BACKGROUND

A conventional ultrasound imaging system creates an internal image (i.e., a B-mode image) of a volume by detecting acoustic impedance discontinuities within the volume. More specifically, conventional ultrasound imaging involves transmitting ultrasound beams into a volume and detecting the returned signals which reflect from acoustic impedance discontinuities within the volume. Since different materials typically exhibit different acoustic impedances, the detected acoustic impedance discontinuities represent the locations of different materials within the volume.

The above-described B-mode images depict qualitative features in tissue but do not directly provide quantitative information regarding the tissue. Quantitative ultrasound systems, on the other hand, can determine an attenuation coefficient (AC) and a backscatter coefficient (BSC) of a Region of Interest (ROI). The AC is a measure of the ultrasound energy loss in tissue and the BSC is a measure of the ultrasound energy returned from tissue. Quantitative ultrasound values such as these are helpful in characterizing properties of tissue such as stiffness and fat fraction. Additional quantitative ultrasound measures would further assist these characterizations.

Determination of an AC and a BSC require compensation for system effects of the acquiring ultrasound system. These effects include transmit-pulse power, transducer sensitivity, beam-focusing pattern, and depth-dependent receiver gain. Conventionally, compensation includes dividing the echo signal power spectrum of a tissue sample in the fundamental frequency band by the echo signal power spectrum of a well-characterized reference phantom in the fundamental frequency band from the same depth. The resulting quotient is a normalized spectrum that depends on the attenuation and backscatter properties of the tissue sample and of the reference phantom. Since the properties of the reference phantom are known, the AC and the BSC of the tissue sample can be derived from the normalized spectrum.

One drawback of the foregoing determination is the need to acquire reference phantom data at the time of the clinical scan. This additional acquisition hinders workflow and patient throughput. Moreover, the accuracy of such determinations has been seen as lacking in many scenarios. The foregoing determination also fails to provide other potentially-useful quantitative measures, such as tissue non-linearity.

