Myocardial tagging and strain analysis at 3 Tesla: Comparison with 1.5 Tesla imaging

Abstract

Purpose: To determine whether imaging at 3 T could improve and prolong the tag contrast compared to images acquired at 1.5 T in normal volunteers, and whether such improvement would translate into the ability to perform strain measurements in diastole. Materials and Methods:Normal volunteers (N ϭ 13) were scanned at 1.5 T (GE Signa CV/i) and 3.0 T (GE VH/i). An ECG-triggered, segmented k-space, spoiled-gradient-echo grid-tagged sequence was used during cine acquisition. Tag contrast was determined by the difference of the mean signal intensity (SI) of the tagline to the mean SI of the myocardium divided by the standard deviation (SD) of the noise (CNR tag ). Matched short-axis (SA) slices were analyzed. Strain measurements were performed on images using a 2D strain analysis software program (harmonic phase (HARP)). Results:The average CNR tag over the cardiac cycle was superior at 3 T compared to 1.5 T for all slices (3 T: 23.4 Ϯ 12.1, 1.5 T: 9.8 Ϯ 8.4; P Ͻ 0.0001). This difference remained significant at cycle initiation, end-systole, and the end R-R interval (at cycle termination: 3 T ϭ 14.0 Ϯ 11.0 vs. 1.5 T ϭ 4.4 Ϯ 3.5; P Ͻ 0.01). Strain measures were obtainable only in early systole for 1.5 T images, but were robust throughout the entire R-R interval for 3 T images.Conclusion: Imaging at 3 T had a significant benefit for myocardial tag persistence through the cardiac cycle. The improvement allowed strain analysis to be performed into diastole. MYOCARDIAL TAGGING using MRI is an evolving noninvasive technique for assessing and quantifying regional myocardial function and strain in the human heart. Since this technique was first described (1,2), several studies have used MRI tagging to measure regional myocardial function with multiphase myocardial strain in normal and diseased states (3-6). Algorithms that are necessary to quantify strain and regional myocardial function are heavily dependent on the contrast between the tag lines and the myocardium. However, myocardial tagging techniques are limited by the rapid fading of tags, which restricts their application to the systolic phases of the cardiac cycle. Given the increasing recognition of the role of diastolic dysfunction in several cardiac disease states (7), it would be of clinical value to overcome the limitations posed by the early decay tags and extend the analysis of regional myocardial function and strain to the entire cardiac cycle. Several methods, including complementary spatially modulated magnetization (CSPAMM) (8,9) and balanced free precession sequences (10,11) have been employed toward that end. Higher-field-strength imaging is becoming more common and provides another pathway to potentially improve tag persistence through prolonged T1 myocardial recovery and enhanced signal-tonoise ratio (SNR).The aim of this study was to compare tag contrast as a function of time within the cardiac cycle in normal volunteers imaged at both 1.5 T and 3 T using a fast spoiled-gradient-recalled echo sequence with spatial modulation of magnetization. The images...

In vivo SNR in DENSE MRI; temporal and regional effects of field strength, receiver coil sensitivity and flip angle strategies

“…Nevertheless, these studies also showed an improvement when using 3T compared to 1.5T, as reported by an 80% increase in tagging CNR [4]. Regional variations across the left ventricle of 50% higher end systolic tagging CNR at 3T for an anterior region compared to an inferior region were also reported previously [6].…”

“…Noise in tagging MRI at 1.5T and 3T has been studied before [4,6,7]. Pulse sequence wise, DENSE and tagging MRI based on 1-1 SPAtially Modulated Magnetization (SPAMM) are closely related [17], and the results found in this study should be transferable to the regime of tagging analyzed with HARP.…”

“…The longer T 1 relaxation at higher field strengths further works in tandem, reducing the rate at which the stimulated echo deteriorates. The differences between 1.5T and 3T have been studied for tagging MRI in a number of studies [4][5][6][7]. These studies all examined the contrast-to-noise ratio (CNR) for tagged vs. untagged myocardium in the magnitude image.…”

“…These studies all examined the contrast-to-noise ratio (CNR) for tagged vs. untagged myocardium in the magnitude image. In one of these studies, substantial CNR variations in two opposing regions of the left ventricle were reported [6], possibly due to variations in coil sensitivity. While CNR is the appropriate measure in classical tagging approaches where the tag lines are tracked in the image, the noise influence on phase based approaches to obtaining per-pixel displacement such as DENSE or HARP [8] is reflected solely in the SNR.…”

Myocardial strain in healthy adults across a broad age range as revealed by cardiac magnetic resonance imaging at 1.5 and 3.0T: Associations of myocardial strain with myocardial region, age, and sex

“…Markl et al26 ( n = 16) compared image quality using tagging at both field strengths and reported an increase in off‐resonance artifact at 3.0T, without an effect on overall image quality. Kramer et al27 ( n = 14) and Valeti et al28 ( n = 13) reported better image quality with tagging at 3.0T.…”