Dose Distribution Verifications of IMRT for NPC

In order to explore a dose distribution verification procedure of intensity modulated radiation therapy （IMRT） for nasopharyngeal carcinoma （NPC） and establish its evaluation criteria, we performed 35 two-dimensional （2D） patient-specific IMRT verifications over the year i006. The percent of pixels passing 7 and the normalized agreement test （NAT） index were mainly used to represent the agreement between the measured and computed dose distributions with three criteria （2%/2 mm, 3%/3 mm and 5%/3 mm） as recommended in the literature. The results were that all cases passed through verifications with three criteria except that the NAT index of one case was beyond the limitation, and the three tolerance levels of 2%/2mm, 3%/3 mm and 5%/3 mm produced similar clinical verification results but led to different percent of pixels passing Y and NAT index. Our data showed that the percent of pixels passing y and the NAT index were complementary to evaluate future IMRT verifications as two significant metrics. Due to the influence of the noise and the trait of the software, we considered an IMRT plan as acceptable in case of the percent ofpixels passing y 〉95% and the NAT index 〈5 with the 5%/3 mm criteria for IMRT patient-specific quality assurance （QA）.

Evaluation of Radiation Exposure Literacy among Mammography Examinees Using Radiation Dose Distribution in Mammography Examinations

Introduction: Radiation is indispensable for diagnosis and treatment and is widely used in medicine. This study aimed to determine patients’ knowledge and ability to understand radiation exposure to assess the usefulness of providing information on radiation doses to examinees. Material and Methods: The radiation exposure literacy of mammography examinees was assessed using a new scale consisting of the following five items: “collection of information from various sources”, “selection of information necessary for oneself”, “understanding and communication of information”, “judgment of the reliability of information”, and “ability to plan and act based on information”. We analyzed the relationship of these items with examinees’ attributes and clarified the level of understanding of radiation exposure dose associated with mammography examinations by providing examinees with visual information in the form of color maps. Results: The relationship between “information collection” and several attributes of radiation exposure literacy was strong. In addition, providing visual information on radiation doses using dose distribution maps in mammography examinations could deepen the understanding of radiation doses among examinees. Conclusion: By understanding the radiation exposure literacy of examinees and comparing it with their attributes, it is possible to provide suggestions for developing methods of providing radiation dose information tailored to individual examinees. In addition, improving radiation exposure literacy will enable the development of skills necessary to provide safe medical care to medical examinees.

Enhancing Precision in Radiotherapy Delivery: Validating Monte Carlo Simulation Models for 6 MV Elekta Synergy Agility LINAC Photon Beam Using Two Models of the GAMOS Code

The most crucial requirement in radiation therapy treatment planning is a fast and accurate treatment planning system that minimizes damage to healthy tissues surrounding cancer cells. The use of Monte Carlo toolkits has become indispensable for research aimed at precisely determining the dose in radiotherapy. Among the numerous algorithms developed in recent years, the GAMOS code, which utilizes the Geant4 toolkit for Monte Carlo simula-tions, incorporates various electromagnetic physics models and multiple scattering models for simulating particle interactions with matter. This makes it a valuable tool for dose calculations in medical applications and throughout the patient’s volume. The aim of this present work aims to vali-date the GAMOS code for the simulation of a 6 MV photon-beam output from the Elekta Synergy Agility linear accelerator. The simulation involves mod-eling the major components of the accelerator head and the interactions of the radiation beam with a homogeneous water phantom and particle information was collected following the modeling of the phase space. This space was po-sitioned under the X and Y jaws, utilizing three electromagnetic physics mod-els of the GAMOS code: Standard, Penelope, and Low-Energy, along with three multiple scattering models: Goudsmit-Saunderson, Urban, and Wentzel-VI. The obtained phase space file was used as a particle source to simulate dose distributions (depth-dose and dose profile) for field sizes of 5 × 5 cm2 and 10 × 10 cm2 at depths of 10 cm and 20 cm in a water phantom, with a source-surface distance (SSD) of 90 cm from the target. We compared the three electromagnetic physics models and the three multiple scattering mod-els of the GAMOS code to experimental results. Validation of our results was performed using the gamma index, with an acceptability criterion of 3% for the dose difference (DD) and 3 mm for the distance-to-agreement (DTA). We achieved agreements of 94% and 96%, respectively, between simulation and experimentation for the three electromagnetic physics models and three mul-tiple scattering models, for field sizes of 5 × 5 cm2 and 10 × 10 cm2 for depth-dose curves. For dose profile curves, a good agreement of 100% was found between simulation and experimentation for the three electromagnetic physics models, as well as for the three multiple scattering models for a field size of 5 × 5 cm2 at 10 cm and 20 cm depths. For a field size of 10 × 10 cm2, the Penelope model dominated with 98% for 10 cm, along with the three multiple scattering models. The Penelope model and the Standard model, along with the three multiple scattering models, dominated with 100% for 20 cm. Our study, which compared these different GAMOS code models, can be crucial for enhancing the accuracy and quality of radiotherapy, contributing to more effective patient treatment. Our research compares various electro-magnetic physics models and multiple scattering models with experimental measurements, enabling us to choose the models that produce the most reli-able results, thereby directly impacting the quality of simulations. This en-hances confidence in using these models for treatment planning. Our re-search consistently contributes to the progress of Monte Carlo simulation techniques in radiation therapy, enriching the scientific literature.

