Fluorescence Angiography for Evaluation of Aneurysm Perfusion and Parent Artery Patency in Rat and Rabbit Aneurysm Models
July 24th, 2019
We present a protocol to efficiently evaluate aneurysm perfusion and vessel patency of sidewall aneurysm in rats and rabbits, using fluorescein-based fluorescence video angiography (FVA). With a positive predictive value of 92.6%, it is a simple but very effective and economical method with no special equipment required.
This method is a reliable and easy technique for visualizing real-time blood flow in aneurysms and vessels and can be used in different animal models. The main advantage of this technique is that it facilitates visualization of blood flow during surgery without requiring any expensive devices or extensive surgery. Before beginning the procedure use black tape to secure a green bandpass filter to act as an excitation filter onto a flashlight.
And check that the flashlight only emits blue light. Equip the camera with a green bandpass filter to function as an emission light filter. Only green light should now be able to pass through.
Then, disinfect the work space with a disinfectant solution and cover the table with sterile drapes to prevent contamination. To perform fluorescein video angiography or FVA in a rabbit confirm that the anesthetized animal does not respond to pain stimulus before positioning the rabbit in the supine position. Shave the neck around the sternocleidomastoic muscle.
Focus the camera on the dissected artery and use aluminum foil to cover a five milliliter syringe containing 100 milligrams/milliliter of fluorescein sodium. Turn off the lights as much as possible and inject 0.3 milliliters/kilogram of fluorescein sodium intravenously into the injection port of the catheter. Next, flush the syringe with 0.5 milliliters of saline solution to ensure that all of the dye has been injected.
And immediately illuminate the surgical field with the modified flashlight. As soon as the light is turned on begin filming with the modified camera. Blood flow should be visible within a few seconds of the injection.
For macroscopic analysis of the vessel after angiography resect the aneurysms and the parent artery complex in follow-up animals, or perform visual confirmation of flow by observing the filling of the aneurysm and/or bypass after removal of the temporary clips. In this representative study, FVA was able to be performed in eight out of 10 rabbits. Of the 16 aneurysms identified in the eight rabbits two aneurysms demonstrated persistent perfusion of the parent artery, while FVA identified five cases with residual perfusion.
14 rabbit aneurysms exhibited no residual perfusion macroscopically, while 11 were subsequently detected using FVA. Residual perfusion was observed macroscopically in 23 of 48 rats, and the other 25 rats showed no macroscopic signs of residual perfusion. 22 of the 23 aneurysms without macroscopic perfusion were then confirmed using FVA.
Overall, 25 of 27 rabbit and rat combined cases could be confirmed, resulting in a positive predictive value of 92.6%a sensitivity rate of 100%and a specificity of 94.1%The most important things when attempting this procedure are to dissect the vessels properly and to work in a darkened room when administering and visualizing fluorescein. This procedure can be used in any animal model to evaluate blood flow in any visible vessel.
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Overview
This article presents a protocol for evaluating aneurysm perfusion and vessel patency using fluorescein-based fluorescence video angiography (FVA) in animal models (rats and rabbits). The method is noted for its high positive predictive value of 92.6%, and its simplicity and cost-effectiveness are emphasized, requiring no special equipment.
Key Study Components
Area of Science
- Neuroscience
- Vascular biology
- Fluorescence imaging
Background
- Aneurysms pose significant clinical challenges in terms of perfusion assessment.
- Existing methods may require expensive equipment and extensive surgical procedures.
- Fluorescein video angiography provides a solution for real-time visualization.
- The technique's versatility across different animal models is noteworthy.
Purpose of Study
- To develop a reliable method for visualizing blood flow in aneurysms.
- To evaluate vessel patency without the necessity of costly equipment.
- To provide a straightforward protocol that can be widely implemented in research.
Methods Used
- Fluorescence video angiography (FVA) was the main platform utilized.
- Animals used included rats and rabbits, specifically assessing blood flow during and post-surgery.
- No multiomics workflows were mentioned.
- The procedure involved anesthetizing animals, preparing the surgical site, injecting fluorescein sodium, and employing a modified camera setup.
- Key steps included ensuring minimal light during visualization and precise timing in image capture post-injection.
Main Results
- The method successfully visualized blood flow in 8 out of 10 rabbits and identified significant residual perfusion cases.
- Of 16 aneurysms assessed, 11 were detectable by FVA that had not been observed macroscopically.
- In rats, residual perfusion was confirmed in 22 of 23 aneurysms without visible macroscopic signs.
- Overall, a combination of 25 of 27 total cases showed confirmation of perfusion using FVA.
Conclusions
- This procedure demonstrates a strong capability for assessing aneurysm blood flow effectively.
- The application of FVA facilitates real-time surgical visualization and assessment of perfusion status.
- The implications extend to improved understanding and evaluation techniques for vascular conditions in research settings.
Frequently Asked Questions
Executive Industry Relevance
Fluorescence video angiography (FVA) provides a low-cost, equipment-free method for real-time assessment of aneurysm perfusion and parent artery patency in preclinical models. Its high sensitivity and specificity support reliable detection of residual perfusion, enabling early identification of incomplete occlusion in aneurysm models. This capability aids in mechanistic de-risking of vascular interventions by offering a quantitative, reproducible readout for preclinical evaluation of device efficacy and surgical technique.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of therapeutic hypotheses by visualizing blood flow dynamics in aneurysm models.
- Operational Value: Supports functional target validation through direct, real-time perfusion assessment without expensive imaging equipment.
Screening & Assay Development
- Scientific Value: Delivers quantitative, binary perfusion outcomes (present/absent) that can be standardized across studies.
- Operational Value: Facilitates assay readiness via simple fluorescein injection and modified flashlight/camera setup, promoting reproducibility.
Translational & Preclinical Research
- Scientific Value: Bridges discovery to preclinical validation by confirming aneurysm occlusion and parent artery integrity in rats and rabbits.
- Operational Value: Provides a translatable perfusion metric that aligns with clinical endpoints for aneurysm treatment evaluation.
Pipeline & Workflow Integration
FVA fits within the discovery continuum from early model validation to preclinical assessment, offering a perfusion-based readout that informs go/no-go decisions prior to lead optimization.
- Discovery Biology: Supports hypothesis testing by revealing residual perfusion that may indicate treatment failure in aneurysm models.
- Screening: Enables standardized, reproducible assessment of vessel patency across multiple animals and timepoints.
- Analytics: Generates clear perfusion readouts (macroscopic and FVA-confirmed) that allow comparison between control and intervention groups.
- Translational Research: Connects preclinical perfusion data to clinical relevance by validating occlusion in anatomically relevant aneurysm models.
- Enterprise Reuse: Represents a platform-agnostic, low-barrier technique applicable across vascular research programs.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence in aneurysm models by detecting perfusion missed by macroscopic inspection.
- Operational Value: Requires only fluorescein sodium, a flashlight, and camera filters, enabling low-cost, high-throughput use.
- Strategic Value: Reduces biological risk in preclinical programs by improving accuracy of occlusion assessment.
- Portfolio Impact: Supports risk-adjusted prioritization of aneurysm interventions based on validated perfusion outcomes.
Implementation Considerations
- Requires expertise in microsurgical vessel dissection and aneurysm model handling.
- Necessitates a darkened environment and modified flashlight with blue excitation and green emission filters.
- Demands standardization of fluorescein dosage (0.3 mL/kg) and saline flush for consistent signal.
- Involves adaptation considerations for different vessel sizes and species-specific anatomy.
- Limited to superficial or accessible vessels due to reliance on external light penetration.
