The application of backscattered ultrasound and photoacoustic signals for assessment of bone collagen and mineral contents.

BACKGROUND This study examines the backscattered ultrasound (US) and back-propagating photoacoustic (PA) signals from trabecular bones, and their variations with reduction in bone minerals and collagen content. While the collagen status is directly related to the strength of the bone, diagnosis of its condition using US remains a challenge. METHODS For both PA and US methods, coded-excitation signals and matched filtering were utilized to provide high sensitivity of the detected signal. The optical source was a 805-nm CW laser and signals were detected employing a 2.2-MHz ultrasonic transducer. Bone decalcification and decollagenization were induced with mild ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite solutions, respectively. RESULTS The PA and US signals were measured on cattle bones, and apparent integrated backscatter/back-propagating (AIB) parameters were compared before and after demineralization and decollagenization. CONCLUSIONS The results show that both PA and US are sensitive to mineral changes. In addition, PA is also sensitive to changes in the collagen content of the bone, but US is not significantly sensitive to these changes.