Quantitative Tagged Magnetic Resonance Imaging of the Normal Human Left Ventricle

Abstract

SummaryMagnetic resonance imaging with tissue tagging is a noninvasive technique for measuring threedimensional motion and deformation in the human heart. Tags are regions of tissue whose longitudinal magnetization has been altered before imaging so that they appear dark in subsequent magnetic resonance images. They then move with the underlying tissue and serve as easily identifiable landmarks within the heart for the detailed detection of motion. Many different motion and strain parameters can be determined from tagged magnetic resonance imaging. Strain components that are based on a high density of tag data, such as circumferential and longitudinal shortening, or parameters that are combinations of multiple strain components, have highest measurement precision and tightest normal ranges. The pattern of three-dimensional motion and strain in the heart is important clinically, because it reflects the basic mechanical function of the myocardium at both local and global levels. Localized abnormalities can be detected and quantified if the pattern of deformation in a given heart is compared to the normal range for that region, because normal motion and strain in the left ventricle is spatially heterogeneous. Contraction strains typically are greatest in the anterior and lateral walls and increase toward the apex. The direction of greatest contraction lies along a counter clockwise helix from base to apex (viewed from the base) and approximates the epicardial muscle fiber direction. This fiber geometry also results in long-axis torsion during systole. Ejection is accomplished primarily by radially inward motion of the endocardium and by descent of the base toward the apex during systole. KeywordsMagnetic resonance imaging; Human heart; Three-dimensional strain; Tissue tagging Accurate three-dimensional (3D) measurement of myocardial deformation throughout the heart during contraction is critical to a fundamental understanding of myocardial function (1). Such an analysis is valuable clinically because most ischemic heart disease, the leading cause of death in the United States, typically affects localized regions of the myocardium (2). The time-resolved local strain map of a heart, as compared to a normal database, permits quantification of both the degree and the physical extent of mechanical dysfunction. In addition, it can be used to improve cardiac analytic and finite element models (3-5), which may help characterize tissue properties and predict the effects on the heart of specific abnormalities and surgical treatments.There are two main problems associated with measuring cardiac deformation. First is the scarcity of readily identifiable landmarks on, and especially within, the heart wall. The second difficulty is that the complex 3D motions of the heart through tomographic images prevent Address correspondence and reprint requests to Dr. Christopher C. Moore, Department of Radiology, The Johns Hopkins University School of Medicine, 600 N. Wolfe Street, Baltimore, MD 21287, U.S.A.. NIH Public Access Author Man...

Strain‐encoded (SENC) magnetic resonance imaging to evaluate regional heterogeneity of myocardial strain in healthy volunteers: Comparison with conventional tagging

“…The anterior apical and anterior midventricular regions showed the highest circumferential peak strain values. The lowest circumferential peak strain values obtained with SENC were seen at the inferior apical and midventricular regions, which is in line with others who have measured myocardial strain using either MR tagging or echocardiographic strain imaging (15,16,23). However, there are groups who observed, contrary to our findings, that the highest strain values can be obtained by MR tagging in the posterior region of the LV (2,22).…”

Alteration in Left Ventricular Strains and Torsional Mechanics After Ultralong Duration Exercise in Athletes

“…11 As a result of the helical orientation of myofibers, 12,13 contraction also induces shear strains within the myocardium. 14 Left ventricular (LV) systolic torsional deformation, one component of shear strains, is one mechanism by which potential energy is stored during ejection to be released during diastole.…”

Dynamic MRS and MRI of skeletal muscle function and biomechanics

“…resting) state to a state following tissue deformation (e.g. muscle contraction) (225). By convention, contraction or shortening of the muscle fibers yields negative strain values, and lengthening results in positive values.…”

“…It should be noted that strain is a tensor and is characterized not only by the magnitude of the length change of the tissue elements but also by the direction of this change. The description of the strain tensor concept is beyond the scope of this review [see (225)]. …”