High-resolution μCT of a mouse embryo using a compact laser-driven X-ray betatron source

Abstract

In the field of X-ray microcomputed tomography (μCT) there is a growing need to reduce acquisition times at high spatial resolution (approximate micrometers) to facilitate in vivo and high-throughput operations. The state of the art represented by synchrotron light sources is not practical for certain applications, and therefore the development of high-brightness laboratory-scale sources is crucial. We present here imaging of a fixed embryonic mouse sample using a compact laser-plasma-based X-ray light source and compare the results to images obtained using a commercial X-ray μCT scanner. The radiation is generated by the betatron motion of electrons inside a dilute and transient plasma, which circumvents the flux limitations imposed by the solid or liquid anodes used in conventional electron-impact X-ray tubes. This X-ray source is pulsed (duration <30 fs), bright (>10¹⁰ photons per pulse), small (diameter <1 μm), and has a critical energy >15 keV. Stable X-ray performance enabled tomographic imaging of equivalent quality to that of the μCT scanner, an important confirmation of the suitability of the laser-driven source for applications. The X-ray flux achievable with this approach scales with the laser repetition rate without compromising the source size, which will allow the recording of high-resolution μCT scans in minutes.

Keywords: X-ray imaging; laser–plasma acceleration; microcomputed tomography.

Fig. 1.

Schematic of the laser and X-ray beamlines. The laser beam (red) is incident upon a gas cell, producing an electron beam (blue) and an X-ray beam (green). All components are inside a vacuum chamber with the exception of the X-ray camera. The sample is kept at atmospheric pressure inside a secondary chamber.

Fig. 2.

Characterization of the laser-betatron X-ray beam. (A) Measured transmission through metallic filters, with overlaid equivalent thicknesses of water in centimeters at this X-ray energy. (B) Distribution of X-ray critical energies $E_{crit}$ recorded during the tomographic scan. (C) Measured line-spread function (LSF) of the X-ray detector. (D) Integrated X-ray beam dose profile measured at the sample position using EBT3 radiochromic film irradiated with 100 X-ray pulses.

Fig. 3.

Tomographic imaging of a 14.5-dpc mouse embryo. (A–D) Single X-ray projections (A and B) and sagittal slices from 3D reconstruction (C and D). A and C were acquired with the laser-betatron source and B and D with a commercial microfocus scanner.

Fig. 4.

An isosurface rendering of the reconstruction from the laser source is depicted in gray. A sagittal slice of the reconstruction is overlaid in blue. Enlarged sections of sagittal, coronal, and transverse slices around the heart and liver are plotted in A and B, respectively. (Scale bars, 1 mm.)

Fig. 5.

The average photon flux and characteristic energy of the X-ray source described here in comparison with previous results on laser-betatron X-ray sources (, , –21). The lines represent the incident photon flux on a typical 4-MP detector after passing through 1 cm of water, assuming the X-ray beam fills the detector.