Radiation protection dosimetry最新文献

The use of a Monte Carlo code in the assessment of residual radioactivity for decommissioning of a medical cyclotron facility requires a reasonable approximation to the facility's history of operations. A periodic irradiation scenario simulating the cyclotron's daily operation for radioisotope production is generally considered reasonable, but its implementation in the code's input file can be cumbersome because more than thousands of irradiation cycles must be modeled. In practice, two simplified scenarios with continuous irradiation are commonly used instead: (i) omitting the downtime between two irradiation periods and (ii) extending the irradiation duration across the entire operational lifespan of the facility, albeit with a reduced beam current to maintain workload consistency. A systematic comparison of residual radionuclide productions across various half-lives under these three scenarios was performed. This technical note presents the resulting correction factors for the two simplified continuous irradiation models, enhancing their applicability in estimating radioactive inventories under a range of circumstances.

This study aims to provide radiation reference levels in orthopaedic surgery. A total of 753 procedures were collected within 1 y. Categories containing several similar procedures were created based on four criteria: same anatomical area, same level of complexity, only single procedures, and at least 10 cases per category. Exposure was defined in terms of air kerma-area product, fluoroscopy time, and air kerma at the patient entrance reference point. For common procedures, median effective doses to patient were calculated using the Monte Carlo Software PCXMC. Most irradiating procedure in this study i.e. intramedullary nailing of the proximal femur was equivalent to an air kerma at the patient entrance reference point of 37.1 mGy, which is ~50 times lower than the threshold for acute deterministic effects of radiation. Optimization remains a must to reduce the dose while maintaining the image quality and reducing the likelihood of stochastic effects.

This paper describes the development of the Safety Performance Indicators (SPIs), the methodology for assessment of the safety culture of radiotherapy institutions using SPIs and common strengths and common areas for improvement. SPIs were categorized into eight sections which all together contain 23 attributes and each attribute has scoring criteria from 0 to 2 (in steps of 0.5). The maximum absolute cumulative score of SPIs was 46. A relative cumulative SPIs score of >80% indicates an institution strong commitment towards safety while score <50% indicates need for additional guidance to enhance safety culture. The assessment using SPIs was conducted for 17 radiotherapy institutions. The methodology of assessment includes interactive discussion, direct observations and document analysis. The relative cumulative SPIs score of seven institutions was found to be >80% while it was found in the range of 67.0% to 80% for the remaining ten institutions. Institutions were communicated about the cumulative SPIs score, areas of strengths, and areas for improvement. SPIs were found to be a good tool for safety culture assessment and can be utilized by the radiotherapy institutes for self-assessment to identify the areas of improvement. Based on SPIs score, regulatory body can grade the institutions from a radiation safety compliance point of view.

Equivalent doses for the eye lenses, thyroid, and mammary glands were measured and compared between one adult and three pediatric anthropomorphic phantoms during chest computed tomography (CT) using 40 mm volume helical scan on the Aquilion ONE GENESIS Edition CT equipment. Placing an optically stimulated luminescence dosemeter (OSLD) on the eye lenses, thyroid, and mammary gland, we measured and compared the equivalent dose of OSLD among different phantoms during chest CT using a helical scan. Compared with adults, the equivalent doses to the eye lens, thyroid, and mammary glands were ~81%, 77%, and 63% lower in newborns, 1-year-olds, and 5-year-olds using comparable image noise during chest CT.

This study introduces the MKM_B model, an approach derived from the MKM model, designed to evaluate the biological effectiveness of Boron Neutron Capture Therapy (BNCT) in the face of challenges from varying microscopic boron distributions. The model introduces a boron compensation factor, allowing for the assessment of compound Biological Effectiveness (CBE) values for different boron distributions. Utilizing the TOPAS simulation platform, the lineal energy spectrum of particles in BNCT was simulated, and the sensitivity of the MKM_B model to parameter variations and the influence of cell size on the model were thoroughly investigated. The CBE values for 10B-boronphenylalanine (BPA) and 10B-sodium (BSH) were determined to be 3.70 and 1.75, respectively. These calculations were based on using the nucleus radius of 2.5 μm and the cell radius of 5 μm while considering a 50% surviving fraction. It was observed that as cell size decreased, the CBE values for both BPA and BSH increased. Additionally, the model parameter rd was identified as having the most significant impact on CBE, with other parameters showing moderate effects. The development of the MKM_B model enables the accurate prediction of CBE under different boron distributions in BNCT. This model offers a promising approach to optimize treatment planning by providing increased accuracy in biological effectiveness.

