Longitudinal changes in gray matter regions after cranial radiation and comparative analysis with whole body radiation: a DTI study

Abstract

Purpose: Radiation-induced white matter changes are well known and vastly studied. However, radiation-induced gray matter alterations are still a research question. In the present study, these changes were assessed in a longitudinal manner using Diffusion Tensor Imaging (DTI) and further compared for cranial and whole body radiation exposure.

Materials and methods: Male mice (C57BL/6) were irradiated with cranial or whole body radiation followed by DTI study at 7T animal MRI system during predose, subacute and early delayed phases of radiation sickness. Fractional anisotropy (FA) and mean diffusivity (MD) values were obtained from brain’s gray matter regions.

Results: Decreased FA with increased MD was observed prominently in animals exposed to cranial radiation showing most changes at 8 months post irradiation. However, whole body radiation induced FA changes were mostly observed at 1 month post irradiation as compared to controls.

Conclusions: The differential response after whole body and cranial irradiation observed in the study depicts that radiation exposure of 5 Gy could induce permanent alterations in gray matter regions prominently as observed in Caudoputamen region at all the time points. Thus, our study has bolstered the role of DTI to probe microstructural changes in gray matter regions of brain after radiation exposure.

Keywords:

• DTI
• cranial radiation
• whole body radiation
• gray matter

Acknowledgement

Authors would like to thank Prof. R K S Rathore, Department of Mathematics, Indian Institute of Technology, Kanpur, India for using his inhouse built JAVA based software for DTI analysis. This work was a part of S &T project INM 311 (4.1) sanctioned by DRDO, Ministry of Defence, India.

Disclosure statement

All authors have no conflicts of interest to declare.

Additional information

Notes on contributors

Apurva Watve

Ms. Apurva Watve and Mamta Gupta, research fellows working on preclinical and Human MR imaging.

Subash Khushu

Dr. Subash Khushu, major research contributions in the field of MR imaging, Functional imaging and MR spectroscopy.

Poonam Rana

Dr. Poonam Rana, involved in identification of metabolic and imaging markers for radiation stress using MR techniques and metabolomics.