Magnetic resonance imaging compared to ultrasonography in fetal weight and volume estimation in diabetic and normal pregnancy

Abstract

High-resolution magnetic resonance imaging combined with semiautomatic segmentation software was found to be accurate in determining fetal volume and, consequently, better than conventional ultrasound-based techniques in estimating fetal weight. The use of magnetic resonance imaging in fetal weight estimation may be recommended for clinical situations where an accurate weight estimate is considered essential.

Three-dimensional Fetal MR Imaging: Will It Fulfill Its Promise?

“…This can be based on manually tracing fetal outlines, which is very time-consuming, as evidenced by the 6 hours per case in the study of Kubik-Huch et al (15). The use of software to decrease the human time needed to select fetal volumes allows fetal segmentation in as little as 10 minutes (11). With the Cavalieri method of stereologic examination combined with point counting, wherein the volume is estimated on the basis of the sum of the transected areas of the sections through the structure multiplied by the gap between the MR imaging sections, case analysis can occur in as little as 5 minutes per case (12,13,18).…”

“…A number of methods have been described for obtaining the data with which fetal volumetry can be performed (Table) (11)(12)(13)(14)(15)(16). In the current issue of Radiology, Dr Kubik-Huch and colleagues (15) describe two-dimensional MR imaging performed with a half-Fourier single-shot fast spin-echo technique in which fetal, amniotic fluid, and placental volumes were manually segmented and reconstructed with automatic volume calculations.…”

“…Results determined by assuming a mean fetal tissue density coefficient of 1.0 g/cm 3 underestimate fetal weight at term (11,12,15,16). Formulas extracted from small populations of fetuses at term derive density coefficient values that vary from 1.03% to 1.07% (11,16). The equations derived from fetuses at term may be of no use in the second trimester, however, since the proportion of fetal tissues is different.…”

“…It is not possible to extrapolate directly from fetal weight to fetal volume because fetal density varies with factors such as fetal fat, water, muscle, and bone content. Results determined by assuming a mean fetal tissue density coefficient of 1.0 g/cm 3 underestimate fetal weight at term (11,12,15,16). Formulas extracted from small populations of fetuses at term derive density coefficient values that vary from 1.03% to 1.07% (11,16).…”

Fetal growth

“…Magnetic resonance imaging (MRI) also claims to be more accurate in determining fetal volume and, consequently, better than conventional ultrasound based techniques in estimating fetal weight [46][47][48][49][50]. But again this is a time consuming and expensive method.…”