DC MEG indicators of tumor growth and chemotherapy in rat model

Abstract

Abstract The objective of this study was to determine if DC MEG can detect injury currents from tumor growth and chemotherapy in a rat model. Male Fisher rats were randomly divided into five groups: Groups One and Two were implanted with 9 L gliosarcoma cells. Group Three, surgery controls, received saline injections. Group Four were normal controls with no surgery. Group Two rats were treated with chemotherapy (1,3 Bis[2-chloroethy]-1-nitrosuorea, BCNU) five days after tumor implantation. Group Five rats had no surgery or tumor but received the same chemotherapy as Group Two. Baseline DC MEG measurements were taken with a six-channel animal neuromagnetometer using a stereotaxic fixture. DC MEG field measurements were recorded before and after lateral translation of the head 3 cm away from the sensor array and repeated 12–15 times to calculate average absolute field shifts. Ambient and fixture magnetic noise was subtracted from the measured rat signals to determine absolute DC MEG shifts. Post surgery, measurements continued every two days until sacrifice. Anatomical MRIs were performed on selected rats to estimate tumor volume at 4–6 day intervals throughout the experiment. Histology was performed on the sacrificed brains to evaluate final tumor size. DC MEG shifts were seen in the tumored and chemotherapy treated tumored rats, Groups One and Two. In these groups, the field shifts continued until sacrifice. In a few of the saline control rats (Group Three), DC Magnetic Field shifts were also seen but these correlated to rats with surgical side effects, i.e. weight loss or illness, and resolved when the rats recovered. No significant DC shifts were seen in the normal control rats (Group Four) or the chemotherapy with no tumor rats (Group Five). DC shifts seen in Group One and Two animals suggest continued injury currents in the rats' brains.