[The contrast to noise ratio as a measure of tissue contrast in nuclear magnetic resonance tomography]

Abstract

The contrast-to-noise ratio, known from the theory of imaging methods, is applied to magnetic resonance imaging. This ratio is proportional to the product of relative image contrast and the signal-to-noise ratio. After predetermining all intrinsic (T1 and T2 times, proton density) and extrinsic (pulse sequence, layer thickness, number of averagings) parameters, the signal-to-noise and contrast-to-noise ratio can be computed to a proportionality constant for all possible pulse sequences. Studies in six voluntary test subjects and 11 patients with a 0.35 T-unit showed that the measured values for the signal-to-noise ratio and the contrast-to-noise ratio are in good agreement with the computed values. The contrast between gray and white brain matter was used as an example for this. The method is applied in order to gain a better understanding of tissue contrast. However, by using diagrams it can be particularly useful for determining the optimal pulse sequences for answering particular clinical questions. It should thus be possible to enhance the effectiveness of magnetic resonance imaging considerably.