Micronucleus frequencies and clonogenic cell survival in TK6 cells exposed to changing dose rates under controlled temperature conditions

Translocation dose-response curve for 137Cs γ-rays: Dose validation at various dose rate and changing dose rate conditions

A Fluorescence In-Situ Hybridization (FISH) based translocation dose-response curve has been constructed for biodosimetry application in our nuclear establishment at Kalpakkam, India. Peripheral blood sample from a healthy male donor (27 years) was exposed to nine different doses (0.1 Gy-5 Gy) of ¹³⁷Cs γ-rays (100 mGy/min) in an automated calibration facility with a linear distancing system and subjected to FISH assay using chromosome 1, 2 and 4 specific fluorescent probes. Validation of the dose-response curve was done following three different approaches i) by blind test method ii) using blood samples exposed to γ doses (0.5, 1 & 2 Gy) at different dose rates (124, 23 & 10 mGy/min) and iii) with blood samples exposed to 0.5, 1 & 2 Gy γ doses at changing dose rates (increasing and decreasing dose rates). Results showed that a predefined dose-response curve constructed at a particular acute dose rate can be used for dose estimation in exposures involving varying dose rates and changing dose rate scenarios.

Investigation of the level of DNA double-strand breaks and mechanisms of cell death under irradiation of lung cancer and melanoma cells with ultra-high dose rate photon radiation

Research into the effects of radiation delivered at ultrahigh dose rates > 1 × 107 Gy/min to biological objects is a new promising area of radiobiology. The unique characteristics of the high-current nanosecond electron accelerator Mir-M enable its use in medical and biological research, specifically in the experiments aimed at investigating the effect of therapeutic doses at a dose rate up to 100 MGy/s. In this work we study the effects of ultrahigh dose rate photon radiation on human lung carcinoma (A549) and melanoma (MelMtp-x) cells lines and compare them with those of the therapeutic gamma unit Rokus-AM. We show that ultrahigh dose rates induce more significant damage in the studied cell lines at doses between 2 and 7 Gy, radioresistant melanoma being more sensitive to photon radiation delivered at ultrahigh dose rates.

Can high dose rates used in cancer radiotherapy change therapeutic effectiveness?

Current cancer radiotherapy relies on increasingly high dose rates of ionising radiation (100-2400 cGy/min). It is possible that changing dose rates is not paralleled by treatment effectiveness. Irradiating cancer cells is assumed to induce molecular alterations that ultimately lead to apoptotic death. Studies comparing the efficacy of radiation-induced DNA damage and apoptotic death in relation to varying dose rates do not provide unequivocal data. Whereas some have demonstrated higher dose rates (single dose) to effectively kill cancer cells, others claim the opposite. Recent gene expression studies in cells subject to variable dose rates stress alterations in molecular signalling, especially in the expression of genes linked to cell survival, immune response, and tumour progression. Novel irradiation techniques of modern cancer treatment do not rely anymore on maintaining absolute constancy of dose rates during radiation emission: instead, timing and exposure areas are regulated temporally and spatially by modulating the dose rate and beam shape. Such conditions may be reflected in tumour cells' response to irradiation, and this is supported by the references provided.