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Open access

Thokchom Dewan Singh

Abstract

In the radiotherapy practice, regulator defines risk in terms of physically measurable quantities and attempt to implement the results obtained from the risk assessment of this practice, using quantitative approach. Although such approach has significantly brought down radiation dose, injuries and fatalities to the workers as compared to the radiotherapy practices before World War II, the objectivity concept of risk that limits the assessment regarding physically measurable quantities is widely urged throughout the world. This study examined how the risk associated with radiotherapy practice has been perceived, and experienced by both professional and non-professional workers in the radiotherapy facilities located in Manipur, Meghalaya, and Assam. This study found that professional and nonprofessional workers exhibited different risk perception on the same physical risk. Such different risk perceptions influenced the establishment of radiological protection systems in the facility. Non-professional workers are more likely to be the affected group in a facility having weak radiological protection systems.

Open access

Krisanat Chuamsaamarkkee, Putthiporn Charoenphun, Natthaporn Kamwang, Sahakan Monthonwattana, Wirote Changmuang, Kittiphong Thongklam, Arpakorn Kositwattanarerk, Yoch Anongpornjossakul, Wichana Chamroonrat and Chanika Sritara

Abstract

Background: 131I-metaiodobenzylguanidine (mIBG) offers an effectively targeted radionuclide therapy in pediatric patients. According to radiation protection authority in our country, the patient treated with high-dose (>1100 MBq) radioiodine is recommended to stay in the hospital. Hence, this study intends to measure the radiation exposure in nonlead-lined treatment room installing with portable lead shields located in general pediatric ward and surrounding areas. In addition, this study also aims to measure the radiation exposure to the family caregiver in pediatric patients received high dose 131I-mIBG.

Methods: Environmental OSL (optically stimulated luminescence) monitoring devices (InLight®, Al2O3:C) were prepared and calibrated by Thailand Institute of Nuclear Technology (TINT). Twenty-five set of OSLs were placed in and surrounded the treatment room. Dose to family caregiver was recorded by digital semiconductor dosimeter (ALOKA PDM-112) also calibrated by TINT. The measurement was carried for four pediatric patients treated with 131IMIBG (activity 3700 – 5500 MBq).

Results: The ambient doses equivalent and the dose rate were analyzed, the limit of 10 and 0.5 μSv/h are accepted for radiation worker and member of the public, respectively. The dose rate around the patient bed and toilet were high as expected. Dose rates at the wall of adjacent room and corridor were slightly greater than the public limit (range 1.82 to 4.48 μSv/h). Remarkably, the dose rates at caregiver chair (outside the shielding) were exceeded the limits (30.57 ± 5.69 μSv/h). Consequently, this was correlated with high personal dose equivalent to family caregivers which listed as 175, 1632, 6760 and 7433 μSv for the patient age of 15, 5, 1 and 1 year respectively.

Conclusion: These radiation monitoring data provided the important information to manage radiation protection and aware of radiation exposure when using non-lead-lined treatment room in general pediatric ward.

Open access

Linyue Guan, Mingjun Pang, Xuedong Jiang and Yongbin Zhang

Abstract

This paper presents an analysis for a micro/nano wedge-platform thrust slider bearing by using the flow factor approach model. The contact-fluid interfacial shear strength was taken into account for describing the inter-facial slippage. The carried load and friction coefficient of the bearing were calculated when different contact-fluid interactions were used. It was found that the interaction strength between the contact and the fluid has a significant contribution to the load-carrying capacity of the bearing, a weak contact-fluid interaction in the bearing inlet zone and its resulting interfacial slippage on the stationary contact surface is beneficial for both the load-carrying capacity and the friction coefficient of the bearing, while a strong contact-fluid interaction in the bearing outlet zone is contrarily harmful. The relative slip amount is linearly distributed in the bearing inlet zone, when the interfacial slippage occurs on the stationary surface in this subzone because of the low interfacial shear strength.

Open access

G. Stoilov, V. Kavardzhikov and D. Pashkouleva

Abstract

The review of progress in numerical synthesis and study of strain sensors patterns, which can be used for realization of digital image correlation (DIC) and its applications in engineering practice, is presented. Problems related to monitoring a large area of an objects surface while subsequently increasing the image scale and concentrating observation only to the area where the largest deformation has taken place are considered. An algorithm for numerical synthesizing of specialized strain sensor patterns is proposed. Results from a physical experiment are also reported.

Open access

Nikolay K. Vitanov and Roumen Borisov

Abstract

We study the problem of the motion of substance in a channel of a network for the case of channel having two arms. Stationary regime of the flow of the substance is considered. Analytical relationships for the distribution of the substance in the nodes of the arms of the channel are obtained. The obtained results are discussed from the point of view of technological applications of the model (e.g., motion of substances such as water in complex technological facilities).

Open access

Behrouz Rasuli, Naser Tabkhi, Ebrahim Kalantar, Vahid Zarezade and Mohammad Bagher shiran

Abstract

The aim of this work was to investigate the potential of high frequency ultrasound for the cleaning of a Polysulfone (PSU) ultrafiltration membrane used in hemodialysis. The blood substitute solution flowing through the hollow fiber membrane used in the High Flux F60 dialyzers has been sonicated by ultrasonic (US) waves with 1 MHz frequency and 2 W/cm2 in situ intensity. The solution was comprised of toxic compounds such as Urea, Creatinine, Vitamin B12 and Inulin. The effect of US was represented by comparison of the clearance in both OFF and ON ultrasound conditions. The results of these studies have been demonstrated that US can enhance the permeability of the PSU dialyzer membrane. Results revealed that US had significant effect (p-value ˂ 0.05) on the clearance of Inulin as a large molecule (5200 D) and accelerated its filtration by 28%. The proposed dialysis method can be used alongside the existing dialysis machine.

