ULTRASOUND IMAGE RECONSTRUCTION USING BACK-PROPAGATION

An image of an interrogation region of a patient's body is generated from the return signal from an ultrasound pulse, which is directed into the interrogation region by a transducer array, which may be linear (to create a planar image) or planar (to create a 3-D image). The time-domain signal back-scattered to the transducer is sensed at a reference plane (preferably, the transducer plane itself) and is transformed first by a temporal Fourier transform and then by a spatial Fourier transform, in order to generate an angular spectral decomposition of the back-scattered signal. This decomposed reference signal is then propagated to image planes (or lines) at depths other than at the reference plane, throughout the image volume. The resulting propagated signals are then inversely transformed twice, back into the time domain. An entire image is thus reconstructed from the back-propagated signal from a single input pulse. Alternatively, several pulses can be transmitted into the interrogation region, an image can be reconstructed from each, and the reconstructed images can be registered and averaged to improve the resulting image. Increases in speed of image generation of several orders of magnitude are often possible, since the system can generate an entire image after only one round-trip propagation time for the ultrasonic input signal.