Table 2.

Summary of the notation used for vectors and angles

e 1 DTI, e 2 DTI and e 3 DTI	DTI eigenvector corresponding to the most, intermediate and least extended directions of diffusion
v 1 ST, v 2 ST, v 3 ST	the vector of the most, intermediate and least extended orthogonal directions of FLASH signal, determined by structure-tensor analysis.
λ1 ST	eigenvalue (λ) with the subscript indicating the eigenvalue number.
α'v 1 ST and α'e 1 DTI	vector helix angle, used for quantification of the putative myocyte orientation. The vector quantified is identified after α’. The angle is defined in Figure 2.
α''v 1 ST and α''e 1 DTI	vector transverse angle, used for quantification of the putative myocyte orientation.
β'v 3 ST and β'e 3 DTI	vector elevation angle, used for quantification of the putative sheetlet/sheetlet-normal orientation.
β”v 3 ST and β''e 3 DTI	vector transverse angle, used for quantification of the putative sheetlet/sheetlet-normal orientation.
m	the true myocyte orientation vector.
s	the true sheetlet (in-plane) vector.
n	the true sheetlet normal vector. The superscript FI is used in the case of n measured by FLASH/FI.

The angles, cardiac reference planes and cardiac coordinate system are defined in Figure 1 and Figure 2 Note: the putative myocyte helix-angle α’ is projected onto the wall-tangent plane whereas the β’ elevation angles associated with the putative sheetlet in-plane and normal vectors (s and n) are projected onto the long-axis plane. FLASH: fast low angle shot; ST: structure tensor of FLASH data; DTI: diffusion tensor magnetic resonance imaging.