Assemblies are provided comprising a stent and a sensor positioned on andor in the stent. The method of encoding based on intra prediction includes predicting a current block by searching for a pre-encoded area in a current picture using pre-encoded pixels adjacent to the current block, and intra prediction encoding the current block so that information indicating that the current block is intra predicted via the predicting of the current block is included. The net retardance of the system is less than the sum of the retardance contributions of the respective optical elements as the elements are oriented such that the intrinsic birefringences of the individual elements cancel each other out. , a diacetylene or a radiochromic dye, a polymeric binder and optionally a shelf life extender or an activator. A trocar having an elongate trocar body is positioned to extend through the cannula body.