Detection and noninvasive diagnostics of breast cancer with 2-color laser optoacoustic imaging system

Abstract

We have designed, fabricated and tested a new laser optoacoustic imaging system (LOIS-64/16) for quantitative optoacoustic tomography of breast cancer. The system was designed to create a single slice of an optoacoustic image of the breast with 64 ultrawide band acoustic transducers. Other 16 transducers on the back of the acoustic probe were used to reconstruct the light distribution inside the breast. The system resolution was at least 0.5 mm for high-aspect-ratio objects. Maximum system sensitivity was 4.8 mV/Pa and the RMS noise of 3.1 mV, which allowed imaging of small (less than 1 cm) tumors at depths over 3 cm. The directivity of the optoacoustic transducers used in LOIS-64/16 assured that the signal detection was better than 70% of the maximum for about 75% of the imaging slice and reduced quickly for signals coming from out of the imaging slice. Implemented signal processing allowed significant reduction of the low-frequency acoustic noise and localizing the small OA signals. The system was able to differentiate phantoms mimicking tumors and malformations visualized in clinics based on the contrast and morphology of their images obtained at 1064 nm and 757 nm.

Whole-body three-dimensional optoacoustic tomography system for small animals

“…33 Later we optimized this wavelet to replicate the third derivative of the Gaussian wavelet, which can be used to enhance sharpness of the boundaries while significantly reducing low-frequency acoustic trends for optoacoustic sources of arbitrary shapes. 34 Nine scales of this wavelet covering a wide range of frequencies from 4 to 1024 digital samples enabled flexibility in the complex signal processing. An advantage inherent in the multiscale wavelet processing is that the wavelet filter simultaneously serves as an integrator, resulting in conversion of bipolar optoacoustic pressure profiles into monopolar profiles of the absorbed optical energy.…”

Carbon nanotubes as photoacoustic molecular imaging agents in living mice

“… Photoacoustic imaging of living subjects offers higher spatial resolution and allows deeper tissues to be imaged compared with most optical imaging techniques1–7. As many diseases do not exhibit a natural photoacoustic contrast, especially in their early stages, it is necessary to administer a photoacoustic contrast agent.…”

Near-Infrared Fluorescence Imaging and Spectroscopy in Random Media and Tissues

“…Considering prior achievements of diffuse optical imaging using several optical wavelengths, spectroscopic OAT may allow the noninvasive, in vivo imaging and quantification of oxygenated and deoxygenated hemoglobin that reflects physiological functions of breast tumors [119]. Stronger absorption of NIR light in malignant tumors with developed angiogenesis leads to a greater than twofold average optoacoustic contrast in tumors compared with normal tissue [33,35,64,84]. In contrast to pure optical tomography, where the tumor contrast is significantly diminished through integration of the signal over the entire optical path, the optoacoustic imaging permits direct reconstruction of the absorbed optical energy in tumors from the optoacoustic pressure profiles measured on the surface surrounding the breast.…”

“…The high-frequency thermal noise can be removed with a low-pass filter, which typically does not represent a challenge (thus not shown in Figure 21.9a). The removal of the smooth exponential trend in the optoacoustic profile is more difficult but could be achieved either (i) with wavelet filtering [83,84]; (ii) with band-pass numeric hyper-Gaussian filter, which performed better than other band-pass filtering of fast Fourier transformed signals [35]; or (iii) through the principal component analysis [85]. The cutoff frequency and the slope of the transfer function of filters (i) and (ii) could be varied conveniently by the imaging operator, so that the high-frequency thermoelectrical noise can be removed with the same filters as the low-frequency component.…”