Photoacoustic imaging for three-dimensional visualization and delineation of basal cell carcinoma in patients

Abstract

Background: Photoacoustic (PA) imaging is an emerging non-invasive biomedical imaging modality that could potentially be used to determine the borders of basal cell carcinomas (BCC) preoperatively in order to reduce the need for repeated surgery.

Methods: Two- and three-dimensional PA images were obtained by scanning BCCs using 59 wavelengths in the range 680-970 nm. Spectral unmixing was performed to visualize the tumor tissue distribution. Spectral signatures from 38 BCCs and healthy tissue were compared ex vivo.

Results and discussion: The PA spectra could be used to differentiate between BCC and healthy tissue ex vivo (p < 0.05). Spectral unmixing provided visualization of the overall architecture of the lesion and its border.

Conclusion: PA imaging can be used to differentiate between BCC and healthy tissue and can potentially be used to delineate tumors prior to surgical excision.

Keywords: Basal cell carcinoma; Basalioma; Human; Patients; Photoacoustic imaging; Spectral unmixing; Tissue differentiation.

Fig. 1

Photographs of the ex vivo examination setup. (A) An excised lesion suspended in a saline solution. (B) The PA probe attached to an adjustable arm with the stepping motor, used for the examinations.

Fig. 2

The mean PA spectra obtained from BCCs and the surrounding healthy tissue from ex vivo measurements. The dispersion (± one standard deviation) is indicated by the shaded areas. A clear difference can be seen in the spectral signatures of the BCCs and healthy tissue (p < 0.05 for 760 to 945 nm, n=38).

Fig. 3

Representative example of an ex vivo scan of a nodular BCC. The image on the upper left shows the small ROIs superimposed on the ultrasound image. The scale bar is 1 mm. The PA spectra obtained from the ROIs are given below, showing the change from cancerous to healthy tissue. The image on the upper right shows the same H&E-stained histological sample.

Fig. 4

Representative example of a spectrally unmixed 3D multiwavelength PA image of a nodular BCC lesion examined ex vivo. The suspected cancerous tissue is shown as a purple overlay. The colorbar represents the unmixed signal for BCC tissue (a.u.). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 5

Representative example of a spectrally unmixed 3D multiwavelength PA image of a superficial BCC lesion examined ex vivo. The suspected cancerous tissue is shown as a purple overlay. The colorbar represents the unmixed signal for BCC tissue (a.u.). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)