Imaging mass spectrometry method and device

Patent metadata

Field	Value
Publication number	US-9263242-B2
Application number	US-201514722930-A
Country	US
Kind code	B2
Filing date	May 27, 2015
Priority date	Jun 2, 2014
Publication date	Feb 16, 2016
Grant date	Feb 16, 2016

Abstract

A method of performing imaging mass spectrometry of a sample. The method comprises performing a first mass analysis of the sample using a first mass analyzer comprising a multi-pixel ion detector to obtain first mass spectral data representative of pixels of the sample. The method further comprises identifying clusters of pixels sharing one or more characteristics of first mass spectral data. The method also comprises performing a second mass analysis of the sample using a second mass analyzer to obtain second mass spectral data at at least one location in each cluster, wherein the number of locations is significantly less than the number of pixels in each cluster, said second mass analysis being of higher resolution than said first mass analysis. Also a mass spectrometry apparatus configured for carrying out the method.

First claim

The invention claimed is:

1. A method of performing imaging mass spectrometry of a sample, the method comprising:
performing a first mass analysis of the sample using a first mass analyzer comprising a multi-pixel ion detector to obtain first mass spectral data representative of pixels of the sample;
identifying clusters of pixels sharing one or more characteristics of first mass spectral data; and
performing a second mass analysis of the sample using a second mass analyzer to obtain second mass spectral data at at least one location in each cluster, wherein the number of locations is significantly less than the number of pixels in each cluster, said second mass analysis being of higher resolution than said first mass analysis.

2. The method of claim 1 wherein the first mass analysis is performed at least 10 2 times faster than the second mass analysis.

3. The method of claim 1 wherein the second mass analysis has a mass resolution at least 10 2 times higher than the first mass analysis.

4. The method of claim 1 wherein the first mass spectral data has a higher spatial resolution than the second mass spectral data.

5. The method of claim 1 and further comprising conflating the first and second mass spectral data to obtain a mass spectral image of the sample that has the spatial resolution of the first mass spectral data and the mass resolution of the second mass spectral data.

6. The method of claim 1 wherein the first mass analyzer performs mass analysis in at least 1,000 channels in parallel.

7. The method of claim 1 wherein the second mass analyzer performs mass analysis in not more than 10 channels in parallel.

8. The method of claim 7 wherein the second mass analyzer performs mass analysis in 1 channel at a time.

9. The method of claim 1 wherein for the first mass analyzer, the product of a number of parallel detection channels by resolving power exceeds 10 6 .

10. The method of claim 1 wherein for the first mass analyzer, a product of a pixel data acquisition rate by resolving power exceeds 10′ per second.

11. The method of claim 1 wherein for the first mass analyzer, a raw bit rate exceeds 10 8 per second.

12. The method of claim 1 wherein for the second mass analyser of higher resolution, a product of pixel rate by resolving power exceeds 10 5 per second.

13. The method of claim 1 wherein the product of a pixel rate by resolving power is significantly higher for the first mass analyzer than for the second mass analyzer.

14. The method of claim 1 further comprising irradiating the sample with an ionization beam to provide ions for the first mass analysis and second mass analysis and focussing the ionization beam to a smaller area of the sample for the second mass analysis compared to the first mass analysis.

15. The method of claim 1 wherein the first mass analyzer is a time-of-flight mass analyzer.

16. The method of claim 1 wherein the second mass analyzer is a time-of-flight mass analyzer or an electrostatic trap mass analyzer or an FT-ICR mass analyzer.

17. The method of claim 16 wherein the second mass analyzer is an electrostatic trap mass analyzer and wherein the electrostatic trap mass analyzer is an orbital trap mass analyzer.

18. The method of claim 1 wherein the number of clusters is at least 10 times less than the total number of pixels.

19. The method of claim 1 wherein the step of identifying clusters of pixels sharing one or more characteristics of mass spectral data comprises:
determining a degree of similarity of mass spectral data of a plurality of pixels; and
allocating pixels to a particular cluster in the event that the determined degree of similarity of the pixels falls within a predetermined range.

20. The method of claim 19 wherein the step of determining the degree of similarity of mass spectral data of a plurality of pixels comprises determining the degree of similarity of mass spectral data of a plurality of adjacent pixels and adjacent pixels are allocated to a particular cluster in the event that the determined degree of similarity of the adjacent pixels falls within the predetermined range.

21. The method of claim 1 further comprising one or more of the following data processing steps on the obtained first mass spectral data prior to identifying said clusters of pixels:
removing spectral noise from obtained mass spectral data;
aligning a plurality of obtained mass spectral data;
summing a plurality of obtained mass spectral data; and/or
smoothing obtained mass spectral data.

22. The method of claim 1 further comprising:
identifying secondary clusters of pixels within each said cluster sharing one or more characteristics of mass spectral data.

23. The method of claim 1 further comprising:
allocating a confidence score to each cluster on the basis of the degree of similarity between the first and second mass spectral data for said cluster and/or between second mass spectral data at each location within said cluster.

24. The method of claim 1 wherein the step of performing the second mass analysis at at least one location in each cluster includes:
identifying a first location of the one or at least one locations by identifying a pixel within the cluster having a highest similarity of shared characteristics of mass spectral data with one or more immediately adjacent pixels.

25. The method of claim 24 wherein the step of performing the second mass analysis is performed at more than one location in each cluster and further includes:
identifying a second location by identifying a pixel within the cluster having a high similarity of shared characteristics of mass spectral data with immediately adjacent pixels and wherein the pixels of the second location have a low similarity of characteristics with the pixels of the first location.

26. The method of claim 1 wherein the step of performing the second mass analysis at at least one location in each cluster includes:
identifying a plurality of locations substantially equally spaced apart within each cluster.

27. The method of claim 1 wherein the step of performing the first mass analysis of the sample comprises performing a plurality of such analyses, each of a sub-region of the sample, in a consecutive fashion.

28. The method of claim 1 wherein, in the event that the step of performing the second mass analysis includes performing the analysis at more than one location within a given cluster, the method further comprises:
confirming that spectral data derived from the second mass analysis at each of the locations is within an expected margin of spectral data derived from the second mass analysis at each of the other locations; and
where it is outside the expected margin, dividing the cluster into smaller clusters and repeating the high resolution mass spectrometry.

29. The method of claim 1 wherein a multi-modal image is produced from the first and second mass spectral data in combination with one or more of the following: optical imaging, elemental imaging, computer tomography, magnetic resonance imaging, and position emission spectroscopy.

30. A mass spectrometry apparatus comprising:
a first mass analyzer comprising a multi-pixel ion detector for undertaking first mass analysis of a sample to provide first mass spectral data in the form of a mass spectral image of the sample;
a second ma

Assignees

• Thermo Fisher Scient Bremen

Inventors

• Makarov Alexander A

Classifications

• H01J49/0031

  Step by step routines describing the use of the apparatus (H01J49/0081 takes precedence) · CPC title

• H01J49/0004 Primary

  Imaging particle spectrometry · CPC title

• H01J49/025

  Detectors specially adapted to particle spectrometers (data acquisition H01J49/0036; detectors per se G01T, e.g. G01T1/28, G01T1/29) · CPC title

• H01J49/40

  Time-of-flight spectrometers (H01J49/36 takes precedence) · CPC title

• H01J49/4265

  Controlling the number of trapped ions; preventing space charge effects · CPC title