BODY SURFACE EXPOSURE DISTRIBUTION OF EXAMINEES RECEIVED UPPER G．I．T．X－RAY EXAMINATION

A special cloth for keeping LiF(Mg,Cu,P)TL dosimetry elements is worn by examinees. The exposures of 128 examinees .received upper G.I.T (gastro-intestinal tram) X-ray examination are measured. The reference point of the maximum body surface exposure given is at the middle of stomach. The average of this point is (4.97±1.94) × 10-4C.kg-1 person-1 examination-1 and (1.33±0.28)×10-4C.kg-1.min-1.

Application of imidacloprid controlled-release granules to enhance the utilization rate and control wheat aphid on winter wheat

During winter wheat production, aphids need to be controlled with pesticides for the entire growth period. Controlled-release technology has been regarded as an alternative method for the improvement of pesticide efficiency. This study investigated two types of imidacloprid controlled-release granule (CR-GR): 2% imidacloprid CR-GR and 0.2% imidacloprid pesticide-fertilizer controlled-release granule (PF-CR-GR) when wheat was sown in winter. The release performance, utilization rate, terminal residues in edible parts, control effect on aphids, and achieved winter wheat yield were evaluated for both laboratory experiments and field application. Imidacloprid PF-CR-GR released more quickly in aqueous medium than CR-GR because of its good water solubility. After CR-GR treatments, the concentrations in wheat roots and soil were similar throughout the entire sampling period, and the concentrations in shoots were about 10–20% of those in roots. Imidacloprid was better absorbed when CR-GR was used as root treatment, compared with foliar treatment. Field application showed that imidacloprid CR-GR and PF-CR-GR controlled aphids throughout the entire growth period of winter wheat and improved the wheat yield. These findings identified application of imidacloprid CR-GR and PF-CR-GR on winter wheat as an effective way to enhance the pesticide utilization rate and ensure adequate yield. This paper provides a theoretical basis for the scientific use of pesticides and guides scientific pesticide application.

MONTE CARLO CALCULATION OF ENERGY DEPOSITION BY DELTA RAYS AROUND ION TRACKS

The radial distribution of dose around the path of a hemp ion has been studied by a Monte Carlo transport analysis of the delta rays produced along the track of a heavy ion based on classical binary collision dynamics and a single scattering model for the electron transport process. Result comparisons among this work and semi-empirical expression based delta ray theory of track structure, as well as other Monte Carlo calculations are made for 1, 3 MeV protons and several heavy ions. The results of the Monte Carlo simulations for energetic heavy ions are in agreement with experimental data and with results of different methods. The characteristic of this Monte Carlo calculation is a simulation of the delta rays theory of track structure.

Monte Carlo simulation of carbon ion radiotherapy for the human eye

Carbon ion is the mostly common used particle in heavy ion radiotherapy. In this paper, the carbon ion dose in tumor treatment for human eye was calculated with FLUKA code. An 80 MeV/u carbon beam was irradiated into the human eye from two directions. The first was from the lateral-forward direction, which was a typical therapeutic condition. In this case, a maximum dose was deposited in the tumor volume. In the second a beam was irradiated into eyes from the forward direction to simulate a patient gazing directly into treatment beam during therapy, which may cause a certain medical accident. This method can be used for a treatment plan in heavy ion radiotherapy.