measure blood volume, correlated more closely with ASL-CBF and DSC-CBF than with DSC-CBV. Flat panel detector CT perfusion depends on the time point chosen for data collection, which is triggered early in patients with AVMs. This finding, in combination with high data variability, makes flat panel detector CT inappropriate for perfusion assessment in brain AVMs.

Elastography: A Practical Approach

Barr RG. Elastography: A Practical Approach. Thieme; 2016; 200 pp; 400 ill; $119.00

Cover of Barr

This comprehensive book encompasses the principles and techniques used in performing elastography under ultrasound guidance. The stiffness or softness of tissue measured by this innovative technique aids radiologists and clinicians in diagnosing various disease conditions, including cancer and inflammation. The changes (including desmoplastic reaction) induced in tissues due to these pathologic processes alter the compressibility and deformation of the surrounding stroma, which are what elastography measures. Given that stiff lesions are more likely to be malignant, the implications of this application can be huge in terms of lesion characterization and management.

The book begins with an introduction to elastography, including shear-wave and strain; the former provides a quantitative assessment and the latter a qualitative assessment of elastography. The physics and technical background are explained in simple and reader-friendly terms. The techniques required to obtain optimal images with the various methods are discussed in a language that is easy to understand. The text is accurate and concise. Case studies that demonstrate the targeted use of elastographic findings by specific pathologic processes are discussed. Important points, such as precompression, descriptions of the imaging patterns, limitations, and artifacts, are covered for ultrasound machines provided by common vendors in the market. There are many illustrations and diagrams to enhance and enrich readers’ experience. The images are appropriately labeled, helpful, and easily interpretable. The references are comprehensive, current, accurate, and obtained from scholarly publications. Two of the unique features of this book are the “tips and tricks” and the “artifacts and pitfalls” sections at the end of each chapter.

The chapters are written by leading authorities around the world on the subject of elastography and its applications in various organ systems of the body. The chapters include step-by-step descriptions of the …

Questions and Answers in MRI

Elster AD. Questions and answers in MRI. MRI Questions Web site. http://mriquestions.com/index.html.

For radiologists who have devoted their lives and education to medical diagnosis, trying to grasp the advanced physics behind modern MR imaging is like a foray into another world with a completely exotic language. Resources and texts are numerous, but many are written by those who primarily have a formal physics education and write in a language unfamiliar to those without the same background. Out of all the available resources, one shining beacon lights the path to understanding.

With his website mriquestions.com, Dr. Allen Elster, MD, FACR translates the language of MR imaging, beautifully explains complex concepts, and simply transforms the foreign into the familiar. Whenever I have a question about the physics of MR imaging as it relates to my daily radiology practice, I consult the website and almost always have an answer within 5 minutes of reading. While covering numerous topics in MR imaging, Dr. Elster strives to fill each article with practical information that is applicable to optimizing patient imaging. This is why his website stands out among all the others; he is able to take the complexity of MR imaging and distill the information to that which is most valuable for the daily practicing radiologist. Included at the end of each page are references, many of which are interesting historic and landmark papers in the development of MR imaging.

The site design is beautifully practical and it often feels as though he has anticipated the next questions of the reader and placed links to relevant information. All content is free to use and frequently updated with new sections.

The next time a question arises in the reading room about the principles behind an MR imaging sequence, the cause of an artifact, or the …

Evaluation of Collaterals and Clot Burden Using Time-Resolved C-Arm Conebeam CT Angiography in the Angiography Suite: A Feasibility Study

Fellows’ Journal Club

Ten C-arm conebeam CT perfusion datasets from 10 subjects with acute ischemic stroke acquired before endovascular treatment were retrospectively processed to generate time-resolved conebeam CTA. From time-resolved conebeam CTA, 2 experienced readers evaluated the clot burden and collateral flow in consensus by using previously reported scoring systems and assessed the clinical value of this novel imaging technique. The 2 readers agreed that time-revolved C-arm conebeam CTA was the preferred method for evaluating the clot burden and collateral flow compared with other conventional imaging methods. They conclude that comprehensive evaluations of clot burden and collateral flow are feasible by using time-resolved C-arm conebeam CTA data acquired in the angiography suite.

MR Imaging of Individual Perfusion Reorganization Using Superselective Pseudocontinuous Arterial Spin-Labeling in Patients with Complex Extracranial Steno-Occlusive Disease

Editor’s Choice

Super selective pseudocontinuous arterial spin-labeling with a circular labeling spot enabling selective vessel labeling was added to routine imaging in a prospective pilot study in 50 patients with extracranial steno-occlusive disease. The detected vessel occlusions/stenoses and perfusion patterns corresponded between cerebral DSA and super selective pseudocontinuous ASL maps in all cases. Perfusion deficits on DSC-CBF maps significantly correlated with those on super selective pseudocontinuous ASL maps. The authors conclude that super selective pseudocontinuous ASL is a robust technique for regional brain perfusion imaging, suitable for the noninvasive diagnostics of individual patient perfusion patterns.