In India, the prevailing approach to eye lens dosimetry is the placement of an existing dosemeter on the forehead region after slight modification serves as a dedicated Eye Lens Dosemeter. A methodology for estimating the eye lens dose in terms of the Hp(3) has been previously explored employing an algorithm based on the response characteristics of this dosemeter using ISO slab phantom. It was observed that the performance of the dosemeter in terms of Hp(3) using previous algorithm showed under response at higher angles of incidence and photon beams of energy < 200 keV. Further, study was conducted to modify the algorithm following the latest ISO recommendations. This involved generation of data from the response of existing dosemeter on a cylindrical phantom. The results of this study revealed better performance of the newly established algorithm in estimating eye lens dose in terms of Hp(3) when compared to the earlier algorithm.

Objective: Rectal toxicity is one of the primary dose-limiting side effects of prostate cancer radiotherapy, and consequential impairment on quality of life in these patients with long survival is an important problem. In this study, we aimed to evaluate the possibility of predicting rectal toxicity with artificial intelligence model which was including certain dosimetric parameters.

Materials and methods: One hundred and thirty-seven patients with a diagnosis of prostate cancer who received curative radiotherapy for prostate +/- pelvic lymphatics were included in the study. The association of the clinical data and dosimetric data between early and late rectal toxicity reported during follow-up was evaluated. The sample size was increased to 274 patients by synthetic data generation method. To determine suitable models, 15 models were studied with machine learning algorithms using Python 2.3, Pycaret library. Random forest classifier was used with to detect active variables.

Results: The area under the curve and accuracy were found to be 0.89-0.97 and 95%-99%, respectively, with machine learning algorithms. The sensitivity values for acute and toxicity were found to be 0.95 and 0.99, respectively.

Conclusion: Early or late rectal toxicity can be predicted with a high probability via dosimetric and physical data and machine learning algorithms of patients who underwent prostate +/- pelvic radiotherapy. The fact that rectal toxicity can be predicted before treatment, which may result in limiting the dose and duration of treatment, makes us think that artificial intelligence can enter our daily practice in a short time in this sense.

Radon, a radioactive gas can increase the risk of lung cancer when breathe in. Indoor Rn-222 and Rn-220 concentrations were determined using passive radon monitor in some dwellings in a Sn mining area of Jos Plateau. Outdoor gamma radiation was also measured with a hand-held survey meter. The range of Rn-222 and Rn-220 concentrations was from 7-53 Bq m-3 to 41-267 Bq m-3 with averages of 27 ± 17 and 92 ± 65 Bq m-3, respectively. The mean total effective dose due to Rn-222 + Rn-220 was estimated as 2.84 ± 1.57 mSv y-1. Rn-220 contributed between 50 and 95% to the total annual effective dose. There was no correlation between indoor Rn-220 and Rn-222 concentrations in the dwellings. Outdoor gamma radiation measured was between 0.31 ± 0.06 and 0.62 ± 0.08 μSv h-1, and mean annual effective dose calculated was 1.14 ± 0.21 mSv y-1. It is concluded from this study that thoron should not be neglected in dose assessment.

A De-Pangher-type long counter was designed for neutron measurements in standard neutron fields based on the results of simulations using the MCNP6 code at the National Metrology Institute of Japan, the National Institute of Advanced Industrial Science and Technology. The effects of six parameters in the design on the energy response of the long counter were investigated. The energy response was then quantitatively evaluated for eight design candidates selected from the investigation. The calculation results show that these candidates have a flatter energy response from 100 eV to 10 MeV compared to that of the current long counter. These candidates also reduce the difference between the average energy response from 10 eV to 1 MeV and that from 10 to 20 MeV.