Glucose lowering with insulin is an inexpensive, and widely applicable treatment. However, current clinical trials are compromised by uncertainty over the ability of treatment to influence pathophysiology, and have necessarily relied upon a "best guess" for treatment duration. Definition of the biological basis for insulin treatment by MRI criteria and comparative data for different treatment durations would strengthen and inform any positive effect from clinical trials, or prevent premature abandonment of this therapeutic modality should trials be neutral.