Simulation of gamma irradiation system for a ballast water treatment

Invasion by different kinds of ballast water microorganisms is one of the most important marine environment problems around the world; therefore preventing the invasion of these unwanted and harmful stowaways is one of the main strategies of responsible agencies. Some of these methods such as ocean exchange, heating, filtration, hydro cyclones, UV irradiation and chemical treatment, have various problems such as technical deficiency, high costs, lack of safety and environmental side effects. A novel system of treatment by Gamma irradiation is designed to irradiate the blast water uniformly and effectively. To determine the dose distribiution as a function of distance from the irradiation source, the MNCP code was used. The systems used for source implant in this simulation were Paterson-Parker, Paris and Network systems. In each system, Sivert-integral and inverse square law were used in Matlab program to determine the dose distribiution. Results of initial laboratory tests on offshore water samples of Siri Island indicated that the appropriate dose for deactivation of organisms of water samples is approximately one kGy. It has been demonstrated that the dose can be provided by twenty five 100,000 Ci line sources of [60]Co in a triangle implant arranged in a 1x1x1 m[3] cubic shape water pipe. In order to increase efficiency and radiation safety, water passed from two other coaxial and bigger cubes, after passing from the first cube. A one meter thick wall of concrete around the cubes was adequate to shield the system completely. The main advantages of this system such as high efficiency, safety, reliability, minimum environmental adverse effects, proves that this novel method not only can be used for ballast water treatment, but is also effective for drinking water purification

Impact of quality control on radiation doses received by patients undergoing abdomen X-ray examination in ten hospitals

The X-ray machines used for radiodiagnosis should meet certain quality assurance [QA] programmes. These are necessary to have good quality radiographs at reasonably low exposure to patients. Dose reduction methods in abdomen X-ray examination were carried out in 10 hospitals in Tehran. This paper presents the work, which was implemented on 200 patients and evaluated using the entrance skin dose [ESD] in the Anterior-Posterior [AP] abdomen projection measured directly at the center of the X-ray field. In addition, the machine room, and dark room parameters, as well as work practices and repeat rates were studied. The quality control [QC] parameters and the ESD were evaluated utilizing an anthropologic phantom to define the optimal exposure condition at all hospitals before and after QC. Results show that after using the QC parameters and optimization of the exposure condition s, the mean of mAs and ESD can be decrease d by 62% and 65% respectively. The quality of the radiograph s generally increased. The reported method is easily implemented in any clinical situation where optimization of abdomen radiography is necessary

Application of small angle X-ray scattering [SAXS] for differentiation between normal and cancerous breast tissues

Small angle X-ray scattering [to angles less than 10[degree sign]] is predominantly coherent. Coherent scattering leads to diffraction effects and especially constructive interferences. These interferences carry some information about the molecular structure of the tissue. As breast cancer is the most widespread cancer in women, this project evaluated the application of small angle X-ray scattering [SAXS] for differentiation between normal and cancerous breast tissues. The energy dispersive method with a set up including X-ray tube, primary collimator, sample holder, secondary collimator and HP Ge detector was used. The best constructive interference was found to be at 6.5[degree sign] after doing experiments on adipose breast tissue at several angles of 4, 5, 6, 6.5 and 7.3 degrees. The total number of 99 breast tissue samples, including normal and tumor were studied at the 6.5[degree sign]. The corrected intensity versus momentum transfer was obtained for each sample. Adipose tissue shows a sharp peak in low momentum transfer region. It is easy to separate adipose tissue and mixed tissue [adipose and fibroglandular] from tumor in peak positions [each coherent scattering spectrum has a peak that its position is determined by momentum transfer]. Furthermore adipose tissue has shown significantly higher peaks than other breast tissues. Benign and malignant breast tissues were differentiated by both peak positions and peak heights [each peak has a height in coherent scattering spectrum]. Preservation of samples nitrogen tank had no effects on molecular structure of the breast tissue. By energy dispersive small angle X-ray scattering, it is possible to differentiate between normal, benign and malignant breast tissues

Measurement of organ dose in abdomen-pelvis CT exam as a function of mA, KV and scanner type by Monte Carlo method

