An ablation catheter apparatus is disclosed that includes an elongated body member, a basket including a plurality of radially expanding splines and a first electrode located on one of the radially expanding splines, the first electrode configured to apply energy to tissue adjacent to the radially expanding splines during an ablation procedure. At least one of the radially expanding splines includes at least one aperture, a lumen, an optical emitting element inside the lumen and an optical receiving element inside the lumen. The optical emitting element is configured to emit optical radiation through the aperture and into adjacent tissue during the ablation procedure while the optical receiving element is configured to collect optical radiation through the aperture during the ablation procedure, the optical radiation indicating characteristics of adjacent tissue during the ablation procedure.
