Radiologists can play central role in fetal MRI's bright future

This month sees a clutch of national radiological congresses taking place. The annual U.K., German, and Spanish meetings are held during May, but a more specialized event looks set to attract considerable attention: the first International Congress on Fetal MRI, to be staged in Vienna from 12 to 13 May.

This new conference, which is preceded by a one-day course, provides further evidence of fetal MRI's increasing clinical maturity. Moreover, a special focus session on this topic is planned for next year's European Congress of Radiology.

Fetal diagnostics used to be carried out mainly by obstetricians, but because of radiologists' knowledge of the modality, they are well placed to take the lead in fetal MRI. As illustrated by the cover story in this issue of DI Europe, the technique has emerged as a valuable supplement to ultrasound and is rapidly moving from the realm of select university medical centers to the clinical mainstream. It is now being used to shed light on inconclusive sonographic findings and to evaluate sonographically occult diagnoses.

Ultrafast MRI techniques have largely overcome the difficulties posed by movement artifacts. Images can be acquired in less than a second, and multiplanar views enable physicians to make more accurate diagnoses. Earlier identification of potential problems has assisted the planning of fetal surgery and design of postnatal treatments.

Awareness of the limitations of fetal MRI is important, however. For instance, due to the risk of spontaneous abortion, most experts agree that an MR examination should be avoided in women during the first three months of pregnancy.

Safety considerations are of paramount importance, as always. When given in clinical dose ranges, gadolinium-based contrast agents cross the human placenta and into the fetus. To date, there have been no conclusive teratogenic studies into the effects of these agents in pregnant women. Therefore, women at any stage of pregnancy must be informed about the risk-benefit ratio that may warrant the performance of an MR scan.

Acoustic damage is another concern. Loud noises generated by the scanner's coils may cause damage to the fetus, although the risk is thought to be minimal. Furthermore, supine scanning of a pregnant woman in the third trimester may result in aortocaval compression of the major arteries by the fetus, and this compression may reduce uterine-placental blood flow.

In the short term, the use of fetal MRI is likely to remain confined to selected indications, particularly abnormalities of the brain and central nervous system. In the longer term, the technique may have applications in areas such as the abdominal organs and thoracic cavity, as well as the maternal tissues of the placenta, umbilical cord, amniotic fluid, and uterine wall. The congress in Vienna should provide a glimpse into the future of this promising technique.