Radiation and Environmental Biophysics最新文献

Bone metastases are a major clinical problem, mainly in breast and prostate cancers, which comprise the majority of cancer cases. With technological advances that improve precision and efficacy, radiotherapy is an essential palliative solution. In this study, two radiotherapy planning techniques were evaluated, the longitudinal isocenter (LONI), and the three-isocenters (3ISO) that combine the lateral isocenters for pelvis and longitudinal isocenters for lumbar metastases, using the Halcyon^TM2.0 machine with the volumetric modulated arc therapy (VMAT) technique. Dosimetric parameters such as conformity index (CI), homogeneity index (HI), (dose coverage (D_95%), dose max (D_MAX), monitor units (MUs), and conformation number (CN) were analyzed. No significant difference in dose conformity between the two studied techniques was observed. However, remarkable results in terms of dose homogeneity were achieved in the application of the 3ISO modality, with an improvement of 42.8%. Additionally, D_95% for 3ISO was 96.26% against 92.71% for LONI. Regarding CN, which considers both dose coverage and healthy tissue optimization, 3ISO technique resulted in an improvement of 12.3%. It is noted, however, that 3ISO requires more time and accurate patient positioning to guarantee optimal outcomes.

The aim of our study is to evaluate the effects of glutamine, partially hydrolyzed guar gum and combined glutamine and partially hydrolyzed guar gum form in rats with experimental radiation enteritis by histopathological, immunohistochemical and biochemical measurements. 64 Wistar albino rats with an average weight of 220-280 g were used in the study. 1st group only took water, 2nd group only took glutamine, 3rd group only took partially hydrolyzed guar gum, 4th group took partially hydrolyzed guar gum with glutamine, 5th group took only radiotherapy, 6th group took radiotherapy with glutamine, 7th group took radiotherapy with partially hydrolyzed guar gum and 8th group took radiotherapy, glutamine and guar gum. Partially hydrolyzed guar gum was given with radiotherapy, and glutamine and guar gum were given together with radiotherapy in the 8th group. All rats were weighed on the first, seventh and tenth days. On the tenth day, the rats were sacrificed and their clinical status, biochemical, histopathological and immunohistochemical parameters in the terminal ileum were evaluated. Differences between groups were compared statistically. All groups were compared in terms of crypt length, villus height, crypt abscess, congestion, intraepithelial lymphoid infiltration, stool consistency, myeloperoxidase, malondialdehyde, caspase-3% and tumor necrosis factor alpha mean, and statistical significance was observed (p < 0.05). Weight% difference in rats was statistically significant between groups (p < 0.05). Interleukin-10 values were not statistically significant between groups (p > 0.05). In paired comparisons, there was a statistically significant difference between the control group and the group with radiation enteritis in terms of biochemical, histopathological, immunohistochemical and clinical parameters (p < 0.05). There was no statistically significant difference between the 5th group and 6th group, 7th group and 8th groups in terms of biochemical, histopathological, immunohistochemical and clinical parameters (p > 0,05). The result suggest that glutamine, partially hydrolyzed guar gum and combination therapy may not have a protective effect on radiation enteritis.

Antiprotons hold significant potential for radiotherapy due to their unique annihilation mechanism, which could offer dosimetric advantages. The objective of the present study was to assess how different phantom compositions affect the position of the Bragg peak and the biological effectiveness of antiproton beams in terms of the quality factor. This study investigated on-axis depth-dose profiles and the LET-based quality factor (Q_LET) for a 126 MeV antiproton beam in various phantom materials such as Water, Polystyrene, PMMA, RW1, WE210, Solid Water, and A150 using the FLUKA Monte Carlo code. The study also investigated the influence of elemental compositions of phantom materials on the relative contribution of antiprotons and secondary radiations to the total on-axis depth-dose profile. Additionally, the study discusses the variation in the in-flight annihilation cross-section across different phantom materials. The results show that depending on the phantom material, the position of the Bragg peak ranges from 11.49 to 11.82 g/cm². Furthermore, depending on the phantom material, Q_LET ranged from about 1.78 to 1.91 in the entrance region, from about 2.0 to 2.8 in the dose fall-off region, and from about 6.28 to 7.0 near the Bragg peak position. It is concluded that the study provides the theoretical basis of the understanding of depth dose profiles of antiprotons in various solid phantoms.

The rapid evolution of cancer treatment modalities has positioned proton therapy as a highly effective approach for targeting specific tumours. Proton therapy takes advantage of the Bragg peak phenomenon to deliver a concentrated dose to the tumour while minimizing exposure to surrounding healthy tissues. This feature has spurred interest in further enhancing proton therapy through the integration of advanced technologies, such as image-guided proton therapy and nanoparticle (NP) application. The incorporation of NPs into tumour tissues has emerged as a promising strategy to enhance the delivered dose in radiation therapy. This study investigates the dose enhancement factor (DEF) resulting from the presence of various NPs, when irradiated by a spread-out Bragg peak of a 120 MeV proton beam. Additionally, the magnetic dose enhancement factor (MDEF) under transverse magnetic fields of 3 T and 7 T is examined using the Geant4 simulation toolkit. The findings clarify the NP-mediated dose enhancement in proton therapy, particularly in the context of MRI-guided treatments. The highest DEF occurs within NPs (e.g., 1,341% for Ir), while the surrounding tissue exhibits negligible enhancement (< 10% up to a radial distance of 500 nm). The results indicate that magnetic fields up to 7 T do not significantly alter dose distributions around NPs. While validating the compatibility of NP-enhanced proton therapy with MRI guidance, this work provides a comparison of metallic (Au, Ir, Gd, and SPION) and non-metallic (B, C) NPs, establishing a foundation for clinical NP selection and future radiobiology studies.