Abstract
Minibeam radiation therapy (MBRT) is an innovative synchrotron radiotherapy technique able to shift the normal tissue complication probability curves to significantly higher doses. However, its exploration was hindered due to the limited and expensive beamtime at synchrotrons. The aim of this work was to develop a cost-effective equipment to perform systematic radiobiological studies in view of MBRT. Tumor control for various tumor entities will be addressable as well as studies to unravel the distinct biological mechanisms involved in normal and tumor tissues responses when applying MBRT. With that aim, a series of modifications of a small animal irradiator were performed to make it suitable for MBRT experiments. In addition, the brains of two groups of rats were irradiated. Half of the animals received a standard irradiation, the other half, MBRT. The animals were followed-up for 6.5 months. Substantial brain damage was observed in the group receiving standard RT, in contrast to the MBRT group, where no significant lesions were observed. This work proves the feasibility of the transfer of MBRT outside synchrotron sources towards a small animal irradiator.
Highlights
The use of the spatial fractionation of the dose is a strategy to overcome the main limitation in radiotherapy (RT), namely the normal tissue tolerances
The thicker beams used in Minibeam radiation therapy (MBRT) makes that the dose profiles are not as vulnerable as those of MRT to beam smearing from cardiac pulsations[16], very high dose rates are not needed
The criteria of acceptability for the dose calculations compiled in the Technical Report Series 430 (TRS 430) of the International Atomic Energy Agency was used[33]
Summary
The use of the spatial fractionation of the dose is a strategy to overcome the main limitation in radiotherapy (RT), namely the normal tissue tolerances. Grid therapy faces some major limitations due to the important lateral scattering of megavoltage X-rays beam employed This leads to a reduction in the peak-to-valley dose ratios (PVDR), an important indicator for normal tissue sparing[3]. The use of very narrow beams, as in synchrotron microbeam (MRT) and minibeam radiation therapies (MBRT), allows exploiting the dose–volume effect[4]: the smaller the beam size is, the higher the tolerances of the healthy tissue. The very first animal studies with synchrotron-generated x-ray microbeams (MRT) showed the remarkable tissue sparing effect of very narrow beams[5]. In these techniques the irradiation is performed with planar beams. Histology analysis allowed the evaluation of tissue integrity, inflammation, necrosis and calcifications, among others
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