Objective To compare enhancement of the central auditory pathway in cats receiving auditory stimulation between manganese enhanced magnetic resonance imaging (MEMRI) with intraperitoneal manganese injection route and MEMRI with intratympanic manganese injection route,and investigate the optimal method for displaying enhancement of the central auditory pathway.Methods Twenty-seven normal hearing adult cats were randomly divided into three groups,receiving intraperitoneal manganese injection,left intratympanic manganese injection or left intratympanic gadolinium injection respectively.All cats received white noise stimulation of 80 dB in twenty-four hours after injection.Three dimensionally coronal Tt-weighted imaging of the cat brain was obtained with an animal dedicated MRI scanner.The signal noise ratios (SNRs) of bilateral cochlear nuclei (CN),dorsal nuclei of the trapezoid bodies (DNTB),caudal colliculi (CC) and auditory cortices (AC) were measured on reconstructed images and compared.Results Obvious increased SNRs on both sides were shown in intraperitoneal mangasese injection group while left predilection was shown in intratympanic manganese injection group:left CN 45.7 ± 6.0,37.4±11.9,23.9±2.7,F=17.694,P=0.000;left DNTB 50.5 ±11.2,37.1 ±11.2,27.6 ± 7.3,F=11.781,P =0.000;left CC 37.6 ±3.9,22.6 ±3.1,17.9 ±0.7,F=111.898,P =0.000;left AC 27.7 ±2.5,17.3 ±2.3,14.5 ± 1.0,F =105.132,P =0.000;right CN 42.7 ±8.3,23.9 ± 3.0,22.7 ± 2.1,F =41.492,P =0.000;right DNTB 44.1 ±8.3,21.9 ±3.0,23.9 ±4.0,F =27.862,P =0.000;right CC 38.0 ±4.0,21.9 ±3.0,17.6 ±0.9,F =120.032,P =0.000;right AC 26.7 ±3.4,17.1 ±2.9,14.9 ± 1.3,F =64.587,P =0.000.Compared with the left intratympanic gadolinium injection group,the intraperitoneal manganese injection group showed higher SNRs in bilateral CN and CC (P ＜ 0.05),and the left intratympanic manganese injection group showed higher SNRs in left CN,AC and bilateral CC.The SNRs of right CN,bilateral DNTB,CC and AC were significantly higher in the intraperitoneal manganese injection group than those in the left intratympanic manganese injection group (P ＜ 0.05).Conclusion MEMRI with intraperitoneal manganese injection might be the optimal method for displaying enhancement of the central auditory pathway in cats receiving auditory stimulation.%目的 比较经腹腔注射锰剂和经鼓室注射锰剂两种锰增强磁共振成像(MEMRI)方法对猫听觉中枢强化效果的显示情况,探讨最佳的锰增强磁共振成像方法.方法 将27只正常听力的成年家猫随机分为经腹腔注射锰剂组、经左侧鼓室注射锰剂组和经左侧鼓室注射钆剂对照组.三组猫注射锰剂或钆剂后,给予24 h 80 dB白噪声刺激并进行7.0T磁共振扫描.测量并比较三组受试猫蜗神经核、斜方体背侧核、下丘核以及颞叶初级听皮质的信噪比.结果 MEMRI能清楚显示猫听觉中枢结构.经腹腔注射锰剂组、经左侧鼓室注射锰剂组和经左侧鼓室注射钆剂组各结构的信噪比值为:左侧蜗神经核45.7±6.0、37.4±11.9、23.9±2.7,F=17.694,P=0.000;左侧斜方体背侧核50.5±11.2、37.1±11.2、27.6±7.3,F=11.781,P=0.000;左侧下丘核37.6±3.9、22.6±3.1、17.9±0.7,F=111.898,P=0.000;左侧听觉皮质27.7±2.5、17.3±2.3、14.5±1.0,F=105.132,P=0.000;右侧蜗神经核42.7±8.3、23.9±3.0、22.7±2.1,F=41.492,P=0.000;右侧斜方体背侧核44.1±8.3、21.9±3.0、23.9±4.0,F=27.862,P=0.000;右侧下丘核38.0±4.0、21.9±3.0、17.6±0.9,F=120.032,P=0.000;右侧听觉皮质26.7±3.4、17.1±2.9、14.9±1.3,F=64.587,P=0.000.腹腔锰剂组的双侧蜗神经核、斜方体背侧核、下丘核、颞叶初级听皮质信噪比明显高于左侧鼓室钆剂对照组(均P ＜0.05),左侧鼓室锰剂组左侧蜗神经核、初级听皮质及双侧下丘核的信噪比明显高于左侧鼓室钆剂对照组(均P ＜0.05).腹腔锰剂组右侧蜗神经核、双侧斜方体背侧核、下丘核及颞叶初级听皮质信的噪比均高于左侧鼓室锰剂组(均P＜ 0.05).结论 与经鼓室注射锰剂或钆剂方法相比,经腹腔注射锰剂的锰增强磁共振成像显示猫接受听刺激后听觉中枢强化效果最好,是显示猫听觉中枢强化的最佳磁共振成像方法.
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