Public outreach project: Operation M&M count!

How many sweets are in the jar? It’s a popular guessing game at summer fetes but it requires someone to actually open the jar and count them to find out who the winner is. But what if we could do the counting with X-ray CT instead? This project aimed to demonstrate a key aspect of X-ray CT data analysis, quantifying particles in the sample, in a fun and accessible way.

Particle analysis, determining the number, size, shape and distribution of separate elements within a sample, is a regular application of X-ray CT data. We wanted to find a way to explore and explain this aspect of CT in a way that would be approachable for the general public. We settled on the classic guessing game of numbers of things in a jar as a relatable entry point for people unfamiliar with X-ray CT.

We scanned the sample, a jar of M&M’s, using the Nikon High Flux Bay system at a magnification that allowed the jar to be in the full field of view and at an energy range suitable for the relatively low-density materials of plastic and chocolate.

The data was reconstructed and then analysed and visualised using Avizo. The first task was to separate the data and give an accurate “count” of the M&Ms and then visualise the data in an appealing way. The total number of M&Ms in the jar was determined to be 2072 after trying running the analysis several different ways to get a consistent result. For visualisation, the segmented data was manipulated to give the impression of the colourful outer sugar shell surrounding the chocolate core. The colours of the M&Ms were also colour matched to the real sweets.

A video was also produced and the guessing game challenge, along with the original jar and all the visuals, was presented at a Community Science Day at the University of Manchester.

Conducted by Elizabeth Evans and Tristan Lowe on behalf of the staff of the HMXIF.