Accumulation of lead radionuclides in 18 leaf vegetable types in Viet Nam.

Studying the concentration of radioactive lead in soil and plants, and using plants for phytoremediation are important for the environment and human health protection. In this study, we used gamma spectrometry to determine activity concentration in soil - plants, transfer factor. The average activity concentration of lead radionuclides in soil and plants were in the following order of 210Pb > 214Pb > 212Pb. The average activity ratio of 214Pb and 212Pb to 210Pb in soil were 0.70 and 0.59 and in plants were 0.69 and 0.14, respectively. The results showed that there was not much difference between the ratio of radioactive 214Pb and 210Pb concentrations in vegetable and plant samples. Ming aralia (Polyscias fruticose) and lettuce (Lactuca sativa) contained the highest concentrations of 210Pb, and Malabar spinach (Basella alba) contained the lowest concentration. Ming aralia could be used for the radioactive decontamination of 210Pb. There vegetable samples from Ho Chi Minh City were considered safe for human consumption in the aspect of lead radionuclides.

Estimation of the soil to plant transfer factor and the annual organ equivalent dose due to ingestion of food crops in Ho Chi Minh city, Vietnam.

In this study, soil-to-plant transfer factor and annual organ equivalent dose due to ingestion of natural radionuclides in 13 popular food crop samples in Ho Chi Minh city, Vietnam were estimated. The obtained data show that the radioactive elements transported from soil to plants play an essential role as indicators for the nutritional needs of plant and the ability to accumulate radioisotopes and heavy metal elements for environmental decontamination. It is found that B. alba and C. gigantean is useful for decontamination of high content potassium in soil, otherwise, P. fruticosa and C. gigantean may be used for soil with high concentration of 210Pb and 226Ra. In addition, biological effects of the plant ingestion in human body were assessed. The doses due to ingestion of food crop samples varied from organ to organ, depending on the organotrophic properties of the radionuclides. For examples, equivalent dose for 40K in large intestine is higher than other organs. In contrast, equivalent dose for 238U, 226Ra, 210Pb and 232Th were mostly at bone surface. In general, the obtained dose values of lower than the average value recommended by UNSCEAR for food crop ingestion pose no threat to the public's health. However, close investigations are needed in the near future.

Dosimetric and Monte Carlo verification of jaws-only IMRT plans calculated by the Collapsed Cone Convolution algorithm for head and neck cancers.

AIM: The aim of this study is to verify the Prowess Panther jaws-only intensity modulated radiation therapy (JO-IMRT) treatment planning (TP) by comparing the TP dose distributions for head-and-neck (H&N) cancer with the ones simulated by Monte Carlo (MC). BACKGROUND: To date, dose distributions planned using JO-IMRT for H&N patients were found superior to the corresponding three-dimensional conformal radiotherapy (3D-CRT) plans. Dosimetry of the JO-IMRT plans were also experimentally verified using an ionization chamber, MapCHECK 2, and Octavius 4D and good agreements were shown. MATERIALS AND METHODS: Dose distributions of 15 JO-IMRT plans of nasopharyngeal patients were recalculated using the EGSnrc Monte Carlo code. The clinical photon beams were simulated using the BEAMnrc. The absorbed dose to patients treated by fixed-field IMRT was computed using the DOSXYZnrc. The simulated dose distributions were then compared with the ones calculated by the Collapsed Cone Convolution (CCC) algorithm on the TPS, using the relative dose error comparison and the gamma index using global methods implemented in PTW-VeriSoft with 3%/3 mm, 2%/2 mm, 1%/1 mm criteria. RESULTS: There is a good agreement between the MC and TPS dose. The average gamma passing rates were 93.3 ± 3.1%, 92.8 ± 3.2%, 92.4 ± 3.4% based on the 3%/3 mm, 2%/2 mm, 1%/1 mm criteria, respectively. CONCLUSIONS: According to the results, it is concluded that the CCC algorithm was adequate for most of the IMRT H&N cases where the target was not immediately adjacent to the critical structures.

Quality assurance of the jaws only-intensity modulated radiation therapy plans for head-and-neck cancer.

Intensity-modulated radiation therapy (IMRT) is a treatment technique which has become routine in developed countries. In most centers this technique is delivered with multi-leaf collimators (MLCs). However, the use of MLCs is not mandatory. Several oncology centres in developing countries are still using linear accelerators (LINAC) without MLCs, and can potentially deliver IMRT plans with the use of collimator jaws. In this report, we present the results of quality assurance of this Jaws-Only-IMRT (JO-IMRT) technique in treating nasopharyngeal carcinoma (NPC) patients. Twenty-five plans of nasopharyngeal patients were randomly chosen. For each patient, a JO-IMRT plan was generated and a series of pre-treatment verification measurements was performed including (1) point dose measurement with an ionization chamber, (2) planar dose measurement with a 2D-array detector and (3) 3-dimensional dose measurement using a rotatable phantom with a 2D-array detector. The average differences between the measured and TPS-calculated point doses were found to be 1.26±0.77%, which is within the institution's dose constraint limits. For the planar dose and 3D dose measurements, the average gamma index based on 3%/3mm criteria were 96.77±2.33% and 94.72±2.67%, respectively. Our measurements showed that the JO-IMRT treatment plans applied to the H&N patients were accurate for the treatment delivery based on our established pass criteria.

Self-absorption correction in determining the 238U activity of soil samples via 63.3 keV gamma ray using MCNP5 code.

The essential issue in analyzing the activity of (238)U in an HPGe detector based gamma spectrometer via 63.3 keV line is relating to the strong self-absorption of this weak gamma ray in sample material. The present work suggests a method of the self-absorption corrections for 63.3 keV gamma rays by a combination of experimental measurements and Monte Carlo MCNP5 calculations. The effects of sample chemical composition, density and geometry were calculated in terms of self-attenuation factors. The method, developed for a cylindrical sample geometry, accounted for variable sample heights and densities. The analysis of (238)U activity was applied for three main soil types in Vietnam, which are grey, alluvial and red soils. The results obtained with the above outlined method were in good agreement with those derived by other methods.