Real-time GPU-based ultrasound simulation using deformable mesh models.

This paper presents a real-time capable graphics processing unit (GPU)-based ultrasound simulator suitable for medical education. The main focus of the simulator is to synthesize realistic looking ultrasound images in real-time including artifacts, which are essential for the interpretation of this data. The simulation is based on a convolution-enhanced ray-tracing approach and uses a deformable mesh model. Deformations of the mesh model are calculated using the PhysX engine. Our method advances the state of the art for real-time capable ultrasound simulators by following the path of the ultrasound pulse, which enables better simulation of ultrasound-specific artifacts. An evaluation of our proposed method in comparison with recent generative slicing-based strategies as well as real ultrasound images is performed. Hereby, a gelatin ultrasound phantom containing syringes filled with different media is scanned with a real transducer. The obtained images are then compared to images which are simulated using a slicing-based technique and our proposed method. The particular benefit of our method is the accurate simulation of ultrasound-specific artifacts, like range distortion, refraction and acoustic shadowing. Several test scenarios are evaluated regarding simulation time, to show the performance and the bottleneck of our method. While being computationally more intensive than slicing techniques, our simulator is able to produce high-quality images in real-time, tracing over 5000 rays through mesh models with more than 2 000 000 triangles of which up to 200 000 may be deformed each frame.

Simulation of dynamic ultrasound based on CT models for medical education.

In our approach, we first specify a 3D model of the image structure by segmenting a CT dataset into the respective tissues followed by assigning the acoustic properties (velocity, impedance, scattering mean and standard deviation, damping factor and packing factor). Given that model, we simulate the ray propagation, beam forming, and finally the backscattering. Due to the inhomogenities of tissue, different physical models for ultrasound simulation are required: Rayleigh scattering is applied for homogenous regions and ray tracing techniques handle abrupt changes in acoustic impedance on tissue boundaries. The latter leads to different phenomena like refraction (Snell's law), reflection and transmission (Fresnel equation). The gradients needed for these methods are precomputed for each model using a central-difference method with multiple neighbours. Absorption is calculated by the Beer-Lambert law.