New techniques for imaging colorectal cancer: the use of MRI, PET and radioimmunoscintigraphy for primary staging and follow-up.

Modern imaging techniques such as computed tomography (CT) and ultrasound (US) are in the majority of cases able to detect local and metastatic spread of malignancy. Increasingly, the requirement is for even more accurate pre-operative tumour staging to enable the use of new surgical techniques, neo-adjuvant therapies and, postoperatively, to enable detection of tumour recurrence on follow-up. Recent imaging research has focused on magnetic resonance imaging (MRI) for the detection of local tumour extension particularly for rectal tumours and on positron emission tomography (PET) and radioimmunoscintigraphy (RIS) for the detection of metastatic nodal and soft tissue disease. This article briefly describes these three imaging modalities and their role in primary staging, detection of hepatic metastases and local recurrence.