Comparison Between 1.5-T and 3-T MRI for Fetal Imaging: Is There an Advantage to Imaging With a Higher Field Strength?

Abstract

Objective: Fetal MRI at 3 T is emerging as a promising modality for evaluating fetal anatomy. The objective of this study was to compare the quality of images obtained with commonly used fetal imaging sequences at 1.5 T and 3 T. We hypothesized that the visualization and anatomic detail of fetal structures would be better at 3 T than at 1.5 T.

Materials and methods: A retrospective search of the radiology department database at our institution identified 58 fetal MRI examinations performed at 3 T to evaluate body abnormalities during the period from July 2012 to February 2014. A blind comparison was conducted between these examinations and 58 1.5-T MRI examinations of age-matched fetuses undergoing evaluation for similar abnormalities during the same period. The anatomic structures analyzed included the bowel, liver, kidney, airway, cartilage, and spine. Scores for the depiction of anatomic structures ranged from 0 to 4, with 4 denoting the best depiction.

Results: Fetal imaging at 3 T was associated with higher imaging scores in the evaluation of the cartilage and spine when single-shot turbo spin-echo (SSTSE) and steady-state free precession (SSFP) sequences were used and in the assessment of most structures (e.g., bowel, liver, kidney, cartilage, and spine) when SSFP sequences were used. The mean scores for all structures evaluated with the use of SSTSE sequences were higher when MRI was performed at 3 T than at 1.5 T; similar findings were noted when SSFP sequences were used. Evaluation of imaging scores with regard to gestational age showed that scores improved with increasing gestational age on 1.5-T MRI but not on 3-T MRI. Overall, more imaging artifacts were found when imaging was performed at 3 T than at 1.5 T.

Conclusion: An overall advantage to performing fetal imaging at 3 T was made evident by the higher imaging scores obtained with 3-T MRI versus 1.5-T MRI when different fetal anatomic structures were evaluated. These higher scores were predominantly associated with use of SSFP sequences. The findings of this study and future advancements in MRI software and 3-T protocols may allow optimal visualization and examination of fetal pathologic abnormalities, thus better identifying fetal and maternal needs both prenatally and postnatally.

Keywords: 3-T fetal MRI; fetal imaging; prenatal imaging.