th  - 1987 - 51st ENC Conference

Thursday - AM
AN OVERVIEW OF SPATIALLY LOCALIZED SPECTROSCOPY
by
D.I. Houit
Biomedical Engineering and Instrumentation Branch
Division of Research Services
Building 13, Room 3W13
National institutes of Health
Bethesda, Maryland 20892
Obtaining spectra from a localized region is a difficult task which is
further complicated by a number of practical problems which defy easy
solution. The actual act of localization is accomplished with the aid
of gradients in the B 0 and/or B 1 fields in concert with a variety
of selective pulses and cycling schemes. However, as the volume of
interest may be small in comparison to the volume which is capable of
generating signal, suppression of the latter must be excellent, leaving
very little room for experimental imperfection. When one considers
that the sample i5 often alive and may move, that switched-field
gradients may leave residual eddy currents which generate changing
fields during data acquisition, that shimming may be well-nigh
impossible if the volume is remote from the origin of the shim coil set
and that several transmitting and/or receiving coils may be needed, a
headache of royal proportions is clearly made manifest. Thus the talk
will outline in more detail the origins of the- problems, and briefly
summarize progress made in solving them.