Figure 1

Illustration of thermoacoustic tomography. A pulsed microwave generated from a radar penetrates the tissue. Because of dielectric contrast, malignant tissue (such as a tumor) usually absorbs more microwave energy and produces a higher temperature increase than the surrounding normal tissue. The temperature rise leads to the generation of ultrasound due to thermoelastic expansion. An acoustic detector receives the ultrasound signals around the tissue, which are used to reconstruct the microwave absorption distribution.Reuse & Permissions

Figure 2

Three dimensional FDTD grid. $I$, $J$, and $K$ represent the grid spatial indices. $\Delta x$, $\Delta y$, and $\Delta z$ are edge length of the grid. Electric fields locate at the center of the edges, and the magnetic fields locate at the center of the faces.Reuse & Permissions

Figure 3

Simulation model. The malignant tissue is in cylindrical shape, and surrounded by the normal tissue with different dielectric parameters. The microwave illuminates upward along $\widehat{z}$ with polarization along $\widehat{x}$.Reuse & Permissions

Figure 4

Computational domain. The EM plane wave is illuminating along the $\widehat{z}$ direction, with polarization along $\widehat{x}$.Reuse & Permissions

Figure 5

Simulation results of $s\left(\mathbf{r}\right)$ for homogenous cylinders with a length of 15.0 mm each. (a) For the cylinder with a radius of 4.0 mm. (b) For the cylinder with a radius of 8.0 mm.Reuse & Permissions

Figure 6

Porcine fat phantoms used in the experiment. (a) Phantom with a small hole (radius of 4 mm) in the middle filled with gel. (b) Phantom with a large hole (radius of 8 mm) in the middle filled with gel. The microwave illuminates upward along $\widehat{z}$, with polarization along $\widehat{x}$.Reuse & Permissions

Figure 7

Experiment setup. The phantom and transducer are placed in a tank filled with the mineral oil. Microwave is illuminating upward from the horn. The dashed line represents the scanning trajectory.Reuse & Permissions

Figure 8

Reconstructed images by delay-and-sum reconstruction algorithm. (a) Image of the phantom with a water gel cylinder of radius 4.0 mm, using the illumination source with $\widehat{x}$ polarization. There is a clear “split” pattern. (b) Image of the phantom with a water gel cylinder of radius 4.0 mm, using the illumination source with $\widehat{y}$ polarization. (c) Image of the average of (a) and (b). (d) Image of the phantom with a water gel cylinder of radius 8.0 mm, using the illumination source with $\widehat{x}$ polarization. (e) Image of the phantom with a water gel cylinder of radius 8.0 mm, using the illumination source with $\widehat{y}$ polarization. (f) Image of the average of (d) and (e).Reuse & Permissions