Photoacoustic imaging, which can provide the maximum intensity contrast in tissue depth imaging without ionizing radiation, will be a promising imaging trend for tumor detection. In this paper, a column diffusion fiber was employed to carry a pulsed laser for irradiating stomach directly through esophagus based on the characteristics of gastric tissue structure. A long focused ultrasonic transducer was placed outside the body to detect photoacoustic signals of gastric tissue. Phantom and in vitro experiments of submucosal gastric tumors were carried out to check the sensitivity of scanning photoacoustic tomography system, including the lateral and longitudinal resolution of the system, sensitivity of different absorption coe±cient in imaging, capability of transversal detection, and probability of longitudinal detection. The results demonstrate that our innovative technique can improve the parameters of imaging. The lateral resolution reaches 2.09 mm. Then a depth of 5.5mm with a longitudinal accuracy of 0.36mm below gastric mucosa of early gastric cancer (EGC) has been achieved. In addition, the optimal absorption coe±cient differences among absorbers of system are 3.3–3.9 times. Results indicate that our photoacoustic imaging (PAI) system, is based on a long focusing transducer, can provide a potential application for detecting submucosal EGC without obvious symptoms.

Determining the light absorption distribution (LAD) of uterine tissue helps the detection of endometrial carcinoma. In this work, a 3-dimensional optical model of the human uterus is proposed and examined. The model is filled with strong scattering medium (undiluted raw and homogenized milk, URHM) or air at 630 nm and 800 nm wavelengths. Monte Carlo simulations are used to find the absorption profiles of photons by transcervical laser illumination, with a cylindrically diffused light source (CDLS) or spherically diffused light source (SDLS). The results show that 800 nm is a good laser wavelength value for the detection of endometrial carcinoma by photoacoustic imaging (PAI). At the same time, the shape of the light source becomes less important in a relatively large cavity. The impacts of different scattering coefficients of CDLS on the irradiated area are demonstrated. Strong scattering medium is helpful to the il-lumination of the uterus cavity.

Quantification of fiber orientation is the key to characterizing the tissue mechanical properties and diagnosing diseases. A center line-based algorithm is presented for estimating the orientation distribution that first skeletonizes a binary image of fibers, followed by orientation estimation using a weight vector summation algorithm along the center line of image. Then we use the orientation at the skeleton to approximate the orientation of each pixel between the boundary and skeleton. The algorithm is applied for characterizing collagen fibers of mouse skins in second harmonic generation (SHG) image, and the circle standard deviation of orientation could be a biomarker to differentiate the naturally aging skins.

Absorption coefficient of biological tissue is an important parameter in biomedicine, but its determination remains a challenge. In this paper, we propose a method using focusing photoacoustic imaging technique and internal light irradiation of cylindrical diffusing fiber (CDF) to quantify the target optical absorption coefficient. Absorption coefficients for ink absorbers are firstly determined through photoacoustic and spectrophotometric measurements at the same excitation, which demonstrates the feasibility of this method. Also, the optical absorption coefficients of ink absorbers with several concentrations are measured. Finally, the two-dimensional scanning photoacoustic image is obtained. Optical absorption coefficient measurement and simultaneous photoacoustic imaging of absorber non-invasively are the typical characteristics of the method. This method can play a significant role for non-invasive determination of blood oxygen saturation, the absorption-based imaging and therapy.