Development of custom lead shield and strainer for targeted irradiation for mice in the gamma cell chamber

We presented a development of a custom lead shield and mouse strainer for targeted irradiation from the gamma-cell chamber. This study was divided into two parts i.e., to (i) fabricate the shield and strainer from a lead (Pb) and (ii) optimize the irradiation to the mice-bearing tumour model with 2 and 8 Gy absorbed doses. The lead shielding was fabricated into a cuboid shape with a canal on the top and a hole on the vertical side for the beam path. Respective deliveries doses of 28 and 75 Gy from gamma-cell were used to achieve 2 and 8 Gy absorbed doses at the tumour sites.

A PHANTOM STUDY SHOWING THE IMPORTANCE OF BREAST SHIELDING DURING HEAD CT

This study aimed to investigate the dose to the breasts during head computed tomography (CT) if lead shielding is used. The study was performed in two major hospitals using helical and axial protocols on an anthropomorphic phantom. Measurements were performed with and without the use of a lead shield of 0.5 mm equivalent density. The results showed a significant decrease in dose with the lead shielding in both hospitals. During the helical protocol, the use of shielding significantly reduced the dose by 96% in Hospital A and 82% in Hospital B. The dose reduction during axial protocol was also significant: 95% in Hospital A and 86% in Hospital B with lead shielding. Considering the significant dose reduction of 82% up to 96% during this study, we highly recommend the shielding of breasts regardless of the protocol used during head CT examinations.

Comparative Study of Calculation Methods for Shield Thickness of Typical Materials against Gamma Rays

The paper aims to analyze the shielding properties of concrete and lead materials against gamma rays at different energies, and the relationships between the shield thickness of the two materials and gamma ray energy and attenuation factor have been obtained by using the method of attenuation multiple and the method of half-value-thickness, respectively. The results show that when the gamma ray energy and the attenuation factor are determined, the thickness of the concrete shield layer obtained by the method of attenuation multiple is greater than that obtained by the half-value-thickness method. The relative magnitude of thickness of lead shield obtained by the method of attenuation multiple and the method of half-value-thickness method is relate to the gamma ray energy. When the gamma ray energy is lower than 8 MeV, the thickness of lead shield calculated by the method of attenuation multiple is larger than that obtained by the half-value-thickness method, while when the gamma ray energy is higher than 8 MeV, the conclusion is opposite.

A Low Background Gamma Ray Spectrometer with Anticosmic Shielding

The article describes a gamma ray spectrometer protected by a lead shield (Model 747E Canberra lead shield) and an active shield made of an 80~cm \(\times\) 80~cm \(\times\) 3~cm plastic scintillator plate in anticoincidence on top of the lead shield. The detector used as low background gamma-spectrometer is a high purity Germanium crystal of model GC2018 Canberra. The background count rate currently achieved (30-2400 keV) is 1.27 cps without anticoincidence. The level of background suppression obtained from the active protection is 0.80 overall and about 0.43 for the 511 keV gamma line. The gamma ray spectrometer is installed and operated in the Nuclear Laboratory, Department of Nuclear Physics, University of Science, HCMC-Vietnam National University.