Abstract. Intraoperative applications of near-infrared (NIR) fluorescent contrast agents can be aided by instrumentation capable of merging the view of surgical field with that of NIR fluorescence. We demonstrate augmented microscopy, an intraoperative imaging technique in which bright-field (real) and electronically processed NIR fluorescence (synthetic) images are merged within the optical path of a stereomicroscope. Under luminance of 100,000 lx, representing typical illumination of the surgical field, the augmented microscope detects 189 nM concentration of indocyanine green and produces a composite of the real and synthetic images within the eyepiece of the microscope at 20 fps. Augmentation described here can be implemented as an add-on module to visualize NIR contrast agents, laser beams, or various types of electronic data within the surgical microscopes commonly used in neurosurgical, cerebrovascular, otolaryngological, and ophthalmic procedures.
Background
Preservation of adequate blood flow and exclusion of flow from lesions are key concepts of vascular neurosurgery. Indocyanine green (ICG) fluorescence videoangiography is now widely used for intraoperative assessment of vessel patency.
Objective
Here we present proof of concept investigation of fluorescence angiography with augmented microscopy enhancement (FAAME): real-time overlay of fluorescence videoangiography within the white light field-of-view of conventional operative microscopy.
Methods
The femoral artery was exposed in seven anesthetized rats. The dissection microscope was augmented to integrate real-time electronically processed near-infrared (NIR) filtered images with conventional white light images seen through the standard oculars. This was accomplished using an integrated organic light emitting diode display to yield superimposition of white light and processed NIR images. ICG solution was injected into the jugular vein and fluorescent femoral artery flow was observed.
Results
FAAME was able to detect ICG fluorescence in a small artery of interest. Fluorescence appeared as bright green signal in the ocular overlaid with the anatomical image and limited to the anatomical borders of the femoral artery and its branches. Surrounding anatomical structures were clearly visualized. Observation of ICG within the vessel lumens permitted visualization of the blood flow. Recorded video loops could be reviewed in offline mode for more detailed assessment of the vasculature.
Conclusion
The overlay of fluorescence videoangiography within the field-of-view of the white light operative microscope allows real-time assessment of the blood flow within vessels during simultaneous surgical manipulation. This technique could improve intraoperative decision-making during complex neurovascular procedures.
This paper presents a feasibility study of the application of giant magneto resistive (GMR) sensors in detecting motion of slow moving fluids. A motivating application for the proposed effort is the development of a smart catheter capable of monitoring the amount of body fluid drained from the ventricles of the brain. Microfabricated ferromagnetic flaps are used to detect motion of the surrounding fluid. The deflection of the flaps is detected by an ultrasensitive GMR sensor placed outside of the lumen of the catheter. Numerical and experimental results are provided demonstrating a resolution of 1.4 mL/h. Numerical analysis of the fluid past the sensing element show an optimal hinge length of the flexible flaps, as well as a significant increase in sensitivity with reduction of the by-pass gap to ∼50 µm. The effect of electro-magnetic interference and other sources of low-frequency noise (drift) has also been investigated. The results from the study are used to derive a set of design rules that may lead to the successful development of a smart catheter. [2014-0148] Index Terms-Liquid flow sensor, GMR sensor, smart catheter, ventriculoperitoneal (VP) shunt.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.