You might’ve heard of the Visible Human Project, but you probably don’t know what it actually is. It’s been around for many years and has had a significant impact on medicine and science. Its influences are far more significant than most people realize. What is it? Why does it matter?
For centuries, the human body’s anatomy has fascinated us, and we’ve tried to capture its complexity. In the past, this mainly has been accomplished through drawings that look at various body components from different angles and levels of dissection. Typically, pictures are made based on structure (skeleton), function (digestive tract), region (head), or layer (deep muscles). This use of real bodies to create anatomical text is not new.
Unfortunately, medical research has a long historical association with punishment and torture because, in the past, subjects of anatomical dissection were frequently executed criminals. In recent years, cadavers are voluntarily donated to medical schools for dissection.
However, in 1989, the federal government commissioned a unique dissection, the Visible Human Project (VHP). The goal was to create complete, anatomically detailed, three-dimensional representations of a human male body and a human female body. Unlike traditional cadaver studies, digital images can be examined for decades. Since the pictures were released, the VHP has been featured in most mass-circulation magazines from Time to Wired, been the subject of numerous radio and television programs throughout the world, and has over one hundred websites devoted to it.
The idea for VHP came from a biomedical engineer at the National Library of Medicine (NLM), Michael Ackerman, who presented it to the agency’s director, Donald A.B. Lindberg. The library decided to fund the project and hoped that medical schools or companies might find a use for the data. Acquiring the images was a massive technical feat. The NLM used a bidding process to find a laboratory to complete the task. About 100 American medical schools, collaborating in various combinations, formed six groups to apply for the contract, which was narrowed to three.
Each of the finalists was asked to submit pictures of slices, taken 1 millimeter apart (the thickness of a dime), from the abdomen of an animal or human body. Then, a committee of anatomists and radiologists examined these images and chose the best. The winner was a group of institutions from Colorado, Texas, and Maryland. The actual work on the cadavers occurred at the University of Colorado Health Sciences Center in Denver. The NLM paid about $1.4 million for the work.
The process started with the bodies first undergoing head-to-toe CT (Computed Tomography), and MRI (Magnetic Resonance Imaging) scans before being frozen solid. Next, the bodies were cut into four pieces with a special saw to make them easier to handle. Each of the three cuts separated the body into sections containing head, neck, and thorax; abdomen and pelvis; thighs and knees; and legs, ankles, and feet. The cuts only lost 1.5 mm of tissue, represented by black space in the stacked final images.
The bodies were packed in dry ice and surrounded by a slurry of frozen alcohol at temperatures between minus-90 and minus-60 degrees Fahrenheit. Starting from one end of a body section, a rotary rasp ground down the tissue to a specified depth. For the male, this was 1 mm. For the female, it was .33 mm, essentially providing three times as much detail.
Each round of milling exposed a smooth, rock-hard surface. This allowed the anatomical features to be visible, much like the grain in a log. The cuts were cross-sections, which means if the bodies had been upright, the cuts would have been parallel to the floor. The surface was photographed with both digital and conventional film cameras and rescanned by CT and MRI before the process was repeated.
Each cycle took anywhere from three to 15 minutes to complete, so the team could do about 50 each day. The tissue that came off in a frozen powder was collected, stored until the project was completed, and then cremated respectfully.
While the VHP data set doesn’t have an infinite number of cross-sectional planes, there are thousands more than had been made previously in a transverse dissection of a human body. Other teams have created anatomical renderings from MRI and CT scans of living volunteers, but the resolution is not as good because entire body scans take several hours, and any slight movement blurs the image. These scans, unlike the VHP, lack color, which is essential for understanding different tissues.
Much of the work to transform the raw data was conducted in dozens of computer labs worldwide. Since the male data set consists of 1,871 cross-sections for both CT and anatomical images, approximately 15 gigabytes, it took nearly four months to complete. The female data set has 5,189 anatomical photos, around 40 gigabytes, so it took almost ten months to process all the data.
For each cross-section, all the images were transformed into digital code that computers can process and manipulate. As a result of software that renders images in two or three dimensions, the body can be explored from any angle or point of view. The three-dimensional volume of an object can be approximated by stacking and summing an infinite number of two-dimensional views. This allows organs to be isolated and rotated, blood vessels to be traversed from the inside, different depths in the body to be represented topographically, the skin to be peeled back, and the skeleton to be removed.
Also, animated flythroughs can be created. In addition, the virtual cadaver can be animated and programmed to simulate vital functions, such as breathing and blood circulation.
According to the 1998 NLM report, the VHP data sets had “been licensed for use worldwide by some 1000 research, academic, and industrial groups in 28 countries. The images are being used for teaching, modeling radiation absorption and therapy, equipment design, surgical simulation, and simulation of diagnostic procedures.”
As of 2019, a license is no longer required to access them, which means the model is freely available and can be modified using basic software already used in labs worldwide. By the end of the licensure period, about 4,000 licensees from 66 countries were authorized to access the datasets. The most apparent use of the VHP data is as an instructional aid for teaching anatomy.
