Effect of irradiation distance on image contrast in epi-optoacoustic imaging of human volunteers.

Gerrit Held,Stefan Preisser,Sara Peeters,Martin Frenz,Michael Jaeger,H Günhan Akarçay

doi:10.1364/boe.5.003765

Abstract

In combined clinical optoacoustic (OA) and ultrasound (US) imaging, epi-mode irradiation and detection integrated into one single probe offers flexible imaging of the human body. The imaging depth in epi-illumination is, however, strongly affected by clutter. As shown in previous phantom experiments, the location of irradiation plays an important role in clutter generation. We investigated the influence of the irradiation geometry on the local image contrast of clinical images, by varying the separation distance between the irradiated area and the acoustic imaging plane of a linear ultrasound transducer in an automated scanning setup. The results for different volunteers show that the image contrast can be enhanced on average by 25% and locally by more than a factor of two, when the irradiated area is slightly separated from the probe. Our findings have an important impact on the design of future optoacoustic probes for clinical application.

Highlights

In optoacoustic (OA) imaging, the tissue is irradiated by pulsed laser light, leading subsequently to the generation of thermo-elastic pressure transients inside optically absorbing structures
We investigated the influence of the irradiation geometry on the local image contrast of clinical images, by varying the separation distance between the irradiated area and the acoustic imaging plane of a linear ultrasound transducer in an automated scanning setup
For the case of deep clinical OA imaging, we have previously proposed based on simulations and phantom studies that the location of irradiation considerably influences the signal-to-clutter contrast, and that an increased separation distance between irradiation and detection can lead to an improved image contrast [15]

Summary

Introduction

In optoacoustic (OA) imaging, the tissue is irradiated by pulsed laser light, leading subsequently to the generation of thermo-elastic pressure transients inside optically absorbing structures The detection of these pressure transients by an acoustic probe allows a reconstruction of the absorbing structures deep inside biological tissue [1, 2]. The preferred setup for this modality is based on epi-mode, which implies that tissue irradiation and OA signal detection take place at the same tissue surface. This allows imaging of body parts, where in transmission mode bones or attenuating soft tissue would obstruct ultrasound propagation from the irradiated tissue region to the acoustic probe [12, 13]

Objectives

Methods

Findings

Conclusion