Characterizing a photoacoustic and fluorescence imaging platform for preclinical murine longitudinal studies

Abstract

Significance: To effectively study preclinical animal models, medical imaging technology must be developed with a high enough resolution and sensitivity to perform anatomical, functional, and molecular assessments. Photoacoustic (PA) tomography provides high resolution and specificity, and fluorescence (FL) molecular tomography provides high sensitivity; the combination of these imaging modes will enable a wide range of research applications to be studied in small animals.

Aim: We introduce and characterize a dual-modality PA and FL imaging platform using in vivo and phantom experiments.

Approach: The imaging platform's detection limits were characterized through phantom studies that determined the PA spatial resolution, PA sensitivity, optical spatial resolution, and FL sensitivity.

Results: The system characterization yielded a PA spatial resolution of $173\pm 17\mu m$ in the transverse plane and $640\pm 120\mu m$ in the longitudinal axis, a PA sensitivity detection limit not less than that of a sample with absorption coefficient ${\mu }_a=0.258{\mathrm{cm}}^{-1}$ , an optical spatial resolution of $70\mu m$ in the vertical axis and $112\mu m$ in the horizontal axis, and a FL sensitivity detection limit not $<0.9\mu M$ concentration of IR-800. The scanned animals displayed in three-dimensional renders showed high-resolution anatomical detail of organs.

Conclusions: The combined PA and FL imaging system has been characterized and has demonstrated its ability to image mice in vivo, proving its suitability for biomedical imaging research applications.

Keywords: fluorescence; medical imaging; mouse; photoacoustic; tomography.