4Durfee SM, Frates MC. Sonographic spectrum of the corpus luteum in early pregnancy: gray-scale, color, and pulsed Doppler ap pearance. J Clin Ultrasound, 1999,27(2) :55- 59.
5吴钟瑜.实用妇产科超声诊断学.2版.天津:天津科技翻译出版公司.2002:121.
6Stein MW, Ricei ZJ, Novak L. Sonographic comparison of the tubal ring of ectopic pregnancy with the corpus luteum. J Ultrasound Med, 2004,23 ( 1 ) : 57-62.