Performance benchmarks of an array-based hand-held photoacoustic probe adapted from a clinical ultrasound system for non-invasive sentinel lymph node imaging

Abstract

Clinical translation of photoacoustic (PA) imaging can be facilitated by integration with commercial ultrasound (US) scanners to enable dual-modality imaging. An array-based US scanner was modified for hand-held PA imaging. The performance was benchmarked in terms of signal-to-noise ratio (SNR), axial spatial resolution and sensitivity. PA images of a tube, filled with methylene blue (MB; approx. 30 mM) and placed at various depths in chicken tissue, were acquired. A 5 cm penetration depth was achieved with an 18.6 dB SNR using a laser fluence of 3 mJ cm −2 , only one-seventh of the safety limit (20 mJ cm −2 ). An axial resolution of approximately 400 mm was maintained at all imaging depths. The PA sensitivity to MB placed 2.3 cm deep in chicken tissue was less than 100 mM. Further, after intradermal injection of MB (approx. 30 mM), a rat sentinel lymph node was clearly identified in vivo, beneath a 3.8 cm thick layer of chicken breast. The accumulated concentration of MB in the node was estimated to be approximately 7 mM. The noiseequivalent sensitivities (approx. 2 cm depth) were 17 and 85 mM, ex vivo and in vivo, respectively. These results support the use of this PA system for non-invasive mapping and image-guided needle biopsy of sentinel nodes in breast cancer patients.

Photoacoustic tomography and fluorescence molecular tomography: A comparative study based on indocyanine green

“…The SNR for 2 lM at 7 mm depth was about 2.2 dB, giving a measured noise-equivalent sensitivity of 0.22 lM at 7 mm depth. 33 For FMT, it is noticed from Fig. 6 that the recovered target position has greater errors compared to the cases with smaller target depth or larger fluorochrome concentration.…”

Real-time photoacoustic and ultrasound dual-modality imaging system facilitated with graphics processing unit and code parallel optimization

“…Because US imaging of the same object can also be conducted in real-time without being affected, the US, which has been accepted as a standard tool, can assist in guiding PA procedures and helping in the interpretation of PA image findings. Our next step for updating this dual-modality system is to synthesize PA and US images into one image 18 in real time to merge individual information from both imaging methods.…”

Mesoscopic and Macroscopic Optoacoustic Imaging of Cancer

“…Although the high acceptance and sensitivity of the radiotracer/gamma probe method may hinder the translation of new methods, the potential elimination of ionizing radiation by optical imaging is attractive and can simplify procedures and safety concerns involved in the intraoperative use of radioactivity. Optoacoustic lymphatic mapping using clinically approved ICG and MB or novel agents has been shown in rats (58,85,86) and imaging systems capable of detection at depths of 5 cm have been reported previously (36). For melanoma staging, lymph node metastases, which commonly display a high melanin content, can be intrinsically detected in optoacoustic images (see Fig.…”