Assessment of total annual effective doses to representative person, for authorised and accidental releases from the Nuclear Medicine Department at Cattinara Hospital (Trieste, Italy).

PURPOSE: Clinical procedures in a Nuclear Medicine Department produce radioactive liquid and solid waste. Regarding waste release into the environment from an authorised hospital, it is mandatory to verify the compliance with European Directive 2013/59/EURATOM, adopted by the Italian Government via the Legislative Decree 101/2020. METHODS: Different activity release pathways into the environment from Trieste Nuclear Medicine Department have been analysed: liquid waste from patients' excreta discharged by sewage treatment system into the sea, and atmospheric releases following solid waste incineration. Reference models, provided by NCRP and IAEA guidelines, have been implemented to assess the impact of the discharged radioactivity for coastal waters and atmospheric transport conditions. Finally, an accidental fire event occurring in Radiopharmacy Laboratories has been simulated by HotSpot software. RESULTS: Advanced screening models give an effective dose to population of 5.3 · 10-3 µSv/y and 1.4 · 10-4 µSv/y for introduction by sewage system into coastal waters and atmospheric releases by the incinerator, respectively. Workers involved in the maintenance of the sewage treatment plant receive a total annual effective dose of 3.8 µSv/y, while for incinerator staff the total annual exposure is 5.9 · 10-8 µSv/y. For the accidental fire event the maximum total effective dose to an individual results 3.8 · 10-8 Sv with mild wind, and 4.1 · 10-7 Sv with strong wind. CONCLUSIONS: The total annual effective doses estimated to representative person, due to both Nuclear Medicine authorised clinical practices and in case of an accidental fire event, are in compliance with regulatory stipulations provided by Directives.

Monte Carlo based determination of dose distribution for some patch sources employed for radionuclide skin therapy.

Several methods are introduced for skin cancer treatment. An encouraging method is radionuclide skin therapy, where high-energy beta emitting radionuclides such as 32P, 90Y, 188Re and 166Ho are employed for skin irradiation. This study aimed to calculate the dose distribution for mentioned radionuclides at different layers of skin phantom through Monte Carlo simulation. Depth dose distribution, transverse dose profile and isodose curves related to the patch sources under investigation were calculated by MCNPX code. All of calculations were performed inside a developed skin phantom. Obtained results were compared with those reported by other studies to evaluate the validity of simulations. The results showed that the 166Ho and 32P have steeper dose gradient within the depth which can lead to the better normal tissue sparing. Simulated depth dose distributions were in a good agreement with other published studies and confirmed the validity of performed simulations. The obtained transverse dose profiles at 0.2 mm depth had acceptable symmetry and flatness that can improve the dose uniformity within the target area. Calculated isodose curves showed that the 90% isodose level covers a circular area with the diameter of around 8 mm for all studied beta sources. From the results, it can be concluded that 166Ho and 32P are more effective in treatment of superficial skin lesions, while, 90Y and 188Re are more rational choices in treatment of deeply distributed skin tumors. Size of employed patch source should be based on the target area to minimize the delivered dose to the adjacent tissues.

New simple and low-cost methods for periodic checks of Cyclone® Plus Storage Phosphor System.

The recent large use of the Cyclone® Plus Storage Phosphor System, especially in European countries, as imaging system for quantification of radiochemical purity of radiopharmaceuticals raised the problem of setting the periodic controls as required by European Legislation. We described simple, low-cost methods for Cyclone® Plus quality controls, which can be useful to evaluate the performance measurement of this imaging system.

Indoor radon measurement and effective dose assessment of 150 apartments in Mashhad, Iran.

Environmental monitoring and indoor radon measurement are important for public health, to estimate the cancer risk of respiratory system and, if necessary, to suggest proper methods that reduce indoor radon level. In this research, indoor radon concentration in the air has been measured in 150 apartments in Mashhad city. The result demonstrates about 94.7% of apartments have radon concentration less than 100 Bq/m(3), taken by WHO as the action level, and 5.3% have the concentration higher than this level. As well as, annual radon dose has been assessed using the equation for annual effective dose calculation introduced by United Nations Scientific Committee on the Effects of Atomic Radiation.

Thyroid volume's influence on energy deposition from (131)I calculated by Monte Carlo (MC) simulation.

BACKGROUND: It is well known that the success of the radiomethabolic (131)I treatment of hyperthyroidism could depend on the absorbed dose to the thyroid. It is, thus, very important to calculate the individual radiation dose as accurately as possible for different masses of thyroid lobes. The aim of this work is to evaluate the influence of thyroid volume on the energy deposition from beta and gamma rays of (131)I by Monte Carlo (MC) simulation. MATERIALS AND METHODS: We have considered thyroid lobes having an ellipsoidal shape, with a density of 1.05 g/ cm(3) and the material composition suggested by International Commission on Radiological Protection (ICRP). We have calculated the energy deposition of (131)I rays for different volumes of thyroid lobes by using the MCNPX code, with a full transport of beta and gamma rays. RESULTS AND CONCLUSIONS: The results show that the total energy deposition has a significant difference, till 11%, when the lobe's volume varies from 1 ml to 25 ml, respect to the value presented in MIRDOSE for a 10 g sphere. The absorbed energy fraction increases by volume, because the increasing volume to surface ratio of ellipsoidal lobe causes the decrease of beta ray fraction escaping from the lobe.

Monte Carlo simulation of intrinsic count rate performance of a scintillation camera for diagnostic images.

This paper describes Monte Carlo simulation of intrinsic count rate performance of a scintillation gamma camera. MCNP Monte Carlo code was employed to calculate pulse height spectrum and detector efficiency. A custom code written in Fortran language was then developed to simulate, by Monte Carlo method, the distortion in pulse height spectrum due to the pile-up effect for paralyzable and nonparalyzable systems. The results of the simulations, compared with the experimental measurement of count rate performance, showed a good agreement between the two different approaches.