| Abstract: | Magnetic resonance (MR) is a state-of-the art imaging modality which does not use ionizing radiation. It is now widely available as an imaging technique in the U.K. and is no longer confined to specialist centres. MR has now become part of the clinician's diagnostic armamentarium and is not merely a research utility. A magnetic field and radio-frequency waves are used to excite protons and produce an image. Protons exist in many different environments but for imaging purposes the hydrogen protons in fat and water are used. The rate at which excited protons relax is described by two characteristic times, T1 and T2, which vary in different tissues. T1-weighted images show normal anatomy, whilst T2-weighted images generally highlight abnormal tissue. Injection of a paramagnetic gadolinium-based contrast agent enhances T1-weighted images by reducing relaxation times. Initially it was felt that MR would be tissue-specific,1 enabling correlation with histopathological findings. Unfortunately, research and clinical use has shown that MR does not fulfil these expectations at present.2 Future developments such as spectroscopy may improve tissue specificity and hence diagnostic accuracy. The value of MR for imaging the neuro-axis and musculo-skeletal system is well established. New developments are increasing its applications in breast, thorax, and liver imaging. There has been much research into the role of MR in staging malignant tumours, particularly in the areas of bladder and lung carcinomas. The present article concentrates on this specific application. |