CT is a diagnostic imaging modality giving higher patient dose in comparison with other radiological procedures, so the calculation of organ dose in CT exams is very important. While methods to calculate the effective dose have been established [ICRP 26 and ICRP 60], they depend heavily on the ability to estimate the dose to radiosensitive organs from the CT procedure. However, determining the radiation dose to these organs is problematic, direct measurement is not possible and comparing the dose as functions of scan protocol such as mA is very difficult. One of the most powerful tools for measuring the organ dose is Monte Carlo simulation. Materials and Today the predominant method for assessment of organ absorbed dose is the application of conversion coefficients established by the use of Monte Carlo simulations. One of the most famous dose calculation software is CTDOSE, which we have used it for calculation of organ dose. In this work we measured the relationship between the mA, KV and scanner type with the equivalent organ dose and effective dose in mathematically standard phantom [Hermaphrodite 170cm/70Kg] in an abdomen-pelvis CT exam by Monte Carlo method. For this measurement we increased the mA in steps of 10 mA and plot curves for organ dose as a function of mA for different KV setting. As expected, with increasing mA, patient organ dose increased, but the simulation results showed that the slope of organ dose as a function of mA increased with KV increasing. By increasing KV from 120 to 140 the increase in slope of curves representing patient organ dose versus mA for different scanner types show almost similar behavior whereas the slope of the corresponding curves in scanners which equipped xenon detectors was almost 22% more than the slope of scanners equipped with scintillation detectors. Our research showed that regarding equivalent dose the system incorporating scintillation detector has a superior performance. Incorporating such software in various CT scanners, marketed by different vendors, will offer the ability to get a print out of patient organ dose in any examination according to the imaging parameters used for imaging any part of the body

Evaluation of the effect of various parameters on the amount of radiation dose received by family members after 131-I therapy

The main concern with respect to discharge of patients from hospital after 131-I therapy is contamination of their surroundings and exposure of people who are in close contact with them. In this study, we evaluated absorbed dose received by homemates of these patients within one week of discharge from hospital. This study was based on 100 patients [23 patients with thyroid cancer together with 70 members of their families and 2 hyperthyroid patients plus 5 of their family members]. Measurements were performed by TLD. Patients were discharged from hospital if the dose rate from a meter distance of their thyroid was below 20 micro Sv/hr [ICRP-60]. The hospitalization period for those patients with thyroid cancer varied between 2-3 days [Depending on the amount of radioactivity received]. Hyperthyroid patients were treated as outpatients. Our data indicate that although hyperthyroid patients received much less activity in comparison to those with thyroid cancer, but due to the slow iodine discharge rate from their bodies, they radiated more to their surroundings. For patients with thyroid cancer, when the given activity increased from 100 mCi to 150 mCi, the average dose absorbed by their family members increased by a factor of 3. The duration of hospitalization as well as the amount of activity given to the patients have a significant effect on the amount of radiation dose received by the family members. In a group of patients who received 100 mCi of 131-I, the average radiation dose received by the family members of those patients who were hospitalized for 2 days were 1.5 times more than that of those patients who were hospitalized for 3 days, whereas following therapy with 150 mCi of 131-Iodine, the average radiation dose received by the family members of those patients who were hospitalized for 2 days were about 6.5 times more than that of those who were hospitalized for 3 days. The size of the patient's house and the time that family spends with the patient at house are other considerable factors. Our data show that by increasing the house size from 45-50 m to 75-100 m, the average radiation dose received by the family members reduce by a factor of 4, wheras by increasing the house size from 75-100 m to about 120-400 m, this dose only reduce by a factor of 1.5. The average dose for family members who were at house for less than 10 hours a day is about 5 times less than that of the individuals who were at house for more than 10 hours a day. In addition, average absorbed dose by children was about 9 times more than that of spouses. On the basis of this study findings, we suggest that parameters such as the amount of received activity, type of disease, house size, presence of children at house, duration of time which family members spend with the patient at house and differences in cultural behaviors between children and their parents should be considered in order to decrease the exposure of the family members and also to decide for duration of hospitalization and the approtiate time of discharge