Create a Pub/Sub topic, and enable a Cloud Storage trigger for the Pub/Sub topic. Create an application that sends all medical images to the Pub/Sub topic.

Create a script that uses the gcloud storage command to synchronize the on-premises storage with Cloud Storage, Schedule the script as a cron job.

Create a Pub/Sub topic, and create a Cloud Function connected to the topic that writes data to Cloud Storage. Create an application that sends all medical images to the Pub/Sub topic.

In the Google Cloud console, go to Cloud Storage. Upload the relevant images to the appropriate bucket.