US 6,392,408 B1 · Method and system for cancellation of extraneous signals in nuclear quadrupole resonance spectroscopy

Abstract

A method and system for canceling extraneous signals in a nuclear quadrupole resonance (NQR) system used for the detection of explosives and drugs. A specimen is irradiated with a specific sequence of electromagnetic pulses, referred to as a spin-locked inversion mid-echo (SLIME) pulse sequence with each pulse having a specified phase and duration. The pulses are separated by specified time intervals. The SLIME pulse sequence has a single excitation pulse. As a result of the characteristics of the SLIME pulse sequence, if the target substance to be detected is present in the specimen, sets of oppositely-phased NQR echo signals are generated from the target substance. NQR echo signals of one phase are subtracted from NQR echo signals having the opposite phase, rendering a cumulative echo signal, and simultaneously subtracting out the same-phase extraneous signal.

Claims106

Dependent claims

A method for producing improved NQR signals by canceling extraneous signals in an NQR detection system for detecting the presence of a target substance in a specimen, the target substance having quadrupolar nuclei, the nuclei having an NQR resonant frequency, the method comprising:

irradiating the specimen with at least one scan of a sequence of electromagnetic pulses having only a single excitation pulse, the pulse sequence being a spin-locked inversion mid-echo (SLIME) pulse sequence, the frequency of the pulses in the irradiating pulse sequence generally corresponding to the NQR resonant frequency of the target substance, the parameters of the pulses and pulse sequence being functionally effective to excite from the target substance at least one A NQR signal with any contemporaneous extraneous signals, and at least one B NQR signal with any contemporaneous extraneous signals, the phase of each A NQR signal being about opposite to the phase of each B NQR signal and with the phase of the respective extraneous signals being about the same during each A and B NQR signal;
at least once, detecting an A NQR signal and a B NQR signal;
and
subtracting said B NQR signals and contemporaneous extraneous signals from said A NQR signals and contemporaneous extraneous signals, thereby producing a cumulative NQR signal and canceling out the extraneous signals.

1 more element

A method for canceling extraneous signals in an NQR detection system for detecting the presence of a target substance in a specimen, the target substance having quadrupolar nuclei, the nuclei having an NQR resonant frequency, the method comprising:

employing a spin-locked inversion mid-echo (SLIME) pulse sequence:
(a) irradiating the specimen with only a single excitation pulse of said pulse sequence having a phase of about X, and a duration of about τex, and then;
(b) waiting a time of about τ3;
(c) at least once irradiating the specimen with a first refocusing pulse of said pulse sequence having a phase of about Y, and duration of about τref, and then;
(d) receiving during a time of about 2τ an A echo signal and any contemporaneous extraneous signals transmitted from the specimen;
(e) irradiating the specimen with a second refocusing pulse of said pulse sequence having a phase of about Y, and a duration of about τref, and then;
(f) waiting a time of about τ1;
(g) irradiating the specimen with a first inverting pulse of said pulse sequence having a phase selected from the group consisting of about X and about {overscore (X)}, and having a duration of about 2τinv, and then;
(h) waiting a time of about τ1;
(i) at least once irradiating the specimen with a third refocusing pulse of said pulse sequence having a phase of about Y, and a duration of about τref, and then;
(j) receiving during a time of about 2τ a B echo signal and any contemporaneous extraneous signals transmitted from the specimen;
and
(k) subtracting one or more B echo signals and contemporaneous extraneous signals from one or more A echo signals and contemporaneous extraneous signals to produce a cumulative echo signal and to cancel out the extraneous signals.

10 more elements

A method employing NQR for canceling extraneous signals and for detecting the presence of a target substance in a specimen, the target substance having quadrupolar nuclei, the nuclei having an NQR resonant frequency, the method comprising:

employing a spin-locked in version mid-echo (SLIME) pulse sequence;
(a) irradiating the specimen with only a single excitation pulse of said pulse sequence having a phase of about X, and a duration of about τex, and then;
(b) waiting a time of about τ3;
(c) at least once irradiating the specimen with a first refocusing pulse of said pulse sequence having a phase of about Y, and duration of about τref, and then;
(d) receiving during a time of about 2τ an A echo signal and any contemporaneous extraneous signals transmitted from the specimen;
(e) irradiating the specimen with a second refocusing pulse of said pulse sequence having a phase of about Y, and a duration of about τref, and then;
(f) waiting a time of about τ1;
(g) irradiating the specimen with a first inverting pulse of said pulse sequence having a phase selected from the group consisting of about X and about {overscore (X)}, and having a duration of about 2τinv, and then;
(h) waiting a time of about τ1;
(i) at least once irradiating the specimen with a third refocusing pulse of said pulse sequence having a phase of about Y, and a duration of about τref, and then;
(j) receiving during a time of about 2τ a B echo signal and any contemporaneous extraneous signals transmitted from the specimen;
(k) subtracting said B echo signals and contemporaneous extraneous signals from said A echo signals and contemporaneous extraneous signals, thereby producing a cumulative echo signal and canceling out the extraneous signals;
(l) comparing at least one characteristic of the cumulative echo signal with at least one known characteristic of an NQR signal from at least one target substance to determine the presence of the target substance, the absence of the target substance, or an indeterminate result;
and
(m) indicating either the presence of the target substance, the absence of the target substance, or an indeterminate result.

