Prof M Soleimani

Volumetric X-ray CT

ETL has released GPU based cone beam CT imaging software, called TIGRE jointly with CERN.

Tomographic imaging is of vital importance to modern medicine, as it provides a safe and non-invasive method to see inside the human body. The X-ray CT is also a key tool in many other application areas. 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 and micro-CT. A dual modality EIT/CT has been developed. Return to Prof Soleimani’s 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.

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.

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