A system for visualizing a time-variant parameter at a plurality of positions in a biological structure, the system comprising: - a determination unit configured to - determine from a series of medical image scans a value of the time-variant parameter at a plurality of positions in the biological structure, the structure extending in mutually perpendicular X, Y and Z directions; - determine the positions of a first and a second boundary extending in the Z direction, and the positions of a first volume extending in Z disposed between the first and second boundaries; - determine the positions of a second volume generated by extending the first volume in the X-direction to both the first and the second YZ boundary; - determine a first visualization parameter for a plurality of time intervals from the time-variant parameters at a plurality of positions in the first volume; - determine a second visualization parameter from the time-variant parameters at a plurality of positions in the second volume, and - a visualization display configured to - display a first representation showing the first visualization parameter at the plurality of time intervals, and - display a second representation showing the first and second visualization parameters. - a determination unit configured to - determine from a series of medical image scans a value of the time-variant parameter at a plurality of positions in the biological structure, the structure extending in mutually perpendicular X, Y and Z directions; - determine the positions of a first and a second boundary extending in the Z direction, and the positions of a first volume extending in Z disposed between the first and second boundaries; - determine the positions of a second volume generated by extending the first volume in the X-direction to both the first and the second YZ boundary; - determine a first visualization parameter for a plurality of time intervals from the time-variant parameters at a plurality of positions in the first volume; - determine a second visualization parameter from the time-variant parameters at a plurality of positions in the second volume, and - determine from a series of medical image scans a value of the time-variant parameter at a plurality of positions in the biological structure, the structure extending in mutually perpendicular X, Y and Z directions; - determine the positions of a first and a second boundary extending in the Z direction, and the positions of a first volume extending in Z disposed between the first and second boundaries; - determine the positions of a second volume generated by extending the first volume in the X-direction to both the first and the second YZ boundary; - determine a first visualization parameter for a plurality of time intervals from the time-variant parameters at a plurality of positions in the first volume; - determine a second visualization parameter from the time-variant parameters at a plurality of positions in the second volume, and - a visualization display configured to - display a first representation showing the first visualization parameter at the plurality of time intervals, and - display a second representation showing the first and second visualization parameters. - display a first representation showing the first visualization parameter at the plurality of time intervals, and - display a second representation showing the first and second visualization parameters.