Anatomical morphology of auditory bones in a 24-week fetal specimen by 3.0 T MRI
Xiao Lianxiang1,2,3, Shan Dejuan1, Wang Maobo1, Lin Xiangtao4
1Department of Radiology, Shandong Provincial Maternal and Child Health Care Hospital Affiliated to Qingdao University, Jinan 250021, China; 2Key Laboratory of Birth Regulation and Control Technology of National Health Commission of China, Jinan 250021, China; 3Key Laboratory of Birth Defect Prevention and Genetic Medicine of Shandong Health Commission, Jinan 250021, China; 4Shandong University, Provincial Hospital Affiliated to Shandong First Medical University, Jinan 250012, China
摘要目的 探讨24孕周胎儿标本听小骨3.0 T MR影像的解剖形态。方法 以1具24孕周流产胎儿冷冻标本为研究对象,女性,发育指标正常,双顶径62 mm,头围22.3 cm,腹围18.9 cm,身长27.5 cm,体质量580 g。使用西门子3.0 T MR对胎儿标本的双侧颞骨进行扫描,获取中耳的各向同性薄层MR断层图像。选取山东大学解剖教研室胎儿标本库中的1具25孕周发育指标正常的女性胎儿标本的颞骨CT扫描图像,以及1例来山东省妇幼保健院就诊的发育正常的2岁儿童颞骨CT图像,将CT图像与24孕周流产胎儿的MRI进行形态结构对照。观察项目：观察胎儿听小骨的MRI信号特点;比较CT图像与MRI对听小骨的显示效果;经多向调整多平面重组（MPR）,分别显示锤骨、砧骨、镫骨及相关结构的典型断层解剖形态,标识重要解剖结构;通过最大密度投影（MIP）重组对听骨链进行三维显示。结果 （1）MRI信号特点：胎儿听小骨在MR T2WI上显示为低信号,其中骨化完全部分呈明显低信号、未完全骨化部分为较低信号;中耳鼓室中充满羊水,表现为均匀T2WI高信号,在羊水信号衬托下,听小骨可清晰显示。（2）24孕周胎儿标本3.0 T MRI显示听小骨形态优于25孕周胎儿标本颞骨CT影像,听小骨结构形态的显示与2岁儿童颞骨CT近似。（3）多向调整MPR显示典型断层解剖形态：斜轴位锤骨长轴层面可显示锤骨头、锤骨颈、锤骨柄、锤砧关节、砧骨体、砧骨长脚、镫骨肌;斜冠状位锤骨长轴层面可显示锤骨头、锤骨颈、锤骨外侧突、锤骨柄（长突）、鼓膜张肌;砧骨三个正交方位可显示锤骨头、锤砧关节、砧骨短脚、砧骨体、砧骨长脚、鼓膜张肌、镫骨前脚、镫骨底（卵圆窗）、前庭;镫骨长轴位可显示镫骨前脚、镫骨后脚、镫骨头、镫骨肌、镫骨底、前庭;镫骨短轴位可显示卵圆窗、镫骨前脚、镫骨后脚、耳蜗底转、后半规管。（4）利用MIP重组可对听骨链进行锤骨前面观、锤骨后面观、砧骨正面观、镫骨正面观不同方位的三维形态显示。结论 3.0 T MRI及多向调整MPR重组技术的应用,可清晰显示24孕周胎儿标本的锤骨、砧骨、镫骨及相关结构的典型断层解剖形态。
Abstract：Objective This study aimed to investigate the anatomical morphology of auditory ossicles in a 24-week fetus on 3.0 T MRI. Methods A frozen sample of a 24-week aborted female fetus with normal development (biparietal diameter of 62 mm, head circumference of 22.3 cm, abdomen circumference of 18.9 cm, length of 27.5 cm, and bodyweight of 580 g) underwent 3.0 T MR scanning of bilateral temporal bones. Isotropic thin slice MRI sectional images of the middle ear were obtained. Temporal bone CT images of a 25-week developmentally normal female fetal specimen from the fetal Specimen Bank of the Shandong University Anatomy Department and a 2-year-old normally developing child who visited Shandong Provincial Maternal and Child Health Care Hospital were compared with MRI. Observation items: MRI signal characteristics of fetal auditory ossicles were observed. The effect of CT image and MRI on auditory ossicles was compared. The typical sectional anatomy of the malleus, incus, stapes, and related structures were displayed respectively by multi-planar reformation (MPR) with multi-directional adjustment to identify important anatomical structures. The ossicular chain was displayed by 3D maximum intensity projection(MIP) reconstruction. Results (1) MRI signal characteristics: fetal auditory ossicles showed low signal on MR T2WI, in which the complete ossification showed significantly low signal, and the incomplete ossification showed low signal. The tympanum of the middle ear was filled with amniotic fluid, showing a uniform T2WI high signal, and the auditory ossi could be clearly displayed against the amniotic fluid signal. (2) 3.0 T MRI of a 24-week fetal sample showed superior ossicular morphology to that of a 25-week fetal temporal bone CT, and the structural morphology of the ossicles showed an approximation to that of a 2-year-old child. (3) The long axis section of the malleus in the oblique axis position can show the head, neck, and handle of the malleus, as well as the malleus anvil joint, incus body, long foot of the incus, and the stapes muscle. In the oblique coronal view, the long axis of the malleus can show the head, neck, lateral process, and handle of the malleus (long process), as well as the tensor tympani muscle. The three orthogonal directions of the incus can show the malleus head and anvil joint, as well as the short foot of the incus,the incus body, long foot of the incus, tensor tympani muscle, the forefoot and bottom of stapes (oval window), and vestibule. The long axis positions of stapes can show the stapes forefoot, stapes hind foot, stapes head, stapes muscle, stapes bottom, and vestibule. The short axis positions of stapes can show oval windows, stapes forefoot, stapes hind foot, cochlear floor turn, and posterior semicircular canal. (4) MIP reconstruction can be used to display the auditory ossicular chain in different directions from the anterior and posterior views of the hammer, as well as the anterior views of the incus and stapes. Conclusion The application of 3.0 T MRI and multi-directional adjustment MPR reconstruction technology can clearly show the typical sectional anatomy of the malleus, incus, stapes, and related structures in 24-week fetal specimen.
