Curiosity is the main goal. Spider hearts evolved into this centralised organ whereas most other invertebrates didn't go for this adaptation whereas vertebrates did. Spiders then are a sort of halfway house between the two. Their brains are somewhat similar as well and there have been some interesting studies looking at behaviour and memory in spiders that it would be interesting to think about from a 'centralisation' angle.
It would be great to bring in a genetic angle to this as well to see if the same genetic 'solutions' have been evolved or if the same physiological results can be derived from different genetic underpinnings. That could have some effect on clinical understanding of the causes of heart disease in humans.
Another goal is demonstrating the practicality of using MRI and associated analysis for general biological research as well as its more usual biomedical/clinical use. Alongside this is demonstrating that by studying a wider pool of 'model' organisms we might accelerate our understanding of biology etc.
I would like to repeat the study in a bunch of spiders of different ages and types and see what results we get. Data from a study back in terms 1970s suggested heart rate might be very different depending on habitat for example and there are some seriously weird shaped spiders out there that must be having weird hearts too.
I once scanned a very old spider (same species as in paper) who exhibited markedly different behaviour to all the others. Her scan results were so different and 'off trend' to the others I had to exclude her from this initial paper. My thought is that age and/or rearing degrades health in the long-term.
I've also done some work on other invertebrates including caterpillars metamorphing into moths and butterflies which might have use in agriculture as well as general research.
MRI is however a ludicrously expensive and complex technique for most researchers to use regularly though. And I don't work in an MRI lab anymore. And the one I did has had a change in management recently which makes these amusing and fun side projects we did for free less likely now.