Open access

Osamu Tanaka, Hisao Komeda, Shigeki Hirose, Takuya Taniguchi, Kousei Ono, Eiichi Yama and Masayuki Matsuo

Abstract

Gold markers (GM) are increasingly used for CT and MRI registration during in intensity-modulated radiation therapy for prostate cancer. Additionally, diffusion-weighted imaging has been adopted to measure the effects of radiotherapy for prostate cancer, similar to tests of blood prostate-specific antigen levels. As diffusion-weighted imaging (DWI) is often affected by a magnetic component, we evaluated the influence of GM on the Diffusion weighted images in three cases. We found that the size range of signal void of GM in MRI was 2–5 mm. We conclude that a GM would not affect the quality of DWI in daily practice.

Open access

T.D. Awodola

Abstract

In this investigation, the flexural vibration of a prestressed and simply supported rectangular plate carrying moving concentrated masses and resting on bi-parametric (Pasternak) elastic foundation is considered. In order to solve the governing fourth order partial differential equation, a technique based on separation of variables is used to reduce the equation with variable and singular coefficients to a sequence of coupled second order ordinary differential equations. The modified method of Struble and the integral transformations are then employed for the solutions of the reduced equations. The numerical results in plotted curves show that as the value of the axial force in x-direction (Nx) increases, the response amplitudes of the plates decrease, the same effect is produced as the axial force in y-direction (Ny) increases for both cases of moving force and moving mass problems of the prestressed and simply supported rectangular plate resting on Pasternak elastic foundation. The deflection of the plate also decreases in each case as the values of the Shear modulus G 0 and the rotatory inertia correction factor R 0 increase. Also, the transverse deflections of the prestressed rectangular plates under the actions of moving masses are higher than those when only the force effects of the moving loads are considered, the analysis of resonance shows that resonance is attained earlier in moving mass problem than in moving force problem and the critical speed for the moving mass problem is reached prior to that of the moving force problem which implies that it is risky to rely on a design based on the moving force solution. Furthermore, the response amplitudes of the moving mass problem increase with increasing mass ratio and approach those of the moving force as the mass ratio approaches zero for the prestressed and simply supported rectangular plates resting on uniform Pasternak elastic foundation.

Open access

Gowri Balan, Anu Radha Chandrasekaran, Ramasubramanian Velayudham, Gopiraj Annamalai and Mohan Ramachandran

Abstract

Purpose: To estimate the midpoint dose delivered to cervical cancer patients treated by conventional technique using Electronic Portal Imaging Device (EPID).

Materials and Methods: Clinac 2100 equipped with aS500 EPID was used in this study. A methodology was developed to generate a Gy/Calibration Unit (CU) look up table for the determination of midpoint dose of patients. 25 patients of cervical cancer were included in this study and the delivered dose to the midpoint of the patients was estimated using EPID. The deviation between the prescribed and the measured dose was calculated and analysed.

Results: EPID showed a linear response with increase in Monitor unit and the Gy/CU look up table was validated for different field sizes and depth. 250 fields were measured for 25 patients, 10 measurements per patient, weekly once and for 5 weeks. The results show that out of 250 measurements, 98% of the measurements are within ±5% and 83.2% are within ±3% for with a standard deviation of 1.66%.

Conclusion: The outcome of this study proves the efficacy of this methodology for the estimation of midpoint dose using EPID with minimal effort, time and without any inconvenience to the patients unlike other in-vivo dosimeters.

Open access

Elias Alibeyki, Saeid Karimkhani, Sepide Saadatmand and Parvaneh Shokrani

Abstract

Purpose: Hodgkin lymphoma (HL) is one of the most frequent malignancies among pediatric patients. One of the common causes of death in HL survivors after radiation therapy (RT), is radiation-induced heart disease (RIHD). The aim of this study was to compare several dosimetric parameters for two methods of early stage Hodgkin lymphoma radiotherapy with reference to potential risk of RIHD.

Materials and Methods: Using a series of computed tomography slices of 40 young patients, treatment planning was done in two methods of HL RT, including involved field (IFRT) and involved site (ISRT) in doses of 20, 30, and 35 Gy. Contouring of clinical target volume as well as the organs at risk, including the heart, was performed by a radiation oncologist. The mean and maximum dose of heart (Dheart-mean and Dheart-max), the volume of heart receiving a dose more than 25 Gy (V25), and the standard deviation of dose as a dose homogeneity index in heart, were used to compare the RIHD risk.

Results: The mean value for Dheart-mean in ISRT method in all doses was less compare to IFRT. Maximum reduction in mean value of Dheart-mean occurred at moving from 30 Gy IFRT to ISRT by 9.53 Gy (p < 0.001) and minimum was between 35 Gy IFRT and ISRT. The mean value for Dheart-max was fewer in IFRT rather than ISRT and the maximum difference was between 35 Gy IFRT and ISRT (1.35 Gy). The mean of V25 of heart was 26.66% and 23.74% in 35 Gy IFRT and ISRT, respectively, and dose distribution was more homogeneous in IFRT.

Conclusions: If Dheart-max and V25 of heart or homogeneity of dose distribution in heart are considered as determining factors in RIHD, then IFRT can be considered optimum, especially in 35 Gy IFRT; while, assuming the Dheart-mean as the most important factor in RIHD, superiority of ISRT over IFRT is observed.