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.

Deploy a Dataflow job from the batch template, 'Datastore to Cloud Storage.' Schedule the batch job on the desired interval.

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

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