# Standardization and Validation of Brachytherapy Seeds’ Modelling Using GATE and GGEMS Monte Carlo Toolkits

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## Abstract

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## Simple Summary

## Abstract

## 1. Introduction

## 2. Materials and Methods

#### 2.1. AAPM TG-43 Formalism (Anisotropy, Radial Dose, Dose Constant)

_{k}, measured in U, where U stands for cGy cm

^{2}h

^{−1}; the geometry factor, G(r, θ); the dose rate constant, Λ.

**r**is the distance to the point of interest and

**θ**is the angle with respect to the long axis of the source (Figure 1).

**r**denotes the distance (in cm) away from the centre of the active source to the point of interest,

**r**denotes the reference distance which is specified to be 1 cm, and

_{0}**θ**denotes the polar angle specifying the point of interest

**P(r,θ)**, relative to the source longitudinal axis. The reference angle,

**θ**, defines the source transverse plane, and is specified to be 90° or π/2 radians (Figure 1). The Z- and Y-axis are chosen as the longitudinal and transverse axes, respectively. The origin is taken as the centre of the active part, with the positive Z-axis directed through the source tip [11].

_{0}#### 2.2. Brachytherapy Seeds (Oncoseed, Isoseed, VS2000, M-19, mHDR-v1, mPDR-v2)

^{125}I sources, the Amersham Oncoseed 6711 and the Bebig Isoseed I25.S06; three High Dose Rate (HDR)

^{192}Ir sources, Nucletron mHDR-v1 (classic), Varian VS2000 and SPEC HDR-M19; and one Pulsed Dose Rate (PDR)

^{192}Ir source, the Nucletron mPDR-v2 [11].

#### 2.3. MC Simulations (GATE/GGEMS)

#### 2.4. Physics List

#### 2.5. Phase Space Files (Blender–GATE–GGEMS)

^{6}primaries. For this PHSP only gamma particles were recorded, and no secondary particles were taken into account.

^{6}particles.

#### 2.6. Clinical Case (Brachytherapy Plan with 67 Seeds)

^{8}primaries were simulated in both GATE and GGEMS. In both cases, the Track Length Estimator (TLE) [30] was used, to reduce the statistical uncertainty of the recorded energy deposition, as well as to accelerate simulations. The TLE actor involves a local energy deposition by secondary electrons. In addition, TLE recorded the absorbed dose during the whole trajectory of each simulated energy particle, consequently reducing the required number of primaries needed to converge. Organ dose distributions were also investigated in terms of the cumulative Dose Volume Histogram (cDVH), as it is important clinical information that is utilized by any TPS during planning.

## 3. Results

#### 3.1. Validation of GATE Simulated Data–TG-43 Protocol

^{12}primaries. The statistical difference between the simulated and the TG-43 provided RDF values was lower than 1%, which is the limit advised for acceptance by the TG-43. Figure 3 displays the RDF comparison for every studied source. It must be mentioned that the same points were calculated for both simulation toolkits and the same points had been used by the TG-43 (even if some data are shown in continuous lines).

^{−1}U

^{−1}; U equals cGy cm

^{2}h

^{−1}.

#### 3.2. Validation of GGEMS with GATE

#### 3.2.1. Amersham Health 6711-Anisotropy, Radial Dose, Dose Constant, Dose Profiles

#### 3.2.2. One (1) Seed–Patient CT

#### 3.2.3. Sixty-Seven (67) Seeds–CT Phantom–Clinical Case

^{8}primaries in a computer cluster of 120 processors (ARIS High Performance Computers). The same simulation was executed in GGEMS in only 162 s on a single NVIDIA 960M GTX GPU, on a single PC. The presented significant time reduction of MC simulation using GGEMS while keeping the same computational accuracy, compared to GATE, may allow the integration of the proposed method in routine clinical practice.

## 4. Discussion

^{8}primaries in a computer cluster of 120 processors (ARIS Hyper computer). To achieve lower statistical uncertainty (<1%) for the whole body 10

^{10}primaries could be used. This would result to an increase in computational time by at least 100 times. Thus, we did not produce such results.

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**Geometric representation for the calculation of radial dose function and anisotropy function, for cylindrical sources.

**Figure 4.**Radial Dose Function for Amersham Health 6711 (LDR). Comparison between GATE and GGEMS simulation results.

**Figure 5.**Profile of absorbed dose in water sphere (15 cm radius) of the Amersham Health 6711 Brachytherapy

^{125}I seed. The voxel size is 0.25 mm, and image dimensions are 89 × 13 × 89 voxels (this does not cover the whole water sphere). The seed is in the middle and oriented towards the inside of the paper.

