Pregnancy diagnosis and embryo counting are important end points in reproductive, developmental biology and toxicology studies. The purpose of the present study was to assess the feasibility and efficacy of magnetic resonance imaging (MRI) for early pregnancy diagnosis and embryo counting in the laboratory rat. Female Wistar rats were subjected to whole-body MRI scanning using a 1.5T MRI scanner, employing a isotropic T2-weighted 3D short-tau inversion recovery sequence from day 8 to day 12 post coitum (pc) or without prior mating, under general anaesthesia for pregnancy diagnosis and embryo counting. MRI examination was followed by laparotomy and visual inspection of the uterus to verify MRI findings. By day 8 pc, uterine bulges, characteristic of pregnancy, were depicted as oval-shaped structures of high intensity signal. By day 10 pc, embryonic vesicles were detected at the medial side of the uterine bulges. Pregnancy was diagnosed with 0% false-negative diagnosis and 100% accuracy by day 11 pc, while embryos were counted with 100% accuracy by day 12 pc. In conclusion, MRI proved to be a feasible and reliable non-invasive imaging method of early pregnancy diagnosis and embryo counting in the laboratory rat.

妊娠诊断和胚胎计数是生殖、发育生物学和毒理学研究的重要终点。本研究的目的是评估磁共振成像 (MRI) 在实验室大鼠早期妊娠诊断和胚胎计数中的可行性和有效性。使用 1.5T MRI 扫描仪对雌性 Wistar 大鼠进行全身 MRI 扫描，采用各向同性 T2 加权 3D 短 tau 反转恢复序列，从性交后 (pc) 的第 8 天到第 12 天或没有事先交配，在全身麻醉下用于妊娠诊断和胚胎计数。MRI 检查之后进行剖腹手术和目视检查子宫以验证 MRI 结果。到第 8 天，妊娠特征的子宫隆起被描绘为高强度信号的椭圆形结构。到第 10 天，在子宫隆起的内侧检测到胚胎囊泡。到第 11 天，怀孕被诊断为 0% 的假阴性诊断和 100% 的准确度，而到第 12 天，胚胎计数的准确度为 100%。综上所述，MRI被证明是一种可行且可靠的实验室大鼠早期妊娠诊断和胚胎计数的无创成像方法。