NMR Imaging of the Human Brain-Insights into Neurological Diseases

Abstract

Since its introduction in the early 1980’s, magnetic resonance imaging (MRI) has proven to be an excellent imaging device for the diagnosis of a number of neurological diseases. MRI exquisitely displays soft tissue anatomy, and is able to distinguish among soft tissues such as white matter, gray matter, cerebrospinal fluid (CSF), fat, muscle, and bone far more precisely than can computerized tomography (CT). The sensitivity to abnormalities of the soft tissues is extremely high, an order of magnitude higher than CT which is far superior to conventional x-rays with a film/screen combination (latchaw 1985; Brant-Zawadzki et al 1987). Unfortunately, the specificity of MRI findings is low using our current pulsing sequences, and there is sufficient overlap that differential diagnosis or characterization of an abnormal tissue type relies primarily on morphological findings and the clinical context. In other words, we are still using the same parameters for diagnosis as we have in CT for years. The location of the lesion, its margins, change in blood-brain-barrier as denoted by an intravenously administered contrast agent, and evolution over time are all weighed in the context of the clinical findings ³¹P. It is mandatory that we take a dispassionate view at what MR has given us to date. We need to determine where MR has proven beneficial to the diagnosis and treatment of disease, focusing on the following parameters:

• 1) Clinical efficacy of diagnosis.

• 2) Quality of treatment that results from diagnosis.

• 3) Outcome of that treatment; i.e., though there may be more efficacious diagnosis and even easier or more rational types of therapy, has this resulted in any better outcome for a given disease process?

• 4) Increased knowledge of the pathophysiology of a disease process, so that better forms of therapy might be available in the future.

• 5) The potential lack of specificity of MR findings, requiring more tests.

• 6) The diseases in which other tests may prove more efficacious.

• 7) The limiting factors in the overall treatment of and outcome from a particular disease; i.e., it may be that therapeutic modalities available today are simply not up to the level of the diagnosis, or that we may be imaging the anatomical changes from a disease that is not based on an anatomical abnormality, and therefore requires far better understanding of the underlying pathophysiology for appropriate therapy.