Vascular gene therapy is an exciting approach for the cure and mitigation of atherosclerosis and related cardiovascular diseases. Monitoring transgene expression using noninvasive imaging techniques is a necessary complement for the success of clinical gene therapy. Optical imaging based on fluorescence signal detection from biomarker genes holds promise in the area. Green fluorescent protein (GFP) is one of the most commonly used biomarkers for the purpose. We have developed a novel percutaneous optical imaging system to track fluorescent marker expression from vasculatures following GFP gene transfer. To investigate the performance of the percutaneous system we performed experiments on porcine meat slabs. A polyethylene capillary tube was used to mimic the vessel geometry beneath a tissue layer. Under ultrasound-guidance, we placed the percutaneous optical probe nearby the 'vessel'. After obtaining control optical images of the 'vessel' filled with phosphate buffered saline (PBS), we imaged the same tube again, in which the PBS was replaced by human 293T cells transduced with GFP-carrying lentivirus. The results showed higher bright signal detected for the tube with GFP/sup +/ cells than that with PBS. This study demonstrates the capability of the system and provides insights for improvements of the current system.