REVIEW ARTICLE
Myocardial Tissue Characterization With Magnetic Resonance Imaging Vishal Sharma, MD,* Sukumaran Binukrishnan, MD,*w U. Joseph Schoepf, MD,z and Balazs Ruzsics, MD, PhD*
Abstract: The availability of an accurate, noninvasive method using cardiac magnetic resonance imaging (MRI) to distinguish microscopic myocardial tissue changes at a macroscopic scale is well established. High-resolution in vivo monitoring of different pathologic tissue changes in the heart is a useful clinical tool for assessing the nature and extent of cardiac pathology. Cardiac MRI utilizes myocardial signal characteristics based on relaxation parameters such as T1, T2, and T2 star values. Identifying changes in relaxation time enables the detection of distinctive myocardial diseases such as cardiomyopathies and ischemic myocardial injury. The presented state-of-the-art review paper serves the purpose of introducing and summarizing MRI capability of tissue characterization in present clinical practice. Key Words: tissue characterization, cardiac magnetic resonance imaging, T1-weighted imaging, T2-weighted imaging
(J Thorac Imaging 2014;29:318–330)
T
he use of pulse sequences with cardiac magnetic resonance imaging (CMRI) enables radiologists to characterize tissue changes in the heart that can reflect myocardial disease. Tissue characterization can be useful to identify several different myocardial diseases including cardiomyopathies and infracted and infiltrative myocardial tissue changes. The most widely used techniques are precontrast T1-weighted imaging, postcontrast T1-weighted delayed enhancement (DE) imaging, and precontrast T2weighted imaging. Precontrast T1-weighted and T2-weighted imaging sequences are often acquired with and without fat and water suppression. Postcontrast images are acquired 5 minutes (early) and 10 minutes (delayed) after gadoliniumdiethylene triamine pentaacetic acid (Gd-DTPA) contrast injection (DE) (Table 1).
TISSUE CHARACTERIZATION BASED ON MRI SIGNAL CHARACTERISTICS Cardiac T1 Signal Characteristics Both spin and gradient echo (GRE) sequences can be used to identify myocardial T1-weighted signal intensity From the *Department of Cardiology, Royal Liverpool and Broadgreen University Hospitals; wDepartment of Radiology, Liverpool Heart and Chest Hospital, Liverpool, UK; and zDepartment of Radiology and Radiological Sciences, Medical University of South Carolina, Charleston, SC. U.J.S., is a consultant of Bayer and Siemens, has grant support from Bayer, GE, Siemens, Bracco, Medrad. All the other authors declare no conflict of interest. Reprints: Balazs Ruzsics, MD, PhD, Department of Cardiology, Royal Liverpool and Broadgreen University Hospitals, Prescot Street, Link 7Z, Liverpool L7 8XP, UK (e-mail: balazs.ruzsics@ rlbuht.nhs.uk). Copyright r 2013 by Lippincott Williams & Wilkins
318 | www.thoracicimaging.com
changes. Usually, T1-weighted images provide anatomic evaluation of the myocardium and the great vessels. To improve visualization and overall contrast to noise ratio, black-blood images are often desired. Blood suppression can be achieved with spin echo–based sequences, and bright blood images are usually acquired with gradient or spoiled GRE sequences. From a practical point of view, it is worthy to note that the effect of electrocardiogram (ECG)-gated T1weighted sequences depends on the heart rate; if the heart rate is slow the T1 effect can be reduced [because of increased repetition time (TR) between radiofrequency (RF) pulses]. Echo time (TE) needs to be the shortest, usually
Myocardial Tissue Characterization With Magnetic Resonance Imaging Vishal Sharma, MD,* Sukumaran Binukrishnan, MD,*w U. Joseph Schoepf, MD,z and Balazs Ruzsics, MD, PhD*
Abstract: The availability of an accurate, noninvasive method using cardiac magnetic resonance imaging (MRI) to distinguish microscopic myocardial tissue changes at a macroscopic scale is well established. High-resolution in vivo monitoring of different pathologic tissue changes in the heart is a useful clinical tool for assessing the nature and extent of cardiac pathology. Cardiac MRI utilizes myocardial signal characteristics based on relaxation parameters such as T1, T2, and T2 star values. Identifying changes in relaxation time enables the detection of distinctive myocardial diseases such as cardiomyopathies and ischemic myocardial injury. The presented state-of-the-art review paper serves the purpose of introducing and summarizing MRI capability of tissue characterization in present clinical practice. Key Words: tissue characterization, cardiac magnetic resonance imaging, T1-weighted imaging, T2-weighted imaging
(J Thorac Imaging 2014;29:318–330)
T
he use of pulse sequences with cardiac magnetic resonance imaging (CMRI) enables radiologists to characterize tissue changes in the heart that can reflect myocardial disease. Tissue characterization can be useful to identify several different myocardial diseases including cardiomyopathies and infracted and infiltrative myocardial tissue changes. The most widely used techniques are precontrast T1-weighted imaging, postcontrast T1-weighted delayed enhancement (DE) imaging, and precontrast T2weighted imaging. Precontrast T1-weighted and T2-weighted imaging sequences are often acquired with and without fat and water suppression. Postcontrast images are acquired 5 minutes (early) and 10 minutes (delayed) after gadoliniumdiethylene triamine pentaacetic acid (Gd-DTPA) contrast injection (DE) (Table 1).
TISSUE CHARACTERIZATION BASED ON MRI SIGNAL CHARACTERISTICS Cardiac T1 Signal Characteristics Both spin and gradient echo (GRE) sequences can be used to identify myocardial T1-weighted signal intensity From the *Department of Cardiology, Royal Liverpool and Broadgreen University Hospitals; wDepartment of Radiology, Liverpool Heart and Chest Hospital, Liverpool, UK; and zDepartment of Radiology and Radiological Sciences, Medical University of South Carolina, Charleston, SC. U.J.S., is a consultant of Bayer and Siemens, has grant support from Bayer, GE, Siemens, Bracco, Medrad. All the other authors declare no conflict of interest. Reprints: Balazs Ruzsics, MD, PhD, Department of Cardiology, Royal Liverpool and Broadgreen University Hospitals, Prescot Street, Link 7Z, Liverpool L7 8XP, UK (e-mail: balazs.ruzsics@ rlbuht.nhs.uk). Copyright r 2013 by Lippincott Williams & Wilkins
318 | www.thoracicimaging.com
changes. Usually, T1-weighted images provide anatomic evaluation of the myocardium and the great vessels. To improve visualization and overall contrast to noise ratio, black-blood images are often desired. Blood suppression can be achieved with spin echo–based sequences, and bright blood images are usually acquired with gradient or spoiled GRE sequences. From a practical point of view, it is worthy to note that the effect of electrocardiogram (ECG)-gated T1weighted sequences depends on the heart rate; if the heart rate is slow the T1 effect can be reduced [because of increased repetition time (TR) between radiofrequency (RF) pulses]. Echo time (TE) needs to be the shortest, usually
