Reply to 'The method matters: free water imaging in Parkinson's disease is not a binary verdict'.

We reply to the Matters Arising on our study comparing neuromelanin and free water imaging for early Parkinson's disease diagnosis. The authors raised considerations regarding image registration, age imbalance, repetition time, and conceptual framing. We clarify that our registration pipeline is validated for subcortical structures, that age does not account for neuromelanin's superior performance, and that our acquisition parameters meet recommended standards. Our findings reflect comparative performance, not a verdict.