Đánh giá ảnh hưởng của hốc khí và trường chiếu nhỏ tới phân bố liều của kế hoạch JO - IMRT trên bệnh nhân ung thư đầu cổ bằng phương pháp MONTE CARLO

2020 ◽  
Author(s):  
Oanh Luong Thi
Keyword(s):  
Monte Carlo ◽  
Head And Neck ◽  
Dose Distribution ◽  
Interface Region ◽  
Field Size ◽  
Imrt Plan ◽  
Air Cavity ◽  
Study Results ◽  
Tissue Interface ◽  
Dose Reductions

Purposes: The goal of this study was to use Monte Carlo (MC) simulation to examine the dosimetric effects of the air cavity on JO-IMRT dose distribution at air-tissues interfaces in head-and-neck (H&N) patients. Methods: The EGSnrc - MC code system was used to calculate the dose reductions in air-tissue interface region for single field irradiations with 1×1, 2×2, 3×3, 4×4, and 5×5 cm2 in solid acrylic phantoms (30×30×20 cm3) and seven fields in a JO-IMRT plan. With phantom, the PDD values in both with and without an air cavity (15×4×4 cm3) which is 2.5 cm away from the anterior surface of phantom were used to evaluate. With the JO-IMRT plan, the dose-volume histograms (DVH), slice by slice isodose, and the gamma index using global methods implemented in PTW-VeriSoft with 3%/3 mm criteria were used to evaluate. Results: The study results indicate that the dose reductions in the air-tissue interface region of the phantom are strongly dependent on field size. The average percentage dose reductions at 1 mm from the air‑water interface for the field size 1×1, 2×2, 3×3, 4×4, and 5×5 cm2 are 62.04%, 52.34%, 40.71%, 26.72%, and 19.85%, respectively. Additionally, the mean MC dose in the PTV (65.58 Gy) of patients were lower than the TPS predicted dose (71.41 Gy). Conclusions: From this study, we conclude that the dose reduction in near air-tissue interfaces is a significant effect on JO-IMRT dose distribution in head-and-neck (H&N) patients.

scholarly journals Investigating the Effect of Air Cavities of Sinuses on the Radiotherapy Dose Distribution Using Monte Carlo Method

2019 ◽  
Vol 9 (1Feb) ◽  
Author(s):  
F Seif ◽  
M R Bayatiani ◽  
S Hamidi ◽  
M Kargaran
Keyword(s):  
Monte Carlo ◽  
Dose Distribution ◽  
Sphenoid Sinus ◽  
Neck Region ◽  
Cavity Size ◽  
Air Cavity ◽  
Head And Neck Region ◽  
Radiotherapy Dose ◽  
Dose Deposition ◽  
Air Cavities

Background: Considering that some vital organs exist in the head and neck region, the treatment of tumors in this area is a crucial task. The existence of air cavities, namely sinuses, disrupt the radiotherapy dose distribution. The study aims to analyze the effect of maxillary, frontal, ethmoid and sphenoid sinuses on radiotherapy dose distribution by Monte Carlo method.Materials and Methods: In order to analyze the effect of the cavities on dose distribution, the maxillary, frontal, ethmoid and sphenoid sinus cavities were simulated with (3×3.2×2) cm3, (2×2×3.2) cm3, (1×1×1.2) cm3 and(1×1×2) cm3 dimensions.Results: In the analysis of the dose distribution caused by cavities, some parameters were observed, including: inhomogeneity of dose distribution in the cavities, inhomogeneity of dose on the edges of the air cavities and dispersion of the radiations after the air cavity. The amount of the dose in various situations showed differences: before the cavity a 0.64% and a 2.76% decrease, a 12.06% and a 17.17% decrease in the air zone, and a 2.25% and a 5.9% increase after the cavity.Conclusion: The results indicate that a drop in dose before the air cavities and in the air zone occurs due to the lack of scattered radiation. Furthermore, the rise in dose was due to the passage of more radiation from the air cavity and dose deposition after the air cavity. The changes in dose distribution are dependent on the cavity size and depth. As a result, this has to be noted in the treatment planning and MU calculations of the patient.

scholarly journals Investigating the Effect of Air Cavities of Sinuses on the Radiotherapy Dose Distribution Using Monte Carlo Method

2019 ◽  
Vol 9 (1Feb) ◽  
Author(s):  
F Seif ◽  
M R Bayatiani ◽  
S Hamidi ◽  
M Kargaran
Keyword(s):  
Monte Carlo ◽  
Dose Distribution ◽  
Sphenoid Sinus ◽  
Neck Region ◽  
Cavity Size ◽  
Air Cavity ◽  
Head And Neck Region ◽  
Radiotherapy Dose ◽  
Dose Deposition ◽  
Air Cavities

