# Evaluation of the Effect of X-Ray Therapy on Glioma Rat Model Using Chemical Exchange Saturation Transfer and Diffusion-Weighted Imaging

## TL;DR

This study uses MRI to evaluate how X-ray therapy affects brain tumors in rats, showing reduced tumor metabolism and limited water diffusion after treatment.

## Contribution

The study introduces a novel use of CEST and DWI to assess the effects of X-ray therapy on glioma in a rat model.

## Key findings

- X-ray therapy reduced creatine concentration in the tumor.
- X-ray therapy inhibited the increase in water molecule diffusion.
- MTR values at multiple ppm levels decreased significantly in the irradiated group.

## Abstract

Several preclinical studies have been conducted on the efficacy of high-field MRI in treating brain tumors. This study aims to determine the effects of X-ray therapy on a rat model of brain tumors using magnetic resonance imaging (MRI). We performed MRI before and after X-ray therapy to determine the treatment effects on brain metabolites and water molecule diffusion. The results showed that X-ray therapy reduced the creatine concentration in the tumor and inhibited the increase in water molecule diffusion. We revealed the impact of X-ray therapy on brain tumors. The results obtained in this study may be beneficial for predicting prognosis.

Background/Objectives: This study aimed to examine the changes in brain metabolites and water molecule diffusion using chemical exchange saturation transfer (CEST) imaging and diffusion-weighted imaging (DWI) after 15 Gy of X-ray irradiation in a rat model of glioma. Methods: The glioma-derived cell line, C6, was implanted into the striatum of the right brain of 7-week-old male Wistar rats. CEST imaging and DWI were performed on days 8, 10, and 17 after implantation using a 7T-magnetic resonance imaging. X-ray irradiation (15 Gy) was performed on day 9. Magnetization transfer ratio (MTR) and apparent diffusion coefficient (ADC) values were calculated for CEST and DWI, respectively. Results: On day 17, the MTR values at 1.2 ppm, 1.5 ppm, 1.8 ppm, 2.1 ppm, and 2.4 ppm in the irradiated group decreased significantly compared with those of the control group. The standard deviation for the ADC values on a pixel-by-pixel basis increased from day 8 to day 17 (0.6 ± 0.06 → 0.8 ± 0.17 (×10−3 mm2/s)) in the control group, whereas it remained nearly unchanged (0.6 ± 0.06 → 0.8 ± 0.11 (×10−3 mm2/s)) in the irradiated group. Conclusions: This study revealed the effects of 15 Gy X-ray irradiation in a rat model of glioma using CEST imaging and DWI.