  Our title alludes to the three Christmas ghosts encountered by Ebenezer
Scrooge in \textit{A Christmas Carol}, who guide Ebenezer through the past,
present, and future of Christmas holiday events. Similarly, our article will
take readers through a journey of the past, present, and future of medical AI.
In doing so, we focus on the crux of modern machine learning: the reliance on
powerful but intrinsically opaque models. When applied to the healthcare
domain, these models fail to meet the needs for transparency that their
clinician and patient end-users require. We review the implications of this
failure, and argue that opaque models (1) lack quality assurance, (2) fail to
elicit trust, and (3) restrict physician-patient dialogue. We then discuss how
upholding transparency in all aspects of model design and model validation can
help ensure the reliability of medical AI.
