Cost-effective laser diode scanning 3D photoacoustic microscopy of melanocytic dermal tumors in situ

Management of melanoma skin cancer involves a wide excision followed by histopathological analysis to confirm the diagnosis, which is only guided by superficial dermoscopy. Dermatological oncology can thus benefit from high-resolution, 3D images provided by photoacoustic microscopy; however, its clinical translation is hindered by its elevated cost. Opening a pathway to point-of-care 3D melanoma assessment, we present the first demonstration of a cost-effective photoacoustic microscope (CePAM) utilizing fast laser diode scanning with a focused transducer in reflection mode. A novel application of a direct model inversion (DiMI) algorithm allowed a 55-fold enlargement of the image field of view beyond the transducer acoustic focus, reaching a 1-square millimeter laser-scanned area with uniform sensitivity (>20 dB). Furthermore, DiMI improved the intrinsic axial resolution of the system via multiple selective-plane scanning. The feasibility of CePAM is demonstrated by quantitative tests on phantoms and in vivo imaging of murine melanocytic dermal tumors, yielding accurate 3D images and virtual cross-sections consistent with histology.