Visible Human Project
The Visible Human Project is an effort to create a detailed data set of cross-sectional photographs of the human body, in order to facilitate anatomy visualization applications. A male and a female cadaver were cut into thin slices which were then photographed and digitized. The project is run by the U.S. National Library of Medicine (NLM) under the direction of Michael J. Ackerman. Planning began in 1989; the data set of the male was November 1994 and the one of the female in November 1995. The project can be viewed today at the National Museum of Health and Medicine in Washington, DC.  There are currently efforts to repeat this project with higher resolution images but only with parts of the body instead of a cadaver.

# Data
The male cadaver was encased and frozen in a gelatin and water mixture in order to stabilize the specimen for cutting.  The specimen was then cut in the axial plane at 1 millimeter intervals.  Each of the resulting 1,871 slices were photographed in both analog and digital, yielding 15 gigabytes of data. In 2000, the photos were rescanned at a higher resolution, yielding more than 65 gigabytes.  The female cadaver was cut into slices at .33 millimeter intervals, resulting in some 40 gigabytes of data.
The term cut is a bit of a misnomer, yet it is used to describe the process of grinding away the top surface of a specimen at regular intervals.  The term slice, also a misnomer, refers to the revealed surface of the specimen to be photographed; the process of grinding the surface away is entirely destructive to the specimen and leaves no usable or preservable slice of the cadaver.
The data is supplemented by axial sections of the whole body obtained by computed tomography, axial sections of the head and neck obtained by magnetic resonance imaging, and coronal sections of the rest of the body also obtained by magnetic resonance imaging.
The scanning, slicing and photographing took place at the University of Colorado's Health Sciences Center, where additional cutting of anatomical specimens continues to take place.

# Donors
The male cadaver is from Joseph Paul Jernigan, a 38-year-old Texas murderer who was executed by lethal injection on August 5, 1993. At the prompting of a prison chaplain he had agreed to donate his body for scientific research or medical use, without knowing about the Visible Human Project. Some people have voiced ethical concerns over this. One of the most notable statements came from the University of Vienna which demanded that the images be withdrawn with reference to the point that the medical profession should have no association with executions, and that the donor's informed consent could be scrutinised.
The female donor, 59-year-old, remains anonymous. In the press she has been described as a Maryland housewife who died from a heart attack and whose husband requested that she be part of the project.

# Problems with the data sets
Freezing caused the brain of the man to be slightly swollen, and his inner ear ossicles were lost during preparation of the slices. Nerves are hard to make out since they have almost the same color as fat, but many have nevertheless been idenfitifed. Small blood vessels were collapsed by the freezing process.  Tendons are difficult to cut cleanly, and they occasionally smear across the slice surfaces.
The male has only one testicle, is missing his appendix, and has tissue deterioration at the site of lethal injection.
The reproductive organs of the woman are not representative of those of a young woman.  The specimen contains several pathologies, including cardiovascular disease and diverticulitis.

# Discoveries
By studying the data set, researchers at Columbia University found several errors in anatomy textbooks, related to the shape of a muscle in the pelvic region and the location of urinary bladder and prostate.

# License
The data may be bought on tape or downloaded free of charge; one has to specify the intended use and sign a license agreement that allows NLM to use and modify the resulting application. NLM can cancel the agreement at any time, at which point the user has to erase the data files.

# Applications using the data
Various projects to make the raw data more useful for educational purposes are under way. It is necessary to build a three-dimensional virtual model of the body where the organs are labeled, may be removed selectively and viewed from all sides, and ideally are even animated. The commercial application Voxel-Man 3D-Navigator from the University of Hamburg accomplishes most of these goals . NLM itself has started the open source project Insight Toolkit whose aim is to automatically deduce organ boundaries from the data.
The data was used for Alexander Tsiaras's book and CD-ROM Body Voyage which features a three-dimensional tour through the body .
A "Virtual Radiography" application creates Digitally Reconstructed Radiographs and virtual surgery, where endoscopic procedures or balloon angioplasty are simulated: the surgeon can view the progress of the instrument on a screen and receives realistic tactile feedback according to what kind of tissue the instrument would currently be touching.