Final answer:
The oldest and largest radiologic science professional organization is the American Society of Radiologic Technologists (ASRT).
Step-by-step explanation:
The oldest and largest radiologic science professional organization is the American Society of Radiologic Technologists (ASRT). Radiography technicians, including those specializing in MRI and other imaging techniques, might seek membership in a professional organization for community, resources, and continuing education. Among the options listed, ASRT is the correct answer, providing support to professionals within the radiologic technology field.