Design of a Flow Phantom for the Evaluation of Quantitative ICG Fluorescence Angiography

Fluorescence video angiography is used in neurosurgery to intraoperatively monitor the vascular function, namely the blood flow. This is done by injecting the dye Indocyanine green (ICG) intravenously. After excitation by a near-infrared light source, the fluorescence signal is captured by a camera system. The recorded signal is used to qualitatively assess the vascular function during the intervention. This provides the surgeon with an immediate feedback of the quality of his surgery. Nevertheless, this qualitative assessment needs to be extended and a quantitative value should be calculated to assist the surgical staff. This step requires a standardized and validated test setup mimicking cerebral vessels for studies, such as measurement of the flow and flow profile. This includes the confirmation of the suitability of the investigation site in the phantom. Therefore, a flow phantom is designed according to the requirements and set up. The requirements include a variable diameter of the vessel mimicking tubes, variable flow range within the clinical relevant range, a handy and precise injection system with an initial ICG concentration which minimizes quenching effects, a non-toxic and low cost blood analogue with similar viscosity as human blood and finally a last requirement which need more explanation. ... mehrReal blood should not be used due to the contamination of the pump, so water is used as flow media. But the ICG is dissolved in a protein solution and should be surrounded by a protein solution to ensure mixing and diffusion into the same solution media, so the ICG should not get into touch with the flow media water. The investigation sites are given in the ranges which are confirmed to be suitable. The flow phantom provides a consistent testing environment and will be used to conduct studies analyzing the suitability of different methods to assess the flow by fluorescence imaging.