Perspectives for microbeam irradiation at the SYRMEP beamline

Effects of Microbeam Irradiation on Rodent Esophageal Smooth Muscle Contraction

BACKGROUND

High-dose-rate radiotherapy has shown promising results with respect to normal tissue preservation. We developed an ex vivo model to study the physiological effects of experimental radiotherapy in the rodent esophageal smooth muscle.

METHODS

We assessed the physiological parameters of the esophageal function in ex vivo preparations of the proximal, middle, and distal segments in the organ bath. High-dose-rate synchrotron irradiation was conducted using both the microbeam irradiation (MBI) technique with peak doses greater than 200 Gy and broadbeam irradiation (BBI) with doses ranging between 3.5-4 Gy.

RESULTS

Neither MBI nor BBI affected the function of the contractile apparatus. While peak latency and maximal force change were not affected in the BBI group, and no changes were seen in the proximal esophagus segments after MBI, a significant increase in peak latency and a decrease in maximal force change was observed in the middle and distal esophageal segments.

CONCLUSION

No severe changes in physiological parameters of esophageal contraction were determined after high-dose-rate radiotherapy in our model, but our results indicate a delayed esophageal function. From the clinical perspective, the observed increase in peak latency and decreased maximal force change may indicate delayed esophageal transit.

The Microbeam Insert at the White Beam Beamline P61A at the Synchrotron PETRA III/DESY: A New Tool for High Dose Rate Irradiation Research

Simple Summary

The excellent preservation of normal tissue function after high dose rate radiotherapy has been shown in pre-clinical studies. Normal tissue in the tumor environment is well preserved even after target doses of several hundred Gy while reliably destroying the tumor cells. These results have triggered the establishment of appropriate research structures at the synchrotron PETRA III on the DESY campus in Hamburg, Germany. Dose rates of hundreds of Gy/s can be achieved, compared to 6–20 Gy/min in clinical radiotherapy. We describe the design, development, key parameters, and first use of a mobile insert for high dose rate radiotherapy research, a new research instrument at P61A, the first polychromatic beamline of PETRA III. The data obtained at the end station P61A will support the international interdisciplinary effort to improve radiotherapy concepts for patients with malignant tumors that are considered radioresistant with the currently established clinical radiotherapy techniques.

Abstract

High dose rate radiotherapies such as FLASH and microbeam radiotherapy (MRT) both have developed to the stage of first veterinary studies within the last decade. With the development of a new research tool for high dose rate radiotherapy at the end station P61A of the synchrotron beamline P61 on the DESY campus in Hamburg, we increased the research capacity in this field to speed up the translation of the radiotherapy techniques which are still experimental, from bench to bedside. At P61, dose rates of several hundred Gy/s can be delivered. Compared to dedicated biomedical beamlines, the beam width available for MRT experiments is a very restrictive factor. We developed two model systems specifically to suit these specific technical parameters and tested them in a first set of experiments.

Flying rats and microbeam paths crossing: the beauty of international interdisciplinary science

PURPOSE

Microbeam radiotherapy (MRT) is a still experimental radiotherapy approach. Two combined parameters contribute to an excellent normal tissue protection and an improved control of malignant tumors in small animal models, compared to conventional radiotherapy: dose deposition at a high dose rate and spatial fractionation at the micrometre level. The international microbeam research community expects to see clinical MRT trials within the next ten years.Physics-associated research is still widely regarded as a male domain. Thus, the question was asked whether this is reflected in the scientific contributions to the field of microbeam radiotherapy.

METHOD

A literature search was conducted using Pubmed, Semantic Scholar and other sources to look specifically for female contributors to the field of microbeam radiotherapy development.

CONCLUSION

The original idea for MRT was patented in 1994 by an all-male research team. In approximately 50% of all publications related to microbeam radiotherapy, however, either the first or the senior author is a woman. The contribution of those women who have been driving the development of both technical and biomedical aspects of MRT in the last two decades is highlighted.

Quantification of Differential Response of Tumour and Normal Cells to Microbeam Radiation in the Absence of FLASH Effects

Microbeam radiotherapy (MRT) is a preclinical method of delivering spatially-fractionated radiotherapy aiming to improve the therapeutic window between normal tissue complication and tumour control. Previously, MRT was limited to ultra-high dose rate synchrotron facilities. The aim of this study was to investigate in vitro effects of MRT on tumour and normal cells at conventional dose rates produced by a bench-top X-ray source. Two normal and two tumour cell lines were exposed to homogeneous broad beam (BB) radiation, MRT, or were separately irradiated with peak or valley doses before being mixed. Clonogenic survival was assessed and compared to BB-estimated surviving fractions calculated by the linear-quadratic (LQ)-model. All cell lines showed similar BB sensitivity. BB LQ-model predictions exceeded the survival of cell lines following MRT or mixed beam irradiation. This effect was stronger in tumour compared to normal cell lines. Dose mixing experiments could reproduce MRT survival. We observed a differential response of tumour and normal cells to spatially fractionated irradiations in vitro, indicating increased tumour cell sensitivity. Importantly, this was observed at dose rates precluding the presence of FLASH effects. The LQ-model did not predict cell survival when the cell population received split irradiation doses, indicating that factors other than local dose influenced survival after irradiation.