Phase-B alias explainability

Scope: Existing NPZ maps only. STEP-derived receive surrogate, unloaded ideal-decoupled layout surrogate, Psi=I. Not measured g-factor, not true clinical SNR.
Purpose: Explain whether hard Phase-B bands follow the alias direction and R-factor logic or indicate FOV/mask/alias-grouping artifacts.

Contract

{
  "ok": true,
  "candidate_name": "phase_b_alias_explainability_current",
  "workers_used": 3,
  "source_candidate": "/home/daniel/coil_compare/data/output/tool_checks/ppa_surrogate_v1_phase_ab_20260506_142330",
  "loop_audit_source": "/home/daniel/coil_compare/data/output/tool_checks/step_loop_extraction_audit_20260506_143853",
  "records_expected": 32,
  "records_loaded": 32,
  "image_count": 8,
  "npz_count": 32,
  "qa_flag_count": 17,
  "fatal_qa_flag_count": 0,
  "warn_qa_flag_count": 17,
  "purpose": "Explain hard bands in Phase-B PPA/1-g-like maps by showing alias-direction profiles and nominal fold guide lines.",
  "important_scope": "No new numerical method; this audits existing NPZ maps. STEP-derived surrogate, Psi=I, not measured g-factor.",
  "decision_rule": "If bands align with expected alias direction and profiles are interpretable, keep Phase-B as method-audit surrogate. If bands are inconsistent with alias direction or dominated by mask jumps, debug alias grouping/FOV before report integration."
}

b0_y_transverse_xz_sagittal_hf_r2_alias_explainability.png

b0_y_transverse_xz_sagittal_hf_r3_alias_explainability.png

b0_y_transverse_xz_transversal_rl_r2_alias_explainability.png

b0_y_transverse_xz_transversal_rl_r3_alias_explainability.png

b0_z_transverse_xy_sagittal_hf_r2_alias_explainability.png

b0_z_transverse_xy_sagittal_hf_r3_alias_explainability.png

b0_z_transverse_xy_transversal_rl_r2_alias_explainability.png

b0_z_transverse_xy_transversal_rl_r3_alias_explainability.png

Tables