# SU-E-T-558: Monte Carlo Photon Transport Simulations On GPU with Quadric Geometry

## Abstract

Purpose: Monte Carlo simulation on GPU has experienced rapid advancements over the past a few years and tremendous accelerations have been achieved. Yet existing packages were developed only in voxelized geometry. In some applications, e.g. radioactive seed modeling, simulations in more complicated geometry are needed. This abstract reports our initial efforts towards developing a quadric geometry module aiming at expanding the application scope of GPU-based MC simulations. Methods: We defined the simulation geometry consisting of a number of homogeneous bodies, each specified by its material composition and limiting surfaces characterized by quadric functions. A tree data structure was utilized to define geometric relationship between different bodies. We modified our GPU-based photon MC transport package to incorporate this geometry. Specifically, geometry parameters were loaded into GPU’s shared memory for fast access. Geometry functions were rewritten to enable the identification of the body that contains the current particle location via a fast searching algorithm based on the tree data structure. Results: We tested our package in an example problem of HDR-brachytherapy dose calculation for shielded cylinder. The dose under the quadric geometry and that under the voxelized geometry agreed in 94.2% of total voxels within 20% isodose line based on a statisticalmore »

- Authors:

- The University of Texas Southwestern Medical Ctr, Dallas, TX (United States)

- Publication Date:

- OSTI Identifier:
- 22496273

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Medical Physics; Journal Volume: 42; Journal Issue: 6; Other Information: (c) 2015 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 61 RADIATION PROTECTION AND DOSIMETRY; 62 RADIOLOGY AND NUCLEAR MEDICINE; ALGORITHMS; BRACHYTHERAPY; CHARGED-PARTICLE TRANSPORT; COMPUTERIZED SIMULATION; GEOMETRY; MONTE CARLO METHOD; PHOTON TRANSPORT; RADIATION DOSES; SHIELDING

### Citation Formats

```
Chi, Y, Tian, Z, Jiang, S, and Jia, X.
```*SU-E-T-558: Monte Carlo Photon Transport Simulations On GPU with Quadric Geometry*. United States: N. p., 2015.
Web. doi:10.1118/1.4924920.

```
Chi, Y, Tian, Z, Jiang, S, & Jia, X.
```*SU-E-T-558: Monte Carlo Photon Transport Simulations On GPU with Quadric Geometry*. United States. doi:10.1118/1.4924920.

```
Chi, Y, Tian, Z, Jiang, S, and Jia, X. Mon .
"SU-E-T-558: Monte Carlo Photon Transport Simulations On GPU with Quadric Geometry". United States.
doi:10.1118/1.4924920.
```

```
@article{osti_22496273,
```

title = {SU-E-T-558: Monte Carlo Photon Transport Simulations On GPU with Quadric Geometry},

author = {Chi, Y and Tian, Z and Jiang, S and Jia, X},

abstractNote = {Purpose: Monte Carlo simulation on GPU has experienced rapid advancements over the past a few years and tremendous accelerations have been achieved. Yet existing packages were developed only in voxelized geometry. In some applications, e.g. radioactive seed modeling, simulations in more complicated geometry are needed. This abstract reports our initial efforts towards developing a quadric geometry module aiming at expanding the application scope of GPU-based MC simulations. Methods: We defined the simulation geometry consisting of a number of homogeneous bodies, each specified by its material composition and limiting surfaces characterized by quadric functions. A tree data structure was utilized to define geometric relationship between different bodies. We modified our GPU-based photon MC transport package to incorporate this geometry. Specifically, geometry parameters were loaded into GPU’s shared memory for fast access. Geometry functions were rewritten to enable the identification of the body that contains the current particle location via a fast searching algorithm based on the tree data structure. Results: We tested our package in an example problem of HDR-brachytherapy dose calculation for shielded cylinder. The dose under the quadric geometry and that under the voxelized geometry agreed in 94.2% of total voxels within 20% isodose line based on a statistical t-test (95% confidence level), where the reference dose was defined to be the one at 0.5cm away from the cylinder surface. It took 243sec to transport 100million source photons under this quadric geometry on an NVidia Titan GPU card. Compared with simulation time of 99.6sec in the voxelized geometry, including quadric geometry reduced efficiency due to the complicated geometry-related computations. Conclusion: Our GPU-based MC package has been extended to support photon transport simulation in quadric geometry. Satisfactory accuracy was observed with a reduced efficiency. Developments for charged particle transport in this geometry are currently in progress.},

doi = {10.1118/1.4924920},

journal = {Medical Physics},

number = 6,

volume = 42,

place = {United States},

year = {Mon Jun 15 00:00:00 EDT 2015},

month = {Mon Jun 15 00:00:00 EDT 2015}

}