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Structural imaging in the clinical diagnosis of Alzheimer's disease: problems and tools

The techniques of CT and MRI are the most commonly used instrumental aids in the diagnosis of dementia and Alzheimer's disease. Their use is often uncritical or suboptimal as to when the examination should be prescribed, which of the two techniques should be used, how much information can be obtained, and how often the information gives significant help in the differential diagnostic process. This claim is supported by the discrepancy between clinical practice—where imaging is generously used—and evidence based guidelines advising that imaging is not needed except in a few particularly uncertain cases.1 

New imaging tools are emerging2 that might significantly change the way we presently use structural CT and MRI, but full mastery of current standard techniques is mandatory for the clinical neurologist and psychiatrist for at least two reasons. Firstly, the new tools might not be available for routine clinical work for years to come, and the challenges of improved differential and preclinical diagnosis will for the time being need to be met with traditional tools. Secondly, when new expensive technology will be available, physicians will need to place it in the proper clinical context of cost-effectiveness. The increasing gap between reduced financial resources on the one hand and the increasing availability of expensive diagnostic options on the other3 will make harder the task of estimating in each patient whether the large additional cost of new technology might be justified by the expected additional clinical information. In doing this, cost-effectiveness studies will probably not be available as supports,4 and decisions will rely only on the physician's own clinical skill and expertise.

Lastly, the increasing interest in the preclinical stages of dementia—be it Alzheimer's disease5 or vascular dementia6 7—will probably make imaging even more relevant in the near future. In these cases, …