MR-IMAGING OF THE FETUS BY A IN HASTE SEQUENCE

OBJECTIVE. The value of a half-Fourier acquisition single-shot turbo s pin-echo (HASTE) sequence, in which high-resolution heavily T2-weighte d images can be obtained within 2 sec, was evaluated in the imaging of the fetus during the second or third trimester. MATERIALS AND METHODS . Eighteen women with complicated pregnancies as revealed on a sonogra m during the second and third trimesters (16-36 weeks' gestation) were studied with a 1.5-T superconductive MR imaging unit that used a body phased-array coil. After informed consent, T1-weighted fast low-angle shot images, T2-weighted turbo spin-echo images, and HASTE images wer e obtained without any premedication. Images were analyzed with regard to image quality, degree of blurring, visualization of the normal fet al organs, and visualization of fetal and maternal abnormalities. RESU LTS. On HASTE sequences, visualization of the fetal brain, Visceral or gans (lung, heart, liver, kidney, and bladder), extremities, and umbil ical cord were significantly better than on fast low-angle shot or tur bo spin-echo sequences (p < .01). In the brain, the white matter-gray matter distinction, gyrus formation, and myelination of the brain were clearly revealed by the HASTE sequence. Pathologic processes includin g fetal abnormalities (anomalies of the central nervous systems [n = 5 ], placenta previa [n = 2], ascites [n = 1], and transverse lie in the third trimester [n = 1]) and maternal abnormalities (leiomyoma [n = 5 ], ovarian tumors [n = 3], and hydronephrosis [n = 1]) were clearly se en on HASTE imaging. The peak specific absorption rate for RF exposure in these studies was less than 1.5 W/kg. CONCLUSION. In situations wh en sonography is suggestive but not definitive, MR imaging with a HAST E sequence allows clear fetal imaging with high T2-weighted contrast.