ESTRO 2024 - Abstract Book

S5238 ESTRO 2024 2 hours post-RT. For this time point, the violin plots in the cortex region revealed a great intensity increase of the Amide I to Amide II spectral ratio (Fig. 1, left), used as a marker of modifications in the secondary structure of proteins. Conversely, a reduction in absorbance of the phosphate bands of the nucleic acids was indicative of the radiation-induced damage to the DNA and carbohydrates, especially for the BB modality. Most of the pMBRT induced damage appears to be repaired 24 hours post-RT, as shown in Fig. 1 (right). Regarding the tumour-bearing rats, the hyperspectral maps of the brains revealed spectral differences between the tumours and surrounding healthy tissues. Concerning the variations among irradiation configurations, the violin plots in the tumours showed enhanced DNA-damage due to pMBRT, associated with absorbance modifications of the phosphate bands. As for the lipids spectral region, both RT modalities appeared to produce similar modifications in the acyl hydrocarbon chain lengths. Radiobiology - Normal tissue radiobiology

Figure 1. Violin plots showing the distribution of the Amide I to Amide II spectral ratio in the cortex region of healthy rat brain sections, fixed at 2 hours (left) and at 24 hours (right) post-RT. Colours indicate the irradiation modality: control in blue, BB-irradiated in red, and pMBRT-treated in green.

Conclusion:

This is the first study to report in vivo biochemical modifications resulting from pMBRT irradiations. Spectral differences were dependent on the brain region, irradiation configuration and fixation time. In healthy rats, most of the early damage induced by pMBRT seemed to be repaired one day after treatment. The results also suggested increased DNA modifications in the tumours of glioma-bearing rats due to pMBRT compared to conventional proton RT.

Keywords: Infrared spectroscopy, minibeam radiotherapy

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