TCIA Get Manufacturer Values

Get the distinct scanner Manufacturer values present in a TCIA collection (optionally filtered by modality or body part). This is a faceting tool analogous to TCIA_get_modality_values and TCIA_get_body_part_values, but for equipment manufacturer (e.g., 'GE MEDICAL SYSTEMS', 'SIEMENS', 'Philips', 'TOSHIBA'). Use to discover which scanner vendors appear in a collection.