An American woman’s body has been reconstructed digitally from very thin slices, creating a model for experiments too risky to try on the living.
SHE died two decades ago, but her body lives on in digital form. An American woman’s cadaver has been sliced more than 5000 times to create the world’s most detailed digital body. The “human phantom” is available online and will make it possible to perform experiments no live human could undergo.
Not much is known about the woman, not even her name. All we know is that she was obese and died of heart disease at the age of 59 somewhere in Maryland. Her husband gave permission for her body to be used by the Visible Human Project, set up by the US National Library of Medicine in Bethesda, Maryland.
The original aim of the project was to provide digital subjects for medical education, but researchers have since begun to appreciate their potential for modelling dangerous experiments.
When the project began, the bodies of two people, a woman and a man, were imaged extensively using MRI and CT scanning. They were then frozen, thinly sliced and photographed. The first photos were released back in the 1990s, and have been accessed thousands of times for research. Many teams have also pieced together digital versions of the man’s body.
Now the woman’s body has been recreated, in far greater detail. She has been digitised at a much higher resolution, thanks to the thinner slices used. The male cadaver was sectioned at 1 millimetre intervals; the woman at intervals of just a third of a millimetre.
The virtual body is the work of Sergey Makarov at the Worcester Polytechnic Institute in Massachusetts and his colleagues. They used software to help them stitch the thousands of images together, and the final model was checked by five doctors, each with a different medical specialism. “It needs to be anatomically correct,” says Makarov, who presented the work at the IEEE Engineering in Medicine and Biology Society meeting in Milan, Italy, last month.
Their phantom is the most detailed digital reconstruction of a whole human body ever to be pieced together. She has 231 tissue parts, ranging from windpipe to eyeballs, but is missing nose cartilage and 14 other bits of the body.
“It took a lot of work, but now anyone can run an experiment on the phantom on their laptop”
Other teams have created phantoms from MRI and CT scans of living volunteers, but the resolution is nowhere near as good. Entire body scans take several hours and any slight movements blur the image. The scans also lack colour, which is important for understanding different tissues, says Makarov.
“Sectioned colour images allow you to distinguish virtually all the anatomical structures we are made of,” says Silvia Farcito at the Foundation for Research on Information Technologies in Society, based in Zurich, Switzerland, although she says that blood vessels tend to collapse in cadavers.
“They have ten times as much information as you’d get from an MRI scan,” says Fernando Bello, who develops simulations for medical procedures at Imperial College London. “It means the team will have much more information about organs and their structuring.”
The high resolution of the model makes it ideal for virtual experiments. Each of the woman’s tissues has a well-defined set of parameters, such as density and thermal conductivity. This makes it possible to compute the impact that radiation, for example, and various imaging techniques are likely to have on living tissues.
“The phantom gives us a great opportunity to study human tissues without having to do human studies, which are lengthy and expensive,” says Ara Nazarian, an orthopaedic surgeon at Harvard Medical School who is collaborating with Makarov.
Ideal test subject
Makarov’s team has already started running tests that are too risky to try on living people. In one, they gave their model a metal hip or femur, and studied the effect of putting it in an MRI scanner. Metal implants heat up in the scanner’s strong magnetic field, and little is known at present about how best to scan people who have them.
The researchers were able to test what happens at different strengths of magnetic field, and feed their results back to clinical staff. Doctors may be able to use their data to develop safer, more effective scanning procedures for people with implants.
Having a female phantom allows us to better investigate diseases that more commonly affect women, Makarov says. He hopes to improve breast cancer screening, for example, to give more reliable mammogram results.
He is also testing the effect 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. “We have a pretty good model of the brain, encased in a shell of cerebrospinal fluid,” says Makarov.
Early results suggest that tDCS might create larger electrical currents when it is used more deeply in the brain and in white matter, which could have implications for how it is applied and whether it is safe. Makarov points out, though, that although his team is running the experiments, it will be down to people with specialist knowledge to interpret the findings.
The Maryland woman’s obesity makes her particularly relevant, Makarov says, given the high levels of obesity in many countries today. But because the phantom is fully digital, the researchers have also been able to create two thinner versions, with less skin and fat.
The team have made the model freely available, and it can be modified using basic software already used in labs all over the world. “Creating the phantom took a lot of work, but now anyone can run an experiment on their laptop,” says Nazarian.
This means the virtual woman can be put through endless tests worldwide. “There are lots of possible uses,” says Bello. “It is really exciting.”
The project to build fully digitised human bodies was launched in the mid-1980s. Except for a few missing pieces (see main story), the female virtual model is now complete, but her male counterpart was finished years ago.
The body it was based on was that of Joseph Paul Jernigan, a 39-year-old Texan convicted of murder and put to death by lethal injection. Digital versions of his body were announced in 2010, but ethical questions over using his data remain. Although it is reported that Jernigan willingly donated his body to science, he probably could not have known the extent to which it would be used and circulated.
His body was also missing several pieces. When he died, Jernigan was short of an appendix, a testicle and several teeth. These body parts have since been added using scans of living volunteers.
For example, Paul Segars at Duke University in Durham, North Carolina, used MRI scans to replace some of the missing parts. “I ended up replacing both testicles and the penis so everything matched,” he says.
Segars also replaced Jernigan’s brain, which he said looked abnormally swollen. The result is a patchwork, almost like Frankenstein’s monster, he says.