**Figure 6.**Profile of absorbed dose of the simulation of Amersham Health 6711 inserted in the CT phantom. Transverse orientation is used (as seen in Figure 7). (

**A**) is the profile plot at the centre of the seed, (

**B**) is the profile plot at the edge of the source, and (

**C**) is a profile plot away from the seed. In (

**D**), the profile plot when all slices were summed into one is depicted for the whole developed phantom.

**Figure 7.**Simulation of a clinical case with 67 Amersham Health 6711 seeds in a prostate. Dose maps are shown for both toolkits (

**A**) GATE and (

**B**) GGEMS. White stands for maximum absorbed dose (100%). In (

**C**) a profile comparison is depicted for both simulation tools. The line seen on (

**A**) and (

**B**) images is the region where the dose profile is taken.

**Figure 8.**Slice of prostate irradiation, with the segmentation of organs and the deposited energy. Left: GATE simulation. Right: GGEMS simulation. (

**A**) Transverse, (

**B**) Coronal and (

**C**) Sagittal slice. With colour, areas with similar dose are shown. Blue: Dose > 50%. Green: Dose > 100%. Red: Dose > 150%.

**Table 1.**Average Statistical Difference of Anisotropy Function, for all seeds, when simulation output is compared with TG-43 data.

Source | Distance (cm) | Average Difference (%) |
---|---|---|

Amersham Health 6711 ^{125}I | 0.5 | 2.8 |

1.0 | 3.0 | |

2.0 | 2.8 | |

3.0 | 2.6 | |

5.0 | 3.8 | |

Bebig Theragenics ^{125}I | 0.5 | 6.0 |

1.0 | 3.7 | |

2.0 | 3.8 | |

3.0 | 3.1 | |

5.0 | 5.4 | |

Nucletron mHDR-v1 ^{192}Ir | 0.5 | 3.5 |

1.0 | 4.1 | |

2.0 | 3.5 | |

3.0 | 4.1 | |

5.0 | 4.5 | |

Varian VS2000 ^{192}Ir | 0.5 | 2.6 |

1.0 | 1.4 | |

2.0 | - | |

3.0 | 2.8 | |

5.0 | 2.1 | |

Nucletron mPDR-v2 ^{192}Ir | 0.5 | 3.4 |

1.0 | 2.9 | |

2.0 | 1.6 | |

3.0 | 1.7 | |

5.0 | 2.0 | |

SPEC Μ-19 ^{192}Ir | 0.5 | 3.4 |

1.0 | 2.7 | |

2.0 | 3.7 | |

3.0 | 3.7 | |

5.0 | 3.8 |

**Table 2.**Dose Rate Constant (in cGy h-1 U-1), for all seeds, when simulation output is compared with TG-43 data.

Source | GATE | TG-43 | Difference % |
---|---|---|---|

Amersham Health 6711 ^{125}I | 1.012 | 1.012 | 0.0 |

Bebig Theragenics ^{125}I | 1.012 | 1.012 | 0.0 |

Nucletron mHDR-v1 ^{192}Ir | 1.114 | 1.109 | 0.5 |

Varian VS2000 ^{192}Ir | 1.097 | 1.098 | 0.1 |

Nucletron mPDR-v2 ^{192}Ir | 1.101 | 1.108 | 0.6 |

SPEC Μ-19 ^{192}Ir | 1.1 | 1.13 | 2.7 |

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**MDPI and ACS Style**

Chatzipapas, K.P.; Plachouris, D.; Papadimitroulas, P.; Mountris, K.A.; Bert, J.; Visvikis, D.; Mihailidis, D.; Kagadis, G.C.
Standardization and Validation of Brachytherapy Seeds’ Modelling Using GATE and GGEMS Monte Carlo Toolkits. *Cancers* **2021**, *13*, 5315.
https://doi.org/10.3390/cancers13215315

**AMA Style**

Chatzipapas KP, Plachouris D, Papadimitroulas P, Mountris KA, Bert J, Visvikis D, Mihailidis D, Kagadis GC.
Standardization and Validation of Brachytherapy Seeds’ Modelling Using GATE and GGEMS Monte Carlo Toolkits. *Cancers*. 2021; 13(21):5315.
https://doi.org/10.3390/cancers13215315

**Chicago/Turabian Style**

Chatzipapas, Konstantinos P., Dimitris Plachouris, Panagiotis Papadimitroulas, Konstantinos A. Mountris, Julien Bert, Dimitris Visvikis, Dimitris Mihailidis, and George C. Kagadis.
2021. "Standardization and Validation of Brachytherapy Seeds’ Modelling Using GATE and GGEMS Monte Carlo Toolkits" *Cancers* 13, no. 21: 5315.
https://doi.org/10.3390/cancers13215315