Nuclear magnetic resonance in gastroenterology

Insufficient clinical results are yet available to determine the likely clinical role of NMR in gastroenterology. In some instances unique information is available from NMR imaging but ultrasound and CT also provide valuable information in a wide variety of diseases. Many of the organs and tissues within the abdomen are accessible to biopsy, and a variety of other biochemical tests have specific roles in assessing disease within the abdomen and pelvis. Virtually all NMR machines in current use are research prototypes rather than clinical instruments designed for routine use. Major questions about design are unresolved, such as whether resistive, permanent or cryogenic magnets should be used. There is also little agreement about the optimum field for imaging. The value of spectroscopy in research and clinical use is another unknown factor and it is probable that this will provide useful information in research applications at least. At the present time it is important to note the developments occurring in NMR imaging and the potential of this technique, although it is not yet possible to predict what value it may have in clinical practice. There are many current research developments, such as flow imaging and the imaging of 23Na which have been demonstrated in the laboratory but have not yet been applied in clinical practice. It is also possible that respiratory gating may result in considerable improvement in image quality. The use of paramagnetic contrast agents is another developing field. These agents, including molecular O2, iron, manganese and gadolinium, have the effect of decreasing T1 and T2. Gadolinium chelates have been used in animals and will soon be evaluated in humans. Not only do these materials act as contrast agents in their own right but they may be linked as markers to metabolites, antibodies and other compounds. Direct measurements of T1 and T2 may prove to be of value although initial results indicate that they are rather non-specific. Whether NMR will remain largely of research interest or will play a useful role in clinical practice remains to be seen but will certainly be the subject of intense investigation over the next few years.