Absorbed Dose Uncertainty Estimation for Proton Therapy

Successful radiotherapy treatment depends on the absorbed dose evaluation and the possibility to define metrological characteristics of the therapy beam. Radiotherapy requires tumor dose delivery with expanded uncertainty less than +/- 5 %. It is particularly important to reduce uncertainty during therapy beam calibration as well as to apply all necessary ionization chamber correction factors. Absorbed dose to water was determined using ionometric method. Calibration was performed in reference cobalt beam. Combined standard uncertainty of the calculated absorbed dose to water in 65 MeV proton beam was +/- 1.97% while the obtained expanded uncertainty of absorbed dose for the same beam quality was +/- 5.02%. The uncertainty estimation method has been developed within the project TESLA

Positron Emission Tomography (Pet) in Medical Imaging

Positron Emission Tomography (PET) is a radiotracer imaging technique, in which tracer compounds labelled with positron-emitting radionuclides are injected into the subject of the study. One of the prime reasons for the importance of PET in medical research and practice is the existence of positron-emitting isotopes of elements Such as carbon, nitrogen, oxygen and fluorine, which may be processed to create a range of tracer compounds which are similar to naturally occurring substances in the body. The largest area of clinical use of PET is in oncology, cardiology and neurology. The most widely used tracer in oncology is (18)F-fluoro-deoxy-glucose (EDG) which follows a similar metabolic pathway to glucose in vivo, except that it is not metabolised to CO, and water, but remains trapped within a tissue. This makes it well-suited to use as a glucose uptake tracer. This is of interest in oncology because proliferating cancer cells have a higher than average rate of glucose metabolism. (11)C-methionine is also used in oncology, where it acts as a marker for protein synthesis. In our country, one of the experimental channels Of TESLA Accelerator Installation will be used for production Of long-living positron emitters (e.g. (124)I, (86)Y, (76)Br, (64)Cu) and alpha emitters (e.g. (211)At and (149)Tb).9th International Symposium on Interdisciplinary Regional Research, Jun 21-22, 2007, Univ Novi Sad, Novi Sad, Serbi

Estimation of Patient Effective Dose from I-131 Using Monte Carlo Calculation

During the oral application of radionuclide therapy it is from the vital importance to measure effective dose in stomach in which the (NaI)-I-131 therapeutic capsule stays during the 15 minutes which is long enough to make risky exposure. As it is not possible to determine it by direct measurements there is a strong recommendation to estimate the dose by calculation. The main goal is to calculate effective dose and risk as a result of I-131 capsules remaining in stomach before the absorption starts. Monte Carlo code MCNP4b was used to model the transport of gamma and beta particles emitted by radionuclide I-131 treated as a point source at the bottom of the stomach. Absorbed energy per unit transformation in stomach and surrounding organs has been calculated. The dose equivalents in these organs have been calculated in aim to determine the effective doses using appropriate tissue weighting factor values. The local doses in stomach wall reached the values in order of several hundreds of grays in a very short time. In such case the traditional concept of risk is not applicable, so it becomes necessary to create the very new concept which is able to cover higher risks under presented circumstances.19th IMEKO World Congress, Proceedings, Sep 06-12, 2009, Lisbon, Portuga

Effective dose estimation using Monte Carlo simulation for patients undergoing radioiodine therapy

Therapeutic or diagnostic radiopharmaceutical capsule containing Na131I stays in stomach for about 15 minutes before the absorption starts, long enough to make possible risky exposure

Patient dose measurements in diagnostic radiology procedures in Montenegro

It was the aim of the study presented here to estimate for the first time patient dose levels in conventional diagnostic radiology in Montenegro. Measurements of patient dose in terms of entrance surface air kerma (ESAK) and kerma-area product (KAP) were performed on at least 10 patients for each examination type, in each of five randomly selected health institutions in Montenegro, so that a total of 872 patients for 16 different examination categories were included in the survey (817 patients for 1049 radiographies and 55 fluoroscopy patients). Exposure settings and individual data were recorded for each patient. Mean, median and third quartile values ESAK of patient doses are reported. The estimated mean ESAK values obtained are as follows: 4.7 mGy for pelvis anteroposterior (AP), 4.5 mGy for lumbar spine AP, 7.8 mGy for lumbar spine lateral (LAT), 3.1 mGy for thoracic spine AP and 4.3 mGy for thoracic spine LAT. When compared with the European diagnostic reference values, the mean ESAK for all studied examination types are found to be below the reference levels, except in chest radiography. Mean ESAK values for chest radiography are 0.9 mGy for posteroanterior (PA) projection and 2.0 mGy for LAT. The results exhibit a wide range of variation. For fluoroscopy examinations, the total KAP was measured. The mean KAP value per procedure for barium meal is found to be 22 Gy cm(2), 41 Gy cm(2) for barium enema and 19 Gy cm(2) for intravenous urography. Broad dose ranges for the same types of examinations indicate the necessity of applying practice optimisation in diagnostic radiology and establishment of national diagnostic reference levels

Hydrogeochemical investigation of the influence of natural radionuclides on the environment, NW Backa, Serbia

