Integrated 3-D vascular ultrasound and spectroscopic photoacoustic imaging for noninvasive characterization of human arteries

Background: The complex nature of atherosclerosis requires the assessment of various arterial properties to accurately diagnose the severity of the disease. The aim of this study is to develop and test a noninvasive vascular imaging method combining ultrasound, and spectroscopic photoacoustic (PA) imaging to diagnose superficial arteries. Methods: The experiments were performed using excised human atherosclerosclerotic arteries. The sample was positioned in a water tank filled with saline and flushed with blood at a pulsatile flow (2 Hz, 50 cm/s). The artery was scanned using a 40MHz linear array transducer surrounded by 2 optical fibers and Vevo 2100 ultrasound system. Ultrasound 3-D data sets were formed from 256 echo lines and 150 frames. The 3-D PA images were acquired at 1210-1230 nm wavelengths. A multi-wavelength spectroscopic PA algorithm based on linear minimum mean squared error estimation and optical absorption spectra was used to distinguish lipids from surrounding tissue and blood. Results: Ultrasound images revealed arterial morphology, which guided tissue segmentation, such as lumen-intima interface. The spectroscopic PA image overlapping the ultrasound image showed the location of lipids (marked by yellow color in Fig. 1C-D). Using 3-D spectroscopic PA data the volume of the lipid pool were directly derived. The spectroscopic PA imaging results were confirmed by Oil Red O histology staining. Discussion and Conclusions: The results of our study demonstrate that the proposed method is feasible, and integrated 3-D ultrasound, and spectroscopic PA imaging provides localized and global detailed characterization of arterial morphology, and composition.