Electricity: measuring and testing – Particle precession resonance – Using a nuclear resonance spectrometer system
Reexamination Certificate
2000-12-06
2003-06-24
Lefkowitz, Edward (Department: 2862)
Electricity: measuring and testing
Particle precession resonance
Using a nuclear resonance spectrometer system
C324S309000, C324S318000
Reexamination Certificate
active
06583622
ABSTRACT:
The present invention relates to nuclear magnetic resonance (NMR) techniques, and in particular to field cycling spectrometry.
Field cycling relaxometry is an extremely powerful NMR technique for studying molecular dynamics within a sample or object under analysis. In field cycling, the dependence of the longitudinal relaxation time T
1
(&ohgr;
0
) on spectrometer frequency &ohgr;
0
is typically determined over frequencies ranging from 0.01 to 10 MHz. It is called field cycling because the spectrometer frequency is related to the magnetic field strength as &ohgr;
0
=&ggr;B
0
where &ggr; is the proton gyromagnetic ratio. The frequency dependence of T
1
is therefore determined by rapidly cycling through different field strengths, B
0
.
Commercial availability of field-cycling spectrometers is strictly limited at the present time. There are several reasons for this slow commercialization of field cycling spectrometers. Firstly, relaxation times can be as short as a few milliseconds, so it is necessary to be able to switch magnetic field strengths very rapidly while maintaining field homogeneity. This requires very efficient magnet cooling and a special power supply capable of delivering high power (ca. 15 kW) very rapidly. This makes such equipment both complex and expensive.
An alternative approach to field cycling is to mechanically shuffle the sample between high and low magnetic fields. This has the advantage that rapid field switching is not required. However, known applications of this idea are based on linear translation of the sample in a back-and-forth movement between magnetic fields. This is mechanically demanding and also very Slow, so that short T
1
values cannot be measured. The NMR acquisition is also made when the sample is stationary within the magnetic fields, so that a time delay is necessary to allow mechanical vibrations to damp down before acquisition can begin.
The present invention seeks to provide a field cycling NMR spectrometer which overcomes some or all of the problems of the prior art as enumerated above.
According to one aspect, the present invention provides an apparatus for making nuclear magnetic resonance measurements on an object, comprising:
means for conveying the object under analysis, at predetermined angular velocity, successively through a first, spatially characterized, constant magnetic field B
0
and a second, spatially characterized, constant magnetic field B
s
; and
means for detecting nuclear magnetic resonance signals weighted with at least one nuclear magnetic resonance parameter from said object.
According to a further aspect, the present invention provides a method of making nuclear magnetic resonance measurements on an object under analysis, comprising the steps of:
rotating the object at a first predetermined angular velocity about a point so that the object is repeatedly conveyed along a circular path, which circular path sequentially passes through a first magnet having a first, spatially characterized, constant field strength B
0
and a second magnet having a second, spatially characterized, constant field strength B
s
; and
detecting nuclear magnetic resonance signals weighted with at least one nuclear magnetic resonance parameter from said object after said at least part of an object passes through said second magnet.
REFERENCES:
patent: 5462054 (1995-10-01), Rapoport et al.
patent: 5570021 (1996-10-01), Dachniwskyj et al.
patent: 5754048 (1998-05-01), Bielecki
patent: 6255824 (2001-07-01), Barbara
Jerrold T. Bushberg, The essential Physics of Medical Imaging; Williams& Wilkins;pp. 717-722.*
Noak, F., NMR Field Cycling Spectroscopy: Principles and Applications, Progress in NMR spectroscopy; vol. 18, p. 171-276.
Dickstein , Shapiro, Morin & Oshinsky, LLP
Lefkowitz Edward
Vargas D.
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