Background: Considering that some vital organs exist in the head and neck region, the treatment of tumors in this area is a crucial task. The existence of air cavities, namely sinuses, disrupt the radiotherapy dose distribution. The study aims to analyze the effect of maxillary, frontal, ethmoid and sphenoid sinuses on radiotherapy dose distribution by Monte Carlo method.Materials and Methods: In order to analyze the effect of the cavities on dose distribution, the maxillary, frontal, ethmoid and sphenoid sinus cavities were simulated with (3×3.2×2) cm3, (2×2×3.2) cm3, (1×1×1.2) cm3 and(1×1×2) cm3 dimensions.Results: In the analysis of the dose distribution caused by cavities, some parameters were observed, including: inhomogeneity of dose distribution in the cavities, inhomogeneity of dose on the edges of the air cavities and dispersion of the radiations after the air cavity. The amount of the dose in various situations showed differences: before the cavity a 0.64% and a 2.76% decrease, a 12.06% and a 17.17% decrease in the air zone, and a 2.25% and a 5.9% increase after the cavity.Conclusion: The results indicate that a drop in dose before the air cavities and in the air zone occurs due to the lack of scattered radiation. Furthermore, the rise in dose was due to the passage of more radiation from the air cavity and dose deposition after the air cavity. The changes in dose distribution are dependent on the cavity size and depth. As a result, this has to be noted in the treatment planning and MU calculations of the patient.

scholarly journals Non-Covalent Forces in Naphthazarin—Cooperativity or Competition in the Light of Theoretical Approaches

2021 ◽  
Vol 22 (15) ◽  
pp. 8033
Author(s):  
Aneta Jezierska ◽  
Kacper Błaziak ◽  
Sebastian Klahm ◽  
Arne Lüchow ◽  
Jarosław J. Panek
Keyword(s):  
Monte Carlo ◽  
Perturbation Theory ◽  
Potential Energy ◽  
Proton Transfer ◽  
Ir Spectra ◽  
Quantum Monte Carlo ◽  
Density Functional ◽  
Theoretical Approaches ◽  
Study Results ◽  
Intramolecular Hydrogen

Non-covalent interactions responsible for molecular features and self-assembly in Naphthazarin C polymorph were investigated on the basis of diverse theoretical approaches: Density Functional Theory (DFT), Diffusion Quantum Monte Carlo (DQMC), Symmetry-Adapted Perturbation Theory (SAPT) and Car-Parrinello Molecular Dynamics (CPMD). The proton reaction paths in the intramolecular hydrogen bridges were studied. Two potential energy minima were found indicating that the proton transfer phenomena occur in the electronic ground state. Diffusion Quantum Monte Carlo (DQMC) and other levels of theory including Coupled Cluster (CC) employment enabled an accurate inspection of Potential Energy Surface (PES) and revealed the energy barrier for the proton transfer. The structure and reactivity evolution associated with the proton transfer were investigated using Harmonic Oscillator Model of Aromaticity - HOMA index, Fukui functions and Atoms In Molecules (AIM) theory. The energy partitioning in the studied dimers was carried out based on Symmetry-Adapted Perturbation Theory (SAPT) indicating that dispersive forces are dominant in the structure stabilization. The CPMD simulations were performed at 60 K and 300 K in vacuo and in the crystalline phase. The temperature influence on the bridged protons dynamics was studied and showed that the proton transfer phenomena were not observed at 60 K, but the frequent events were noticed at 300 K in both studied phases. The spectroscopic signatures derived from the CPMD were computed using Fourier transformation of autocorrelation function of atomic velocity for the whole molecule and bridged protons. The computed gas-phase IR spectra showed two regions with OH absorption that covers frequencies from 2500 cm−1 to 2800 cm−1 at 60 K and from 2350 cm−1 to 3250 cm−1 at 300 K for both bridged protons. In comparison, the solid state computed IR spectra revealed the environmental influence on the vibrational features. For each of them absorption regions were found between 2700–3100 cm−1 and 2400–2850 cm−1 at 60 K and 2300–3300 cm−1 and 2300–3200 cm−1 at 300 K respectively. Therefore, the CPMD study results indicated that there is a cooperation of intramolecular hydrogen bonds in Naphthazarin molecule.

Dose distribution from x-ray microbeam arrays applied to radiation therapy: An EGS4 Monte Carlo study

2005 ◽  
Vol 32 (8) ◽  
pp. 2455-2463 ◽  
Author(s):  
M. De Felici ◽  
R. Felici ◽  
M. Sanchez del Rio ◽  
C. Ferrero ◽  
T. Bacarian ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Radiation Therapy ◽  
Dose Distribution ◽  
Monte Carlo Study ◽  
X Ray
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