Functional Imaging with Photic Stimulation -Diffusion Weighted MRI-

Research Project

Project/Area Number	09670937
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Single-year Grants
Section	一般
Research Field	Radiation science
Research Institution	HIROSHIMA UNIVERSITY
Principal Investigator	KAJIMA Toshio Hiroshima University Faculty of Medicine, Research Associate, 医学部, 助手 (00224410)
Co-Investigator(Kenkyū-buntansha)	ITO Katsuhide Hiroshima University Faculty of Medicine, Professor, 医学部, 教授 (20034035)
Project Period (FY)	1997 – 1998
Project Status	Completed (Fiscal Year 1998)
Budget Amount *help	¥3,100,000 (Direct Cost: ¥3,100,000) Fiscal Year 1998: ¥500,000 (Direct Cost: ¥500,000) Fiscal Year 1997: ¥2,600,000 (Direct Cost: ¥2,600,000)
Keywords	Functional MRI / Diffusion Weighted Image / Photic Stimulation / 拡張強調画像 / 灌流強調画像
Research Abstract	[Background and Purpose] The studies of the brain function using MRI have been done with the T2^* weighted images, on that the origin of the signal intensity changes is the oxygenation of the hemoglobin. Recently the diffusion weighted images-(DWI) is expected as a new method to investigate brain function because this method can estimate movement of the water molecules in some physiological changes. But few studies were reported about the diffusion weighted functional MRI.The purpose of this study is to evaluate the ability of application of DWI to the functional image. [Materials and Methods] 1. The photic stimulation that was an objective and easy method of neural activation was applied in this study. The usual functional images and the diffusion weighted functional images of normal volunteers were scanned by the 1 .5T MRI system with and without looking at the images on the screen. 2. The differences of the signal intensities between images with stimulation and without stimulation were examined. [Results] The changes of signal intensity in the visual field of cerebral cortex were observed in accordance with the stimulation on the usual functional image but were not observed on the diffusion weighted functional images. [Discussion] Nevertheless the increase of diffusion with the nerve stimulation was speculated in the literature, the signal changes were not observed in this study. The increase of focal blood flow and oxyhemoglobin caused by the nerve stimulation raise the signal intensity but increase of diffusion caused by the nerve stimulation lower the signal intensity. So these two factors would be cancelled out. [Conclusion] Diffusion weighted images could not detect focal signal changes with the nerve stimulation. The new diffusion weighted technique that raise the signal intensity with the increase of diffusion was thought to be necessary in the application of functional MRI.