In 1895 Wilhelm Conrad Rontgen was Professor of Physics and Director of the Physical
Institute at Worzburg. As part of his work using evacuated glass bulbs he noted that
when a current was passed across the bulb, a barium platinocyanide screen was seen
to fluoresce. He at once realised the significance of this observation. On the 28th
of December 1895, hismanuscript “On a New Kind of Ray” was submitted to the Worzburg
Physical Medical Institute. The essential features of X-rays were described and the
new discovery aroused considerable interest. The description of the ability to see
through the body was greeted by many with incredulity and early accounts had to reassure
the public that this was a serious discovery by a respected scientist
Because the apparatus was readily available the experiment could be easily repeated.
The Crookes tube was to be found in most physics departments. In the simple tube
designed by Sir William Crookes (1832-1919) the tube consists of a partially evacuated
glass bulb with the anode in a side arm. The electrons hit the end of the glass bulb
which acted as a large target and resulted in a poor image. From 1895, Crookes had
experimented with the passage of current across such tubes. There was an initial
modification by Herbert Jackson of King’s College to the simple tube, the Jackson
focus tube. In his modification, the cathode became a dish which produced some focusing
of the electrons and the anode was made of platinum and placed opposite the cathode.
The Jackson focus tube produced a considerable improvement in image quality.
The apparatus gradually improved and hospitals started to acquire the equipment.
Many hospital X-ray departments were located in the cellars and basements and were
often poorly ventilated and damp. The dampness made it difficult to work the apparatus
and made it more difficult to pass the current across the glass tube. The first hour
of the day was often spent in drying the apparatus. Event at the Royal London
Hospital in 1897 there was no electric current in the hospital and the accumulator
of Grove cells was taken out of the hospital by a porter to a nearby establishment
to charge it. The initial apparatus was usually mounted on a trolley with the accumulator
on the lower level and the induction coil and contact breaker on the upper level.
The tube was held in a wooden clamp and was a bare bulb with no protection for the
operator. The trolley could then be taken around the hospital. Various individuals
were involved in what was called “The New Photography ”including photographers and
general practitioners. At King’s College Hospital, two medical students were sent
to use the new apparatus. After some time, a Doctor Mayou was put in charge of them
since it was felt they were spending too much money on plates! Financial considerations
were important even then. He was warned by the students not to expose his hands to
the X-rays. the advice was ignored and soon he had X-ray dermatitis on every finger.
at that time, it was not obvious at to why these injuries were occurring and some
workers thought that they were caused by the developer or the high tension. It took
some time to realise that it was the X-rays themselves that were causing the injuries.
Unfortunately the absence of protection around the early X-ray tubes resulted in
considerable injury to the operators. The problem was compounded by the common practice
of fluoroscoping the operator’s own hand to test the tube. these dangers were gradually
recognised and standards for exposure and protection were gradually introduced. It
was following the shock at the death at the age of 42 in 1921 of Dr Ironside Bruce
from Charing Cross Hospital in London that the British X-ray and Radium Protection
Committee came into being.
By 1905, the apparatus in the Department at King’s Colege Hospital consisted of a
10- inch induction coil, a condenser, a Mackenzie Davidson mercury break and several
Moller gas tubes with vacuum regulation. The induction coil provided the high tension.
The mercury break interrupted the current by means of a motorised electrode dipping
in and out of a pool of mercury. To prevent sparking, the mercury was covered with
either methylated spirits or coal gas which often resulted in the apparatus catching
fire or exploding.
The radiographs were initially made onto glass photographic plates which had to be
placed into light tight cassettes or envelopes. The photographic plates were coated
with emulsion on one side only. The emulsion had a habit of slipping off during developing
and the job of a junior was to wax the edges of the plates to help to keep the emulsion
in place. Film was introduced by Eastman in 1918 by Eastman, however film only came
into general use from about 1923. It should be remembered that the image quality
on glass was excellent and it took some time for film to replace the older technique.
Unlike the glass plates, the film could be coated on two surfaces with emulsion (“Dupli-Tized”).The
base was made of celluloid nitrate and was highly inflammable. This high risk property
was tragically shown in the infamous Cleveland Clinic fire when the X-ray film store
caught fire and 129 people died. In 1924 Eastman introduced the cellulose acetate
base as safety film. This innovation was more expensive and it was only the accidents
with the previous film that forced its introduction.
Most of the early X-ray work was performed by doctors and the departments were often
combined with electro-therapeutic departments. However from about 1903, lay X-ray
operators as they were then called were appointed to assist in the work. They had
no special training and learnt on the job. Gradually more and more of these lay X-ray
operators were appointed and training courses were set up. The culmination was in
the formation of the Society of Radiographers in 1920.
The gas tubes were difficult to use and the skill of the operator lay in proper seasoning
of the new tube and caring for it during use. It was only following the introduction
of the Coolidge tube in 1913 that predictable results were obtained. In the Coolidge
tube, that could be completely evacuated and electrons were liberated from a heated
spiral cathode. The results were far more uniform and it was possible to vary the
current and voltage independently. In the early tubes, the high tension cables were
attached to the ends of the tube producing a considerable risk of electrocution.
Sealed and electrically insulated “shock-proof” apparatus was gradually introduced
from the 1930s.The self protected Metalix tube was designed by Bouwers of Philips
in 1924 and this tube also incorporated the principal of line focus. Bowers also
designed the first rotating anode tube, the Rotalix, which was first marketed in
1929.
X-rays were used for therapy from the earliest times. Skin lesions were easily amenable
to therapy and gradually techniques evolved to treat deeper lesions. These techniques
depended on the development of more powerful apparatus, the use of multiple therapy
beams and in the use of Radium. The doctors in the X-ray department were involved
in both therapy and diagnosis. It was only from the 1930s that doctors were appointed
with specific interests in diagnosis or therapy.
In the 1950s came the development of the image intensifier and X-ray television.
The initial systems produced a brightness gain of about 1000 and meant that the red
goggles needed for dark adaptation when viewing a simple fluoroscopic screen could
be dispensed with. the result was also that the operator looked at the television
and not at the patient. The use of image intensification has stimulated the flowering
of techniques in the last 20 years, including the associated development of catheters,
needles and contrast media.
Many new techniques have been introduced in recent years and transformed clinical
practice. The principles of CT scanning were discovered by Godfrey Hounsfield and
the first prototype EMI scanner was installed in 1972 at Atkinson Morley’s Hospital.
Work was progressing on Magnetic Resonance Imaging in the 1970s and the first human
image was obtained at Aberdeen in 1977. Ultrasound was started in the 1950s and gained
popularityin the 1960s. “Real-time” ultrasound machines were introduced in the late
1970s. These new techniques have displaced many of the older X-ray techniques and
this process will continue.
Readings:
Pioneers and Early Years, A History of British Radiology. Edward H Burrows, Colophon(1986)
The Invisible Light. 100 Years of Medical Radiology. Edited by AMK Thomas. Assisted
by I Isherwood and PNT Wells. Blackwell Science (1995)
Classic Papers in Modern Diagnostic Radiology. Adrian M K Thomas, Arpan K Banerjee
& Uwe Busch. Springer Verlag (2004)
