FIGURE 10-57 A. Coronal image of normal lungs on a balanced sequence at 29 weeks' gestation. The liver (L) and stomach (5) lie below the diaphragm. B. Left-sided congenital diaphragmatic hernia (CDH) (dotted ellipse) seen on balanced sequence at 33 weeks. C. The T1o-weighted sequence confirms the subdiaphragmatic position of the liver and better delineates the small bowel (arrow) and meconium-containing colon (arrowhead) that have herniated into the chest. D. Another image of a left-sided CDH at 22 weeks demonstrates no normal lung, the heart (H) displaced into the right chest, and an elevated liver (dotted ellipse).
sonographically, whereas pseudocysts and resultant abnormalities of meconium migration are better delineated with MR imaging .
• Adjunct to Fetal Therapy
As indications for fetal therapy have grown, MR imaging is used preoperatively to outline abnormalities. At some centers, before laser ablation of placental anastomoses for twin-twin transfusion syndrome, MR imaging is performed to assess the fetal brain for IVH or periventricular leukomalacia (Chap. 45, p. 878) (Hu, 2006; Kline-Fath, 2007). Because of its precision in visualizing brain and spine indings in cases of myelomeningocele, it is often used preoperatively. For sacrococcygeal teratomas, if fetal surgery is considered, MR imaging may identiY tumor extension into the fetal pelvis (Avni, 2002; Neubert, 2004; Perrone, 2017). With a fetal neck mass for which an EIT is considered, MR imaging may help delineate the lesion extent and its efect on the oral cavity, hypopharynx, and trachea (Hirose, 2003; Lazar, 2012; Ogamo, 2005; Shiraishi, 2000). Finally, vfR imaging can also calculate a jaw index when an EIT procedure may be needed for severe micrognathia (MacArthur, 2012; Morris, 2009). Fetal therapy is discussed in Chapter 16 (p. 327).
FIGURE 10-58 A. Sagittal short T1 inversion recovery (STIR) image through a fetus with posterior urethral valve at 23 weeks' gestation. Notice the characteristic dilation of the posterior urethra (arrowhead). B. At 31 weeks, a coronal image shows progression of severe hydronephrosis, cystic changes in the parenchyma, hydroureter, and anhydramnios. The lungs (L) show a decreased signal and are small. C. An axial balanced sequence shows a distended bladder (B) with thickened wall (arrows).
The clinical importance of identiying women with placenta accreta is discussed in Chapter 41 (p. 777). Sonography is gen erally used to identiy placental invasion into the myometrium, however, MR evaluation is an adjunct for indeterminate cases.
bands on T2-weighted images, focal bulging, and placental heterogeneity (Leyendecker, 2012). When used in a comple mentary role, MR imaging sensitivity is high for detection of placental invasion, although the depth of invasion is diicult to predict. Clinical risk factors and sonographic indings should be taken into account when interpreting MR placental images.