Volumetric X-ray CT

Tomographic imaging is of vital importance to modern medicine, as it provides a safe and non-invasive method to see inside the human body. We are working to improve the mathematical techniques on which tomography is based, with the aims of increasing image contrast and minimizing artefacts. A range of algebraic iterative methods have been developed for cone beam CT. A dual modality EIT/CT has been developed. Return to main page.

Improving medical imaging algorithms

A problem frequency encountered in medical imaging is that different tissues can appear very similar, making it difficult to interpret an image. One solution is for the patient to ingest, to inhale, or to be injected with a contrast medium, which highlights certain tissues, allowing greater detail to be seen. This, however, is often unpleasant for the patient, and in very rare cases has proven dangerous. Furthermore, for many applications, there is no known contrast medium capable of differentiating between the relevant tissue types. For these reasons, it is highly desirable to enhance contrast using mathematics rather than chemicals.

Image of a human head, taken with cone-beam tomography.

Contrast enhancement is also important for methods which trade resolution for high imaging speed. (An example is helical cone-beam tomography. In most X-ray CT scanners, a series of cross-sectional images are obtained by taking a 360 degree set of X-rays for each individual section. In a helical cone beam scanner, the entire subject is imaged at once, by moving the X-ray source and detector in a spiral pattern about the subject. This is much faster, but provides much less data for tomographic reconstruction.)

Tomographic images often contain artefacts (i.e. the impression of features which aren't actually there). In the case of X-ray CT, these can be caused by the presence of metallic objects within the patient, different materials preferentially absorbing different frequencies of X-ray, and many other effects. By modifying reconstruction algorithms to account for these effects, such artefacts can be reduced.

Motion of the structures being imaged will also cause artefacts. To prevent this, patients are usually required to remain extremely still for long periods of time. This is often difficult and uncomfortable, and in the case of involuntary movement (such as the heart beating) becomes impossible. Therefore, we are developing tomographic algorithms which account for movement. In the longer term, motion-tolerating techniques could be used in portable hand-held tomographic devices.

X-ray CT publications

Journal papers:

1. Qiu Wei, Pengpan T, Smith ND, Soleimani M, 2012, Evaluating iterative algebraic algorithms in
 terms of convergence and image quality for cone beam CT, Computer Methods and Programs in Biomedicine.

2. Pengpan, T., Smith, N. D., Qiu, W., Yao, A., Mitchell, C. N. and Soleimani, M., 2011. A motion-compensated cone-beam CT using electrical impedance tomography imaging. Physiological Measurement, 32 (1), pp. 19-34.

3. Greco, M. K., Tong, J., Soleimani, M., Bell, D. and Schäfer, M. O., 2012. Forthcoming. Imaging live bee brains using minimally-invasive Diagnostic Radioentomology. Journal of Insect Science

4. Pengpan, T., Qiu, W., Smith, N. and Soleimani, M., 2012. Cone-beam CT using motion-compensated algebraic reconstruction methods with limited data. Computer Methods and Programs in Biomedicine, Volume 105, Issue 3, March 2012, Pages 246–256.

5. Pengpan, T. and Soleimani, M., 2012. Electrical impedance tomography guided motion-compensated cone beam CT using a conjugate gradient least squares Algorithm. submitted

6. Pengpan, T., Mitchell , C.N. and Soleimani, M., 2010. A dual modality of cone beam CT and electrical impedance tomography for lung imaging. Journal of Physics: Conference Series, 224 (1), 012026.

7. Qiu, W., Titley-Peloquin , D. and Soleimani, M., 2012. Blockwise conjugate gradient methods for image reconstruction in volumetric X-Ray CT. In press Computer Methods and Programs in Biomedicine

8. Qiu, W., Tong, J., Mitchell, C., Marchant, T., Spencer, P., Moore, C.J. and Soleimani, M., 2010. New iterative cone beam CT reconstruction software: parameter optimisation and convergence study. Computer Methods and Programs in Biomedicine, 100 (2), pp. 166-174.

Conference papers:

9. Qiu, W., Soleimani, M., Mitchell, C.N., Marchant, T. and Moore, C.J., 2010. Iterative image reconstruction methods in Cone Beam CT applied to phantom and clinical data. In: International Conference on Computer Vision: Theory and Applications (VISAPP 2010), 17-21 May 2010, Angers, France.

10. Pengpan, T., Mitchell, C. N. and Soleimani, M., 2010. Compensating for motion artefacts in x-ray CT using electrical impedance tomography data. In: 6th World Congress on Industrial Process Tomography (WCIPT6), 6-9 September 2010, Beijing, China.

11. Pengpan , T. and Soleimani, M., 2010. Data fusion of combined high spatial resolution x-ray CT and high temporal resolution electrical impedance tomography imaging. In: SIAM Conference on Imaging Science (SIAG-IS) (IS10), 12-14 April 2011, Chicago, USA.

12. Soleimani, M., Qiu, W. and Mitchell, C., 2010. A Modular tomography software for soft field and hard field tomography. In: 6th World Congress on Industrial Process Tomography (WCIPT6), 6-9 September 2010, Beijing, China.