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Figure 1b. Ovarian edema in a 28-year-old woman with twins (initially quadruplets) at 14 weeks gestation who had undergone ovulation induction and had an enlarging solid left ovarian mass at US. (a) Sagittal turbo spin-echo MR image (5,139/90, two acquisitions, 140 x 256 matrix, echo train length of seven, 5-mm section thickness, 26 x 35-cm field of view, acquisition time of 3 minutes 3 seconds) of the gravid uterus (U) and enlarged (14 x 9 x 8 cm) left ovary with small peripheral follicles (arrows). The follicles have low signal intensity, which is likely due to hemorrhage. The enlargement of the left ovary was histopathologically shown to be caused by massive ovarian edema. Because of the long imaging time, fetal structures could not be identified. (b) Half-Fourier RARE MR image (single shot/60; field of view, 26 x 35 cm; matrix, 192 x 256; echo train length, 72; one signal acquired; section thickness, 5 mm) in the coronal plane demonstrates the gravid uterus (U) with the body of one fetus (arrowhead), hyperstimulated right ovary (open arrow), and edematous left ovary (O). (c) Coronal RARE MR image obtained slightly more anteriorly shows fetuses (one of which is not alive) in three gestational sacs.