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In this study, we investigated the characteristics of the ultrasound reflective image obtained by a CMOS sensor
array coated with piezoelectric material (PE-CMOS). The laboratory projection-reflection ultrasound prototype
consists of five major components: an unfocused ultrasound transducer, an acoustic beam splitter, an acoustic
compound lens, a PE-CMOS ultrasound sensing array (Model I400, Imperium Inc. Silver Spring, MD), and a
readout circuit system. The prototype can image strong reflective materials such as bone and metal. We found
this projection-reflection ultrasound prototype is able to reveal hairline bone fractures with and without intact skin
and tissue. When compared, the image generated from a conventional B-scan ultrasound on the same bone
fracture is less observable. When it is observable with the B-scan system, the fracture or crack on the surface
only show one single spot of echo due to its scan geometry. The corresponding image produced from the
projection-reflection ultrasound system shows a bright blooming strip on the image clearly indicating the fracture
on the surface of the solid material. Speckles of the bone structure are also observed in the new ultrasound
prototype. A theoretical analysis is provided to link the signals as well as speckles detected in both systems.
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