I have some users trying to evaluate MRI contrast agents and they use
a technique of very long (4 s) cw irradiation at relatively high
power (30 dB) in a series of 1D experiments. My rule has always been
to limit presaturation (1.5 s. irradiation) to 56 dB or 50 dB in
extreme cases. I also tell people to monitor the lock level and the
probe (thermocouple) temperature as soon as the experiment is started.
These seem like dangerous levels for such high duty cycles, but I
don't like to get in the way of research. I'd like to know what
people think in terms of possible damage to probe and
amplifiers. The user says he has done this routinely on "other
machines". The probes we are using are Nalorac (Varian) 3-res 3-axis
gradient HCN and Bruker Dual (non grad) CH, all 5 mm.
Thanks.
Neil
Neil E. Jacobsen, Ph.D.
NMR Facility Manager
Department of Chemistry
119 Old Chemistry
1306 E. University
University of Arizona
Tucson, AZ 85721
520-621-8146
FAX 520-621-8407
Received on Tue Nov 18 2008 - 10:47:14 MST