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Published July 2008 | Published
Journal Article Open

Effects of acoustic heterogeneities on transcranial brain imaging with microwave-induced thermoacoustic tomography


The effects of acoustic heterogeneities on transcranial brainimaging with microwave-induced thermoacoustic tomography were studied. A numerical model for calculating the propagation of thermoacousticwaves through the skull was developed and experimentally examined. The model takes into account wave reflection and refraction at the skull surfaces and therefore provides improved accuracy for the reconstruction. To evaluate when the skull-induced effects could be ignored in reconstruction, the reconstructed images obtained by the proposed method were further compared with those obtained with the method based on homogeneous acoustic properties. From simulation and experimental results, it was found that when the target region is close to the center of the brain, the effects caused by the skull layer are minimal and both reconstruction methods work well. As the target region becomes closer to the interface between the skull and braintissue, however, the skull-induced distortion becomes increasingly severe, and the reconstructed image would be strongly distorted without correcting those effects. In this case, the proposed numerical method can improve image quality by taking into consideration the wave refraction and mode conversion at the skull surfaces. This work is important for obtaining good brainimages when the thickness of the skull cannot be ignored.

Additional Information

© 2008 American Association of Physicists in Medicine. Received 08 October 2007; Revised 09 May 2008; Accepted 12 May 2008; Published online 19 June 2008. The authors wish to thank the Washington National Primate Research Center for providing the monkey sample, and George Stoica and Alejandra Garcia-Uribe for their advice and help with the tissue sample. We acknowledge the useful comments from the reviewers as well. This project was sponsored by National Institutes of Health Grants R01 NS46214 and R01 EB000712.

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