Ultrasound Simulation Notes

Ultrasound Simulation: Rationale and Core Concepts

• Simulation in medical education imitates real scenarios, processes, pathologies, or procedures in a safe, controlled environment to train and evaluate learners.
• Benefits demonstrated include improved educational outcomes and clinical performance, with standardized assessment of skills.
• Medical education has borrowed simulation from high-stakes fields (aviation, military) where experiential learning is central.
• In emergency ultrasound, simulation is widely used; AIUM strongly recommends simulation to train learners in all aspects of ultrasound training, while ACEP supports simulation for emergency physicians.
• Three major POCUS competency microskills can be trained with simulation: image acquisition, image interpretation, and medical decision-making.
  • Simulation tends to be most effective for microskills of image acquisition and interpretation, which require tactile, visual, and haptic feedback and repetitive practice.
  • Image acquisition benefits from repetitive digital/physical feedback to build psychomotor skills and reduce cognitive load during scanning.

$ext{POCUS competency} = ext{image acquisition} + ext{image interpretation} + ext{medical decision-making}$

Roles of Simulation in Training and Deliberate Practice

• Deliberate practice: focused, goal-directed practice with immediate feedback to improve performance.
• Simulation supports deliberate practice for high-risk/low-frequency, invasive, or sensitive exams (e.g., transvaginal pelvic ultrasound, scrotal ultrasound) in a controlled setting.
• Simulation allows exposure to rare/pathologic presentations and less commonly encountered pathologies.
• Procedural skills benefit especially from simulation due to the need for haptic feedback and muscle memory (e.g., ultrasound-guided procedures, regional anesthesia).
• During COVID-19, simulation addressed reduced in-person training and patient contact, proving particularly useful for maintaining ultrasound education.

Effectiveness, Transfer, and Assessment

• Simulation can be as effective as or augment traditional hands-on education in teaching basic ultrasound skills; some studies show immediate and sustained improvement in objective ultrasound skills with simulation plus traditional training.
• Some studies show no added benefit over traditional live-model teaching, but still demonstrate simulation can augment learning.
• Transfer of simulation-acquired skills to clinical performance is variable; some evidence supports improved clinical performance immediately and over time, while others show limited or no additional benefit.
• Use of simulation for evaluation/assessment is evolving; some tools exist with initial reliability/validity for specific ultrasound applications, but no universally validated universal assessment tool currently.
• Limitations of simulation for evaluation: lack of a fully validated universal assessment tool; feedback quality varies; real-time, targeted feedback may be less than in live education.

Limits and Practical Considerations

• Limitations: simulation will never be perfectly identical to real patient scenarios; skills may not fully transfer to clinical settings.
• Feedback gap: some simulators provide immediate feedback, but high-quality learning often requires expert, targeted feedback from educators.
• Costs and resource allocation: cost savings may arise from more efficient scans by experienced learners, but it is not guaranteed that savings translate to emergency medicine settings.
• Evidence base in emergency ultrasound transfer is more limited than in some other areas; ongoing research is needed to quantify transfer and long-term retention.
• Ethical and practical implications include ensuring patient safety during training and balancing learner exposure with patient care needs, especially in high-stakes environments.

Ultrasound Simulation Equipment: Overview

• Equipment can be categorized by fidelity: low-fidelity vs high-fidelity.
• Low-fidelity simulators are static models requiring an ultrasound machine to image the simulated model.
• High-fidelity simulators include lifeform manikins, a mock ultrasound probe, and a computer that generates images based on probe location relative to the model.
• High-fidelity systems may use RFID or electromagnetic tracking to connect probe position with simulated imaging.
• Both types can be used for various ultrasound applications, including vascular access, regional anesthesia, thoracentesis, paracentesis, and more.

Table 13.1: Low- vs High-Fidelity Simulators

• Low fidelity:
  • Requires a separate ultrasound machine (static imaging).
  • Imaging findings: few, static.
  • Supplied: Homemade or commercial.
  • Cost: $-$
• High fidelity:
  • Does not always require a separate ultrasound machine (integrated systems can include a computer-based simulator).
  • Imaging findings: multiple, dynamic.
  • Supplied: Commercial (comprehensive products).
  • Cost: $-$$$
• Imaging and realism: Low fidelity provides basic, static representations; high fidelity provides dynamic interaction and realistic image acquisition under varied clinical scenarios.

Low-Fidelity Ultrasound Simulation Equipment

• Focus on ultrasound-guided procedures with static imaging targets (e.g., central line placement, peripheral IV access, lumbar puncture).
• Task trainers often have removable components to allow cleaning or replacement after multiple invasive attempts.
• Some low-fidelity models simulate the imaging changes before, during, and after a procedure (e.g., fluid targets during chest/abdominal procedures).
• General trend: low-fidelity models are accessible, modifiable, and suitable for repetitive practice, especially in resource-limited settings.
• Widely used commercial options include Simulab and Blue Phantom products for various procedures.
• Homemade gel phantoms are common alternatives with materials such as gelatin, ballistic gel, meat-based substitutes, agar, and paraffin wax.
• Preference studies suggest learners may favor homemade phantoms for realism and cost-effectiveness.

