Fatemeh Rastegar Jouybari^{1}, Elham Mohammadi^{1}, and Abbas Nasiraei Moghaddam^{1}

Left ventricle function can be evaluated by measuring circumferential strain. CIRcumferential COMpression Encoding (CIRCOME), as a technique for quantification of circumferential strain, needs local frequency and displacement maps during deformation. This study aims to use sine wave modeling approach for estimation of local spatial frequency and displacement maps used in CIRCOME for radially tagged series of images. Circumferential strain computed from proposed method shows expected results in agreement with previous studies.

**Introduction**

**Materials and Methods **

The previously developed CIRCOME uses the spatial frequency of each point that estimated by sequential band pass filtering of k-space data. This procedure is a time-consuming step of CIRCOME. Moreover, in order to compute local strain map, it needs a tracking process. In the SinMod, tagged image intensity in the vicinity of each pixel is modeled as a moving sine wave with local frequency, amplitude and phase. Based on this modeling local spatial frequency and displacement field for series of images can be estimated. This spatial frequency is used as the frequency required for CIRCOME, while the estimated displacement helps to find the corresponding points before and after deformation. Therefore, the two inputs for CIRCOME are obtained in one step.

Short-axis breath-hold radial tagging images were acquired on Mid-ventricle for 8 healthy volunteers. Number of radial taglines was set to 11 taglines per half circle. The epicardium and endocardium contours were delineated manually and the myocardial region was converted to polar coordinate. Afterward, SinMod was implemented to obtain local spatial frequency and circumferential displacement field (Figure 1). The thickness change in consecutive myocardium masks was used to track the local radial displacement. The circumferential strain for each point was then computed by the relative changes of its spatial frequency during deformation. Finally, the resulting strain maps were transformed into the Cartesian coordinates for visualization.

**Conclusion**

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Figure1: Short axis images of LV
at 33% of cardiac cycle in polar coordinate overlaid by (a) displacement field
and (b) local frequency map calculated by SinMod.

Figure2: Lagrangian circumferential
strain maps displayed on radially tagged images of one volunteer for three
different cardiac phases

Figure3: (a) The mean and standard deviation of global circumferential
strain curve in 8 normal volunteers obtained by radially tagged images. (b) Box-plots
of circumferential strain peaks for subjects.