In the future, computer-generated tours of the human body will probably become a standard part of anatomy courses. The other primary use for the data is virtual experiments. One example is using it to compute the impact that radiation from various imaging techniques on living tissues without having to do human studies, which are lengthy and expensive.
Computer scientists and engineers are developing methods for turning the conventional two-dimensional images made by CT and MRI into three-dimensional ones that doctors can use to rehearse surgery and examine internal organs not easily or safely analyzed otherwise. Researchers at the Mayo Clinic in Rochester, Minnesota, created a program that permits neurosurgeons to “see,” on a video screen, what’s ahead of them when they probe a patient’s brain during an operation.
Some experts predict that procedures, like colonoscopies, will be done using conventional CT scans reconfigured to produce 3-D images. Other areas being studied are testing the effects of long-term cellphone use on the brain and assessing the safety of a brain stimulation technique called transcranial direct current stimulation (tDCS), which is being developed as a possible treatment for a range of conditions, including depression, dementia, schizophrenia, and chronic pain. More researchers are looking at using the datasets to make better crash-test dummies and to design prosthetic joints.
Many people are curious about who the man and woman used for the Visible Human Project. The man, Joseph Jernigan, was a convicted felon executed by lethal injection in a Texas prison. He donated his body to science before his execution.
Not much is known about the woman, not even her name. We know that she was obese and died of heart disease at the age of 59 somewhere in Maryland. Her husband permitted her body to be used. Her obesity makes the study of her body particularly relevant since there are such high levels of the condition globally. An interesting feature is that since she’s fully digital, the researchers have also created a version with less skin and fat. One hope of having a female body is that it allows scientists to better investigate diseases that more commonly affect women and improve exams, like breast cancer screenings, to give more reliable results.
The Visible Human Project data isn’t flawless. A few cryosections are marred by errors produced during freezing and milling. The NLM is paying several research groups to investigate these problems and suggest remedies. Also, even the .33 mm sectioning done on the female doesn’t produce sufficient detail in some regions of the body. The head is the principal place where this appears to be the case.
To do this, more specimens are needed to get more images. While the formal funding for the project ended in 2001, the lab at the University of Colorado is still doing research. In 2000, they had another person volunteer to be a part of VHP. Susan Potter sold flowers in front of the chancellor’s office on the Ninth Avenue campus every Christmas and did many things to support the medical school. Her last wish was to support it as best she could by donating her body.
At first, the team refused because she wasn’t young and healthy (the project’s initial requirements). They finally agreed because they realized the value of having a body that has multiple medical conditions. Potter was in her 70s with a history of chronic diseases and physical disabilities that confined her to a wheelchair due to a severe car accident. When the team finally acquiesced to her request, Potter asked to see the large freezer where the cadavers are stored and inspect the equipment used to grind the cadavers. Her only request was that flowers be kept near the freezer because she felt the place needed more color and cheer.
In 2004, National Geographic assigned a photographer and writer to chronicle Potter’s journey; they expected a one-year assignment because she was expected to die within a year due to her medical issues. However, she didn’t die until 2015 at the age of 87. During the elapsed time, National Geographic continued to follow her story. This is important because early in their education, medical students at the university are introduced to the cadaver process and hear from people who want to donate their bodies.
The documentation of Potter’s life allows students to get a fuller picture of the nuance of her history and story beyond the higher-resolution images and advanced scanning techniques. They’ll also see how passionate she was about improving the understanding of the human body. The goal is to have a representation that’s more like a living human and less like a cadaver.
Potter’s portion of the project was funded by Touch of Life Technologies and the University of Colorado School of Medicine, which offered lab and office space. The original project had around a dozen full-time workers and more than 100 students and interns. The newer work is primarily supported by a small team and about 25 students a year that are part of the university’s master’s degree in modern human anatomy program.
To achieve the more detailed cuts that they were looking for, scientists ground off Potter’s body 63 microns at a time, resulting in thousands of photographs. For comparison, a human hair is about 75 microns, and the original male specimen was ground into sections of 1,000 microns, and the original female was 300 microns.
The new aim of the project is to expand beyond photos. Touch of Life Technologies is developing ways to give the feeling of living tissue, essentially to form a living cadaver that you can see move or move in response to what you ask her to do. The objective is to correlate the anatomical structures with her feelings and behavior by combining the pictures and technology with documentation of her life provided by National Geographic. By caring about everything, it’ll bring Potter to life in a way that no physical cadaver ever could be.
As of 2019, the Visible Human Project is looking for volunteers. The thought is to create a bookshelf of human bodies that encompass a variation in age, gender, race, and body build and pathology disparities within those groupings. Scientists agree that VHP shouldn’t be just the original male and female bodies and Susan Potter.
While it might appear gruesome to some, engaging in projects like this will enable the medical community to further comprehend the human anatomy and better understand how the body is impacted by disease, and provide insight into possible solutions.