A longitudinal study on both 3D and 2D photoacoustic and Doppler ultrasound imaging of human hand rheumatoid arthritis progression has been performed using an automatic imaging system based on GEHC VividTM E95 with L8-18i-D probe and OPOTEK tunable laser system. Bi-weekly imaging has been performed starting from baseline (before patients start medication). Both photoacoustic and Doppler ultrasound can confirm the disease development, however, photoacoustic has higher correlation coefficients (with a median of 78.9%, p = 0.039) with patients’ PGA score.
Crohn's Disease often leads to obstructing intestinal strictures caused by inflammation, fibrosis, and muscular hypertrophy. In this work, we developed a translational ultrasound/photoacoustic catheter probe that is compatible with standard colonoscopy procedures to differentiate normal, acute inflammation and fibrotic conditions in intestinal obstruction in rabbits. The prototype catheter probe consists of a 600-um core optical fiber for photoacoustic illumination and a miniaturized ultrasound array with 48 elements operating at 9.1 MHz for photoacoustic signal reception. A hydrostatic balloon covers the optical fiber and ultrasound array for acoustic coupling. Initial validation in rabbits was successful, and human subject evaluation is ongoing.
Quantification of fibrosis is critical for the management of inflammatory bowel disease. In this study, photoacoustic (PA) strain imaging were used to estimate intestinal stiffness during the progression of intestinal fibrosis in 23 rabbits in vivo. The tissue was then harvested to measure the young’s modulus ex vivo. Collagen-to-Hb ratio measured using spectroscopic PA imaging was also recorded. Results show that PA-strain is positively correlated to Young’s Modulus with a correlation coefficient of 0.81. PA-strain distinguishes the low histological fibrosis (0-2) and high histological fibrosis (3-5) significantly (p-value<0.001). Collagen-to-Hb ratio and PA-strain are highly correlated with the histological fibrosis (0-5) with correlation of 0.67 and 0.64, respectively.
Quantification of fibrosis is critical for the management of inflammatory bowel disease. In this study, two measurements, collagen-to-Hb ratio quantified by spectroscopic analysis and tissue stiffness quantified by PA-strain, measured by our PA-US balloon catheter were employed to quantify intestinal fibrosis in 23 rabbits in vivo. Results show that both measurements can distinguish the low histological fibrosis (0-2) and high histological fibrosis (3-5) with statistical significance (p-value<0.001). Collagen-to-Hb ratio and PA-strain are highly correlated with the fibrosis stages with correlation of 0.67 and 0.64, respectively. PA-strain is positively correlated to Young’s Modulus measured ex vivo using microelastometer with correlation 0.81.
A longitudinal study on both 3D and 2D photoacoustic and Doppler ultrasound images of rat leg rheumatoid arthritis development has been performed using an automatic imaging system based on a GE HealthCare VividTM E95 unit with a L8-18i-D probe, an OPOTEK tunable laser system, and a Universal Robots UR3 robotic arm. Daily imaging of ankle bones was performed starting from day 0 when the lyophilized Mycobacterium butyricum was injected to induce the disease. Although both photoacoustic and Doppler ultrasound can confirm the disease development, photoacoustic imaging is more sensitive to microvasculature and enables earlier detection of inflammation than Doppler ultrasound.
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