1 © 2016 IOP Publishing Ltd Printed in the UK 1. Introduction There is a widespread need for micron scale x-ray imaging, for example in the imaging of human bone. As the population ages, degenerative diseases such as osteoporosis are becoming increasingly common and costing health services billions of pounds per year [1]. This disease is characterised by bone tissue deterioration caused by an imbalance in bone remod- elling rates, leading to lowered bone density and increased fracture risk. Trabecular, or cancellous bone is a porous form of bone responsible for the transmission of forces from the joints to load-bearing surfaces. Its high surface area means it is the site of a large fraction of bone metabolic activity, and is therefore particularly sensitive to any metabolic dis- ruption [2]. Traditional diagnosis of osteoporosis is based on the deviation from the mean of an individual’s average bone density, which is an accurate predictor of fracture risk over the population. However for a particular patient up to 90% of Plasma Physics and Controlled Fusion Tomography of human trabecular bone with a laser-wakeield driven x-ray source J M Cole 1 , J C Wood 1 , N C Lopes 1,2 , K Poder 1 , R L Abel 3 , S Alatabi 1 , J S J Bryant 1 , A Jin 4 , S Kneip 1 , K Mecseki 1 , S Parker 5 , D R Symes 6 , M A Sandholzer 7 , S P D Mangles 1 and Z Najmudin 1 1 The John Adams Institute for Accelerator Science, Blackett Laboratory, Imperial College London, London SW7 2AZ, UK 2 GoLP, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, 1049-001, Portugal 3 MSk Laboratory, Department of Surgery and Cancer, Charing Cross Hospital, Imperial College London, London W6 8RF, UK 4 Department of Mechanical Engineering, City and Guilds Building, Imperial College London, London SW7 2AZ, UK 5 Department of Physics, Imperial College London, London SW7 2AZ, UK 6 Central Laser Facility, Rutherford Appleton Laboratory, Didcot OX11 0QX, UK 7 MRC Harwell, Harwell Science and Innovation Campus, Didcot OX11 0RD, UK E-mail: j.cole11@imperial.ac.uk Received 26 June 2015, revised 4 September 2015 Accepted for publication 10 September 2015 Published 20 October 2015 Abstract A laser-wakeield driven x-ray source is used for the radiography of human bone. The betatron motion of accelerated electrons generates x-rays which are hard (critical energy > E 30 crit keV), have small source size (<3 μm) and high average brightness. The x-rays are generated from a helium gas cell which is near-instantly replenishable, and thus the average photon lux is limited by the repetition rate of the driving laser rather than the breakdown of the x-ray source. A tomograph of a human bone sample was recorded with a resolution down to 50 μm. The photon lux was suficiently high that a radiograph could be taken with each laser shot, and the fact that x-ray beams were produced on 97% of shots minimised failed shots and facilitated full micro-computed tomography in a reasonable time scale of several hours, limited only by the laser repetition rate. The x-ray imaging beamline length (not including the laser) is shorter than that of a synchrotron source due to the high accelerating ields and small source size. Hence this interesting laboratory-based source may one day bridge the gap between small microfocus x-ray tubes and large synchrotron facilities. Keywords: laser wakeield, betatron, x-ray, tomography, bone (Some igures may appear in colour only in the online journal) 0741-3335/16/014008+7$33.00 doi:10.1088/0741-3335/58/1/014008 Plasma Phys. Control. Fusion 58 (2016) 014008 (7pp)