High resolution imaging apparatus and method
The present invention relates to the high resolution imaging of samples using imaging mass spectrometry (IMS) and to the imaging of biological samples by imaging mass cytometry (IMC™) in which labelling atoms are detected by IMS. LA-ICP-MS (a form of IMS in which the sample is ablated by a laser, the ablated material is then ionised in an inductively coupled plasma before the ions are detected by mass spectrometry) has been used for analysis of various substances, such as mineral analysis of geological samples, analysis of archaeological samples, and imaging of biological substances. However, traditional LA-ICP-MS systems and methods may not provide high resolution. Described herein are methods and systems for high resolution IMS and IMC.
1. An apparatus for analyzing a biological sample comprising:
a sample stage;
a source of charged particles, the source of charged particles configured to pass a beam of charged particles to a location on the sample stage; and
a first laser source and first focusing optics configured to direct a laser beam emitted by the first laser source towards the sample stage,
wherein the source of charged particles, the first laser source, and the first focusing optics are configured such that the beam of charged particles and the laser beam are directed towards opposite sides of the sample stage.
2. The apparatus of claim 1 wherein the first focusing optics is configured to synchronise a pulse of laser beam to arrive at the location on the sample stage directly after a pulse of charged particles.
3. The apparatus of claim 1 wherein the first focusing optics is configured to synchronise a pulse of laser beam to ionise a plume of material sputtered by a pulse of charged particles.
4. The apparatus of claim 1 further comprising a second laser source and second focusing optics, wherein the second focusing optics are configured to synchronise a pulse of laser beam from the second laser source to ionise a plume of material sputtered by a pulse of charged particles.
5. The apparatus of claim 4 wherein the first laser source, the first focusing optics, the second laser source, and the second focusing optics are configured such that the laser beam from the first laser source and the laser beam from the second laser source are directed towards the same side of the sample stage.
6. The apparatus of claim 4 wherein the first laser source, the first focusing optics, the second laser source, and the second focusing optics are configured such that the laser beam from the first laser source and the laser beam from the second laser source are directed towards opposite sides of the sample stage.
7. The apparatus of claim 4 wherein the first laser source or the second laser source is configured to ionise material by avalanche ionisation.
8. The apparatus of claim 1 wherein the source of charged particles is a primary ion beam source or an electron beam source.
9. The apparatus of claim 1 wherein the first laser source is a pulsed laser source.
10. The apparatus of claim 9 wherein the first laser source is adapted to have a pulse energy of between 1 nanoJoule and 100 microJoules.
11. The apparatus of claim 1 wherein the beam of charged particles is pulsed.
12. The apparatus of claim 1 comprising a charged particle beam scanning system adapted to scan the beam of charged particles across a plurality of locations on the sample stage.
13. The apparatus of claim 1 further comprising an electron microscope.
14. The apparatus of claim 13 wherein the source of charged particles is an electron beam source, wherein the electron beam source is an electron source in the electron microscope.
15. The apparatus of claim 1 wherein the sample stage is transparent or the sample stage comprises a cut-out portion.
16. The apparatus of claim 1 comprising a variable delay line.
17. The apparatus of claim 1 further comprising a sample chamber and a pump.
18. The apparatus of claim 1 further comprising a mass spectrometer.
19. An apparatus for analyzing a biological sample comprising:
a sample stage;
a source of charged particles, the source of charged particles configured to pass a beam of charged particles to a location on the sample stage; and
a first laser source and first focusing optics configured to direct a laser beam emitted by the first laser source towards the sample stage, wherein:
the first laser source is a pulsed laser source, and
the first laser source is adapted to have a pulse energy of between 1 nanoJoule and 100 microJoules.
20. An apparatus for analyzing a biological sample comprising:
a sample stage;
a source of charged particles, the source of charged particles configured to pass a beam of charged particles to a location on the sample stage;
a first laser source and first focusing optics configured to direct a laser beam emitted by the first laser source towards the sample stage; and
a second laser source and second focusing optics, wherein:
the second focusing optics are configured to synchronise a pulse of laser beam from the second laser source to ionise a plume of material sputtered by a pulse of charged particles, and
the first laser source or the second laser source is configured to ionise the material by avalanche ionization.