RETURN TO ABSTRACT LISTING


Objective:
Intrathymic injection of genetically modified progenitor cells is a unique method for assessing cell longevity in vivo. Ultrasound-guided hand injections is one of the most accurate and efficient methods for introducing modified cells into a mouse thymus. This technique involves the use of a free hand method, whereby the investigator must control the ultrasound probe along with the needle, as is typically done in humans for percutaneous ultrasound-guided, fine-needle aspirations and biopsies. The technique of free-hand intrathymic injection has several advantages over machine-guided injections, including increased speed, adaptability for aged and immunosuppressed mice, and higher accuracy. However, the method requires a relatively high level of expertise to achieve accurate and precise injections. The level of expertise available may vary depending on the institution, and training individuals can quickly become costly and time consuming. Therefore, we propose a solution using a 3D-printed mouse model to train individuals in free-hand percutaneous ultrasound-guided injections. The use of on-site, 3D-printed models for educational purposes is becoming a widespread technique for medical and scientific education. Three-dimensional printed anatomical models have been used for training practitioners in percutaneous thyroid biopsies, vascular access techniques, and for neonatal sonography, among others. With our proposed 3D-printed mouse model, we can teach and train personnel how to 1) perform simulated ultrasound on the model, 2) learn how to guide a needle into the model, and 3) place the needle tip into a simulated mouse thymus.

Materials and Methods:
A digital model of a young mouse was created based on imaging of a live mouse. This model was based on the supine position of a mouse on a procedural stage. Three-dimensional modeling and CAD software was then used to create a mold of the mouse. This mold was then manufactured using 3D printing. The mold was used to create a soft, flexible, ultrasound-compatible replica of the mouse model using household products (gelatin and psyllium husk). Ultrasound of the mouse model was performed, and image-guided injections were attempted on a simulated target (thymus).

Results:
The 3D-printed mouse mold was an effective method for creating an ultrasound-compatible mouse phantom. The mouse phantom was to scale, and creating multiple phantoms from one mold was easy and straightforward. The ease of needle visualization and placement in the model was similar to that of live mice. Trainees without much prior experience in ultrasound-guided interventions were afforded time and a no-risk environment to practice the procedure.

Conclusion:
A 3D-printed ultrasound mouse phantom is an effective tool for trainees to gain skill and experience in ultrasound-guided interventions for research purposes, specifically percutaneous intrathymic injections. This method has multiple benefits over a training schema involving live mice including a more humane method, which eliminates morbidity and mortality to live mice, decreased cost, and easy scalability.