12 more elements

In an NQR substance detector for detecting the presence of a target substance in a specimen, the target substance having quadrupolar nuclei, the nuclei having an NQR resonant frequency, there being extraneous signals with the detected NQR response signals, a system for producing improved echo signals by canceling the extraneous signals, the system comprising:

(a) means for generating a spin-locked inversion mid-echo (SLIME) pulse sequence;
(b) means for irradiating the specimen with only a single excitation pulse from said pulse sequence, the excitation pulse having a phase of about X, and a duration of about τex, and then waiting a time of about τ3;
(c) means for, at least once, irradiating the specimen with a first refocusing pulse from said pulse sequence, the first refocusing pulse having a phase of about Y, and duration of about τref;
(d) means for receiving during a time of about 2τ an A echo signal and any contemporaneous extraneous transmitted from the specimen;
(e) means for irradiating the specimen with a second refocusing pulse from said pulse sequence, the second refocusing pulse having a phase of about Y, and a duration of about τref, and then waiting a time of about τ1;
(f) means for irradiating the specimen with a first inverting pulse from said pulse sequence, the first investing pulse having a phase selected from the group consisting of about X and about {overscore (X)}, and having a duration of about 2τinv, and then waiting a time of about τ1;
(g) means for, at least once, irradiating the specimen with a third refocusing pulse from said pulse sequence, the third refocusing pulse having a phase of about Y, and a duration of about τref;
(h) means for receiving during a time of about 2τ a B echo signal and any contemporaneous extraneous transmitted from the specimen;
and
(i) means for subtracting said B echo signals and contemporaneous extraneous signals from said A echo signals and contemporaneous extraneous signals to produce a cumulative echo signal and to cancel out the extraneous signals.

7 more elements

An NQR detection system for canceling extraneous signals and detecting the presence of a target substance in a specimen, the target substance having quadrupolar nuclei, the nuclei having an NQR resonant frequency, the system comprising:

(a) means for generating a spin-locked inversion mid-echo (SLIME) pulse sequence;
(b) means for irradiating the specimen with only a single excitation RF pulse of said pulse sequence having a phase of about X;
(c) means for, at least once, irradiating the specimen with a first refocusing RF pulse from said pulse sequence, the first refocusing pulse having a phase of about Y;
(d) means for receiving an A RF echo signal transmitted from the specimen;
(e) means for irradiating the specimen with a second refocusing RF pulse from said pulse sequence, the second refocusing pulse having a phase of about Y;
(f) means for irradiating the specimen with a first inverting RF pulse from said pulse sequence, the first inverting pulse having a phase selected from the group consisting of about X and about {overscore (X)};
(g) means for, at least once, irradiating the specimen with a third refocusing RF pulse from said pulse sequence, the third refocusing pulse having a phase of about Y;
(h) means for receiving a B RF echo signal with any contemporaneous extraneous signals transmitted from the specimen;
(i) means for subtracting said B RF echo signals and contemporaneous extraneous signals from said A RF echo signals and contemporaneous extraneous signals to produce a cumulative RF echo signal and to cancel out the extraneous signals;
(j) means for comparing at least one characteristic of the cumulative RF echo signal with at least one known characteristic of an NQR signal from at least one target substance to determine the presence of the target substance, the absence of the target substance, or an indeterminate result;
and
(k) means for indicating the presence of the target substance, the absence of the target substance, or an indeterminate result.

9 more elements

(a) means for generating a spin-locked inversion mid-echo (SLIME) pulse sequence;
(b) means for irradiating the specimen with only a single excitation pulse from having a phase of about X, and a duration of about τex, and then waiting a time of about τ3;
(c) means for, at least once, irradiating the specimen with a first refocusing pulse from said pulse sequence, the first refocusing pulse having a phase of about Y, and duration of about τref;
(d) means for receiving during a time of about 2τ an A echo signal with any contemporaneous extraneous transmitted from the specimen;
(e) means for irradiating the specimen with a second refocusing pulse from said pulse sequence, the second refocusing pulse having a phase of about Y, and a duration of about τref, and then waiting a time of about τ1;
(f) means for irradiating the specimen with a first inverting pulse from said pulse sequence, the first inverting pulse having a phase selected from the group consisting of about X and about {overscore (X)}, and having a duration of about 2τinv, and then waiting a time of about τ1;
(g) means for, at least once, irradiating the specimen with a third refocusing pulse from said pulse sequence, the third refocusing pulse having a phase of about Y, and a duration of about τref;
(h) means for receiving during a time of about 2τ a B echo signal with any contemporaneous extraneous signals transmitted from the specimen;
(i) means for subtracting said B echo signals and contemporaneous extraneous signals from said A echo signals and contemporaneous extraneous signals to produce a cumulative echo signal and to cancel out the extraneous signals;
(j) means for storing at least one characteristic of an NQR signal from at least one target substance;
(k) means for comparing at least one characteristic of the cumulative echo signal with at least one stored characteristic of an NQR signal from at least one target substance to determine the presence of the target substance, the absence of the target substance, or an indeterminate result;
and
(l) means for indicating the presence of the target substance, the absence of the target substance, or an indeterminate result.

10 more elements

Dependencies are inferred from the claim text.

Method and system for cancellation of extraneous signals in nuclear quadrupole resonance spectroscopy

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Method and system for cancellation of extraneous signals in nuclear quadrupole resonance spectroscopy

Life of this patent

Abstract

Claims106