Study of clutter origin inin-vivoepi-optoacoustic imaging of human forearms

Abstract

Epi-optoacoustic (OA) imaging offers flexible clinical diagnostics of the human body when the irradiation optic is attached to or directly integrated into the acoustic probe. Epi-OA images, however, encounter clutter that deteriorates contrast and significantly limits imaging depth. This study elaborates clutter origin in clinical epi-optoacoustic imaging using a linear array probe for scanning the human forearm. We demonstrate that the clutter strength strongly varies with the imaging location but stays stable over time, indicating that clutter is caused by anatomical structures. OA transients which are generated by strong optical absorbers located at the irradiation spot were identified to be the main source of clutter. These transients obscure deep in-plane OA signals when detected by the transducer either directly or after being acoustically scattered in the imaging plane. In addition, OA transients generated in the skin below the probe result in acoustic reverberations, which cause problems in image interpretation and limit imaging depth. Understanding clutter origin allows a better interpretation of clinical OA imaging, helps to design clutter compensation techniques and raises the prospect of contrast optimization via the design of the irradiation geometry.

Multiple irradiation sensing of the optical effective attenuation coefficient for spectral correction in handheld OA imaging

“…This technique exploits the wavelength-dependent optical absorption properties of specific chromophores in tissue ( e.g. hemoglobin), to provide quantitative estimates of their spatially varying concentrations [2] , [3] , [4] , [5] , [6] , [7] . A physiologically important example is the determination of local blood oxygen saturation, based on the distinct absorption spectra of oxy- and deoxyhemoglobin in the near-infrared range [8] , [9] .…”

Reliability assessment for blood oxygen saturation levels measured with optoacoustic imaging

“…The arm was immobilized by an arm holder to reduce motion artifacts. 25 US gel was used for acoustic coupling between the transducer and the skin. While acquiring real-time OA and US images, the position of the transducer was adjusted such that the vessels of interest became visible in the field of view of the transducer.…”

Special issue on optoacoustic imaging and sensing

“…An optical coherence photoacoustic microscopy system that combines the merits of optical coherence tomography and photoacoustic imaging is proposed and tested in vivo on mouse ears and ex vivo on porcine eyes [9]. This special issue also includes papers on the clinical applications of photoacoustic imaging in atherosclerosis [10], human forearms [11], preclinical imaging of mouse tumor models [12], imaging studies of defects detected on metal surfaces [13], and an investigation of SO 2 measurements in a single blood vessel as a function of the relative angle between the axis of light illumination and ultrasonic detection [14].…”