A mapping catheter is positioned in a heart chamber, and active electrode sites are activated to impose an electric field within the chamber. In one example approach, a method comprises, during a diurnal condition, providing a first amount of venting to a fuel vapor canister, and during a purge condition, providing a second amount of venting to the fuel vapor canister, where the second amount is greater than the first amount. Then, that thread is used to execute the JAVA application. Other variations and implementations are also described. 4D-DSA images can also be generated by selectively combining a time-series of 2D-DSA images generated from individual projections from a rotational x-ray acquisition with a 3D image reconstructed from substantially all of the projection views acquired during the rotational x-ray acquisition.