treatment devices soon eclipsed the early electronic
generators. Cobalt 60, with an energy of 1.33 million
electron volts, emerged in the late 1950s as the
workhorse for radiation therapy.
The second direction was the development of lower
energy isotopes such as iodine 131 for use as diagnostic
tools. Trace amounts of iodine or other isotopes could
be given a patient. By measuring the output of urine, for
example, using a Geiger counter, a physician could assess
kidney function. With scintillation crystal detectors,
a doctor could study an image of radioactive iodine
uptake in the thyroid gland, to study function and to
infer the presence of tumors.
Advances in X-ray techniques continued apace.
Russell Morgan at the University of Chicago developed
phototiming, a method of matching exposures to
physical characteristics of patients. Morgan, Edward
Chamberlain of Temple University and, principally,
John Coltman of the Westinghouse Corporation are
credited with the conceptual development of electronic
image intensification, together bringing fluoroscopic
studies out of darkened rooms. Reduced amounts
of radiation could be fed into a fluoroscopic screen
and brightened several thousandfold before being displayed
on an output screen. This procedure allowed
recording of motion, such as the flutter of a heart valve,
on motion picture film or videotape without subjecting
patients to unacceptable levels of radiation.
Radiologists and some other physicians began to
expand the uses of hollow catheters to inject contrast
liquids into the vascular system and other body channels.
The skills needed to thread a catheter tip into
position to visualize the coronary arteries or the vessels
of the head were compared by one investigator to the
task of pushing a rope through twisted passageways.
A major advance in isotopic diagnosis resulted from
the development by Harold Anger of the University of
California of the gamma camera, with its array of
photomultiplier tubes and a large crystal which shortened
scanning time. This was coupled with the development
of various chemical forms of technetium 99m,
an isotope with a six-hour half life. Technetium could
be tagged to various chemicals to allow concentration
in different organs of interest. Given its six-hour decay
period, relatively larger amounts of isotope could be used
without increasing patient exposures. Soon isotope