Evaluation of T1-Weighted Magnetic Resonance Images by Entropy Method

概要

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The relationshipb etween repetition time (TR)a nd image quality for T1-weightedm agnetic resonance images was assessed using the entropy method, and the optimum imaging conditions for the T1-weighted images were determined. The relative efficiency of transmission(η)and the conditional entropy(Hx(Y))were obtained as indices of evaluation. The value of η which is the measurement related to both contrast and noise was maximum at TR=500msec. This value agreed with TR values obtained empirically in many other centers, and the evaluation of image quality by η correlated well with visual observation of the clinical images. Accordingly, η was a good index to determine the optimum imaging conditions. Hx(Y)which represents the noise component was minimum at TR=400msec. The increment in Hx(Y) was small when TR was increased. η and Hx(Y)are influenced by several parameters including the number of signals averaged, slice thickness, echo time. Accordingly, the optimum imaging conditions change when these parameters change.
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