Biography
Biography: Manohar Roda
Abstract
USG is the primary technique for fetal imaging due to its proven utility, availability and low cost. Technical and therapeutic advances have driven the development of fetal MRI which now plays an increasingly important role in the evaluation of sonographically complex or occult anomalies of the fetal body. MRI during pregnancy was initially being used for maternal and placental abnormalities. Modern fetal MRI began with the availability of T2W- ultrafast sequences which provides an excellent contrast declination between the fluid (CSF) and tissues (developing brain). Fetal MRI was initially primarily utilized for evaluation of the fetal brain-neurological abnormalities. Development of more ultrafast breath hold sequences like T1, diffusion, echo planar, led to the MRI evaluation of the fetal organs. Continued progressive works of various groups has added signifcantly to the further development of this technique. Fetal MRI now offers an unrivaled method for advanced detailed anatomic imaging with a high degree of flexibility in the image contrasts. All the fetal cavities are fluid filled and appear T1 hypointense, T2 hyperintense; mouth, nose, ear, GI tract including stomach, kidneys, UB, GB, trachea, lungs, ventricles, CSF spaces and amniotic cavity. The bowel meconium, pituitary, thyroid and liver appears T1 hyperintense. Robust use of bright blood imaging and dark blood imaging sequences also helps in fast imaging as vessels and heart can appear bright/dark based on different imaging sequences. Fast MRI sequences have overcome fetal motion, hence scanning with adequate slice thickness, resolution, quality and SNR is now feasible. Parallel imaging is a general method for reducing the time of data processing required to produce images by simultaneous data collection on multiple separate channels with total imaging time ~30-45 minutes. Standard MRI screening and consent is obtained and scan is performed without any IV contrast administered. Main fetal safety concerns are first trimester teratogenesis and acoustic damage. Although safety has not been positively established, hazards appear negligible and outweighed by diagnostic benefit. Hence, pregnant women in the second and third trimester can be reassured that MRI poses no known risk to the fetus. My presentation will elaborate on common indications, ultrafast MRI technique, normal fetal anatomy and major congenital anomalies. All radiologists involved in prenatal imaging should be aware of the applications, safety concerns and limitations of this evolving modality.