Self-made transparent optoacoustic detector for measurement of skin lesion thickness in vivo .

In skin cancer diagnosis and treatment, one of the key factors is tumor depth, which is connected to the severity and the required excision depth. Optoacoustical (OA) imaging is a relatively popular technique that provides information based on the optical absorption of the sample. Although often demonstrated with ex vivo measurements or in vivo imaging on parts of small animals, in vivo measurements on humans are more challenging. This is presumably because it is too time consuming and the required excitation pulse energies and their number exceed the allowed maximum permissible exposure (MPE). Here, we demonstrate thickness measurements with a transparent optoacoustical detector of different suspicious skin lesions in vivo on patients. We develop the signal processing technique to automatically convert the raw signal into thickness via deconvolution with the impulse response function. The transparency of the detector allows optical excitation with the pulsed laser to be performed perpendicularly on the lesion, in contrast to the conventional illumination from the side. For validation, the measured results were compared to the histological thickness determined after excision. We show that this simple transparent detector allows to determine the thickness of a lesion and thus, aid the dermatologist to estimate the excision depth in the future.