Fig. 2: Single-breath-hold FRSOM imaging of healthy and psoriatic skin.

a, b Raw optoacoustic signals from FRSOM measurements of healthy skin on the back of a healthy volunteer (female), acquired during (a) normal breathing and (b) while the breath was held for 15 s (single-breath-hold). Dashed lines mark the positions of the skin surface in all A-line optoacoustic signals, which reflect the breathing motion. The x-axis represents the alignment of all A-line optoacoustic signals recorded in the 15 s from a fixed position. c, d Corresponding motion graphs of (a) and (b), which show significantly different motion patterns between normal breathing and the held breath. e, f Cross-sectional MIP images of healthy skin on the back of the healthy volunteer, acquired during (e) normal breathing and (f) while the breath was held for 15 s (single-breath-hold). A marked improvement in image quality is achieved when the breath is held during scanning compared to when normal breathing motions occur. g, h Cross-sectional MIP images of psoriatic skin and adjacent healthy skin from a patient’s back (male). i, j Corresponding MIP images in the coronal direction of the epidermis (EP) layers of (g) and (h). k, l MIP images in the coronal direction of the vascular networks in the dermis (DR) layer of (g) and (h). All images are color-coded to represent the two reconstructed frequency bands (red: larger structures in the bandwidth of 10–40 MHz; green: smaller structures in the bandwidth of 40–120 MHz). The healthy volunteer and patient with psoriasis were measured multiple times with similar results. All scale bar: 500 µm.