# Large Numbers for Small Children—Up to What Age Do Infants Benefit from a Longer Echo Time in Cerebral T2 MRI Sequences?

## TL;DR

This study finds that using a longer echo time in MRI scans helps improve brain image contrast in infants only up to six months of age.

## Contribution

The study identifies a specific age cutoff for using long echo times in infant cerebral MRI to optimize grey–white matter contrast.

## Key findings

- Long echo time (TE) significantly improves grey–white matter contrast until six months of age.
- After ten months, medium TE provides better contrast than long TE in infant MRI.
- The optimal TE for infants changes with age, suggesting a shift in MRI protocols over time.

## Abstract

In newborns, white matter shows a high T2-weighted (T2w) signal in MRI with poor grey–white matter contrast. To increase this contrast, an extremely long echo time (TE) is used in the examination of children. It is not known up to what age this long TE should be used. The purpose of this study was to find up to what age a long TE should be used in infants. In the prospective study, 101 infants (0–18 months) underwent cranial MRI at 3 Tesla. T2-weighted Fast Spin Echo sequences with long TE (200 ms) and medium TE (100 ms) were used. The signal intensities of the cortex and white matter were measured and the grey–white matter contrast (MC) was calculated. A cut-off age was determined. The T2w sequences with long TE had a statistically significantly higher MC until the age of six months (medium TE: 0.1 ± 0.05, Long TE: 0.19 ± 0.07; p < 0.001). After the tenth month, the T2w sequence with medium TE provided significantly better MC (Medium TE: 0.1 ± 0.05; long TE: 0.05 ± 0.4; p < 0.001). The use of a long TE is only helpful in the first six months of life. After the tenth month of life, a medium TE should be favored as is used in adult brain MRI.