Applied Radiation and Isotopes最新文献

Introduction

Antibiotic resistance is a burden on the healthcare system. In present study, we have labeled an antibiotic named Colistimethate sodium (CMS) with technetium-99m (^99mTc) to develop a SPECT based imaging tracer.

Methods

We standardised the labeling using 0.5–2 mg of CMS (in water) using stannous chloride dihydrate as a reducing agent followed by addition of 370 ± 74 MBq of ^99mTc. A group of mice were injected intravenously (in tail vein) with 4–6 MBq of [^99mTc]Tc-CMS diluted with saline and euthanized at various time intervals. microSPECT Imaging (ϒ-eye) was acquired to study the biodistribution in the healthy mice.

Results

We standardised the labeling using 0.5 mg of colistin in 0.5 ml of saline with addition of 30 μg stannous chloride dihydrate. The retention factor value was 0.1–0.3 as compared to 0.9–1.0 for free ^99mTc by TLC and retention time was found to be 14.2 ± 1.3 min as evaluated by HPLC. The biodistribution data showed uptake in lungs, spleen, and liver at 30 min but the uptake decreased in lung at 60 min. The imaging data corroborated with the biodistribution data.

Conclusions

We could successfully label [^99mTc]Tc-CMS ^99mTc and we could study its biodistribution in healthy mice.

This study examines the use of gypsum for radiation dosimetry using Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) techniques. It is observed that gypsum preserves the information of radiation dose despite the loss of water upon heating in a laboratory. Deconvolution of the thermoluminescence glow curve suggests thermoluminescence glow peaks at 125, 150, 280, 320, and 440 °C. The glow peak at 440 °C has a minimum detectable dose of 200 mGy, and it bleaches to approximately 50% with 300 min of daylight exposure. The Blue Light Stimulated Luminescence (BLSL) comprises a slow component and is correlated to 255 °C TL glow peak. The alpha efficiency of luminescence production per unit Gy of alpha dose with respect to the beta dose for the TL glow peaks at 440 °C is calculated at 0.18 ± 0.01. For BLSL, the value is calculated at 0.15 ± 0.01. A measurement protocol for the use of gypsum for retrospective dosimetry is also presented.

Boron Neutron Capture Therapy is being promoted with the development of accelerator neutron sources, and many new accelerator-based BNCT facilities are being built. In Particle Accelerator Facility project of Sun Yat-sen University, we plan to build a terminal for BNCT research based on an 8 MeV, CW 3 mA proton accelerator. In this paper, we present a beam-shaping assembly for this proton accelerator with such low 24 kW beam power, using composite moderator materials composed of five elements: Mg, Al, F, O, and Li. The calculation result of FLUKA with ENDF/B and JENDL libraries shows that the epithermal neutron beam flux is $1.57\times {10}^{9}n/{\text{cm}}^2/s$ with the CW 3 mA proton beam. The fast neutron component and the gamma ray component under free-air condition are $1.49\times {10}^{-13}\text{Gy}\bullet {\text{cm}}^2$ and $8.12\times {10}^{-14}\text{Gy}\bullet {\text{cm}}^2$ respectively, in line with IAEA-TECDOC-1223 design recommendations. The thermal analysis shows that the maximum temperature of beryllium target is 706.5 K, and the structure materials of BSA do not melt.

Purpose

Investigating the effects of unequal sub-arc personalized collimator angle selection on the quality of Volumetric Modulated Arc Therapy (VMAT) plans for treating multiple brain metastases.

Methods

This study included 21 patients, each with 2–4 target volumes of multiple brain metastases. Two stereotactic radiotherapy (SRT) approaches were utilized: sub-arc collimator VMAT (SAC-VMAT) and fixed collimator VMAT (FC-VMAT). In the SAC-VMAT group, multi-leaf collimators (MLC) shaped the target area, dividing the full arc into four unequal sub-arcs under the beam's eye view (BEV). Each sub-arc had an appropriate collimator angle selected to mitigate ‘island blocking problems'. Conversely, the FC-VMAT group used a fixed collimator angle of 15° or 345°. A comparative analysis of the dosimetric parameters of the target volumes and normal tissues, along with the monitor units (MU), was conducted between the two groups.

Results

The mean dose and dose-volume to normal brain tissue (2–26 Gy, with a step of 2 Gy) were significantly lower in the SAC-VMAT group (P < 0.01). There was no statistical difference between the two groups in dose to the target volumes, conformity index (CI), homogeneity index (HI), and other normal tissues (P > 0.05). Compared with the FA-VMAT group, the SAC-VMAT group significantly reduced the gradient index (GI) (4.5 ± 0.59 vs 5.2 ± 0.75, P < 0.001) and MU (1774.33 ± 181.77 vs 2001.0 ± 344.86, P < 0.001). Notably, with an increase in the number of PTV, the SAC-VMAT group demonstrated more significant improvements in the dose-volume of normal brain tissue, GI, and MU.

Conclusions

In this study, personalized selection of the unequal sub-arc collimator angle ensured the prescribed dose to the PTV, CI, and HI, while significantly reducing the GI, MU, and the dose to normal brain tissue in the VMAT plan for multi-target brain metastases in the cohort of cases with 2–4 target volumes. Particularly as the number of targets increase, the advantages of this method become more pronounced.

The solution-combustion approach was used to create CaB₄O₇:Eu³⁺phosphors using Ba (NO₃)₂, Eu (NO₃)₃·5H₂O, H₃BO₃, NH₃(ON)H₂, and NH₄NO₃ as source materials. We investigated the thermoluminescence (TL) characteristics of beta (β)-irradiated CaB₄O₇:Eu³⁺. When the TL intensity was evaluated at different dosages of β, it rose with the dose. Changes in peak temperature were observed because of the investigation of the effects of varying heating rates on TL glow curves. Moreover, the positions of the peak temperature and the TL intensity did not change when the same sample was measured again, suggesting that the sample was stable. Additionally, the study calculated several kinetic parameters, including activation energy (E), frequency factor (s), and geometrical factor (μg), for distinct TL glow curves. Through geometric analysis of TL glow peaks, the study determined activation energies and kinetic orders, enabling the calculation of the frequency factor. The findings highlight the suitability of the prepared phosphor for dosimetry and provide insights into trap characteristics crucial for continuous illumination at room temperature. The study also emphasises the importance of optimising trap depth for prolonged afterglow, shedding light on the interplay between trap energies and luminescence characteristics. These findings deepen our comprehension of phosphor behavior and open the door to better dosimetry applications.