Optical Motion Capture-Assisted Ultrasound for Pediatric ESWL

A Randomized Controlled Study on the Localization Efficiency of Optical Motion Capture-Assisted Ultrasound Pre-localization in Pediatric Extracorporeal Shock Wave Lithotripsy

The incidence of pediatric urinary system stones has shown an upward trend in recent years, and Extracorporeal Shock Wave Lithotripsy (ESWL) has become one of the most important minimally invasive treatments for pediatric upper urinary tract stones. Currently, the widely used clinical ultrasound mechanical coupling localization mode suffers from issues such as limited scanning degrees of freedom and difficulty in intuitively grasping the spatial relationship between the stone and the focal point. These issues lead to prolonged stone pre-localization times, significant reliance on operator experience, and a steep learning curve for young and primary care physicians, thereby restricting the standardization and widespread promotion of pediatric ESWL.

Building upon existing ESWL equipment, this project independently constructs an "Optical Motion Capture-Assisted Ultrasound Pre-localization System." By utilizing multi-camera infrared motion capture to acquire the 3D pose of the ultrasound probe and the shock wave source in real-time and establishing a unified spatial coordinate system, the system achieves automatic conversion and visual display of the stone's position from the ultrasound image to the shock wave focal point coordinates. This guides the operator to quickly complete focal point pre-localization after freely scanning for the stone. Results from preliminary phantom studies and initial clinical pilot experiments indicate that, while maintaining the routine ESWL workflow, this system can significantly shorten the first effective pre-localization time for pediatric stones from approximately 15 minutes to around 5 minutes, without a significant decrease in the stone clearance rate. This suggests the technology possesses good engineering feasibility and clinical application prospects.

This study proposes to conduct a single-center, prospective, single-blind randomized controlled clinical trial. Pediatric patients with upper urinary tract stones eligible for ESWL will be randomly assigned 1:1 to an experimental group and a control group. The experimental group will use the Optical Motion Capture-Assisted Ultrasound Pre-localization System for stone pre-localization, while the control group will use the routine ultrasound mechanical coupling localization method.

The **primary outcome measure** is the time to first effective stone pre-localization. **Secondary outcomes** include the stone clearance rate evaluated by imaging at 4 and 12 weeks post-operation, the total number of shock waves released and total energy, total procedure time, intraoperative and postoperative complication rates, sedation/anesthesia dosage, and family satisfaction. Additionally, the study will systematically evaluate the system's impact on physician learning curves and work intensity by analyzing the localization success rate of operators with different seniority levels, learning curves (the trend of localization time versus the number of cases), and subjective workload scores.

The core scientific question this project aims to answer is: Under the premise of not compromising the therapeutic efficacy and safety of pediatric ESWL, can optical motion capture-assisted ultrasound pre-localization significantly improve stone localization efficiency, reduce operator workload, and shorten the learning curve for young physicians, thereby enhancing the standardization and accessibility of pediatric ESWL? The expected results will provide an evidence-based foundation for optimizing pediatric ESWL localization modes and formulating relevant technical standards and training programs. Furthermore, it will lay the clinical validation groundwork for future intelligent lithotripsy systems integrating functions such as intelligent identification and robotic arm automatic tracking.

Inclusion Criteria:

• Pediatric patients aged 0 to 14 years with a confirmed diagnosis of upper urinary tract stones.
• Diagnosis confirmed by ultrasound or low-dose CT; stone long diameter ≤ 20 mm (for upper ureteral stones, diameter ≤ 15 mm); absence of urinary tract structural malformations.
• Meeting the indications for ESWL with no absolute contraindications, and scheduled to undergo ESWL treatment.
• Guardians provide informed consent and voluntarily sign the written informed consent form; willing and able to cooperate with the 4-week postoperative follow-up and related examinations.
• Preoperative assessment reveals no contraindications to ESWL, such as uncontrolled infection, severe coagulation disorders, or severe impairment of cardiopulmonary, hepatic, or renal function.

Exclusion Criteria:

• Presence of absolute contraindications for ESWL: Uncontrolled severe urinary tract infection or sepsis; severe uncorrected coagulopathy or current use of anticoagulant/antiplatelet medications; severe renal impairment (significantly decreased GFR); active severe cardiopulmonary disease rendering the patient unable to tolerate anesthesia or shock wave therapy; or absence of an anatomically safe shock wave path (e.g., due to severe skeletal deformities).
• Stones suspected to be extremely hard or complex: Refractory stones indicated by excessively high CT Hounsfield Units (HU) or ultrasound Shear Wave Elastography (SWE) values > 13.7 kPa; or cystine stones in children > 2 years of age (associated with significantly low ESWL success rates).
• Anatomical or physiological challenges: Severe obesity that compromises ultrasound localization; or patients with a solitary kidney or poor contralateral renal function accompanied by a large stone burden.
• Prior intervention: History of prior ESWL or other lithotripsy procedures at the target site, which may confound the evaluation of therapeutic efficacy.
• Underlying systemic conditions: Comorbid severe metabolic diseases or hereditary stone diseases (e.g., cystinuria) requiring priority comprehensive management.
• Compliance issues: Guardians unable to cooperate with the complete follow-up process, or patients with a high anticipated risk of being lost to follow-up.