An ablation study systematically removes or isolates individual components of a system to measure each one's individual contribution to overall performance. In a multimodal pipeline combining MRI scans and radiology reports, a proper ablation study requires training and evaluating separate unimodal pipelines — an image-only model on MRI scans alone, and a text-only model on radiology reports alone — alongside the full multimodal pipeline. Comparing these unimodal baselines against the combined system's performance is what actually demonstrates whether fusion is adding genuine diagnostic value beyond what either modality provides independently, and it surfaces whether one modality is doing most of the work while the other contributes marginally (or is even introducing noise) — critical information for both model design decisions and clinical validation in a high-stakes diagnostic context.

Option A describes an early-fusion design choice, not an ablation methodology — it's a modeling decision, not a validation technique for understanding component contribution. Option C proposes abandoning one modality's diagnostic value entirely, which undermines rather than tests the multimodal hypothesis. Option D describes data quality/preprocessing work relevant earlier in the pipeline, not the comparative, component-isolating structure that defines an ablation study.

In a clinical context specifically, this ablation approach is also essential for regulatory and interpretability purposes — demonstrating that a diagnostic claim rests on genuine cross-modal signal, not a spurious correlation from a single dominant input.