Although one man is credited with the discovery, there were actually many pioneers who paved the way by using equipment and making improvements on the equipment that eventually led to the actual discovery.

In the early 19th century, many scientists were experimenting with electricity (discovered by Benjamin Franklin) and little else. William Watson demonstrated electrical current. Michael Faraday induced electricity by passing a magnet through the magnetic field of a coil of wire. This led to experimentation with electromagnetic induction and the advent of generators and transformers with higher voltages.

A scientist named William Goodspeed was experimenting with cathode rays and the different energies that they emit. He made the actual first radiograph on February 22, 1890; however, he did not publish his work and was therefore not credited with the actual discovery of x-ray. In the mid-1890s, Sir William Crookes, an English physicist, was studying gas, and in order to continue with his work, he created a vacuum tube. It was a glass tube that contained both positive and negative electrodes and an induction coil (Fig. 1-1). He passed high-voltage electrical currents through the tube, which would allow him to study the conductivity of gases that had been put into the tube. Crookes was able to demonstrate that matter emitted from a cathode-ray tube had enough energy to turn a wheel that was located in the tube. Shortly afterward, Philipp Lenard, a German scientist, discovered the cathode ray while he was working with a Crookes tube. Lenard changed the original tube to include an aluminum window that allowed the cathode rays to pass through to the outside. During one of his experiments, a piece of barium platinocyanide soaked paper glowed when the rays were directed at it. Unfortunately for him, Lenard failed to further investigate what made the paper glow, thus allowing Wilhelm Conrad Röntgen to make the discovery only a few months later.

The x-ray was seen as a miracle to the world of medicine when it was discovered in 1895. In fact, it was the negative side of the miracle that was beginning to show itself. In the early 1900s, many problems, such as burns, infections, swelling, and cancer, finally forced the scientists to reinvestigate the whole process of x-ray and how it worked. Even amputations had to occur because of the lesions caused by overexposure to x-ray. Thomas Edison’s assistant and good friend Clarence Dally lost all of his hair, all of the fingers on both hands, and finally both of his hands before he finally succumbed to the effects caused by excessive radiation. He was in constant pain and finally died in 1904. He is the first known fatality of overexposure. Edison himself complained of skin rashes and sore eyes. It was this event that caused Edison to stop his work on radiation and start to look at the problems it caused. X-ray technicians fell victim to the terrible side effects. Twenty-eight Americans suffered the fatal effects from experimentation.

Early radiologist Mihran Kassabian photographed the horrible effects to his hands in hopes that future technicians would not suffer the same deformities. Kassabian was an early radiologist who would hold the fluoroscope with his right hand and put his left hand into the beam to show the patient that there was nothing to be afraid of. After months of constant exposure, the third and fourth fingers of the left hand had to be amputated.

The public was frightened when it became aware of these deaths and demanded that something be done. Physicians tried to calm the patients by telling them that they could not be harmed. The damage had been caused by overexposure to electricity, allergies, and even circumstances of the ozone created by static, excessive heat, and moisture. Scientists, on the other hand, knew that the x-ray was the cause and warned against its unwarranted use. If it must be used, lead shielding should be applied. Figure 1-2 shows the early protective suits and metal helmets that were introduced to protect against x-radiation.

Protection from radiation exposure is two-fold: protection for the patient and protection for the occupational worker. The National Council on Radiation Protection and Measurement (NCRP) established dose limits for both the patient and the occupational personnel. These dose limits must not be exceeded. The current annual occupational dose limit is 5 rem (50 mSv). In 2009, NCRP no. 160 determined that the new annual dose limit should be 2 rem because continuing long-term studies have continued to indicate that radiation is three to four times more damaging than originally thought. Although the NCRP is currently reviewing the dose limits, the limit remains at 5 rem. The annual dose limit for the general public is one-tenth the amount of the occupational dose: 0.5 rem (5 mSv). Students in radiology training younger than 18 years have an annual dose limit of 0.1 rem (1 mSv).
Pregnant workers are allowed to receive 0.5 rem (5 mSv) in a 9-month gestation period and 0.05 rem (0.5 mSv) in any given month. Radiation workers are allowed to receive more per year than the general population because the workforce is a much smaller group as compared with the general public. In addition, radiation personnel are taught the safety measures necessary to protect themselves from large doses. Display 1-1 shows the effective dose limits for each of the different populations receiving radiation.

In order to observe these protection standards, the concept of As Low As Reasonably Achievable (ALARA) must always be practiced. The three parts of this concept include time, distance, and shielding.