Using a standard MRI atlas with non-equitable sex representation introduces spurious sex effects

Motivation: Overcoming sex bias in preclinical research requires unbiased tools. Equitable sex representation in the creation of the atlas is seldom achieved, but failing to do so might introduce bias in the analysis. Goal(s): Our goal was to create a mouse MRI template that includes animals of both sexes, incorporating both structural and diffusion contrasts, and then compare it with a single-sex template. Approach: We scanned a large cohort of mice, including both sexes, to generate a template and registered the Allen annotation to it. Results: Using single-sex templates generates spurious sex differences that are not present when using resources with equitable sex representation. Impact: The MouseX DW-Allen Atlas is the first mouse MRI template that adopts the Allen annotation and is built with both sexes. It fills an important gap in preclinical imaging research, promotes gender equality, and fosters collaborative and multi-approach science.