A short history of x-rays

by Arne Hessenbruch

• Abstract
• The new radiation: what is it good for?
• The medical market
• X-ray diffraction: a tool for probing the atomic scale
• Protection: an infrastructure
• The marriage of the computer with the x-ray
• Controlling and quantifying: Sources and detectors

The medical market

Medicine constituted the dominant market for x-ray equipment (until it was rivalled by military concerns in the mid-twentieth century). By the beginning of World War I, most hospitals had an x-ray outfit, many had an x-ray department, and in many places x-ray diagnosis was becoming routine and integrated into an accountancy scheme that kept track of costs and to some extent of exposures. The development of radiotherapy exacerbated the need to carefully monitor and record exposure. Therapy also demanded more of the equipment, both the x-ray producing tubes and the means of detection (dosimetry). In the 1920s, radiotherapy celebrated most of its successes in the treatment of cancer, especially with female patients: breast and uterine cancers. A model of almost factory-style treatment of subcutaneous cancers emerged. It seemed rational both in terms of science and in terms of business. Patients were treated in quick succession and much of the labour was delegated to radiological assistants. The medical doctor was involved only once, at the time of diagnosis. The diagnosis had to identify the type of cancer along with its precise location, and the indication [this is the medical term for the specification how treatment ought to proceed] would specify the amount of radiation to be applied to the region of the cancerous growth. The rest of the treatment was a technical, not a clinical matter. This form of rational treatment contrasted with the hitherto common practice of iterative irradiation and medical diagnosis, which repeatedly involved the doctor at great expense [6] . The gender issues are not to be overlooked: male and highly-paid experts treating female patients as if on an assembly line, and female, low-paid assistants performing the routine work. But the patients flocked in because the treatment was considered singularly successful, and even the low-status jobs as a kind of glorified nurse evaporated for women in the Third Reich, where men took over and women's jobs became scarcer still [7] .

Over the years radiology has become evermore routine: the frequency of x-ray examinations in the "developed" countries is now about one per year per capita. In the US, the number of radiologist has far outgrown the population [8] :

Table1: Growth in the number of radiologists (US)

In the 1930s and 40s, mass screening for tuberculosis was undertaken in many countries of Europe, North America, and beyond. In the 1960s mammography expanded to detect cancerous growths early, partly because a new low-dose examination was developed [9] . In the 1970s, linear accelerators came to dominate the market for x-ray sources and computerized tomography (CT) began yielding much greater anatomical differentiation of body tissues. The 1980s saw the beginning of many clinical trials with new innovative fractionation schemes. All this expansion of radiology went hand in hand with a better control of exposure and protection. But the doses administered also increased with the new technologies: the deep therapy of the 1920s upped the ante as did the CT scan: a CT chest exam in 1991 in the UK was on average 8 milliGray, about 200 times the dose of a ordinary x-ray exam. In 1990 in the US, some 9% of diagnostic x-ray utilization was CT.