High definition X-ray microtomography using a conventional impact X-ray source

Although superior in most aspects, synchrotron (as opposed to laboratory) X-ray microtomography (XMT) scanners are not available or appropriate for all types of application. Scanners based on laboratory X-ray generators tend to produce images with poor signal to noise ratio (SNR) because of the relatively low output power of the micro-focus source. Such systems, in common with synchrotron XMT systems, are also susceptible to ring artefacts because of their third generation geometry. We have overcome both of these limitations by designing a laboratory scanner with a high dynamic range CCD X-ray camera, employing time delay integration readout for ring artefact elimination. A further advantage of this readout method is that the recorded image length (in terms of number of pixels) can exceed the length of the CCD. Prior to reconstruction, projections are corrected for beam hardening by use of a 5(th) order calibration curve derived from a 7 stage Al step wedge. Use of this system is illustrated with an embedded human femoral head specimen, approximately 6 cm in diameter, imaged with 30 mum cubic voxels. The resultant 3D image showed good SNR, in spite of the specimen's large diameter (in pixels).