Characterization and quantification of cerebral edema induced by synchrotron x-ray microbeam radiation therapy

Abstract

Cerebral edema is one of the main acute complications arising after irradiation of brain tumors. Microbeam radiation therapy (MRT), an innovative experimental radiotherapy technique using spatially fractionated synchrotron x-rays, has been shown to spare radiosensitive tissues such as mammal brains. The aim of this study was to determine if cerebral edema occurs after MRT using diffusion-weighted MRI and microgravimetry. Prone Swiss nude mice's heads were positioned horizontally in the synchrotron x-ray beam and the upper part of the left hemisphere was irradiated in the antero-posterior direction by an array of 18 planar microbeams (25 mm wide, on-center spacing 211 mm, height 4 mm, entrance dose 312 Gy or 1000 Gy). An apparent diffusion coefficient (ADC) was measured at 7 T 1, 7, 14, 21 and 28 days after irradiation. Eventually, the cerebral water content (CWC) was determined by microgravimetry. The ADC and CWC in the irradiated (312 Gy or 1000 Gy) and in the contralateral non-irradiated hemispheres were not significantly different at all measurement times, with two exceptions: (1) a 9% ADC decrease (p < 0.05) was observed in the irradiated cortex 1 day after exposure to 312 Gy, (2) a 0.7% increase (p < 0.05) in the CWC was measured in the irradiated hemispheres 1 day after exposure to 1000 Gy. The results demonstrate the presence of a minor and transient cellular edema (ADC decrease) at 1 day after a 312 Gy exposure, without a significant CWC increase. One day after a 1000 Gy exposure, the CWC increased, while the ADC remained unchanged and may reflect the simultaneous presence of cellular and vasogenic edema. Both types of edema disappear within a week after microbeam exposure which may confirm the normal tissue sparing effect of MRT.

Optimizing dose enhancement with Ta 2 O 5 nanoparticles for synchrotron microbeam activated radiation therapy

“…Some pre-clinical trials note the development of minor cerebral oedemas following MRT [18]. However, the oedemas disappear within a week after the MRT treatment, in agreement with studies that highlight the success of normal tissue sparing with MRT [9][10][11][12][13][14][15][16][17].…”

“…Therefore, the future applications of MRT are aimed at treating brain tumours. There is good prognosis for child brain cancers, with less risk of damage to the developing CNS than conventional broad beams [18].…”

An Experimental Study of Acute Radiation-Induced Cognitive Dysfunction in a Young Rat Model

“…16 Previous animal studies have addressed whole-brain irradiation-induced cognitive impairment after both single and fractionated radiation dose schedules by use of x-ray and cobalt 60 as the source of radiation. 17,18 As the linear accelerator becomes more and more widely applied, protocols with use of a linear accelerator as the source of radiation are getting more and more similar to conventional radiation therapy protocols used for patients in the clinic. In this study, we established an early-onset young rat model of radiation-induced cerebral in Fig 1. Effects of brain irradiation on place navigation function of rats in water maze.…”

A preclinical microbeam facility with a conventional x‐ray tube

“…The remarkable resistance of normal tissue to microbeams has been demonstrated in various preclinical studies, beginning with neutron beams in the 1960s (Refs. 7, 8, 9, 10) to synchrotron generated photon beams in the last 25 years 2 , 5 , 6 , 11 , 12 …”