# Low-Cost and Easily Fabricated Ultrasound-Guided Breast Phantom for Breast Biopsy Training
## 2 Materials and Methods
### Breast Hantom Validation Workshop  
A workshop was organized to evaluate the effectiveness of the developed single-layered phantom in improving participants' core needle biopsy skill (Figure 4a). A clinical ultrasound system with an 8 MHz high-frequency linear probe, core needles and a gelatin-based breast phantom (Figure 4b) were prepared. Six participants with different experience levels were invited to perform preinstructional biopsy. The including criteria was physicians who are in their residency training, fellows, or attendings. The workshop has no specific excluding criteria. The participants were asked to take an experience level questionnaire (Appendix A) to determine if they were inexperienced, moderately experienced, or experienced. We ensured that all three levels of participants were recruited in this workshop. An experienced doctor then delivered a hands-on tutorial to the participants. The participants were given 10 min to practice the biopsy as many times as desired. A postinstructional biopsy was then performed by the participants after their practice session.  
At the beginning of the workshop, the participants' levels of experience with ultrasound-guided core needle biopsy were assessed through three questions, resulting in a score range of 0-7. The participants were then categorized as inexperienced (score of 0), moderately experienced (1-4) or experienced (5-7), see Appendix A.  
The effectiveness of the gelatin-based breast phantom at improving the participants' confidence in performing challenging ultrasound-guided core needle biopsy was assessed through a self-assessment questionnaire (Appendix B). Before the simulation training, each participant completed a questionnaire scored using a 10-point Likert scale to assess his or  
Figure 4: (**a**) Workshop for evaluating the efficiency of the phantom in improving core needle biopsy skill of participant. (**b**) Single-layered gelatin-based phantom (glandular tissue embedded with simulated tumors).  
her confidence in performing the ultrasound-guided breast biopsy without causing chest wall injury (Appendix C).  
During the practical session, a participant's skill level of performing core needle biopsy was evaluated by comparing their preinstructional and postinstructional scores. A total of two points could be awarded for each needle biopsy operation if the biopsy was found to be a success in ultrasound imaging (+1) and a sufficient portion of the simulated malignant tumor had been retrieved in the biopsy needle (+1). However, a through-and-through puncture or penetration of the phantom backing was considered a chest wall hit, which resulted in the deduction of one point (\(-1\)). The participants were encouraged to perform as many practice biopsies as necessary before and after instruction. The percentage score was the total score of the participant divided by the highest possible score based on the number of biopsies performed. The percentage scores of participants before and after instruction were compared. The percentage mean scores of preinstructional and postinstructional tests were plotted on standard distribution curves.  
After the simulation training, each participant repeated the questionnaire to assess their confidence in performing the ultrasound-guided breast biopsy. The satisfaction of the participants with the gelatin-based breast phantom was evaluated. Feedback was collected regarding the ultrasound image quality produced by the phantom and haptic feedback of the phantom that the participants received during core needle placement (Appendices D and E). Through this survey, the aspects of the phantom that residents valued the most could be better understood.  
A further study on the multilayered gelatin-based phantom (fat tissue, glandular tissue embedded with simulated tumors) was conducted. The ultrasound images of embedded objects and simulated tissue layers were examined. The user feedback was also collected.