Inferring 3D particle size and shape characteristics from projected 2D images: Lessons learned from ellipsoids

This paper investigates the relationship between the 3D size and shape characteristics of ellipsoids and their 2D counterparts obtained from projected images. We found that the average radius of ellipsoids can be satisfactorily estimated from the statistical mean or median of the average radius of the corresponding 2D projected images. However, the shape characteristics evaluated from the images may not always yield reliable quantitative prediction of the corresponding 3D descriptors. The results suggest that quantifying particle shape characteristics from projected 2D images may only work well for particles similar in shape to prolate spheroids.