Computed tomography of the palatal anatomy with micrometer resolution

Palatoplasty in infants with cleft palate aims to reconstruct the intricate three-dimensional anatomy and restore the velopharyngeal function, which is essential for swallowing, speech, and ventilation of the middle ear through the opening of the Eustachian tube. The non-destructive analysis of the microarchitecture around the pterygoid hamulus using hard x-rays should enhance the existing knowledge from dissection and histological studies. Specifically, the micro-anatomical relationship between the palatine aponeurosis, the tendon of the tensor veli palatini muscle, and the pterygoid hamulus must be characterized to understand their structural relationship and functional implications. At the cellular level, the arrangement of fibers within muscle fascicles needs to be clarified. The right half of a historical plastinated infant cadaveric head was examined with two laboratory-based micro computed tomography (μCT) systems: phoenix|xray nanotom^® m for imaging of the entire specimen with a pixel size of 55μm; and Zeiss Xradia 610 Versa for local tomography with a pixel size of 3.4μm. Using synchrotron radiation-based microtomography, additional measurements were performed with a pixel size of 3.24μm. The resulting images were rigidly registered and analyzed. Automated threshold-based segmentation of bones and manual segmentation of muscles, tendons, and aponeurosis, were performed to visualize their topographic relationships in three dimensions. An unstained segment of a human gracilis muscle was examined using the Exciscope Polaris with a pixel size of 0.35μm, and the fiber architecture was visually inspected. Laboratory-based x-ray μCT systems are suitable for virtual-histology examination of soft tissues and visualization of subcellular structures therein. Synchrotron radiation-based μCT with phase retrieval provided additional contrast within the plastinated soft tissues. The findings of this study support the hypothesis that the palatal muscles form a complex muscle sling around the pterygoid hamulus, underscoring the importance of preserving this bony protuberance during cleft palate repair.