Abstract
The sharp high dose Bragg peak of a carbon-ion beam helps it to deliver the highest dosage to the malignant cells while leaving the normal cells relatively unharmed. However, the precise range in which it distributes dosages that significantly induce cell death or genotoxicity surrounding its Bragg peak remains unclear. To evaluate biological effects of carbon-ion radiation through entrance to post Bragg peak in a single biological system, CHO and xrs5 cells were cultured in T-175 cell culture flasks and irradiated with 290 MeV/n monoenergetic carbon-ions with initial dosages upon entrance to the flask of 1, 2, or 3 Gy for cell survival assays or 1 Gy for cytokinesis block micronuclei assays. Under all initial dosages, the biological Bragg peak and the highest micronuclei formation was observed at the depth of 14.5 cm. Moreover, as the initial dosage increased the range displaying a significant decrease in survival fraction increased as well (P < 0.0001). Intriguingly from 1 Gy to 3 Gy, we observed a significant increase in reappearance of colony formation depth (P < 0.05), possibly indicating the nuclear fragmentation lethality potential of the carbon-ion. By means of our single system approach, we can achieve a more comprehensive understanding of biological effects surrounding of carbon-ions Bragg peak.
Highlights
Emerging advantages of carbon-ion radiotherapy (CIRT) have led to an increase of these facilities worldwide, with 12 operational facilities to date and 25,702 patients treated per end of 20171–3
Beyond 14.5 cm, the Fricke gel remained its originally yellow color, indicating a steep drop off of dosage shortly following this depth. These results indicated that the biological Bragg peak should be within the ranges of depths of 13.8 and 14.5 cm (Fig. 1a)
As the initial dosage increased, the range in which there was a dramatic decrease in colony formation surrounding our biological Bragg peak was observed to increase
Summary
Emerging advantages of carbon-ion radiotherapy (CIRT) have led to an increase of these facilities worldwide, with 12 operational facilities to date and 25,702 patients treated per end of 20171–3. The sharp high dose, as well as, the high-LET properties of the carbon-ion beam allow for maximum biological effectiveness at the Bragg peak and aid CIRT in achieving the fundamental principle of radiotherapy, to ensure precise localization of dose distribution to the target tumor while minimizing dose/damage to the surrounding normal tissues[15,16,17]. Because of the carbon-ion sharp narrow Bragg peak and dose from the nuclear fragmentation, the extent of cell damage surrounding the Bragg peak remains unclear and must be addressed to further understand the precision of carbon-ion biological dose distribution and help define the extent of unwanted cellular damage surrounding its Bragg peak These results will aid medical professionals utilizing CIRT to specify the dose distribution to the target tumor. Our development of an in-vitro cell survival assay variant technique has enabled us with the ability to investigate biological effects near the Bragg peak precisely
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