KEYWORDS: Tumors, Acoustics, Tissues, Signal detection, Monte Carlo methods, Tissue optics, Cancer, Diffusion, Photoacoustic imaging, Signal generators
Photoacoustic imaging (PAI) has recently emerged as a promising imaging modality for gastric cancer. In order to describe and study photoacoustic (PA) signal generation principles and study the effect of variation in PA parameters. This paper presents a finite element (FE)-based numerical simulation model of PAI of gastric tissue and the related tumor. This study attempts to describe how a commercially available Finite Element software (COMSOL), can serve as a single platform for simulating PA that couples the electromagnetic, thermodynamic and acoustic pressure physics involved in PA phenomena. A three-dimensional optical model of uniform gastric tissue embedded with spherical tumor and external irradiation short pulse laser point source was constructed. Four sets of simulation models were integrated together to describe the physical principles of PAI: 1) Diffusion equation was used to describe light propagation; 2) Temperature changes were simulated using bio-thermal equations; 3) With stress-strain model, the process of the PA signal generation could be simulated; 4) Pressure acoustics was used to simulate the propagation of acoustic pressure. In addition, point probes placed in the interior and boundary of the FE model can provide acoustic pressure data, which conforms to the rules of PA signal. This study not only confirm the effectiveness of the PA model, but also provide certain significance for better excitation and detection of PA signal.
Photoacoustic Imaging (PAI) has potential for clinical applications in real-time after a tiny modification of a current US scanner. The shared detector platform facilitates a natural integration of PA and US imaging creating a hybrid imaging technique that combines functional and structural information. In this work, two blood vessels phantom experiment was conducted by coregistered photoacoustic and ultrasonic imaging using clinical ultrasonic system. The vessels were placed about 6 cm away from the transducer. With conventional irradiation, real-time PA and US images could be obtained during the experiment. 450 of 2D PA and US images and reconstructed 3D imaging were taken by transducer scanning. The result indicates the system has the ability to get the PA signal in a deep tissue depth. 3D PA image clearly describes the tissue structure and benefits the detecting in clinical application.
Laser-induced thermotherapy (LITT) predicts the effects of laser applications in LITT and optimizes the efficacy of irradiation plans, the light distribution in liver tissue, the optical tissue properties, and the changes caused by thermal denaturation. In this paper, COMSOL Multiphysics, a commercially available Finite Element (FE) simulation software package, was used to simulate the interaction between laser and liver tissue. A short-pulse laser point source, coagulated liver tissue and uniform soft tissue submerged in water were established. In this study, two sets of simulation models were used to describe the principles: 1) Diffusion equation was used to simulate light propagation; 2) Temperature changes were simulated using biothermal equations. The experimental results show that there are significant differences in penetration depth and light energy distribution of native and coagulated liver tissues under laser irradiation with different wavelengths. The penetration depth of the liver tissue after heat coagulation is significantly reduced. In addition, the simulation can present the temperature curve during the clinical hyperthermia of liver cancer and determine the effect by various treatment parameters. These results provide a better understanding of laser-tissue interactions and may be helpful to researchers in the fields of laser medical.
Photoacoustic imaging (PAI) is a promising technique to image tumor angiogenesis development and detect endometrial carcinoma in earlier stages. The light absorption distribution of uterine tissue determines the imaging depth and range of PAI. In this work, a 3D triangular meshes tumor-embedded uterine optical model was established by the histological structure of uterus. The model is filled with strong scattering media (undiluted raw and homogenized milk, URHM) and air, respectively. Monte Carlo simulation is implemented based on the molecular optical simulation environment (MOSE) to find the absorption profiles of photons by transcervical laser illumination with cylindrically diffused light source (CDLS) or spherically diffused light source (SDLS) at wavelength 800nm. The results show the media with an extremely high scattering coefficient and an extremely low absorption coefficient like URHM helps the light propagations in a relatively small cavity. CDLS performs better when the tumor happens far from the light source center than the SDLS. On the same time, embedded tumors of the model filled with URHM are easier to detect by the transcervical laser illumination of CDLS than SDLS in the fundus of the uterus. The conclusions are helpful to optimize the laser source and to improve the imaging depth in a photoacoustic imaging system.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.