Method of and apparatus for nuclear quadrupole resonance testing a sample

Abstract

A method of nuclear quadrupole resonance testing a sample is disclosed in which the excitation applied to the sample is arranged so that phase and amplitude information may be obtained from the response signal, and in which the signal is resolved into two components. Particularly if a parameter such as radio-frequency field strength varies with position, this may give an indication of the distribution of nuclei in the sample, preferably from the phase of the response signal. Positional information can also be obtained by measuring from two or more reference points. This may be employed in imaging. The phase information may be employed to improve the signal to noise ratio obtainable in other methods where only amplitude information was previously available, for example in distinguishing genuine NQR response signals from spurious signals.

1 . A method of nuclear quadrupole resonance testing a sample containing quadrupolar nuclei, said method comprising applying excitation to said sample, said excitation being arranged to produce a response signal, said response signal containing detectable phase and amplitude components resulting from nuclear quadrupole resonance interaction between said excitation and said quadrupolar nuclei, detecting said response signal, resolving said response signal into phase and amplitude dependent components and processing said response signal on the basis that both of said components vary substantially independently.  
   
   
       2 . A method according to  claim 1 , wherein a plurality of values of said response signal are sampled, said response signal having a phase and an amplitude, and a plurality of values of a phase parameter varying as a function of said phase of said response signal substantially independently of said response signal amplitude are determined.  
   
   
       3 . A method according to  claim 1 , wherein said excitation comprises first and second pulses differing in phase by a predetermined angle.  
   
   
       4 . A method according to  claim 3 , wherein said predetermined angle is about 90 degrees.  
   
   
       5 . A method according to  claim 3 , wherein said pulses are substantially contiguous.  
   
   
       6 . A method according to  claim 3 , wherein said pulses are of substantially equal duration.  
   
   
       7 . A method according to  claim 3 , wherein said second pulse is arranged substantially to lock magnetisation produced by said first pulse.  
   
   
       8 . A method according to  claim 3 , wherein said excitation includes at least a third pulse arranged to lock at least a part of net magnetisation produced by said first and second pulses  
   
   
       9 . A method according to  claim 3 , wherein said excitation includes a third pulse arranged to produce an echo from said response to said first and second pulses.  
   
   
       10 . A method according to  claim 1 , wherein said phase and amplitude dependent components comprise two components having a quadrature phase relationship to each other.  
   
   
       11 . A method according to  claim 10 , wherein a parameter varying as a function of phase is obtained from a ratio of said two components.  
   
   
       12 . A method according to  claim 1 , wherein said excitation has a field strength, wherein said field strength varies throughout at least a portion of said sample according to a given pattern.  
   
   
       13 . A method according to  claim 12 , wherein said excitation has an excitation pulse duration, wherein said field strength and said excitation pulse duration are selected to produce flip angles within a range of 0 to 360 degrees throughout a region of interest of said sample.  
   
   
       14 . A method according to  claim 1 , wherein a positional parameter of said nuclei is obtained based on at least said phase of said response signal.  
   
   
       15 . A method according to  claim 1 , wherein quantity information representative of an amount of said nuclei is obtained based on at least said amplitude of said response signal.  
   
   
       16 . A method according to  claim 1  including analysing said components to obtain profile information representative of a distribution of said nuclei in said sample.  
   
   
       17 . A method according to  claim 1  including analysing said components to obtain profile information representative of variation of an environmental parameter which affects said NQR response in said sample.  
   
   
       18 . A method according to  claim 14  comprising applying said excitation repeatedly to said sample, and repeating said analysing to obtain a plurality of sets of said profile information.  
   
   
       19 . A method according to  claim 18 , wherein at least one further set of profile information of at least one of higher resolution and higher signal-to-noise ratio is obtained from said plurality of sets.  
   
   
       20 . A method according to  claim 19 , wherein at least one factor affecting said NQR response is varied as said excitation is repeated.  
   
   
       21 .- 58 . (canceled)