Myocardial T1 mapping as a diagnostic tool in pediatric patients with a concern for cardiac disease
Journal of Cardiovascular Magnetic Resonance volume 18, Article number: P167 (2016)
Myocardial tissue characterization with both native T1 mapping and T1 mapping following gadolinium based contrast agents (T1 enhanced) has emerged as an important asset of CMR imaging . However, there is only minimal experience in pediatrics . Native T1 has shown to be a marker of myocardial edema, and may play a role in pathologic states such as myocarditis . T1 enhanced mapping has shown to be a useful biomarker for disease sates with diffuse fibrosis, such as hypertrophic cardiomyopathy (HCM), and is comparable to myocardial biopsy .
Purpose: To examine the effectiveness of CMR myocardial characterization by native T1 and T1 enhanced mapping in a heterogenous group of pediatric patients with signs concerning for cardiomyopathy or myocarditis.
We reviewed our initial experience of an ongoing study with T1 mapping in 10 subjects (aged 15.4 ± 2.5 years). All patients underwent CMR due to signs suggestive of cardiac disease. Cohort included 4 patients with concern for myocarditis, 4 with concerns for HCM, and 2 with concern for myocardial ischemia. 3 of the acquisitions were made in 3T AcheivaTM, remainder used 1.5T IngeniaTM scanner (Philips Healthcare, Best Netherlands).
Acquisition Protocol: All clinically indicated MRI sequences were performed, including delayed enhanced phase sensitive inversion recovery sequence, after injection of contrast (MagnevistTM). T1 mapping (modified Look Locker - MOLLI) sequence was performed prior to contrast injection and post contrast (15 minutes after contrast) injection. The MOLLI sequence had a bSSFP readout TR/TE/α = 3/1.5 ms/20°; A 5,5,3 inversion acquisition scheme was used, and acquisition time was 13 heart beats.
The T1 was measured by manually drawing a region of interest at both the interventricular septum and the free wall after exporting the data to a custom made MatlabTM program. Pixels with a zero value - representing a noisy T1 fit were ignored from the calculations.
The native and enhanced T1 were calculated for all patients except 1 who had significant artifact in the free wall on the native T1 sequence. The 2 patients with concern for myocardial ischemia, and 1 patient with possible HCM were assessed on the 3T. As assessed on the 1.5T, the native T1 of the free wall in patients who were clinically treated for myocarditis (n = 3) was significantly higher than the native T1 in all other patients (n = 4), 1094 ± 38 ms vs. 986 ± 23 ms (p < 0.05). Likewise, the septal T1 enhanced of patients who were diagnosed with HCM (n = 3) was lower than the remaining patients (n = 4), 460 ± 16 ms vs. 533 ± 16 ms (p <0.05).
Myocardial characterization may be an effective tool in pediatric patients with a potential diagnosis of cardiomyopathy or myocarditis. Within a heterogenous group of patients, the native T1 was able to distinguish myocarditis from other potential cardiac disorders, while the enhanced T1 was able to distinguish HCM.
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Noel, C.V., Krishnamurthy, R. & Krishnamurthy, R. Myocardial T1 mapping as a diagnostic tool in pediatric patients with a concern for cardiac disease. J Cardiovasc Magn Reson 18 (Suppl 1), P167 (2016). https://doi.org/10.1186/1532-429X-18-S1-P167