Author: Michael B. Altman, Marlene Campos Guerrero, Stephanie Markovina, Aaron Silvus 👨🔬
Affiliation: Washington University School of Medicine 🌍
Purpose: Currently, fluid injections or needle biopsies in small animals are conducted with limited optical guidance introducing an inherent risk of infecting or injuring the animal and limits precision. Integrating optical guidance into these procedures may minimize the risk of unduly injuring surrounding tissue and increase the precision and accuracy of in vivo studies.
Methods: The speculum was designed using Solid Edge and printed using a resin-based stereolithography 3D-printer. The speculum body was designed as a vaginal speculum for mice consisting of a tapered conical structure with an opening on each end. Length markings are integrated onto the device both inside and outside allowing for accurate and precise movements of the speculum and needle. A digital otoscope was used to validate the image-guidance aspect of the speculum via visual inspection of the cervix. Design alterations were needed based on initial studies in mice.
Results: The speculum was fabricated, and internal diameters were verified for both precision and accuracy across multiple prints using needle gauges. The focal length of the digital otoscope used is fixed requiring design considerations around the placement and angle of the needle port such that there is no interference between the needle and camera. A new needle syringe was chosen to reduce the injected volume which required alteration of the needle port angle. The change in syringe necessitated changing the angle of the needle port as the early speculum design pared with the new syringe bypassed the cervix and guided the needle into the perineal region. In hopes of further reducing this risk, a needle stop was added.
Conclusion: The integration of real-time optical guidance with needle-based interventions on small animals using a novel 3D-printed speculum is feasible. Ongoing studies are testing the use of the image-guided method for increased accuracy and safety for cervical tumor implantation.