M.Sc Thesis

M.Sc StudentIlgayev Ovadia
SubjectImaging of Acoustic Vibrations Using Spectrally Encoded
DepartmentDepartment of Biomedical Engineering
Supervisor ASSOCIATE PROF. Dvir Yelin
Full Thesis textFull thesis text - English Version


Acoustic vibrations in tissue are often difficult to image, requiring high-speed scanning, high sensitivity and nanometer-scale axial resolution. Usually, this is done by application of accelerometers or other mechanical methods. However, these methods have to be in mechanical contact with vibrating object. Noncontact optical techniques for imaging vibrations are potentially important tools for diagnosing hearing and vocal folds disorders. Spectrally encoded endoscopy (SEE) is a recent development in miniature endoscopy: a system of a single fiber with miniature optics which uses interferometry for high resolution imaging.

In this work, we propose and demonstrate the measurement of a two-dimensional vibration pattern of tissue surfaces using spectrally encoded interferometry. By analyzing relative spectral phases that correspond to nanometric axial displacements, the vibration patterns of various flexible surfaces, including a paper card, a rubber membrane and the skin of a human volunteer, were imaged at a wide range of acoustic frequencies, with no temporal gating or prior knowledge of the driving acoustic waveform. Due to its simplicity and ease-of-use, the technique has potential to be applied for various in vivo applications that call for accurate evaluation of tissue mechanical properties and its response to various acoustic stimuli. Using compact imaging probes the technique may be useful for diagnosis of various middle ear pathologies, for example by imaging the tympanic membrane or within the middle ear.