A new imaging technique pin-points the exact location and size of prostate cancer

A new imaging technique that pin-points the exact location and size of prostate cancer could help hundreds of thousands of men worldwide. Other types of cancer could also be targeted. The technique combines two existing imaging technologies, computed tomography (CT) and magnetic resonance imaging (MRI), to target radiotherapy to the cancer cells and not surrounding healthy tissue. CT scans are used to plan radiotherapy for most cancers, as the bone structure is easily visible. "The problem with CT, though, is that it doesn't give us detail of the soft tissues," says Peter Hoskins from Mount Vernon Hospital in Middlesex. All radiotherapists see is a "blob". On the other hand, MRI can define tumours and soft tissue very clearly, but is less good at revealing the bone position. This means there is no "map" for use on directing the radiation. The software developed at King's College London and the Royal Marsden Hospital now allows the soft tissue information to be transposed from the MRI to the CT scan. They plan to use this composite imaging in applying brachytherapy, where a series of radiation sources are focused directly into the walnut-sized prostate gland. Radiotherapists must treat the entire tumour, but do not want to irradiate healthy tissue. Side-effects of such damage include diarrhoea, impotence and incontinence. The new imaging technique is expected to be validated later in 2001. The team believes it could avoid normal tissue damage in any cancer where MRI currently gives better images than CT scanning, such as brain tumours.