Measurement of neutron equivalent dose in the thyroid, chiasma, and lens for patients undergoing pelvic radiotherapy: A phantom study.

Radiotherapy is one of the most common methods for treating malignant diseases, whose ultimate goal is to deliver lethal doses to tumor cells. One of the unwanted consequences of radiotherapy is secondary radiation outside the treatment field, which imposes additional doses to healthy tissues and organs, specifically neutron doses, which we aim to evaluate. Therefore, this study aims to measure the fast neutron equivalent dose and the risk of secondary cancer in the thyroid, chiasm, and lenses in the treatment of the pelvic area. In this study, CR-39 detectors were used to measure the equivalent fast neutron dose in different sections of the RANDO Phantom (thyroid, chiasm, and lenses) and were irradiated by the energy of 18 MV on Varian Clinac 2100 C-D linear accelerator. CR-39 detectors were calibrated with predetermined doses by an Am-Be neutron source. Then, after etching and reading processes, the equivalent dose of fast neutrons was determined. According to the results, the fast neutron doses in the thyroid, right and left eye lenses, and chiasm were 0.613 ± 0.024, 0.835 ± 0.040, 0.866 ± 0.016, and 0.685 ± 0.045 mSv/Gy, respectively. Moreover, the secondary cancer risks in the unshielded organs are 0.004, 0.029, 0.030, and 0.025 for the thyroid, right and left eye lenses, and chiasm, respectively. In conclusion, the contribution of neutrons to the secondary doses in the out-of-field organs is significant and should not be ignored.

Hemostatic Effect of Aminated Multiwalled Carbon Nanotubes/Oxidized Regenerated Cellulose Nanocomposites.

We have investigated the covalent conjugation of aminated multiwalled carbon nanotubes (MWCNTNH2)s with Oxidized Regenerated Cellulose (ORC) in order to enhance the hemostatic effect. The MWCNT-NH2s were prepared by functionalization of pristine MWCNTs (pMWCNTs) using amine groups. Neat ORC gauze and MWCNT-NH2s were reacted using glutamic acid as cross linking bridge. We investigated an amination of pMWCNTs as well as the dispersion of MWCNT-NH2s in the ORC gauze as matrix and their interfacial interactions by SEM and FT-IR. The results revealed that relatively strong interaction exists between aminated MWCNTs and the ORC macromolecules. The hydrophilicity test results in the significant increment of water uptake of MWCNT-NH2s/ORC composites with increasing the concentration of MWCNT-NH2s in composite. The in-vitro procoagulation test shows that the MWCNT-NH2s/ORC gauzes have significant procoagulant activity. The hemostatic evaluation of MWCNT-NH2s/ORC composites on rabbits shows that the aminated MWCNTs increase the rate of blood stopping and hence they decrease the blood loosing from injured sites. Hemostatic evaluation indicates that the MWCNT-NH2s/ORC gauze has a valuable hemostatic performance. The products of platelets release reaction, activated platelets glycoprotein and activated clotting enzymes were increased simultaneously. The mechanism of the hemostasis for MWCNT-NH2s/ORC gauze is discussed.