Homemade Phantoms: Materials, Preparation, and Pros/Cons

• Table 13.2 summarizes materials and trade-offs:
  • Gelatin
  • Benefits: Easy to mold into shapes; quick preparation.
  • Limitations: Limited shelf life; can melt with heat.
  • Ballistic gel
  • Benefits: Long shelf life; reusable; can mold to various shapes.
  • Limitations: Requires refrigeration; potential for melting other components.
  • Meat-based or meat substitutes
  • Benefits: Very tissue-like echotexture; similar appearance to human tissues.
  • Limitations: Four+ hour preparation; potential spoilage; sterilization considerations.
  • Agar
  • Benefits: Quick preparation; readily available; long shelf life; reusable.
  • Limitations: Four+ hour preparation; can melt other components; may crack easily.
  • Gel wax
  • Benefits: Can mold to shapes; long shelf life; reusable.
  • Limitations: Four+ hour preparation; potential for separation or echotexture issues.
• General considerations:
  • Homemade phantoms can be tailored to specific educational aims and exam scenarios.
  • They are valuable for ultrasound-guided procedures and soft-tissue pathology identification.
  • A range of materials can be used to adjust echotexture, realism, and target visibility.
  • Example: ocular phantom recipe illustrates a practical, ready-to-use model with step-by-step preparation and a method to simulate pathology (e.g., vitreous hemorrhage).

Table 13.2: Example Homemade Phantom Materials (Details Above)

• Gelatin: quick to prepare; moldable; limited shelf life; requires refrigeration to prevent spoilage.
• Ballistic gel: longer shelf life; good tissue fidelity; needs refrigeration; may interfere with some components if melted.
• Meat-based substitutes: high tissue fidelity; longer preparation or handling considerations; potential spoilage; refrigeration needed.
• Agar: good shelf life; easy to mold; long-lasting; prep time is non-trivial.
• Gel wax: stable; long shelf life; can be molded; may have echotexture limitations.
• Common themes: realism varies by material; preparation time, shelf life, and need for refrigeration/sterilization are important planning factors.

3D Printing and Additive Manufacturing

• 3D printing enables rapid development of low-fidelity ultrasound simulators tailored to specific clinical scenarios.
• Requires design files (e.g., STL) and access to 3D printers and printing material.
• Applications include:
  • Dislocated shoulder embedded in sonolucent gel for glenohumeral joint imaging.
  • 3D-printed trachea with a ballistics gel covering to simulate airway landmarks.
  • 3D-printed erector spinae fascia block models.
• Additive manufacturing labs can assist with printer specifications, materials, and design adaptation.
• Commercial0grade 3D-printed models can be used in conjunction with phantoms and gel layers to enhance realism.

High-Fidelity Ultrasound Simulation Equipment

• High-fidelity systems: computer-based simulators, mock probes, and lifeform mannequins.
• Imaging: The computer generates ultrasound images based on detected probe location relative to the model, often using RFID or magnetic tracking.
• Probe: Mock transducer includes accelerometer, gyroscope, and magnetometer to capture orientation and motion.
• RFID-based approaches enable ultrasound-like scanning on live models or mannequins; tags placed on the model interact with a reader to trigger predefined clips or images.
• Benefits: Dynamic, variable imaging; capability to simulate a wide range of pathologies and patient factors; some systems support virtual reality environments and standardized checklists.
• Commercial examples: HeartWorks, ScanTrainer, pelvic ultrasound simulators for TA/TV scanning, etc.
• Custom implementations: An RFID-based setup can be assembled using USB RFID antenna, tags, and open-source software to trigger simulated images.

RFID-Based and Computer-Integrated Ultrasound Simulation

• RFID-based simulation uses an RFID probe with a reader to map probe position to an embedded computer-generated image.
• Pathology and normal findings can be adjusted in severity to create a spectrum of training scenarios.
• The system can be built from readily available components: RFID tags, USB-based RFID antenna, and open-source software.
• This approach allows simulated scanning with realistic feedback in environments where a full commercial high-fidelity system is not available.

Blended Ultrasound Simulation Environment

• A reproducible training environment can be created with minimal equipment: instructor, learner, ultrasound model, ultrasound machine, and a library of pathological images.
• The instructor can outline clinical scenarios; the learner performs image acquisition; the instructor poses questions about the findings and clinical decisions.
• Blended environments leverage a mix of hardware and software to achieve deliberate practice without relying solely on high-cost simulators.

