Introduction Strain encoding(SENC) is a newly-developed MRI technique for measuring myocardial strain in the throughplane direction [1]. With conventional k-space acquisition, SENC requires two separate acquisitions to obtain two sets of images (low-tune(LT) and high-tune(HT)), which are combined to obtain the strain image. Non-Cartesian k-space trajectories are becoming more popular because they allow for data undersampling with acceptable image quality [2]. In this work, SENC was combined with undersampled radial k-space acquisition and interleaved SENC tunings to reduce scan time to one breathhold. The results were compared to conventional SENC images.
Introduction A number of CMR imaging approaches have been proposed for detecting myocardial edema accompanying acute myocardial infarctions (AMI). Besides the most commonly employed T2-weighted STIR (T2-STIR), T2prepared SSFP (T2-prep SSFP) and cine SSFP (bSSFP) methods have also been proposed. To quantitatively assess myocardial edema, the utility of T1 and T2 maps has been described. However, the relative sensitivities of the various approaches in relation to the routinely used, T2-STIR, method is not fully known.
Arterial spin labeling (ASL) provides noninvasive measurement of tissue blood flow, but sensitivity to motion has limited its application to imaging of myocardial blood flow. Although different cardiac phases can be synchronized using electrocardiography triggering, breath holding is generally required to minimize effects of respiratory motion during ASL scanning, which may be challenging in clinical populations. Here a free-breathing myocardial ASL technique with the potential for reliable clinical application is presented, by combining ASL with a navigator-gated, electrocardiography-triggered TrueFISP readout sequence. Dynamic myocardial perfusion signals were measured at multiple delay times that allowed simultaneous fitting of myocardial blood flow and arterial transit time. With the assist of a nonrigid motion correction program, the estimated mean myocardial blood flow was 1.00 ± 0.55 mL/g/min with a mean transit time of ∼ 400 msec. The intraclass correlation coefficient of repeated scans was 0.89 with a mean within subject coefficient of variation of 22%. Perfusion response during mild to moderate stress was further measured. The capability for noninvasive, free-breathing assessment of myocardial blood flow using ASL may offer an alternative approach to first-pass perfusion MRI for clinical evaluation of patients with coronary artery disease.
This preliminary study aimed to validate a self-gating method in combination with 3D TSE acquisition for gating swallowing motion.The effectiveness in reducing swallowing-related motion artifacts was demonstrated on healthy volunteers and patients.
Background To quantify myocardial T2 value in patients with myocarditis and correlate the distribution of abnormal T2 values with the extent of macroscopic late gadolinium enhancement (LGE). Methods 25 patients with myocarditis were retrospectively evaluated for the utility of T2 mapping in diagnosing myocarditis. Patients with elevated troponins, negative coronary angiogram, and atypical LGE were diagnosed as acute myocarditis. Patients with normal troponins and macroscopic LGE at the time of cardiac MRI were diagnosed as remote myocarditis. As per our institutional protocol, T2 mapping sequences were performed in all cases with suspected myocarditis in addition to standard LGE images on 1.5 T scanner (Magnetom Aera and Avanto, Siemens medical solutions). T2 mapping was performed on three short axis images (base, mid chamber, and apex), yielding 16 myocardial segments for analysis (AHA segments). Single 4 chamber view image was obtained in addition. Minimum, peak and mean segmental T2 values were calculated by the first reader. Average segmental T2 values were documented along with documentation of the number of segments with elevated T2 values. The presence or absence of LGE was documented by a second reader blinded to the T2 results. Average segmental T2 values were then correlated with troponin levels at the time of the MRI examination. Results In patients with acute myocarditis, mean T2 values were elevated in segments showing LGE (average T2 value of 70 msec). The T2 values were also elevated in myocardial segments with no macroscopic LGE (avg 60 msec). On an average, there were 6 additional segments that showed elevated T2 values and no macroscopic LGE. In patients with remote myocarditis, the T2 values were normal in areas of LGE.
