We normally do this when we need a detailed discussion on a certain topic like "Diagnostic Procedures" done by physicians in the hospital assisted by sonographers that we don't do in the campus. Examples are breast biopsy, hysterosonography,amniocentesis and many others. The physician who really does these procedures in the hospital can really discuss this topic thoroughly, simply and with a better understanding for students especially when accompanied by a demo. Students will appreciate these because they start to become aware of their role as sonographers in the field. I really recommend guest speakers to visit our schools.