Spatial frequency domain imaging for in vivo bone healing monitoring in a murine graft model (Conference Presentation)

Revascularization is required to deliver the factors necessary for bone injury healing to the injury site. Therefore, vascularization is usually monitored to assess the bone healing outcome in preclinical settings. Previously, blood flow changes measured by diffuse correlation tomography have shown the potential to predict the healing outcome of the mouse femoral graft in vivo. To obtain more comprehensive hemodynamic information in addition to blood flow, we adapted spatial frequency domain imaging (SFDI) method to quantify the total hemoglobin concentration and oxygen saturation in the mouse bone graft model. An in-house SFDI system was built based on a Texas Instrument digital micromirror device (DMD) and a near-infrared camera. The system was tested using a simplified tissue phantom mimicking the mouse hindlimb with a femoral allograft (avascular) implanted. A single time-point measurement for mouse hindlimbs with and without allograft was performed. The SFDI results were compared with traditional contrast agent-mediated micro-CT for validation. Longitudinal measurements are being performed before and weekly after the allograft surgery. The SFDI-derived properties will be related to the biomechanical outcomes of the healed bones. Preliminary results of tissue phantom experiments showed the capability of SFDI for mapping the absorption and scattering properties of the graft mimicking tube at a 2 mm depth. Since the mouse femur is usually ~1-2 mm under the skin surface, the SFDI technique has the potential for monitoring the vascularization in healing bone grafts.