Flexible cardiac T₁ mapping using a modified look–locker acquisition with saturation recovery

Abstract

A modified Look-Locker acquisition using saturation recovery (MLLSR) for breath-held myocardial T 1 mapping is presented. Despite its reduced dynamic range, saturation recovery enables substantially higher imaging efficiency than conventional inversion recovery T 1 mapping because it does not require time for magnetization to relax to equilibrium. Therefore, MLLSR enables segmented readouts, shorter data acquisition windows, and shorter breath holds compared with inversion recovery. T 1 measurements in phantoms using MLLSR showed a high correlation with conventional single-point inversion recovery spin echo. In vivo T 1 measurements from normal and infarcted myocardium in 41 volunteers and patients were consistent with previously reported values. Twenty subjects were also scanned with MLLSR using an accelerated sampling scheme that required half the scan time (eight vs. 16 heartbeats) but yielded equivalent results The longitudinal magnetization relaxation time T 1 has long been used to characterize tissue and pathology (1-7). For cardiac applications, it has more recently been demonstrated as a noninvasive means for quantifying acute and chronic myocardial infarction (8-11), diffuse fibrosis (12-14), heart failure (15), and myocardial amyloidosis (16). Although T 1 -weighted imaging, such as delayed enhancement MRI (DE-MRI), is part of routine clinical cardiac MR, an inappropriate selection of the inversion time (TI) in these methods result in poor contrast between normal and abnormal myocardium. Furthermore, quantitative analysis of T 1 -weighted images, such as for infarct sizing (17) and gray zone characterization (18), is limited by the qualitative signal intensity variations in individual images. In comparison, T 1 mapping can overcome these limitations and provide the underlying quantitative tissue property of the different types of normal and abnormal myocardium.Because of the growing interest in characterizing the physical properties of myocardium directly through T 1 measurement rather than indirectly through T 1 -weighted imaging, a number of approaches for T 1 mapping have recently been proposed. Iles et al. (12) presented a technique that generates a sequence of rapid inversion recovery (IR) images with increasing TIs. To produce an adequate number of time points, up to four breath holds were necessary; thus, image registration was impacted by the multiple breath holds and changing image planes. Blume et al. (9) demonstrated a navigator-gated IR technique that simultaneously measured myocardial T 1 and T 2 . Because the maximum measured TI was limited by the mid-diastolic trigger delay, it had a heart rate dependence that could affect the accuracy of the T 1 calculation, particularly for postcontrast T 1 s. Using a modification of the Look-Locker (LL) method, the modified look-locker inversion recovery (MOLLI) technique (19,20) acquires single-shot images at 11 TIs spanning five cardiac cycles in a single breath hold. As with other IR-based cardiac T 1 mapping techniques, the greatest limitation of ...

Occult Cardiotoxicity in Childhood Cancer Survivors Exposed to Anthracycline Therapy

“…Normative T1 data on 24 volunteers (46.6±11 years; 15 men) were used for comparison. 23 Precontrast T1 values of the myocardium were higher in study subjects, but the difference did not reach statistical significance (974±312 versus 910±93 milliseconds; P=0.26). Precontrast T1 values did not correlate with risk factors for AIC, global function MRI parameters, or regional changes in peak circumferential (ε cc ) or longitudinal strain magnitude (ειι).…”

“…Grid tag spacing, 7 to 8 mm; field of view, (30-32)×(25-26) cm 2 ; slice thickness, 7 to 8 mm; flip angle, 12°; TE/TR, 3/4.2 milliseconds; views/ segment, 6. (3) T1 mapping using modified Look-Locker with saturation recovery sequence (MLLSR) 23 : scan parameters: 2-2-4 pattern; time to inversion (TI) 0 , 100 milliseconds; TI inc , 100 milliseconds+RR interval resulting in TIs of 100, 1100; 200,1200; 300,1300; and 2300, 3300 milliseconds; echo time/pulse repetition time, 1.7/3.9 milliseconds; flip angle, 45°; 256×160 matrix; phase field of view, 0.75; slice thickness, 8 mm; number of excitations, 0.5; 38 views/segment (148-millisecond readout window). Gadopentetate dimeglumine (Gd-DTPA; Magnevist; Schering, Berlin, Germany) was administered at a dose of 0.1 mmol per 1 kg body weight through a 20-gauge cannula placed in the antecubital vein.…”

“…5 An increasing number of studies have identified diffuse myocardial fibrosis in several cardiac disease states [36][37][38] with the use of various protocols for T1 mapping 16,23,36 and in pediatric patients exposed to anthracyclines. 39 In this study, we demonstrated lower myocardial T1 values 20 minutes after the injection of gadolinium.…”

Accuracy, Precision, and Reproducibility of Four T1 Mapping Sequences: A Head-to-Head Comparison of MOLLI, ShMOLLI, SASHA, and SAPPHIRE

“…Several T1 mapping techniques have been proposed by using different acquisition schemes to sample the T1 recovery signal (1,(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). Multiple images with different T1-weighting are generally acquired and used to provide quantitative T1 estimates by using a model of the T1 recovery signal (1,(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20).…”

“…Multiple images with different T1-weighting are generally acquired and used to provide quantitative T1 estimates by using a model of the T1 recovery signal (1,(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). Despite the promise of these T1 mapping techniques to improve diagnosis, prognosis, and monitoring response to therapy in a variety of Implications for Patient Care n SAPPHIRE and SASHA can be used for accurate myocardial T1 assessment.…”