LCD in Digital Angiography

An important aspect related to angiographic equipment is represented by the high frame-rate of the modality and the performed protocols considered.

Usually employed metric (as Model Observer approaches) are designed to consider only two dimensional images and score is evaluated using only the information taken from single images, without considering any mutual information from contiguous frames. 

It can lead to an underestimation of Performances making these metrics not suitable to be applied with spatio-temporal images at least in condition of high frame rate.

An important temporal characteristic of the human visual system is represented by the noise integration time of the human eye-brain system.

Information derived from cine images are integrated and merged over a fixed period of time; in this way, images noise are globally reduced (increasing detectability) at the cost of a degradation in motion information.

It was estimated as 200 ms.

To accurately predict human performance, the Statistical Method is generalized by introducing the noise integration time of the eye-brain system, estimated at approximately 200 ms.

• Preliminary Averaging: Instead of processing single frames, the method is applied to the average of a group of frames that corresponds to this 200 ms integration window.

• Frame Rate Dependency: The number of merged frames is adjusted based on the acquisition speed—for example, the software averages 3 frames at 15 fps or 6 frames at 30 fps.

• Perceived Noise Reduction: This averaging process globally reduces image noise, simulating how the HVS "cleans" a noisy dynamic run.