Spectra, fluence and absorbed doses in sensitive organs due to scattered X-rays during a chest CT.

The use of ionizing radiation for the treatment and diagnosis of diseases is becoming more frequent. The technologies associated with diagnostic imaging are constantly evolving, allowing faster and cheaper diagnoses to benefit the patient. However, this has caused an increase in the exposure to ionizing radiation of patients and health professionals. One of the diagnostic techniques for obtaining high-resolution anatomical images of patients is computed tomography (CT). Due to the detail and quality of the images obtained with CT, its use is becoming more frequent. The information provided by these images allows the specialist to make better diagnoses; however, exposure to X-rays deposits a dose in the patient. CT represents approximately 20% of all X-ray examinations but it is responsible for 70% of the medical dose accumulated by the patient. During the acquisition of the images, the highest dose is deposited in the area of the body whose image is to be obtained. During the incidence of X-rays, there is dispersion of these that reach sensitive organs whose dose is not evaluated. The objective of this work was to estimate, using Monte Carlo methods, the fluence and X-ray spectra and to obtain a factor that allows knowing the absorbed dose in sensitive organs due to scattered radiation during a chest CT. With the MCNP5 code, the CT equipment and a hybrid anthropomorphic phantom, type BOMAB it was found that the absorbed dose in these organs depends on the size of the organ and the distance between the organ and the surface of the slice on the thorax where the X-rays are incident.

Doses and spectra, of leaking-out and scattered photons from X-ray tubes used in dentistry.

Diagnosis by X-ray image are procedures widely used to improve the diagnosis or to follow the evolution of a medical procedure, also are used to support the cancer treatment with linear accelerators. The procedure involves the X-ray unit and the detection system, while the X-ray beam is projected onto the patient; along this procedure X-rays are scattered out from the patient body and X-rays leak-out from the X-ray unit. Both, the scattered and the leaking out radiation, are important during the evaluation or the design of the shielding barriers. X-ray tube features like voltage, electric current, target and filter are related to the dose due to the scattered and leakage radiation. Also, the dose due to the scattered radiation depends upon the scattering angle; while the dose due to the leaking out radiation, depend upon the X-ray tube housing. The objective of this work was to estimate, using Monte Carlo methods, the X-ray spectra and doses (air Kerma and Ambient dose equivalent) produced by scattered and leaking out radiation of 70, 80 and 90 kV X-ray units.

Effect of changing the neutron moderator in a thermal subcritical nuclear reactor.

Subcritical thermal nuclear reactor is the combination of nuclear fuel, moderator and external neutron source. Nevertheless, the amount of neutrons increases through nuclear fissions in the 235U in the fuel, the absorption and leakage of neutrons maintain the subcriticality condition. There are several subcritical reactors with different features and purposes. The open tank subcritical reactor Nuclear Chicago model 9000 is the heterogeneous combination of natural uranium, in hexagonal lattice, and light water, acting as moderator and reflector of neutrons, that uses a239PuBe neutron source. Worldwide there are several of these reactors mainly used in education, where due to the contact with water the Al tubes have corrosion. A possible solution is to use polyethylene as moderator. Aiming to evaluate the effect of changing the moderator, in this work Monte Carlo methods were used to model the reactor with polyethylene and water as moderators increasing the fuel load. For each model were estimated the keff and the µ parameters, and for Case 10a model was calculated the power, the Ambient dose equivalent and the fluence, of neutrons and γ-rays at five sites outside the reactor.

Shielding features of seven types on natural quartz.

The shielding features of amethyst, chalcedony, crystal rock, milky, pink, flint, and jasper quartz were calculated. The seven varieties of quartz were collected within the territory of the state of Zacatecas in Mexico. Shielding characteristics include the linear attenuation coefficients, the effective atomic numbers and the mass interaction coefficients for 1 keV to 100 GeV photons. The interaction coefficients were calculated for the coherent scattering, the photoelectric absorption, the Compton scattering, and the pair production occurring in the electric field of the atomic nucleus and the electrons. The linear attenuation coefficients were compared with those of the Portland concrete widely used as radiation shielding. In the low energy region where the photoelectric absorption is dominant the mass interaction coefficients and the total linear attenuation coefficients have three resonances due to the Si, Ca and Fe concentration, these resonances are also noticed in the effective atomic number. For photons below 60 keV the shielding performance of quartz can be used to shield X-ray devices working with less than 60 kV.

Nuclear pulse generator embedded in FPGA.

This manuscript presents the design and implementation of an intellectual property core, which acts as a generator of nuclear pulses. The design is embedded in a Field programmable gate array. It is capable of forming pulses with an exponential shape such as those from a radiation detector or Gaussian-shaped pulses such as those provided by a spectroscopy amplifier. Its characteristic is that the amplitude and period of these pulses can be configured by the user through a Virtual instrument generated in graphic language through the LabVIEW development platform. This can greatly reduce the volume, cost and energy consumption in relation to commercial analog nuclear electronics pulse generators.

Doses in eye lens, thyroid, and gonads, due to scattered radiation, during a CT radiodiagnosis study.

X-ray images used for radio-diagnosis are very useful to evaluate the progress of a treatment or to have a better diagnosis. However, during the interaction between the incoming X-ray beam and the body surface, part of the radiation is scattered out reaching other parts of the body delivering an undesirable dose. In this work the dose in eye lenses, thyroid, and gonads of a solid water phantom was measured using thermoluminescent dosimeters, while a Computer Tomography of the torso was obtained. With the measured absorbed dose the effective dose was calculated. Thus, the effective dose in the eye lens, thyroid, and gonads is approximately 57, 214 and 9 µSv respectively. The largest effective dose was on that area located nearest to the region where the radiation is scattered.

Doses in eye lens, thyroid, salivary glands, mammary glands, and gonads, due to radiation scattered in dental orthopantomography.

In the aim to support treatments and diagnostics in Dentistry the most common radiographies are the periapical radiography and the dental panoramic. In the dental panoramic the X-ray beam is addressed into a large zone of the face obtaining the image of the upper and lower jaw. In this procedure part of the X-rays are scattered reaching some other parts of the patient body. In this work the absorbed dose in the eye lens, thyroid, salivary glands, mammary glands, and gonads, was measured in patients undergoing a dental orthopantomography. Measurements were carried out with thermolmuminiscent dosimeters. With the absorbed doses the Effective dose were calculated. The highest dose was obtained in the salivary glands (30.4 µSv) and the lowest dose was obtained in thyroid (3.8 µSv).