A team of physicists, engineers and radiologists recently revived a first-generation X-ray device that had been collecting dust in a Dutch warehouse. The antique machine still sparked and glowed like a prop in an old science fiction movie, and used thousands of times more radiation than its modern counterparts to make an image.

The old machine was originally built in 1896 by two scientists in Maastricht, the Netherlands, just weeks after German physicist Wilhelm Conrad Röntgen reported his discovery of X-rays – an achievement that won him the first-ever Nobel Prize in physics and sparked a rash of copycat experiments.

H.J. Hoffmans, a physicist and high school director in Maastricht, and L. Th. van Kleef, director of a local hospital, assembled the system from equipment already on hand at Hoffmans' high school and used it to take some of the first photographs of human bones through the skin, including in van Kleef's 21-year-old daughter's hand.

Since then, X-rays, which are the right wavelength to tunnel through muscle but are slowed by denser bones, have become almost synonymous with medical imaging. But most of those first X-ray systems were lost to history. Because the techniques and technology to measure radiation doses weren't invented until decades after the first X-ray machines came about, no one knows exactly how powerful those systems were.

"There’s a gap in knowledge with respect to these old machines," said medical physicist Gerrit Kemerink of the Maastricht University Medical Center. "By the time they could measure the properties, these machines were long gone."

About a year ago, when Kemerink's colleague at the hospital dug Hoffmans and van Kleef's aging machine out of storage to use in a local TV program on the history of health care in the region, Kemerink grew curious about what the gadget could do. In a paper published online in Radiology, Kemerink reports the first-ever diagnostics on a first generation X-ray device.

"I decided to try to do some measurements on this equipment, because nobody ever did," he said.

Aside from a modern car battery and some wires, the researchers used only the original equipment, including an iron cylinder wrapped in wire to transfer electrical energy from one circuit to another and a glass bulb with metal electrodes at each end.

The glass bulb, technically called a Crookes tube, contained a tiny bit of air, about a millionth of normal air pressure. When the researchers placed a high voltage over the tube, the electrons in the gas were ripped from their atoms and zipped across the tube from one electrode to the other.

Electrons naturally emit X-rays when they speed up, slow down or change direction. When the electrons hit the glass walls of the Crookes tube, they came to a screeching halt, giving off a ghostly green glow and invisible X-rays.

The machine took some coaxing before it would glow, Kemerink said. The team fiddled with it for a solid half hour with no success.

"At the time we were thinking that it would be possible that we would not succeed with our plans," he said. "But then suddenly something happened, and we were in business."

Kemerink now thinks that the gas pressure inside the bulb was too high for the electrons to travel through the tube. But then a bit of aluminum on one of the electrodes melted, sucking gases from inside the bulb.

"It's a technique used today to improve your vacuum: Evaporate metal and trap some gases," he said. "That is what happened, although we did not do it on purpose."

Images of a hand specimen from an 86-year-old woman taken with the old X-ray machine (left) and a modern one (right). The exposure for the 1896 system took 21 minutes.

The researchers used standard hospital radiation-detecting devices to measure the amount of X-rays needed to take an image of the bones in a human hand (this time, a specimen borrowed from the anatomy department, not from a living person). The old machine took surprisingly clear pictures, but gave the skin a dose of radiation 1,500 times greater than the same image would require today. An exposure that takes 21 milliseconds (thousandths of a second) on a modern machine took up to 90 minutes on the antique system.

"It was interesting that the image quality was actually that good," said radiologist Tom Beck of Quantum Medical Metrics, a company that researches ways to get structural information from bones using medical imaging. "That was surprising."

This first-generation system did not produce enough radiation to cause health problems, although Kemerink and colleagues all stood behind a transparent lead shield whenever the machine was on, just in case. But X-ray devices got steadily more powerful shortly after Hoffmans and van Kleef built their machine, and technicians didn't always take precautions against harmful radiation.

"Within weeks, people reported skin burns, a little bit later even much worse things," like blisters and sores that wouldn't heal, Kemerink said. Some workers had to have fingers or even a whole arm amputated. "Many of these early X-ray workers developed cancer, and many of them died untimely, very young."

The difference in danger highlights how far X-rays have come, he said. In another study published online Feb. 15 in Insights into Imaging, Kemerink and colleagues showed that, with all the shielding used today, modern X-ray workers feel less radiation in the hospital than they do at home.

"There’s so much to say about how far we've come," Kemerink said. "These machines when they started they were extremely dangerous. Now in all those years, they improved technology so far that you can really neglect what you are receiving when you do normal X-ray scans."

Working with the machine was "very special, I must say," Kemerink added. The air smelled of ozone, the interruptor buzzed, lightning crackled in the spark gap, and the insides of the human body showed themselves.

"Our experience with this machine," the researchers wrote, "was, even today, little less than magical."

Video: Maastricht University Medical Center. Images: Courtesy Gerrit Kemerink.

Citations:

"Characteristics of a First-Generation X-Ray System." Martijn Kemerink, Tom J. Dierichs, Julien Dierichs, Hubert J.M. Huynen, Joachim E. Wildberger, Jos M.A. van Engelshoven, Gerrit J. Kemerink. Radiology, online March 16, 2011. DOI: 10.1148/radiol.11101899.

"Less radiation in a radiology department than at home." Gerrit J. Kemerink, Marij J. Frantzen, Peter de Jong and Joachim E. Wildberger. Insights into Imaging, online Feb. 15, 2011. DOI: 10.1007/s13244-011-0074-7

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