Fig. 3

Two-dimensional acoustic impedance images of human tooth pre- and post-radiation therapy recorded by 320 MHz Scanning Acoustic Microscopy (SAM). The resolution was defined through the field of view of 4.8 mm × 4.8 mm for each image with a 300 × 300 scanning points with a scan size of 16 μm. All images were determined to visualize both enamel and dentin within a signal scan. Gradation in color bar (red to yellow) represent the variation after subjection to radiation doses which are clinically used to cure head and neck cancers. Sound dentin shows up higher acoustic impedance (orange to yellow) than that of the softened dentin through radiotherapy