FIGURE 1.

Sequences of pseudocolor diffraction patterns obtained from the same beating rat heart in situ. Each row of patterns illustrates the cyclic changes in reflections obtained from a single muscle layer when the horizontal x-ray beam penetrated the anterior LV wall perpendicular to the long axis of the heart. Diffraction patterns presented were recorded at a sampling rate of 15 ms for a 2-s period but presented here at 30-ms intervals from early diastole (LV filling phase, leftmost column), through to ED, isovolumetric contraction phase (IC) and ES (rightmost column). Every other pattern between the patterns presented here are omitted for clarity. Illustrated are panels 1–4 from the mid-wall (subendocardial layer), 5–8 from the upper-intermediate and epicardial layers, and 9–12 from the surface epicardial layer. Asterisk in panel 9 indicates a flare due to an edge effect. Although the spread of the reflections changes with depth in the LV wall, it is clear from these patterns that vertical restraint limited muscle movements to enable continuous records from the same muscle layer on each occasion.