Research in the Clinical Imaging Sciences Centre
Measuring the effects of disease using quantitative imaging.
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Paul Tofts
Chair in Imaging Physics Brighton and Sussex Medical School
Medical imaging has transformed medicine, yet it is still only used in a simple, qualitative way, much as we would a rather expensive camera. Skilled radiologists report images, noting that an organ seems lighter, darker, smaller or larger than usual. But now a technological revolution has begun, enabling the same imaging machine to be used to measure properties of tissue inside the living body. We aim to achieve the same reliability and sensitivity in making these measurements as we expect from the bathroom scales that we use to measure our body weight.
In medicine there is a real need for better characterisation of tissue inside the body. Often the only way to achieve this is to take a biopsy, a sample of tissue, which then enables detailed study of the cells and their genetics to be made. However, biopsies are often uncomfortable and, for some organs such as the brain, only taken under conditions of great need. Quantitative magnetic resonance imaging (MRI) enables us to measure more properties of tissue than is possible with conventional qualitative imaging. For example, in the brain we can measure subtle damage to the barrier around the blood vessels, and we can assess the amount of myelin (the insulating sheath around neurons), which is lost in demyelinating diseases such as multiple sclerosis.
Another good example is the management of low-grade gliomas - a type of brain tumour. At first they are benign and clinicians prefer to leave them untreated. However, after a few years, they become malignant, and treatment is then effective in prolonging life. Were it possible to predict when these tumours would become malignant, treatment could be started prior to the onset of malignancy. Using certain quantitative MRI techniques, including some novel computer image analysis methods, it is possible to measure subtle damage to the brains of patients, invisible to conventional radiology. We are able to measure the volume of enhancing tissue (ie that with abnormal blood vessels), and this turns out to be a very good predictor of when malignant transformation will happen.
In those patients with more than three millilitres of such tissue, in nearly all cases the tumours become malignant in the next six months.
Quantitative imaging will transform radiology and clinical management in the years to come. At Brighton and Sussex Medical School's Clinical Imaging Sciences Centre we have cutting-edge equipment for MRI, computed tomography (CT) and positron emission tomography (PET, which can measure tumour energy metabolism). Quantitative imaging could be used to study a variety of diseases, including cancer, brain damage in lupus, AIDS, kidney disease and medial nerve damage.
