HIPAA-Compliant Patient Data Anonymization API Design

Design a secure GraphQL schema for anonymizing patient health records while preserving research utility. Create robust type definitions that automatically strip Personal Health Information (PHI) during data transmission, implementing field-level encryption and selective data masking. Demonstrate how the schema handles complex nested medical record structures, ensures HIPAA compliance, and provides granular access controls for different user roles like researchers, clinicians, and administrators.