def ListBeams(plan_dataset):
    """Return a string summarizing the RTPLAN beam information in the dataset"""
    lines = ["{name:^13s} {num:^8s} {gantry:^8s} {ssd:^11s}".format(
        name="Beam name", num="Number", gantry="Gantry", ssd="SSD (cm)")]
    for beam in plan_dataset.BeamSequence:
        cp0 = beam.ControlPointSequence[0]
        SSD = float(cp0.SourcetoSurfaceDistance / 10)
        lines.append("{b.BeamName:^13s} {b.BeamNumber:8d} "
                    "{gantry:8.1f} {ssd:8.1f}".format(b=beam,
                                        gantry=cp0.GantryAngle, ssd=SSD))
    return "\n".join(lines)