In Vivo Dynamic Changes Of Endolymph In Guinea Pigs With 9.4 Tesla MRI

Objective To observe the imaging characteristics of guinea pig cochlea structure used in magnetic resonance imaging system in 9.4 Tesla test at differet time points of contrast agent distribution in the inner ear, and explore the optical time for obgerving thewhole inner ear. To explore the pharmacokinetic feature of Gd- DTPA in the inner ear, and find out whether discrimination of endolymph and perilymph can be obtained with the application of contrast agents, providing the basis of imaging for the diagnosis of disorders of the inner ear.Methods Five albino guinea pigs were injected with Gd-DTPA via the right internal jugular vein(3 ml/kg) at the moment when inner ear volume scans on a 9.4T MRI system were completed. Susequent inner ear volume scans were taken after 10 minutes,30 minutes, 60 minutes, 90 minutes and 120 minutes to detect changes of endolymph and perilymph. Using Image J software to acquire magnetic resonance image gray value on the bottom of the cochlear turn, the second, the third turn and apical turn four parts at different time points and drawing the curve of magnetic resonance image changes of each part of cochlea at different time point after intravenous contrast agent, which can know the distribution of Gd-DTPA in the cochlea at different time points.Results Only outlines of the cochlea and vestibule were visible before Gd-DTPA injection with no distinction between endolymph and perilymph. As Gd-DTPA only enter scala tympani and scala vestibuli, and do not enter scala media, we can distinguish between endolymph and perilymph. Cochleo vestibular on T1 weighted images was enhanced at10 minutes after injection of contrast agent, and imaging of each part of cochlea enhanced gradually after injection for 30 minutes, 60 minutes, and at 90minutes cochlea, vestibule, semicircular canal were fully developing, endolymph and perilymph can be distinguish clearly, while at120 minutes imaging was no significantly enhanced than 90 minutes. The speed and volume of contrast agent into the various parts of the inner ear was different, and changes in distribution of contrast agent in each parts of the inner ear showed a rising process in a certain period of time. The distribution of contrast agent in the inner ear had concentration gradient: basal ture contrast most and apical ture least.Conclusions Endolymph of inner ear can be distinguished from the perilymph on a 9.4T MRI system with Gd-DTPA application, and the best observation time of inner ear was90 minutes after intravenous injection of contrast agent. Using gadolinium contrast agent provides imaging evidence of the pathological changes of the lymphatic fluid, and by magnetic resonance imaging can study Gd- DTPA metabolism in the inner ear indirectly, which may provide the conditions for the diagnosis and treatment of inner ear diseases such as Meynier.