ON THE DIAGNOSTIC SIDE,
the 1960s brought the advent
of diagnostic ultrasound
with great promise. Soon ultrasound
devices utilized a crystal transducer
that bounced pulses off body structures
and displayed the echoes as a
scan. Motion was added, and Doppler
techniques rapidly allowed study of
blood flow and other physiological
processes. Even after 30 years, there
are still no indications of harmful
bioeffects from ultrasound exposures
at the energy ranges used for
diagnosis.
By this time, some radiologists
had begun to inquire into the new
information systems based upon
huge, ungainly devices called computers.
But computers soon shrank
in size, grew in power, dropped in
price and began to be available in
research centers. They were used for
complex radiation treatment plans,
allowing far more speed and sophistication
with isodose curves than was
possible with manual calculations.
Diagnosticians
used computers
first for image
analysis, coupling
densitometers
with them
to obtain basic data. These efforts
met with limited success.
Early in the 1970s, diagnostic
radiology made a huge leap into
cross-sectional imaging with the
development of computed tomography
(CT). Earlier, mechanical
tomography had been used for limited
purposes. But here was a completely
new technology, producing
what looked like bloodless slices
across the body area of interest. The
first scanner, devised by Geoffrey
Hounsfeld of EMI in England, could
image only the head, and required
a patient to place his skull into a
water bath while the X-ray tube and
receptor mechanically advanced
around the head. Improvements were
swift as other manufacturers replaced
mechanical parts with electronic
ones. Soon, a ring of X-ray tubes
and receptors could obtain images
of any transverse body plane in
seconds, and complex mathematical
algorithms could draw clear,
sharp images out of millions of bits
of information.
By advancing the plane of the scan
in small steps, a three-dimensional
construct of a suspect organ could be
developed. Elliot Fishman at Johns
Hopkins worked out a reconstruction
method to give surgeons threedimensional
simulations of crushed
or misshapen body parts for guidance
in delicate operations. And radiation
oncologists used computed tomographic
images to plan their treatment
fields.