th  - 1988 - 51st ENC Conference

TUE 11:40
FUN WITH GENES: Ray Freeman, Cambridge University,
] Cambridge CB2 IEP, England.
If you are bored by endlessly searching For minlma in multidimensional
hyperspace, why not try a new approach to the design of NMR pulse sequences?
Now it is the scientist who makes all the important decisions while the
computer merely calculates some figure of merit - for example a frequency-domain
response function. The idea is not to optimlse an experiment but to discover
new ones. Suppose we are interested in shaped selective radiofrequency pulses~
we might multiply a Gaussian by a sinc function or a polynomial and truncate
the tails. Each contribution to the overall shape is assigned a "gene", a
numerical value which can be incremented or decremented to represent a
"mutation". fhe computer evaluates the frequency-domain excitation spectrum
and displays it on an oscilloscope screen, together with its eight "offspring"
obtained by changing one or two genes. If some "desirable" trend can be
recognized, the operator selects that pattern as the parent for the next
generation; if not he chooses arbitrarily or even recklessly, it doesn't
matter. Eventually after several generations something new emerges. After
all, that is how we all originated, through Darwinian natural selection.
Ihis "genetic evolution" technique (I-3) is very general; it has been used in
aeronautical engineering and in the automotive industry. It might just put the
fun back into our own specialized 11ttle NMR games.
(I) R. Dawkins, "The Blind Watchmaker", Longman 1986.
(2) I. Rechenberg, "Evolutionsstra(e~ie'~ Frommann-Holtzboog, 1973
(3) R. Freeman and X.L. Wu, J. Magn. Reson., 75, 18a (1987).
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