The Visible Human Project

Background

The Visible Human Project has its roots in a 1986 long-range planning effort of the National Library of Medicine (NLM). It foresaw a coming era where NLM's bibliographic and factual database services would be complemented by libraries of digital images, distributed over high speed computer networks and by high capacity physical media. Not surprisingly, it saw an increasing role for electronically represented images in clinical medicine and biomedical research. It encouraged the NLM to consider building and disseminating medical image libraries much the same way it acquires, indexes, and provides access to the biomedical literature. Early in 1989, under the direction of the Board of Regents, an ad-hoc planning panel was convened and made the following recommendation: "NLM should undertake a first project building a digital image library of volumetric data representing a complete, normal adult male and female. This Visible Human Project will include digitized photographic images for cryosectioning, digital images derived from computerized tomography and digital magnetic resonance images of cadavers."

Initial aim

The initial aim of the Visible Human Project was to acquire transverse CT, MRI and cryosection images of a representative male and female cadaver at an average of one millimetre intervals. The corresponding transverse sections in each of the three modalities were to be registered with one another. A contract for acquisition of these pixel-based data was awarded in August 1991 to the University of Colorado at Denver, with Victor M. Spitzer, PhD and David G. Whitlock, MD, PhD as the principal investigators.

The Visible Human Male data set consists of MRI, CT and anatomical images. Axial MRI images of the head and neck and longitudinal sections of the rest of the body were obtained at 4 mm intervals. The MRI images are 256 pixel by 256 pixel resolution. Each pixel has 12 bits of grey tone resolution. The CT data consists of axial CT scans of the entire body taken at 1 mm intervals at a resolution of 512 pixels by 512 pixels where each pixel is made up of 12 bits of gray tone. The axial anatomical images are 2048 pixels by 1216 pixels where each pixel is defined by 24 bits of color, about 7.5 megabytes. The anatomical cross-sections are at 1 mm intervals to coincide with the CT axial images. There are 1871 cross-sections for each mode, CT and anatomy. The complete male data set, 15 gigabytes in size, was made available in November 1994.

The Visible Human Female data set, released in November 1995, has the same characteristics as The Visible Human Male with one exception. The axial anatomical images were obtained at 0.33 mm intervals instead of 1.0 mm intervals. This resulted in 5,189 anatomical images, and a data set of about 40 gigabytes. Spacing in the "Z" direction was reduced to 0.33 mm in order to match the 0.33mm pixel spacing in the "XY" plane, thus enabling developers interested in three-dimensional reconstructions to work with cubic voxels.

In August 2000, higher resolution axial anatomical images from the male data set were made available. Seventy millimeter still pictures taken at the same time as the original digital pictures were digitised at a resolution of 4096 pixels by 2700 pixels. These images, in the range of 32 megabytes each, are available for all 1871 cross-sections.

Internet access

Sample full scale images from the original male data set are available via NLM's FTP site: (nlmpubs.nlm.nih.gov). Eleven full-color anatomical images and an explanatory "color24.txt" file can be found on the FTP site in (visible/bitmaps/color24) as (*.raw). Please be careful as each of these images is over 7 megabytes in size. Ten CT scan images and an explanatory "ct.txt" file can be found in (visible/bitmaps/ct) as (*.fre) (5 images captured while the cadaver was fresh) and (*.fro) (5 images captured after the cadaver was frozen). Six MRI scan images and an explanatory "mri.txt" file can be found in (visible/bitmaps/mri) as (*.t1). Scaled down versions of all of these image files can be found on NLM's FTP site in (visible/gifs) as (*.gif). On the World Wide Web, the sample images can be found by linking to "images and animations" under the topic "Further Information." These images are in JPEG format (*.jpg), thereby requiring a web browser enabled to read files of this format. A license agreement for use of the full Visible Human Project data set is required, and application forms can be retrieved from NLM's website.

Users' conferences

In October 1996, the library sponsored its first Users' Conference of the Visible Human Project. The conference brought together early adopters, potential users and developers, as well as interested parties from a wide range of disciplines to discuss and demonstrate results obtained and problems encountered using the Visible Human image data sets. Over 50 Visible Human Project licensees demonstrated products and discussed models and algorithms based on the data sets. A press briefing and demonstrations were held on the opening day of the conference. Press heard how physicians and scientists are using the Visible Human as a substitute for medical school cadavers, to train surgeons and to rehearse surgical procedures. Similar events, The Second and Third Visible Human Project Conferences, were held in October 1998 and October 2000 respectively.

Phase II - From data to knowledge

The second phase of the project is well underway. Segmentation, classification and the building of a prototype database (AnatLine) of the thorax region of the Visible Male has been completed, with AnatLine currently in beta testing. A future web-based atlas of the head and neck region is under development, the intent of which is to be a model for a new wave of educational applications. It is to consist of six functional anatomy teaching modules. The Visible Human Project Imaging Processing Tools, has as its goal to create a self-sustaining development effort to support image analysis research in segmentation, classification and deformable registration of medical images. And, use of the Next Generation Internet (NGI) is being investigated by employing the Visible Human's large image data sets in real time 2D and 3D visualizations under haptic control.

Long-term goal

The Visible Human Project data sets are designed to serve as a common reference point for the study of human anatomy, as a set of common public domain data for testing medical imaging algorithms, and as a test bed and model for the construction of image libraries that can be accessed through networks. The data sets are being applied to a wide range of educational, diagnostic, treatment planning, virtual reality, artistic, mathematical and industrial uses by over 1,400 licensees in 41 countries. But key issues remain in the development of methods to link such image data to text-based data. Standards do not currently exist for such linkages. Basic research is needed in the description and representation of image based structures, and to connect image-based structural-anatomical data to text-based functional-physiological data. This is the larger, long-term goal of the Visible Human Project: to transparently link the print library of functional-physiological knowledge with the image library of structural-anatomical knowledge into one unified resource of health information.

For additional information on the Visible Human Project contact:

Visible Human Project
National Library of Medicine
8600 Rockville Pike
Bethesda, MD 20894
Fax: (301) 402-4080
Email: vhp@nlm.nih.gov
Website: www.nlm.nih.gov/research/visible/visible_human.html