Fig. 1.

Electron tomography (ET) allows for accurate assessment of true T-tubule (T-tub) geometry. (A) Demonstration of the dependence of T-tub cross-section perception on the angle of the cutting plane. Lack of control over the cutting plane leads to potentially false estimation of T-tub shape, volume and surface area. Calculations were based on the law of sines. (B) Representative tomographic slices of the same T-tub at identical Z-height, showing the different perception of T-tub shape at different Y-plane tilts. Scale bar = 200 nm. (C) Example of manual T-tub segmentation along the Z-plane and a resulting 3D meshed model showing true T-tub geometry, with the final model (right) being an accurate image of T-tub cross-section perpendicularly to T-tub long axis. Segmentation was done using a tomographic montage (10 × 10 μm in X-Y). Scale bar = 100 nm.