ABSTRACT
Objective To explore the method of demonstrating main operative section of facial recess approach with multi-slice CT by using double oblique muttiplanar reconstruction.MethodsSimilarly as surgical procedure of facial recess approach,30 (60 eras) normal temporal bones in cadavers were reconstructed to observe main operative sections and anatomical marks.Main images of operative section of facial recess approach were reconstructed using double oblique multiplanar reconstruction on multislice CT.With the reference of operative anatomical marks,the ratios of visibility of anatomical marks on the transverse plane,coronal plane,sagittal plane and double oblique were calculated and compared.The degree,of which major anatomical landmarks were displayed on the same plane ( axial,coronal,sagittal,or doubleoblique sagittal plane),was classified using the following criteria: level 4: 100％ of anatomical landmarks were presented in the same plane; level 3: 90％ to 99％ of anatomical landmarks were presented in the same plane; level 2: 80％ to 89％ of anatomical landmarks were presented in the same plane; level 1: 70％ to 79％ of anatomical landmarks were presented in the same plane ; level 0: ＜ 70％ of anatomical landmarks were presented in the same plane.Classification data were tested by chi-square test.Results Four key operative section were involved in facial recess approach,which were of oblique sagittal orientation.The central mark of the first key operative section was semicircular canal by using double oblique multi-planar reformation.On reconstructed images of the first key operative section,horizontal reference line was short process of incus,and the angle adjusting the reference line on the transverse plane was 22.15° ±5.22°.On the reconstructed images of the first key operative section,coronal reference line was tympanic segment of facial canal,and the angle adjusting the reference line on the coronal plane was 14.35° ± 4.02°.On the reconstructed images of the second key operative section,the central mark was fossa incudis,the horizontal reference line was short process of incus and the angle was 20.15° ± 5.52°,while the coronal reference line was tympanic segment of facial cana,and the angle was 13.15° ± 3.33°.On the reconstructed operative images of the third key section,the central mark was pyramidal eminence,the horizontal reference line was the horizontal portion of the facial nerve and the angle was 32.53° ±5.22°,while the coronal reference line was the tympanic segment of facial nerve,and the angle was 15.05° ± 4.43°.On the fourth reconstructed images of the key operative section,the central mark was the posterior border of round window,the horizontal reference line was the superior border of oval window,and the angle was 50.15° ± 8.02°,while the coronal reference line was the tympanic segment of facial nerve,and the angle was 15.25° ± 4.12°.For the four planes (double-oblique sagittal,axial,coronal,or sagittal plane),the results of the degree to which they could include the major anatomical landmarks in the same layer of the first section were: level 4 in 60 sides,level 2 in 12 sides and level 3 in 48 sides,level 2 in 15 sides and level 3 in 45 sides,level 3 in 10 sides and level 4 in 50 sides,respectively.The results of the second section were: level 4 in 60 sides,level 2 in 11 sides and level 3 in 49 sides,level 2 in 13 sides and level 3 in 47 sides,level 3 in 11 sides and level 4 in 49 sides,respectively.The results of the third section were: level 4 in 60 sides,level 2 in 10 sides and level 3 in 50 sides,level 2 in 11 sides and level 3 in 49 sides,level 3 in 9 sides and level 4 in 51 sides,respectively.The results of the fourth section were: level 4 in 60 sides,level 2 in 9 sides and level 3 in 51 sides,level 2 in 8 sides and level 3 in 52 sides,level 3 in 5 sides and level 4 in 55 sides,respectively.The four planes differed significantly in the degree to which they could include the major anatomical landmarks in the same layer ( x2 =123.3200,121.4231,122.4011,125.4213,all,P ＜ 0.05 ).The visibility ratio of every section is 100％ (60/60).Conclusion Double oblique multi-planar reformation is a new method to demonstrate landmarks of operative section of facial recess approach in one slice.The reconstructive images of operative section with double oblique multi-planer reconstruction may provide valuable information for operation.