A panel for an electromagnetic shield includes a light-weight, porous, electrically-conductive, fluid-permeable planar core layer defined between generally parallel first and second surfaces and a first face sheet laminated to the first surface of the core layer with rigidity properties superior to the rigidity properties of the core layer. A first embodiment comprises a specially configured balloon catheter and extracorporeal pump, wherein the pump operates in a once-through fashion or alternating volume displacement mode. The housing is provided with push-buttons capable of releasing the lens assembly from the retracted position.