MAGNETIC-RESONANCE-IMAGING OF YOUNG AND AGED RAT BRAINS UNDER A MAGNETIC-FIELD OF 7.05-T

Using a homemade MR imaging probe (Helmholtz coil), MR images of brain s of 5-week-old and 23- or 24-month-old Wistar rats were taken under a magnetic field of 7.05 T (Tesla). The probe was designed to fit the r at head and made by winding thin copper film round an acrylic tube wit h a 5-cm i.d., 10-cm length and 2-mm thickness. This was adjusted to r esonate with the 300 MHz radiofrequency corresponding to the resonance frequency of H-1 under a magnetic field of 7.05 T. MR images were obt ained by T1-weighted and two-dimensional Fourier transformation techni ques. The sagittal and coronal sections were imaged in 1-mm-thick slic es. The size of the data matrix was 128 phase-encoded steps. Each imag e was obtained through eight acquisitions. A comparison of the MR imag es with those semi-microscopically taken at the same position of the c oronal section revealed that the cerebral cortex, hippocampus, hypotha lamus and thalamus were clearly imaged by this probe. With aging, MR i mages of cerebral cortices were observed with decreased signal intensi ties. Enlargement of the third ventricles and hypertrophy of cranical parietal bones were also recognized in sagittal MR images of aged rats . These observations were more marked in males than in females. From t hese observations it was concluded that this probe was applicable for MR imaging of rat brains under a magnetic field of 7.05 T.