In the research phase of nuclear materials from the Backa area (NW of Serbia), hydrogeochemical prospecting was applied, which covers an area of about 500 km2. Samples were collected from surface water, from sources and wells, and bores. Combined hydrogeochemical methods included the examination of U, Ra, Pb, Zn, Cu, Mo, Li, Sr; anions HCO3-, SO42-, Cl-; cations Ca2+, Mg2+, Na+, K+, as well as the determination of SiO2, Eh, Ep and pH values. Additional testing determined the water content: NO3, F, Br, J, P. Value content of uranium (U) varied in the range of 0.1 - 125 ppb; Ra 0.026 - 0.33 Bq/l; Rn 1.45 - 32.63 Bq/l. At selected locations the uranium content in the A - horizon (15 - 20 cm) were determined. According to the geological and structural characteristics of the research area, results are shown on the maps in scale of 1:50000 and on appropriate diagrams and tables. The aim of this study was the application of geochemical prospecting method for the identification of geopathogenic zones of the influence of natural radionuclides in the rural settlements environment

Different Approaches in Uncertainty Evaluation for Measurement of Complex Surfaces Using Coordinate Measuring Machine

This paper describes a methodology for uncertainty assessment for Coordinate Measuring Machine measurement of complex real work pieces from industry. The study applied two approaches (in scanning mode only) for estimating the measurement uncertainty with the support of Taguchi plan in the experiment containing five factors: scanning speed, sample density, probe configuration, scanning direction, and position of measuring object. In the first approach the uncertainty was estimated by measuring the basic geometric objects (primitives like sphere and torus) representing the decomposition of complex surfaces and in the second one a complex surface was treated as an unknown quantity. Calculated uncertainty Type A for both measurement tasks was in the range from 0.65 μm to 6.47 μm. Evaluation of the uncertainty Type B covered specifications of the machine and standard uncertainties derived from temperature effects. Total uB component was found to be in order of 0.4 μm. Future research will be directed towards the development and application of simulation method

Concentration of trace elements in blood and feed of homebred animals in Southern Serbia

Background, aim and scope The paper presents concentrations of trace elements in blood of homebred animals (cows and sheep) from Southern Serbia (Bujanovac) and the contents of natural and anthropogenic radionuclides and some heavy metals in feed. The region of Southern Serbia was exposed to contamination by depleted uranium ammunition during NATO attacks in 1999 and therefore, is of great concern to environmental pollution and human and animal health. Materials and methods Conventional instrumental and epithermal neutron activation analyses are used to measure trace elements in cow and sheep blood samples collected randomly at six locations in the region of Bujanovac (village of Borovac) in the spring of 2005. Samples of feed (grass and crops: corn, wheat and oats), collected on the same locations (households), are analysed for the contents of radionuclides on an HPGe detector (Ortec, relative efficiency 23%) by standard gamma spectrometry. The content of Hg, Pb and Cd in feed is determined by standard atomic absorption spectrometry on the VarianSpectra220/ThermoSolar GFS97 spectrometer. Results Concentrations of 29 elements (Na, Al (P), Cl, K, Sc, Cr, Mn, Ni, Fe, Co, Zn, Se, As, Br, Sr, Rb, Sb, In, I, Ba, Cs, La, Nd, Eu, Sm, Tb, Hf, Ta and Th) are determined in blood of the examined animals. In feeds, natural 40K is found in all of the samples, cosmogenic Be-7 and fission product Cs-137 are detected only in the grass samples, while heavy metals Hg, Cd and Pb are found in the range of 0.01-0.02, 0.84-1.15 and 0.74-7.34 mg/kg, respectively. Calculated soil-to-blood transfer factors are in a wide range of 8.10(-6) to 64, as a result of varying significance of the elements in animal metabolism and feeding habits. Discussion The results of trace elements concentrations in animal blood are in good agreement with available data for K, Ni, Zn, Se and Rb. Higher Br concentrations in animal blood are most probably caused by large biomass burning events during blood sampling. Very low concentration of Fe in cows and sheep confirms the results of previous biochemical studies on animal anaemia in the region. High concentration of As correlates with geochemical peculiarities of the Balkans and is also likely influenced by the use of pesticides in the agricultural production. For some of the elements (La, Nd, Eu, Sm, Tb, Sb, Hf, Ta, Th, In, Ba, Sr, Sc and Cs), there are few or no literature data. Therefore, some of the presented data are significant not only for the country and the region, but on a wider scale. Activities of natural radionuclides in feeds are within the average values reported for the region, while the activities of Pb-210 and U-235/238 are below the limit of detection. This is in accordance with previous investigations showing no widespread contamination by depleted uranium in the area. Contents of Hg and Pb in feeds are below the nationally permissible levels, unlike the content of Cd which exceeds it, probably caused by the use of phosphate fertilisers and fossil fuel combustion in the area. Conclusions In general, the concentrations of trace elements in blood of homebred cows and sheep are in good agreement with reference materials, available literature data and the results of previous studies in the area. The exceptions are Fe, As and Br. The contents of natural and anthropogenic radionuclides in feeds are within the expected levels, and there are no signs of contamination by depleted uranium or other fission products. Apart from Cd, there are no signs of pollution by heavy metals in feeds. The highly sensitive method of instrumental neutron activation analysis provides data on the concentration of some elements in animal blood not previously reported for the region and elsewhere. Recommendations and perspectives The presented study is a part of the long term ongoing project on the health risk assessment on animals and humans in the region. The collected data is intended to provide a base for the animal and human risk assessment as well as an estimate of the general pollution status of the environment in the region. Since some of the investigated elements are classified as important trace elements for livestock, the results could also be used to balance and improve the animal diet and thus, improve the growth and reproduction rate