  We describe a simple and fast technique to perform ultrasound differential
phase contrast (DPC) imaging in arbitrarily thick scattering media. Though
configured in a reflection geometry, DPC is based on transmission imaging and
is a direct analogue of optical differential interference contrast (DIC). DPC
exploits the memory effect and works in combination with standard pulse-echo
imaging, with no additional hardware or data requirements, enabling
complementary phase contrast (in the transverse direction) without any need for
intensive numerical computation. We experimentally demonstrate the principle of
DPC using tissue phantoms with calibrated speed-of-sound inclusions.
