scans were the preferred method of
exploring many problems in the
brain and liver.
By the late 1950s, investigators including
Henry Kaplan and the Varian
brothers at Stanford University
were working on a device called a linear
accelerator to generate high
energy X rays or electrons for cancer
treatment. Referred to as linacs, the
devices soon grew smaller, delivered
higher energies and became safer and
more reliable. They produced controlled
energy beams in ranges from
4 to 25 million electron volts, and
gradually displaced cobalt units as
the primary radiation therapy sources
in most advanced countries.
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