Abstract
<title>Abstract</title> <p> <bold>Introduction</bold> The introduction of pulse modulation technologies has expanded the versatility of high-power Holmium lasers. Magneto (M-Ho:YAG) pulse modulation provides low peak power and improved dusting characteristics, while Virtual Basket (VB) may enhance fragmentation efficiency in selected cases. However, the factors prompting intraoperative transition between these modalities remain poorly defined. This study aimed to identify the preoperative and intraoperative variables associated with the need to switch from M-Ho:YAG to VB during flexible ureteroscopy. <bold>Methods</bold> A multicenter observational study analyzed 400 consecutive patients undergoing retrograde intrarenal surgery between January 2025 and March 2026 using the Cyber Ho™ 150W platform. Lithotripsy was initiated with M-Ho:YAG in all cases. Patients were categorized into M-Ho:YAG-only (n=301) and M-Ho:YAG+VB (n=99) groups according to intraoperative pulse modulation strategy. Demographic, stone-related, anatomical, and procedural variables were evaluated. <bold>Results</bold> Mean stone volume was 1804 mm³ and mean stone density was 938 HU. Among the 400 procedures, 99 patients (24.8%) required intraoperative transition from M-Ho:YAG to VB. Stone volume demonstrated a strong correlation with pulse modulation switching (r=0.69), indicating that larger stone burdens were more likely to require VB support. Lower pole stones represented the most frequent anatomical location among patients requiring modulation change. Furthermore, higher stone density was associated with an increased likelihood of switching, suggesting reduced dusting efficiency of low peak-power settings in harder stones. <bold>Conclusions</bold> Large stone burden, lower pole location, and high-density calculi appear to be the main predictors of intraoperative transition from M-Ho:YAG to VB. These findings support a dynamic pulse modulation strategy tailored to stone characteristics to optimize lithotripsy efficiency and procedural performance. </p>