Single-fraction High-dose Brain Irradiation:Experimental MR Spectroscopy and Metabolism Study in Vivo / 实用放射学杂志

ABSTRACT

Objective To analyse the ultrastructural and metabolic changes of brain injury after single-fraction high-dose radiation in rabbits by means of proton 1-hydrogen) magnetic resonance spectroscopy ~1H MRS) ,in order to provide the basic theory for early detection of radiation-induced brain injury.Methods Experimental model of single-fraction high-dose radiation-injured brain was established in 40 rabbits , which were randomly divided into 4 groups and underwent 10, 15, 20 Gy and 30 Gy radiation , respectively. Proton MRS in a clinical MR imager was used to ascertain the amount of whole-brain N-acetylaspartic acid NAA), lactic acid Lac), choline Cho), creatine Cr) before and within 8 weeks after focused single-fraction high-dose irradiation therapy. Metabolic maps of NAA, Lac, Cho and Cr were created from MRS data set. Detection of irradiation injury among the tested models was assessed by receiver operating characteristic analysis and by quantitative signal intensity changes. The peak values of NAA , Lac , Cho and Cr on MRS before and after radiation were measured. Histopathology and electron microscope were used to ascertain changes of the ultrastructural organization in the irradiated area.the results were compared and statisti-cally analyzed. Results Initially MRS was found a slightly decrease. Until obviously change was detected, statistical significance variation of MRS occurred. A significant decrease in~1H MRS occurred at the early stage of brain injury induced by single-fraction high-dose irradiation.Conclusion ~1H MRS may be regarded as a noninvasive and sensitive means for the detection of early radiation-induced brain injury.