Introduction to Magnetic Resonance Imaging for Neurologists (Neuroimaging 2016)

Educational Objectives

The goal of this lecture is to improve patient care through the appropriate and safe use of neuroimaging. After hearing and assimilating this lecture, the clinician will be better able to:

1. Select appropriate MRI sequences for imaging of patients with neurologic conditions.

Summary

Mechanism of MRI: MRI growing in importance because it provides characterization of molecules within tissue; spinning of each molecule creates small magnetic field; high-field magnet of scanner influences spin of molecules; energy absorbed by molecules from external magnetic field cannot be retained; pattern of subsequent release of absorbed energy allows distinction of different characteristics of tissues.

Imaging sequences: T1-weighted images — provide good distinction between fluid and brain tissue and between gray and white matter, and allow visualization of calcifications and fatty substances (ie, fatty substances appear white on images); used to detect space-occupying lesions and survey anatomy; T2-weighted images — can distinguish gray and white matter and display fluid; fluid appears white, while gray and white matter appears somewhat darker; when edema present, degree of whiteness influenced by, eg, protein content of CSF; T2-weighted images show distribution of water content; fluid-attenuated inversion recovery (FLAIR) sequence — has characteristics of T2-weighted image; water therefore detectable, but CSF dark and produces no signal, permitting distinction between water and tissue; more sensitive for detecting destruction of tissue caused by processes other than accumulation of water (eg, multiple sclerosis); diffusion-weighted imaging — reveals movement of water molecules and may distinguish acute vascular lesion from inflammatory process.

Optional sequences: Susceptibility-weighted imaging — especially sensitive for detecting breakdown of hemoglobin, and thus permits recognition of small areas of bleeding; important for evaluating amyloid angiopathy; perfusion-weighted images — useful in patients with acute stroke; contrast increases signal intensity of brain tissue; allows examiner to observe speed at which blood travels through brain tissue; delineates acute infarction and permits measurement of perfusion in patients with Alzheimer disease; evaluating perfusion of tumors permits detection of progression during therapy.

Interpretation: First, view T1-, T2-, and diffusion-weighted images; identify artifacts; determine whether imaging suggests tumors, vascular lesions, infections, or general degeneration; if patient has clinical symptoms and no findings on MRI, rule out inadequate spatial resolution and other technical issues, and consider lesions that may not be visible (eg, infarction of spinal cord, focus of seizure).

Readings

Radue EW, Weigel M, Wiest R, Urbach H. Introduction to magnetic resonance imaging for. Continuum (Minneap Minn) 2016;22(5 Neuroimaging).

Disclosures

For this program, the following was disclosed: Dr. Radue has served as a consultant for Neurologische und Psychiatrische Universitäts Klinik Basel, has received personal compensation for speaking engagements from Novartis AG and Sanofi Genzyme, and receives royalties from Springer-Verlag GmbH. Unlabeled Use of Products/Investigational Use Disclosure: Dr. Radue reports nothing to disclose. To view disclosures of planning committee members with relevant financial relationships, visit: audiodigest.org/continuumaudio/committee. All other members of the planning committee report nothing to disclose.

Acknowledgements

CME/CE INFO

Accreditation:

The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 0 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Audio Digest Foundation is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's (ANCC's) Commission on Accreditation. Audio Digest Foundation designates this activity for 0 CE contact hours.

Lecture ID:

CA051701

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.

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