Single breath-hold CINE imaging with combined simultaneous multislice and region-optimized virtual coils

Abstract

Purpose: To investigate the feasibility of combining simultaneous multislice (SMS) and region-optimized virtual coils (ROVir) for single breath-hold CINE imaging.

Method: ROVir is a recent virtual coil approach that allows reduced-field of view (FOV) imaging by localizing the signal from a region-of-interest (ROI) and/or suppressing the signal from unwanted spatial regions. In this work, ROVir is used for reduced-FOV SMS bSSFP CINE imaging, which enables whole heart CINE with a single breath-hold acquisition.

Results: Reduced-FOV CINE with either SMS-only or ROVir-only resulted in significant aliasing, with severely reduced image quality when compared to the full FOV reference CINE, while the visual appearance of aliasing was substantially reduced with the proposed SMS+ROVir. The end diastolic volume, end systolic volume, and ejection fraction obtained using the proposed approach were similar to the clinical reference (correlations of 0.92, 0.94, and 0.88, respectively with in each case, and biases of 0.1, 1.6 mL, and $-0.6\%$ , respectively). No statistically significant differences for these parameters were found with a Wilcoxon rank test (p = 0.96, 0.20, and 0.40, respectively).

Conclusion: We demonstrated that reduced-FOV CINE imaging with SMS+ROVir enables single breath-hold whole-heart imaging without compromising visual image quality or quantitative cardiac function parameters.

Keywords: CINE MRI; accelerated acquisition; reduced field-of-view imaging; simultaneous-multi-slice; virtual coils.

Figure 1:

Illustration of applying ROVir to representative full FOV images. (a) Four slices of a representative set of images obtained from full FOV data using the original set of coils. The manually-drawn desired signal region and interference regions used for ROVir are overlaid in green and red, respectively. (b) The corresponding full FOV images obtained by applying ROVir with $N_v=13$ to the same data from (a). (c) Images showing the individual characteristics of the original 30 coils from the third slice. (d) The 30 individual virtual coils obtained after applying ROVir. It should be noted that the intensity of these images has been scaled to maximize the visibility of the heart. With this choice, the very large intensity of the fat signal is not depicted accurately, since our visualization saturates at the maximum value of the color scale.

Figure 2:

Plots of the quantitative signal and interference characteristics of ROVir corresponding to the data from Fig. 1. (a) Plots of the desired signal energy and the interference signal energy for each of the individual ROVir coils. (b) Plots of the percentage of retained desired signal energy and retained interference energy as a function of the total number of coils $N_v$ that is used, where percentages are computed relative to the original set of coils. (c) Plot of the signal-to-interference ratio (SIR) as a function of $N_v$.

Figure 3:

Illustration of applying different reconstruction methods to a set of representative reduced FOV SMS data. (a) Simple Fourier transform reconstruction of the original coils, without SMS reconstruction or ROVir; (b) SMS reconstruction of the original coils without ROVir; (c) Simple Fourier transform reconstruction of the ROVir coils, without SMS reconstruction; (d) the proposed approach combining SMS reconstruction with ROVir.

Figure 4:

Representative comparison of clinical reference CINE with the proposed single breath hold SMS+ROVir for whole LV 12-slice images. Only the heart is displayed from reduced FOV.

Figure 5:

Cardiac function quantification comparison between the proposed SMS+ROVir and conventional reference with Correlation plots (a) and Bland-Altman plots (b) for EDV, ESV, SV, and EF. All parameters resulted in significant agreement between the two acquisitions, with a correlation of 0.92, 0.94, 0.88, and 0.88, respectively, and a bias of 0.1ml, 1.6ml, −1.5ml, and −1.2%, respectively.