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Beacon 2013 Symposium

Images derived from tomographic techniques often require processing, to reveal all detail.

Improving medical imaging

(Key people: Manuchehr Soleimani, Nathan Smith, Thanyawee Pengpan, Wei Qiu, Cathryn Mitchell, Jenna Tong, Tom Marchant)

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.


MRI image of Joe Kinrade's spine. (Courtesy Joe Kinrade.)

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.

Insects and insect colonies

(Key people: Mark Greco, Jenna Tong)

Invert, together with the Swiss Bee Research Centre, is undertaking research to view the interiors of beehives without disturbing the bees inside. Using X-ray tomography, the natural behavior of the bees can be recorded. Videos derived from these scans can be seen here. Such information could prove useful in understanding why bee numbers are falling worldwide. (See the BBC news article for more information.)


X-ray CT image of bees in hive (click to enlarge).

The group has recently acquired two beehives for research into both colony structure, and bee anatomy. Due to the non-invasive nature of tomography, the bees will remain unharmed in both cases.

X-ray micro-tomography allows the internal organs of living bees to be examined. The Invert group is particular interested in the brain, and its development over the bee's lifecycle. Videos derived from these scans can be seen here.


Micro-tomographic image of a living bee brain.

X-ray tomography also provides an excellent way of studying prehistoric insects trapped in amber. Features invisible by any other means (besides those damaging the specimen) can be resolved. Videos derived from these scans can be seen here.


X-ray CT image of 20 million year old bee, trapped in amber.