This paper presents a semi-analytic model for the transmitted field, which can be applied to synthetic transmit imaging. The model is more precise than the virtual source concept, does not require the measurement of the transmit field as matched filtration methods do, and can be applied to both strongly and weakly focused transmissions. Furthermore, the model is applicable to tissue harmonic and contrast enhanced ultrasound imaging.
The paper presents the development of the model using the principles of diffraction, and its validation using computer simulations and measurements on a phantom. Finally, the model is demonstrated for synthetic aperture tissue harmonic in-vivo imaging.