I think all depends on sampling accuracy, otherwise a perfusion scan could never be used over time in 3D volumes. The matter will be do we have enough info in 3D to sample quick enough or is a little less accurate sampling in 4D scanning still acceptable? The Infinite amount of 3D samples per second would make above statement almost not true. A lower amount of 3D samples per second would make your statement true. Btw all my personal Insights