Lunch box and fruits as a simulator for teaching basic physics of ultrasound: A mixed research methods study

Aim: To develop and evaluate a practical, low-cost ultrasound training simulator for teaching basic ultrasound physics and knobology, including probe orientation, tissue impedance, essential hand movements, and recognizing image artifacts while observing scanned objects. Methods: The simulator consists of (1) one complete lemon, (2) half a lemon, (3) half a kiwi fruit, and (4) an avocado pit. These objects were secured inside a plastic box using screws, nails and double-sided foam tape, after which the box was filled with water. The estimated total cost was less than 15 US dollars. The simulator was prospectively tested to teach basic ultrasound physics during the period of 4th January 2021 till 14th October 2021 on 59 undergraduate junior surgical clerkship students, who had no prior exposure to ultrasound. Quantitative feedback was collected through a Likert-scale questionnaire evaluating educational value, skill acquisition, and user satisfaction. Qualitative data were obtained from open-ended questions. Descriptive statistics were used for quantitative responses, while inductive thematic analysis was applied to qualitative comments. Results: 58 students filled the questionnaire (response rate of 98.3%), 57 of them (98.3%) recommended the simulator to peers, and all assessed items received the highest median rating (5 out of 5), including items assessing conceptual understanding, procedural skills, and enjoyment. Thematic analysis provided three major themes: Learning Enhancement, Engagement and Motivation, and Training Limitations. Students reported improved understanding of ultrasound physics, artifact recognition, and probe handling. The simulator was described as engaging and enjoyable, promoting self-directed learning. However, students noted limitations related to session duration, realism, and the need for additional practice opportunities. Conclusion: The proposed low-cost ultrasound simulator was highly rated for its educational value and engagement potential. Qualitative insights complemented these findings by revealing strong learner enthusiasm. Expanding session duration and increasing clinical fidelity may further enhance its utility.