Figure 2. Transition from tissue isotropy to anisotropy in the developing human fetal heart.

(A, B) At 10 weeks the diffusion glyphs are disordered and spherical. (B = magnified view of white box shown in panel A). (C) At 14 weeks the orientation of the glyphs resembles that seen in the adult heart but they remain highly spherical. (D) At 19 weeks of gestation the glyphs are highly ordered and are now somewhat elliptical in shape. (E) At P6 (day 6 post-natal) the orientation and elliptical shape of the glyphs is very similar to that seen in adult hearts. (F) Fractional anisotropy (FA) at 10, 14 and 19 weeks of gestation remains very low. While the coherence and orientation of the myofibers has evolved by 19 weeks, their sheet structure has not. *p<0.01.