4[5]Ludwig M,Kaisi M,Bauer O,et al.Heterotopic pregnancy in a spontaneous cycle: do not forget about it! Eur J Obstet Gynecol Reprod Biol,1999,87:91-93.
5[6]Frates MC,Visweswaran A,Laing FC.Comparison of tubal ring and corpus luteum echogenicities:A useful differentiating characteristic.J Ultrasound Med,2001,20:27-31.
6[8]Wherry KL,Dubinsky TJ,Waitches GM,et al.Low-resistance endometrial arterial flow in the exclusion of ectopic pregnancy revisited.J Ultrasound Med,2001,20:335-342.
7[10]Orden MR,Gudmundsson S,Helin HL,et al.Intravascular contrast agent in the ultrasonography of ectopic pregnancy.Ultrasound Obstet Gynecol,1999,14:348-352.
8[11]Kucera E,Helbich TH,Klem I,et al.Systemic methotrexate treatment of interstitial pregnancy-magnetic resonance imaging (MRI) as a valuable tool for monitoring treatment.Wien Klin Wochenschr,2000,112:772-775.
9[12]Barnhart KT,Katz I,Hummel A,et al.Presumed diagnosis of ectopic pregnancy.Obstet Gynecol,2002,100:505-510.
10[13]Dart R,Dart L,Mitchell P,et al.The utility of a dilatation and evacuation procedure in patients with symptoms suggestive of ectopic pregnancy and indeterminate transvaginal ultrasonography.Acad Emerg Med,1999,6:1024-1029.
