**Changelog:**
- Fixed a bug in the script to download the LDCT data that caused the script to crash.
- Use the [NCI Imaging Data Commons](https://portal.imaging.datacommons.cancer.gov/explore/filters/?collection_id=nlm_visible_human_project) hosted version of the Visible Human Project CT data for testing and the introductory example.
- Fixed some typos in the documentation and code.