ehsan alibeigi

Modeling and simulation are crucial in designing and developing complex systems, such as cargo scanner systems. A cargo scanner is a device used to scan and inspect cargo transported by air, land, and sea. These scanners are usually used by customs and security centers to identify potential threats such as weapons, explosives, and contraband. One of the key benefits of using modeling and simulation is that it allows designers to test different scenarios and configurations without the need for physical prototypes. This can save time and money, as well as reduce the risk of costly mistakes. This study examines how the parameter angle affects detector responses in truck cargo scanner systems using the MCNPX code. The angle refers to the angle at which the beam generated from the beam generator interacts with the detector's normal surface, an important factor in ensuring the accuracy and reliability of cargo scanning systems in imaging. Initially, the X-ray spectrum output was calculated from the accelerated 6 MV electrons due to tungsten target impact and validated against spectra from other studies. The results demonstrated good agreement between the output spectra. The changes in counts recorded in the vertical direction of the detector arrays showed that the count difference between the lowest pixel and highest pixel is approximately 33%, while the count changes from the closest pixel to the farthest pixel to the beam generator in the horizontal direction are about 60%. Subsequently, the angle of each array was adjusted so that the emitted rays from the cone beam generator were perpendicular, and this case was compared to cases where the array angle was 20 and 30 degrees. The results revealed that when exposed to perpendicular radiation, the signal recorded in detectors is greater than that of a rotated detector, and the count rate in the detector decreases as the angle increases.

Considering the high death rate of patients on the transplant waiting list, one of the most important ethical challenges of organ transplantation is the lack of transplant organs and different approaches to cover it.

The ethical issues of organ transplantation have been frequently reviewed recently.

Currently, there are 4 sources for organ transplants, which are: a) organ transplant from animal to human b) transplant from a living donor c) transplant from a brain-dead donor d) transplant from a cardiac-dead donor or donors without a heartbeat, and tissue engineering research continues to prepare a transplantable organ. Each of them has its own limitation and specific consideration. In Iran, organ procurement from brain-dead donors and living donors are the most important sources. Many approaches have been considered to increase the number of procured organs from brain-death cases in the world, but have not yet been able to reduce the gap between supply and demand. Therefore, since the 1980s, the program of organ transplantation from cardiac death (donors with irreversible cardiac arrest) in the world has been reviewed again. Based on the classification of cardiac arrest patients, they are placed in two general categories: uncontrolled and controlled. In a controlled condition, death is predictable, and organ removal is possible by eliminating planned medical interventions and patient support. But in the uncontrolled state, death occurs accidentally, which is more likely to prolong the duration of hot ischemia. Italy's organ donation group has recently introduced type 6 deaths in patients on ECMO, which is mentioned as a semi-controlled group. This group is called donors with abnormal blood flow versus brain-dead donors with normal blood flow. In this study, ethical considerations for organ donation from NHBD were discussed. Regarding the procurement of organs from non-heart beating donors, there are many ethical considerations that include both the donors and the recipients. Considering that the clinical conditions of the brain-dead donors are sometimes very unstable, cardiac arrest may occur before organ harvesting. In these cases, donation after cardiac death is an option.

It is necessary to regulate the ethical considerations for organ procurement from NHBD

‎By the rapid development of imaging systems such as PET/CT for diagnosis of cancer‎, ‎the protection of staff and public has become a main health concern‎. ‎Due to serious and irreversible harms of ionization radiations‎, ‎protection of all those who are exposed is the main concern of health issues‎. ‎The main basis of the calculation of the shielding design in the medical imaging systems is that the absorbed dose should not exceed the allowed limit‎. ‎In this study‎, ‎the current shielding status of the PET/CT installations in Tehran's Shariati hospital was investigated using the MCNPX Monte Carlo code to ensure that the dose limits for both the controlled and uncontrolled area are not violated‎. ‎The proposed simulation method was benchmarked with a validated analytical method‎. ‎Shariati hospital provides services to four patients every day‎, ‎leading to a dose rate in the range of 2.6 × 10-6 to 9.35 × 10-3 mSv/week‎. ‎The minimum dose rate in this range represents the value behind the door of the waiting room (public uncontrolled area)‎, ‎while the maximum in this range corresponds to the value behind the glass of the scanner room (operator controlled area)‎. ‎The simulation results for 8 patients/day in this center showed that the dose rate behind the wall of the injection room will increase from 4.88 ×10-6 mSv/week to 2.81 × 10-2 mSv/week‎, ‎which is well below the recommended levels‎. ‎This indicates that the present shielding is adequate for up to four more patients per day‎.

Upon increasing needs and vast application of neutron detectors, especially in nuclear reactors and growing number of linear accelerators, design and manufacturing of neutron detectors is a serious demand. The aim of this project is building neutron detectors capable of compensating gamma and temperature response in a radiation media. A special thermocouple coated with Boron carbide at the junction is developed. In a neutron flux, the nuclear reaction between neutron and Boron carbide which produces alpha particles, induce a voltage across the junction which is proportional to neutron density. To eliminate the effect of gamma and temperature of the medium, a thermocouple coated with Aluminum used as a differentiation mode in the detector, because of close atomic number, density, conduction coefficient and heat coefficient of Boron carbide and Aluminum. Detector is placed into thermal column of TRR. The threshold of measured flux was found to be using indium foil.

Nowadays medical imaging systems like PET/CT are widely used in cancer diagnosis. Due to serious and irreversible harms of ionization radiations, protection of all those who are exposed is the main concern of health issues. The main basis of the calculation of the shielding design in the medical imaging systems is that the absorbed dose should not exceed the allowed limit. Using the Monte Carlo N-Particle Transport Code (MCNP), a potential suite for a positron emission tomography/Computed Tomography (PET/CT) facility was designed. The design considers three different areas as required in a PET/CT facility: scanning room, waiting area, and injection room. MCNP-X calculation code is used to ensure that the controlled and uncontrolled areas (with allowed dose of 0.1 mSv/week and 0.02mSv/week, respectively) does not exceed the limits. Since this center accepts four patients every day with mean total activity of 77 mCi, the dose rates are calculated from 2.6E-06 mSv/Week to 9.35E-3 mSv/week. The simulation results revealed that even if this center increase its service to eight patients per day, the dose rates will be from 4.88E-06 mSv/week to 2.81E-02 mSv/week, which is still below the allowed dose rate.