Automated Medical Image Metadata Database Indexing

Create a Python script that automatically indexes DICOM medical imaging metadata into a scalable database system. Develop a solution using SQLAlchemy and psycopg2 that can handle massive volumes of medical imaging metadata, including patient ID, scan type, timestamp, and imaging modality. Implement an intelligent indexing strategy that allows for fast retrieval of medical images based on complex query conditions, with built-in performance monitoring and database connection pooling.