Johannes C.G. van Hespen

Initial results of in vivo non-invasive cancer imaging in the human breast using near-infrared photoacoustics.

Near-infrared photoacoustic images of regions-of-interest in 4 of the 5 cases of patients with symptomatic breasts reveal higher intensity regions which we attribute to vascular distribution associated with cancer. Of the 2 cases presented here, one is especially significant where benign indicators dominate in conventional radiological images, while photoacoustic images reveal vascular features suggestive of malignancy, which is corroborated by histopathology. The results show that photoacoustic imaging may have potential in visualizing certain breast cancers based on intrinsic optical absorption contrast. A future role for the approach could be in supplementing conventional breast imaging to assist detection and/or diagnosis.

Hybrid photoacoustic ‐ ultrasound transmission parameter imaging in a miniature photoacoustic imager

Photoacoustic imaging is based on detecting laser pulse induced ultrasound transients from absorbing structures in tissue. The technique combines the advantages of a high optical absorption exhibited by tumors for example with the high resolution possible with ultrasound. A conventional photoacoustic imager operating in a CT geometry comprises a light source, an ultrasound detector array and a coupling medium usually water between the subject under investigation and detector. The imaging protocol usually consists of obtaining projections at angles around the subject. Recently we reported a method of measuring the local speed-of-sound variations by the addition of an absorber to the conventional imager, arranged between the light source and subject. This generates an ultrasound signal which interacts with the subject which can then be detected at the far-end by the detector. This allows the measurement of the integrated speed-of-sound (SOS) at projections around the subject leading to the formation of SOS images. In this article we discuss further analysis of the ultrasound obtained at projections to obtain images of the acoustic attenuation as well. In addition conventional photoacoustic images of the subject are also formed. The principle is demonstrated on well-characterized phantoms and we discuss the potential applications of this technique.