Imaging mass analysis data processing method and imaging mass spectrometer

Patent metadata

Field	Value
Publication number	US-10312067-B2
Application number	US-201414257025-A
Country	US
Kind code	B2
Filing date	Apr 21, 2014
Priority date	Apr 22, 2013
Publication date	Jun 4, 2019
Grant date	Jun 4, 2019

Abstract

If spatial measurement point intervals in imaging mass analysis data of two samples to be compared are different and the degrees of spatial distribution spreading of substances are compared, one of the data is defined as a reference, the measurement point intervals in the other of the data are redefined so as to be equalized to the reference, and a mass spectrum at each virtual measurement point set as a result of the redefinition is obtained through interpolation or extrapolation based on a mass spectrum at an actual measurement points. If the arrays of the m/z values of mass spectra are different for each sample, the m/z value positions of the mass spectrum in one of the data are defined as a reference, and the intensity values corresponding to the reference m/z values are obtained through interpolation or extrapolation for the mass spectrum of the other of the data.

First claim

The invention claimed is:

1. A mass spectrometry method, comprising:
a mass spectrum data acquiring step including performing a mass analysis on each of a plurality of measurement points on a first sample of a plurality of samples using an imaging mass spectrometer, performing a mass analysis on each of a plurality of measurement points on a second sample of the plurality of samples using the imaging mass spectrometer, and collecting mass spectrum data for each of the plurality of measurement points on the first and second samples;
a) a mass spectrum data associating step in which the mass spectrum data is associated with spatial position information of the plurality of measurement points to provide a plurality of imaging mass analysis data including imaging mass analysis data for the first sample and imaging mass analysis data for the second sample;
b) a spatial point interval equalization step in which a spatial measurement point interval in the plurality of imaging mass analysis data for one of the first and the second sample is defined as a reference, and mass spectrum data at each of a plurality of virtual measurement point positions in the other imaging mass analysis data for the other of the first and the second sample is obtained through interpolation or extrapolation using mass spectrum data at a plurality of measurement points around each of the plurality of virtual measurement point positions, the plurality of virtual measurement point positions being virtual positions in the other imaging mass analysis data in which a measurement point interval is equalized to the reference;
c) a mass-to-charge ratio equalization step in which a mass-to-charge ratio range common to mass spectra in the plurality of imaging mass analysis data is extracted, mass-to-charge ratio points within the extracted common mass-to-charge ratio range in the plurality of imaging mass analysis data for one of the first and the second sample are defined as references, and an intensity value at each of a plurality of virtual mass-to-charge ratio points in the other imaging mass analysis data for the other of the first and the second sample is obtained through interpolation using an intensity value at an actually measured mass-to-charge ratio point which is greater than the virtual mass-to-charge ratio point and an intensity value at the actually measured mass-to-charge ratio point which is smaller than the virtual mass-to-charge ratio point, or extrapolation using intensity values at a plurality of actually measured mass-to-charge ratio points which are greater than the virtual mass-to-charge ratio point or using intensity values at a plurality of actually measured mass-to-charge ratio points which are smaller than the virtual mass-to-charge ratio point, the virtual mass-to-charge ratio points in the other imaging mass analysis data being mass-to-charge ratio points in which mass-to-charge ratio points in the other imaging mass analysis data are equalized to the references;
d) a combining step, in which the plurality of imaging mass analysis data in which the measurement point intervals and the mass-to-charge ratio points are equalized by performing the spatial point interval equalization step and the mass-to-charge ratio equalization step are combined so as to be treatable as one imaging mass analysis data; and
e) a displaying step in which a two-dimensional mass analysis result image for the samples is displayed based on the combined one imaging mass analysis data;
whereby the displayed two dimensional mass analysis image allows an operator to evaluate the imaging mass analysis data for the first sample and the imaging mass analysis data for the second sample that are displayed simultaneously together; and
wherein the spatial point interval equalization step and the mass-to-charge ratio equalization step are performed by a processor.

2. The mass spectrometry method according to claim 1 , further comprising:
f) a spectrum creation step, in which an arithmetic mass spectrum that is a summed mass spectrum, an average mass spectrum, or a maximum intensity mass spectrum of mass spectra at a plurality of designated or specific measurement points is calculated based on the imaging mass analysis data combined in the combining step;
g) a peak matrix creation step, in which peak detection is performed on the arithmetic mass spectrum, a list of mass-to-charge ratio values of the detected peaks is created, intensity values respectively corresponding to mass-to-charge ratios in the list are obtained from the mass spectrum data at each of the measurement points, and a peak matrix is created by arraying the intensity values in accordance with corresponding mass-to-charge ratio values; and
h) a statistical analysis step, in which a statistical analysis is performed on the peak matrix.

3. The mass spectrometry method according to claim 2 , further comprising
i) an image creation step, in which a mass analysis result image showing two-dimensional distribution of unnormalized intensity values in a designated or specific mass-to-charge ratio or within a designated or specific mass-to-charge ratio range is created based on the imaging mass analysis data combined in the combining step.

4. The mass spectrometry method according to claim 3 , further comprising
a normalization coefficient creation step, in which a normalization coefficient for normalizing intensity values of mass spectrum data at each of a plurality of measurement points according to a predetermined reference is calculated for each of the measurement points, and the calculation result is stored, wherein
the image creation step includes: normalizing intensity values at each of the measurement points on the mass analysis result image using the normalization coefficient; and creating a normalized mass analysis result image.

5. The mass spectrometry method according to claim 2 , further comprising
a normalization coefficient creation step, in which a normalization coefficient for normalizing intensity values of mass spectrum data at each of the measurement points according to a predetermined reference is calculated for each of the measurement points, and the calculation result is stored, wherein
the spectrum creation step includes: normalizing mass spectra at a plurality of designated or specific measurement points using the normalization coefficient based on the imaging mass analysis data combined in the combining step; and calculating at least any one of a summed mass spectrum, an average mass spectrum, and a maximum intensity mass spectrum from the normalized mass spectra.

6. The mass spectrometry method according to claim 2 , further comprising
a compression step, in which, for the imaging mass analysis data combined in the combining step, mass spectrum data at each of the measurement points is compressed in a lossless manner according to a predetermined algorithm, and the resultant compressed data is stored into a memory unit, wherein
any one of an arithmetic mass spectrum, a peak matrix, and a mass analysis result image is created by reading necessary data of the compressed data stored in the memory unit out of the memory unit and decompressing the read data.

7. The mass spectrometry method according to claim 6 , wherein
index information in which the compressed data is associated with position information of intensity values in an array of original data is stored in the memory unit in addition to the compressed data, and
an intensity value corresponding to a specific mass-to-charge ratio is obtained with reference to the index information.

8. An imaging mass spectrometry system that provides the method of claim 1 , the imaging mass spectrometry system comprising:
the imaging mass spectrometer for performing the mass spe

Assignees

• Shimadzu Corp

Inventors

• Ikegami Masahiro
• Kajihara Shigeki

Classifications

• H01J49/0036 Primary

  Step by step routines describing the handling of the data generated during a measurement · CPC title

• H01J49/0004 Primary

  Imaging particle spectrometry · CPC title