Ultrafast MR imaging of the foetus: a study of 25 non-central nervous system anomalies

Abstract

Purpose: The aim of this paper is to suggest Magnetic Resonance (MR) Imaging as a useful tool in prenatal diagnosis. Although ultrasonography (US) is the imaging technique of choice for prenatal screening, in cases of complex malformations US findings may be sub-optimal and give rise to diagnostic difficulties requiring further investigation. Our study is focused on non-central nervous system (CNS) abnormalities of the foetus imaged using the ultrafast sequence EXPRESS.

Materials and methods: 38 women whose foetuses were between 21-34 gestational age were studied. Indications for the examinations included the evaluation of non-CNS abnormalities in 25 cases. Foetal MR imaging was performed on a 1.5 T system (Edge, Marconi Medical System Italia SpA, Vimercate, MI) with the half-Fourier, single-shot, fast spin-echo EXPRESS sequence. Mild maternal and foetal sedation was obtained by oral administration of benzodiazepine (1 mg).

Results: In the 25 foetuses investigated for non-CNS pathologies the abnormalities were localised in the chest (9), abdomen (15) and extremities (1). The MR imaging diagnoses were: in the chest - congenital diaphragmatic hernia (CDH) (5), congenital cystic adenomatoid malformation (CCAM) (1), hydrothorax (1), cystic lymphangioma (1), Jeune syndrome (1); in the abdomen - 10 cases of urinary tract diseases - polycystic kidney (4), crossed renal ectopia (2), unilateral renal agenesis (1), solitary pelvic kidney (1), bilateral stenosis of ureteropelvic junction (1), duplex collecting system in association with controlateral hydroureteronephrosis (1)#151;5 cases of non-urinary tract pathologies#151;cystic lymphangioma of the liver (1), abdominal cystic lymphangioma (1), gastroschisis (1), gastric duplication (1), cavernous haemangioma of the liver (1); in the extremities - longitudinal hemimelia (1).

Conclusions: In our experience MR is to be considered a useful though adjunct study to prenatal US particularly in the evaluation of lung parenchyma, congenital diaphragmatic viscera herniation, thoracic masses, pleural effusion, abdominal cystic masses, and urinary tract malformations. The ultrafast EXPRESS sequence enables a complete study to be performed in a very short time; as a consequence the examination is well tolerated by the patient. Currently there is no legislation which regulates the use of magnetic fields in MR, only a series of recommendations based on studies on animal embryos and foetuses, on pregnant women exposed to magnetic fields and follow-up studies of children exposed to MR during gestation. Therefore the decision to proceed with foetal MR should be made on a case-by-case basis in close consultation with the referring obstetrician. Considering the results, in our opinion the potential of MR in the evaluation of a wide variety of non-CNS foetal diseases will increase in the near future.