Semi-quantification of LPS+Gd-DOTA in the middle ear cavity and inner ear of rat after transtympanic injection demonstrated by T1-weighted 2D MRI. 1.0 mM LPS+Gd-DOTA (containing 500 mM Gd-DOTA) was administered. At 3 h post-administration, LPS+Gd-DOTA nanoparticles were efficiently detected in the perilymph, which reached 21.1% (average of the vestibule, scala vestibuli, and scala tympani) of that in the middle ear cavity. LPS+Gd-DOTA intensity decreased in the middle ear cavity while increased in the inner ear and brainstem form 3 h to 6 h after intra tympanic administration. The region of interest was shown in the images. BS: brainstem; ME: middle ear; ST: scala tympani; SV: scala vestibuli; Vest: vestibule.