1351340 - Non-ECG, Free-Breathing Myocardial T1, T2, T2*, and Fat-Fraction mapping with MR Multitasking: Initial Clinical Experience

Quantitative myocardial tissue characterization has demonstrated potential for early assessment of cardiovascular disease¹. Conventionally, multiparametric mapping is performed with separate scans, requiring multiple breath-holds and ECG-triggering. We have recently developed a free-breathing, non-ECG technique for simultaneous T1, T2, T2*, and fat-fraction (FF) mapping in a single 2.5-min scan². This approach showed agreement with conventional references in a small cohort, which is mostly healthy controls. In this work, we evaluated the performance of this technique in a pilot patient study.

Methods:

The Multitasking sequence (Fig. 1) includes hybrid T2prep/IR preparation modules, followed by radial FLASH readout modules. Acquisitions alternate between a training data readout at 0° spoke and multi-echo imaging data readouts with golden angle increments. The underlying image can be reconstructed by leveraging spatial-temporal correlations³.

The in vivo study was approved by the institutional review board. To validate T1 and T2 measurements, the proposed technique was scanned within a protocol for symptomatic patients suffering from post-acute sequelae of COVID (PASC), where N=13 subjects (age: 52.1 ± 14.5, 7 male) were recruited and scanned on a 3T scanner (MAGNETOM Vida, Siemens Healthineers). MOLLI and T2-prep FLASH were used as T1 and T2 mapping references, respectively.

For further validation on T2* values outside normal native range, our technique was incorporated as part of a clinical study with ferumoxytol enhancement, which mimicked increased myocardial iron content. N=3 patients (age: 70.7 ± 15.5, 2 male) with known ischemic heart diseases (IHD) were scanned on a 3T scanner (MAGNETOM Skyra; Siemens Healthineers). Multi-echo FLASH was used as T2* mapping reference. The images were acquired at baseline and following a 12-min intravenous infusion of ferumoxytol (4.0 mg/kg). The FF measurement was not validated due to the lack of a clinically accepted gold standard for the heart.

Results:

Fig. 2 shows mapping results from Multitasking and available references for two representative PASC patients and an IHD patient pre- and post-ferumoxytol enhancement. The proposed technique produced co-registered maps resembling references and correctly reflected reduced T2* values after contrast administration. The agreement was analyzed using Bland-Altman plots (Fig. 3). The following limits of agreement and coefficients of variation were found: global T1: ±124 ms (6.1%); global T2: ±5 ms (8.8%), and global T2*: ±4 ms (11.2%); segmental T1: ±198 ms (7.7%), segmental T2: ±9 ms (11.4%), and segmental T2*: ±8 ms (20.3%). The limits of agreement and bias were consistent with those of our previous study².

Conclusion:

Relative to conventional references, the Multitasking CMR generated co-registered maps and consistent measurements in a pilot patient study with a free-breathing, non-ECG scan. Further evaluation in a larger patient cohort with more diverse cardiovascular diseases is warranted.