Sequential Turning Acquisition and Reconstruction (STAR) Method for Four-dimensional Imaging of Cyclically Moving Structures

Optical coherence tomography allows for dynamic, three-dimensional (3D+T) imaging of the heart within animal embryos. However, direct 3D+T imaging frame rates remain insufficient for cardiodynamic analysis. Previously, this limitation has been addressed by reconstructing 3D+T representations of the beating heart based on sets of two-dimensional image sequences (2D+T) acquired sequentially at high frame rate and in fixed (and parallel) planes throughout the heart. These methods either require additional hardware to trigger the acquisition of each 2D+T series to the same phase of the cardiac cycle or accumulate registration errors as the slices are synchronized retrospectively by pairs, without a gating signal. Here, we present a sequential turning acquisition and reconstruction (STAR) method for 3D+T imaging of periodically moving structures, which does not require any additional gating signal and is not prone to registration error accumulation. Similarly to other sequential cardiac imaging methods, multiple fast image series are consecutively acquired for different sections but in between acquisitions, the imaging plane is rotated around the center line instead of shifted along the direction perpendicular to the slices. As the central lines of all image-sequences coincide and represent measurements of the same spatial position, they can be used to accurately synchronize all the slices to a single inherent reference signal. We characterized the accuracy of our method on a simulated dynamic phantom and successfully imaged a beating embryonic rat heart. Potentially, this method can be applied for structural or Doppler imaging approaches with any direct space imaging modality such as computed tomography, ultrasound, or light microscopy.