3D Printing and 3D-Printed Models: Practical Notes

• 3D printing requires:
  • Design files (STL format).
  • Access to 3D printers and compatible materials.
  • Repositories of printable designs and software to prepare designs for printing.
• Examples from the literature:
  • Dislocated shoulder embedded in sonolucent gel for glenohumeral joint scanning.
  • 3D-printed trachea model covered with ballistics gel for airway landmark localization.
  • 3D-printed erector spinae fascial plane block model.
• Institutions often have additive manufacturing labs to facilitate collaboration on educational models and to adapt models to local needs.

Table 13.3: Selected Internet Resource Lists

• ACEP Ultrasound Section Simulation Subcommittee: Compendiums of high- and low-fidelity simulators; guide to 3-D printing ultrasound models; DIY ultrasound phantom compendium.
• DIY Ultrasound Phantom Compendium: Resources for creating homemade phantoms and model designs.
• Aliem (Academic Life in Emergency Medicine) DIY Ultrasound Model Compendium: Instructions and pictures for building ultrasound phantoms.
• Zedu DIY Ultrasound Phantom List: Additional community-contributed phantom designs and tutorials.
• Other listed resources include general lists of phantoms by type and hands-on design ideas.

Key Recommendations

• Ultrasound simulation is extremely useful for skill practice and competency assessment.
• Simulation should complement a multimodal approach to ultrasound education (i.e., combine simulations with live models, clinical practice, and didactics).
• A broad range of resources exists to support ultrasound simulation (see Table 13.3). Leveraging these resources can expand access and improve training quality.

Practical Implications and Real-World Relevance

• Simulation supports safe, repeated practice in high-risk or low-frequency scenarios without patient exposure.
• It can help address educator shortages by enabling scalable training experiences that do not solely depend on in-person experts.
• In resource-limited settings, low-fidelity simulators and homemade phantoms can provide meaningful skill development at lower cost.
• Blended and modular approaches allow programs to tailor training to local needs, budgets, and available equipment.

Summary of Takeaways

• Simulation in ultrasound training is supported by major professional bodies and improves educational outcomes and clinical performance when used appropriately.
• The microskills of image acquisition and interpretation are particularly amenable to simulation-based deliberate practice.
• A spectrum of simulation modalities exists:
  • Low-fidelity task trainers for basic imaging and procedures (static imaging).
  • High-fidelity simulators with dynamic imaging, RFID/motion tracking, and computer-based scenarios.
  • 3D-printed models and homemade phantoms to customize echotexture and anatomy.
• Blended environments combining equipment, scenarios, and expert feedback optimize learning.
• Assessment tools for simulation are evolving, with ongoing research needed to establish universally validated measures.
• Practical recommendations emphasize a multimodal approach and leveraging available resources (Table 13.3).

Tables (Condensed Reference)

• Table 13.1: Low vs High-Fidelity Simulators
  • Low fidelity: separate ultrasound machine required; few, static imaging; cost $-$; originated from homemade/commercial sources.</li> <li>High fidelity: no separate machine required (integrated systems); multiple, dynamic imaging; cost$$-$$; commercial products common; may use RFID-based interfaces.
• Table 13.2: Homemade Phantoms by Material
  • Gelatin, Ballistic gel, Meat-based substitutes, Agar, Gel wax: lists benefits/limitations, preparation time, shelf life, echotexture adjustability, and appearance considerations.
• Table 13.3: Internet Resources
  • ACEP simulation subcommittee, DIY phantom compendia (DIY Ultrasound Phantom Compendium), Aliem, Academic Life in EM, Zedu list, plus other community resources.

Notes on Figures Mentioned

• Fig. 13.1: Visual distinction between low-fidelity task trainers (require separate ultrasound machine) and high-fidelity task trainers (include a mock probe and computer-based system).
• Fig. 13.2: Examples of low-fidelity ultrasound simulators (e.g., Simulab, Blue Phantom, homemade gel phantoms).
• Fig. 13.3: Ocular phantom recipe (detailed step-by-step preparation).
• Fig. 13.4: 3D-printed models (shoulder joint embedded in gel; trachea with gel layer; erector spinae block model).
• Fig. 13.5: High-fidelity task trainers (e.g., Heart Works, ScanTrainer, TA/TV pelvic ultrasound simulators).
• Fig. 13.6: RFID-based setup: RFID antenna embedded in a 3D-printed ultrasound probe model, with RFID tags triggering images on a computer.

References (Representative Examples)

• Lewiss et al. 2014; J Ultrasound Med: Point-of-care ultrasound education and simulation.
• Damewood et al. 2018; J Clin Ultrasound: Ultrasound simulation utilization among POCUS users.
• AIUM safety guidelines for ultrasound education (nonpregnant and pregnant participants).
• ACEP Ultrasound Guidelines (Emergency, POCUS, and Clinical Ultrasound Practices).
• Tolsgaard et al. on sustained effects of simulation-based ultrasound training.
• Additional sources embedded in the text discuss cost, transfer of skills, and educational outcomes.

End of Notes