The Value of Advanced Imaging Sequences for Fetal MRI in Clinical Practice

Fetal MRI is rapidly expanding but the choice of sequences (the combination of variables that produce the image and determine whether a specific tissue is highlighted at the expense of other tissues e.g. some sequences highlight areas with a high water content, others highlight tissues with a high fat content) is limited. Additional sequences have the potential to improve the diagnostic accuracy but need to be developed and assessed before replacing the current choices. In addition it is not possible to continue to add sequences to the list used in clinical practice as each one takes time, which is limited in clinical practice. They may also allow other body areas to be imaged successfully e.g. bones and heart that are not currently imaged to a diagnostic level to be useful in clinical practice.

Until recently fetal MRI was restricted in the United Kingdom (UK) to magnet strengths of 1.5T although 3T was safely used in the rest of Europe. The restrictions have been lifted and 3T can now be used in the clinical setting for fetal MRI. The clinical value of this has not been established (1) In this pilot study the investigators will aim to answer the above 4 questions.

1. Currently the T2 SSFSE is used as the main sequence and in some institutions supplemented by T1 and diffusion-weighted imaging (DWI). The investigators wish to look at other sequences that may be better than these for imaging certain areas of the baby. The investigators have noted that the images used for imaging the placenta ( Balanced gradient echo) show the edges of tissues well but do not give much internal detail. However these images would be useful in cases of babies with cysts and may show the extension of the cyst more clearly than the T2. However it is not possible to simply add extra sequences to the scans as this takes extra time and is not appropriate in the clinical setting. This pilot study will allow evaluation of the sequences and formal comparison by a world-leading expert. This information will be used to guide local clinical practice but also with further development in the future to develop national guidelines.
2. 3T can now be used in the UK to image the fetus. Prior to imaging clinically at 3T it is necessary to establish if there is any additional benefit. This pilot will allow us to compare historical 1.5T images with 3T images to assess the potential benefit prior to a larger study.
3. Currently the fetal heart appears as a black ill-defined mass on the images. The investigators hope to use the balanced gradient echo sequence to image the heart. Initially the investigators would like to be able to image 4 chambers reliably and then to see if known pathology can be detected. If this is possible a larger study will be designed for further development. The question the investigators are asking is a very simple - can the investigators image the fetal heart? ' Yes/no and if so can the investigators reliably see 4 chambers? Yes/no. This will not need quantitative analysis.
4. Similar to 3 as currently no definition in fetal bone is seen. The investigators wish to apply sequences that reliably define the bone and then pilot these in cases with known bone pathology.