肖连祥, 单德娟, 王茂波, 林祥涛. 24孕周胎儿标本听小骨3.0 T MR影像的解剖形态观察[J]. 中华解剖与临床杂志, 2023, 28(7): 454-459.
Xiao Lianxiang, Shan Dejuan, Wang Maobo, Lin Xiangtao. Anatomical morphology of auditory bones in a 24-week fetal specimen by 3.0 T MRI. Chinese Journal of Anatomy and Clinics, 2023, 28(7): 454-459.
Manganaro L, Bernardo S, Antonelli A, et al.Fetal MRI of the central nervous system: state-of-the-art[J]. Eur J Radiol, 2017,93:273-283. DOI: 10.1016/j.ejrad.2017.06.004
[2]
Milic A, Blaser S, Robinson A, et al.Prenatal detection of microtia by MRI in a fetus with trisomy 22[J]. Pediatr Radiol, 2006, 36(7):706-710. DOI: 10.1007/s00247-006-0155-9
[3]
Katorza E, Nahama-Allouche C, Castaigne V, et al.Prenatal evaluation of the middle ear and diagnosis of middle ear hypoplasia using MRI[J]. Pediatr Radiol, 2011,41(5):652-657. DOI: 10.1007/s00247-010-1913-2
[4]
Wei J, Ran S, Yang Z, et al.Prenatal ultrasound screening for external ear abnormality in the fetuses[J]. Biomed Res Int, 2014,2014:357564. DOI: 10.1155/2014/357564
[5]
Millischer AE, Sonigo P, Attie T, et al.Fetal MRI findings in a retrospective cohort of 26 cases of prenatally diagnosed CHARGE syndrome individuals[J]. Prenat Diagn, 2019,39(9):781-791. DOI: 10.1002/pd.5429
[6]
Vrabec JT, Lin JW.Inner ear anomalies in congenital aural atresia[J]. Otol Neurotol, 2010,31(9):1421-1426
[7]
Nemzek WR, Brodie HA, Chong BW, et al.Imaging findings of the developing temporal bone in fetal specimens[J]. AJNR Am J Neuroradiol, 1996,17(8):1467-1477
[8]
Moreira NC, Teixeira J, Raininko R, et al.The ear in fetal MRI: what can we really see?[J]. Neuroradiology, 2011,53(12):1001-1008. DOI: 10.1007/s00234-011-0938-z
[9]
张帅, 肖连祥, 渐楠, 等. 正常胎儿标本颈、胸、腰段脊柱发育的MRI研究[J].中华放射学杂志,2020,54(3):221-224. DOI: 10.3760/cma.j.issn.1005-1201.2020.03.009.Zhang S, Xiao LX, Jian N, et al.MRI study on the normal fetal development of cervical, thoracic and lumbar spines in specimens[J]. Chin J Radiol,2020,54(3):221-224. DOI: 10.3760/cma.j.issn.1005-1201.2020.03.009
Robinson AJ, Blaser S, Toi A, et al.MRI of the fetal eyes: morphologic and biometric assessment for abnormal development with ultrasonographic and clinicopathologic correlation[J]. Pediatr Radiol, 2008,38(9):971-981. DOI: 10.1007/s00247-008-0929-3
Tekes A, Ishman SL, Baugher KM, et al.Does microtia predict severity of temporal bone CT abnormalities in children with persistent conductive hearing loss?[J]. J Neuroradiol, 2013,40(3):192-197. DOI: 10.1016/j.neurad.2012.10.002
[14]
Gautam R, Kumar J, Pradhan GS, et al.High-resolution computed tomography evaluation of congenital aural atresia-how useful is this?[J]. J Laryngol Otol, 2020,134(7):610-622. DOI: 10.1017/S002221512000136X
[15]
Gao R, Wang Y, Fan Y, et al.The role of HRCT and three-dimensional VR CT findings in patients of congenital atresia combined with microtia[J]. Int J Pediatr Otorhinolaryngol, 2012,76(12):1779-1784. DOI: 10.1016/j.ijporl.2012.08.024
[16]
Ohtsuki S, Ishikawa A, Yamada S, et al.Morphogenesis of the middle ear during fetal development as observed via magnetic resonance imaging[J]. Anat Rec (Hoboken), 2018,301(5):757-764. DOI: 10.1002/ar.23760.
2023, Vol. 28 
