Lancet: High-field MRI offers non-invasive alternative to fetal autopsy

Whole-body high-field MRI is a reliable option for post-mortem examination of human fetuses and might provide a less invasive alternative to conventional autopsy, according to a U.K. study published online Aug. 6 in Lancet.

Examination after death can provide important data about why a fetus did not survive and help to assess the accuracy of diagnostic methods in utero and the risk to future pregnancies. This information is mainly obtained from autopsies. However, the study authors wrote that there has been a substantial decline in the number of parents agreeing to autopsy over the past decade. This has prompted research into less invasive methods of post-mortem exams.

Conventional whole-body MRI at 1.5T was thought to offer the most realistic alternative, but has been shown to provide inadequate image quality of small fetuses. In contrast, high-field (9.4T) whole-body MRI provides good images and has shown promising results in small animals, but has not been performed in humans, the researchers noted.

Sudhin Thayyil, MD, from the department of cardiovascular imaging at UCL Institute of Child Health and Great Ormond Street Hospital in London, and colleagues examined the feasibility of high-field MRI and compared the diagnostic usefulness of high-field MRI with conventional MRI and traditional invasive autopsy in small human fetuses.

Investigators performed a whole-body MRI at 9.4T and 1.5T on 18 fetuses of less than 22 weeks' gestation before doing a traditional invasive autopsy. Images from the MRI were compared with the findings of invasive autopsy in a blinded manner and assessed for diagnostic accuracy and image quality by a team of specialist pediatric radiologists.

Overall, Thayyil and colleagues found that traditional invasive autopsy did not provide superior diagnostic accuracy compared with high-field MRI in any of the examinations, and in some cases the high-field MRI provided more information than the invasive autopsy.

They also reported that spatial resolution, tissue contrast and image quality for all organ systems were much better with high-field MRI than with conventional MRI.

In addition, all structural abnormalities detected by traditional invasive autopsy and internal examination of visceral organs were also detected with high-field MRI, the authors wrote. In contrast, conventional MRI was found not diagnostically useful in 78 percent of cases.

Based on their findings, the researchers concluded that "specialist pathologists might be able to offer a two-stage post-mortem process to parents [in the future], whereby an MRI at 9.4 T plus information from all other non-invasive tests...is done first, and then, if needed, a targeted internal examination of the body is done (minimally invasive autopsy). Alternatively this form of autopsy might be offered to parents who refuse conventional autopsy...such an approach might increase the autopsy rates and bring back post-mortem research in the UK."

However, Thayyil and colleagues cautioned that these are very preliminary data and further evidence from large prospective studies is required before minimally invasive autopsy can be offered routinely in clinical practice.

In an accompanying commentary, Elspeth Whitby, MD, from the University of Sheffield, in England, and Marta Cohen, MD, from Sheffield Children's Hospital in England, highlighted several practical problems which need to be addressed if post-mortem MRI is to have a significant role in the future. These complications included limited access to MRI scanners, a service already stretched in England; and availability of specialist personnel to perform the scans and interpret the images when there is already a worldwide shortage of radiologists.

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