How to find medical images online

Our dreams of taking a voyage inside the human body have captured the
imaginations of movie creators and theme-park attraction designers. Those
dreams have also captured the imaginations of scientists and
computer-animation specialists so that manifestations of those dreams
have now become available on your desktop computer.

Some places you can look to find these images include the National
Library of Medicine's (NLM) Visible Human Project, the General Electric
Research and Development "fly-throughs" of various body parts, and the
HONmedia section of the Health on the Net Foundation's website. Each of
these sources creates access to digital images, but does not necessarily
license the use of the images. Read each site's documentation for
complete information about the use of the material. NLM's Visible Human
Project sells data on CD-ROM (compact-disk-read-only-memory) because 1)
the sales are a revenue source and 2) the massive file size of digitized
images require long download times through a standard modem
telecommunication connection.  

Why are the files so big?

Digitized images take more space to store than text files because one
must store information about every picture element (called a "pixel").
There are several levels of
definition used for storage of digital images. For online screen
applications,  such as a website, 72 pixels per inch is a common
standard. For printing from your laser or inkjet printer, 300 pixels per
inch is the standard. And for high-quality image processing, such are
photo reproduction, 1200 pixels per inch is a standard. This means that a
file created for printing at 300 pixels per inch will be about four times
the size of the same image file created for screen display. This explains
why so many images one prints off websites look so bad. We are printing a
screen-display image rather than one created for printing.

The Visible Human Project

The idea for a digital human image archive hatched in the mid 1980s when
NLM planners observed the helpfulness of integrating online research in
text material with digital images. In 1989, a planning panel recommended
that "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 from cryosectioning, digital images derived from computerized
tomography and digital magnetic resonance images of cadavers."

The first digitized human willed his body to science after execution by
lethal injection. The database consists of a series of computerized
tomographic images taken as if one were making slices through the body
one millimeter apart plus magnetic resonance images and other anatomical
images. This particular data set was 15 gigabytes. The Visible Human
Female, digitized a year later, was scanned every O.33 millimeter. This
was about three times more scanning than the Visible Human Male and
generated a database of about 40 gigabytes. The reason for the extra
scanning was to provide data for better three-dimensional image creation
and simulation.
 
You can download samples of these images from NLM's Visible Human website
at http://www.nlm.nih.gov/research/visible/visible_human.html. Click on
"Further Information" and then on "Images and Animations." Some of the
sample images are over 7 megabytes in size so consider using a fast
online connection or downloading when you do not expect much incoming
telephone traffic.

GE "Fly-Throughs"

General Electric (GE) has been working on three-dimensional medical
reconstruction and you can view the current work online. There is a colon
fly-through at http://www.crd.ge.com/esl/cgsp/projects/medical/colon.mpg,
a skull fly-through at
http://www.crd.ge.com/esl/cgsp/projects/medical/head_ct.mpg, a brain
fly-through at     
http://www.crd.ge.com/esl/cgsp/projects/medical/brain.mpg,  a lung
fly-through at http://www.crd.ge.com/esl/cgsp/projects/medical/lungs.mpg,
 a torso fly-through at
http://www.crd.ge.com/esl/cgsp/projects/medical/body.mpg,  a heart
arteries fly-through at
http://www.crd.ge.com/esl/cgsp/projects/medical/heart.mpg, and a
baby-delivery simulation at
http://www.crd.ge.com/esl/cgsp/projects/medical/birth.mpg .

HONmedia

Health on the Net (at http://www.hon.ch) has a multimedia center that you
can reach from the home page. It is called HONmedia and it features a
human-created index of over 3,000 medical images and videos using the
National Library of Medicine's Medical Subject Headings for indexing. It
stores no images, but provides hypertext links to images worldwide.
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