I build a tool that reads MRI and CT scans with general vision models and explains the findings in plain language. The most repeated error in that pipeline isn't a missed tumour or an invented measurement. It's left and right . We ran eight real studies through four readers (Claude, Gemini, Grok and Google's MedGemma), with the radiologist's signed report as ground truth. Here's what came back: a 5 cm cyst in the right kidney, placed in the left by two of the four readers a medial ...