PRENATAL DIAGNOSIS Prenat Diagn 2008; 28: 745–748. Published online 20 June 2008 in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/pd.2041 Diffusion-weighted MR imaging and apparent diffusion coefficient of the normal fetal lung: preliminary experience Lucia Manganaro 1 , Anna Perrone 1 *, Simona Sassi 1 , Francesca Fierro 1 , Sara Savelli 1 , Marco Di Maurizio 1 , Alessandra Tomei 1 , Antonella Francioso 1 , Laura La Barbera 1 , Antonella Giancotti 2 and Laura Ballesio 1 1 Department of Radiological Sciences, “Sapienza” University of Rome, Italy 2 Department of Obstetrics and Gynecology, “Sapienza” University of Rome, Policlinico Umberto I, Via Regina Elena, 324 00161 Rome, Italy Objective To assess if a correlation is present between apparent diffusion coefficient (ADC) values and normal lung maturation during gestation to define potential reference values as indicators of the lung development. Methods Our study included 50 pregnant women (gestational age, GA: 18–36 weeks), with normal fetal development of lungs assessed by a previous obstetric ultrasound (US), and then confirmed by our magnetic resonance (MR) examination. We used T2-weighted sequences, diffusion-weighted imaging sequences (DWI) and ADC maps for studying pulmonary tissue. In all cases the resulting ADC values were related to GA using Pearson correlation. Results ADC values ranged from 1,2 μm 2 /ms at 18 weeks’ gestation to 3,9 μm 2 /ms at 36 weeks’ gestation with a mean value, regardless for the gestational age, of 2, 352 ± 0,623106 μm 2 /ms. We found a significant correlation between ADC and gestational age (Pearson correlation = 0,816). Conclusion The ADC values correlate with gestational age since alveolar fluid secretion and angiogenesis increase gradually. Therefore, ADC can be considered as a new parameter for studying lung maturity. Copyright  2008 John Wiley & Sons, Ltd. KEY WORDS: lung maturity; MRI; diffusion INTRODUCTION Infants’ survival relies on fetal lung maturation, partic- ularly if an adequate amount of surfactant is present at birth. Ultrasound (US) is the standard modality for fetal imaging to value pulmonary development. It can detect the presence of congenital thoracic abnormalities, but it does not allow a good correlation between lung matura- tion and gestational age and does not supply always an objective evaluation of lung volumetry (Lee et al., 1996; Moeglin et al., 2005). Moreover echogenicity cannot be used as a parameter to predict pulmonary hypoplasia even if it usually increases during gestation. The recent development of ultrafast MR imaging sequences, with a short scan time, revolutionized fetal imaging, making MR a widely accepted complementary modality to ultrasound in prenatal diagnosis (Levine et al., 1998; Hubbard, 2003; Kumaresan et al., 2005). In the last years two reports hypothesized the pos- sibility to use MR diffusion-weighted imaging (DWI) to predict lung maturation with opposite results (Moore et al., 2001; Balassy et al., 2008). DWI is based on the interpretation of signal variability associated with ran- dom Brownian motion of water molecules: the results of these movements are calculated through the use of *Correspondence to: Anna Perrone, Department of Radiological Sciences, “Sapienza” University of Rome, Italy. E-mail: perrone.anna@gmail.com apparent diffusion coefficient (ADC), a quantitative and objective parameter (Pekar et al., 1992; LeBihan et al., 1988; Luypaert et al., 2001). Our purpose was to assess if a correlation exists between ADC values and normal lung maturation during gestation, in order to define the potential reference values, as indicators of the lung development. MATERIALS AND METHODS The institution review board approved our study. Our study included 50 consecutive pregnant women with 50 singleton fetuses [gestational age (GA) 18–36 weeks; mean, 27 weeks; maternal age range, 18–44 years; mean, 29 years] who were referred to our Depart- ment to undergo prenatal MRI examination after obstet- ric US, from October 2005 to October 2007. Indication for fetal MR imaging included maternal abnormalities (n = 7), suspected fetal anomalies (n = 35), and pla- centa or annexes anomalies (n = 8) found during a rou- tinely ultrasonographic examination Table 1. In Three fetuses oligohydramnios was present. The study inclusion criterion was pregnant women with normal development of fetal lungs assessed by a previous obstetric US, and then confirmed by our MR examination: lung development was considered normal if morphologic development was regular (absence of focal lung lesions and normal lung size determined by volumetry on axial T2-weighted images). Copyright  2008 John Wiley & Sons, Ltd. Received: 17 March 2008 Revised: 5 May 2008 Accepted: 5 May 2008 Published online: 20 June 2008