[Evaluation of the Normal Structures of Parotid Duct Using Magnetic Resonance Hydrography]

Objective To investigate the normal structures of parotid duct by using magnetic resonance(MR)hydrography. Methods MR three-dimensional heavy T2-weighted imaging was performed in 21 normal subjects.After taking 200 mg of vitamin C orally for 3 minutes,the subjects underwent parotid duct coronal hydro-magnetic resonance imaging.The images were transferred to the GE AW4.5 workstation,on which multi-planner reformation was performed using Functool software.The numbers of the parotid duct,accessory parotid duct,segments,and its branches was counted and the length and diameter of the intra-and extra-parotid ducts were measured. Results Accessory ducts were found in 24 parotid glands(57.1%,24/42),with the average length being(9.54±9.98)mm and the average diameter being(0.87±0.88)mm.The intra-parotid ducts were found to be with 3 segments were in 3 cases(7.14%,3/42),with 2 segments in 19 cases(45.23%,19/42),and with 1 segment in 20 cases(47.62%,20/42).The average number of the branches of the first,second and third segment was 2.38,0.88,and 0.1,respectively.The average length of the intra-parotid duct was(36.97±7.97)mm,with its average diameter being(2.01±0.76)mm.The average length of extra-parotid duct was(34.98±10.25)mm,with its average diameter being(2.13±0.79)mm.The average length of the whole parotid duct was(71.95±11.47)mm,with its average diameter being(2.07±0.68)mm. Conclusion The parotid duct,the accessory parotid duct,and the segments and their branches of the intra-parotid duct can be accurately displayed by MR hydrography.