Magnetic Resonance–guided High-intensity Focused Ultrasound (MRgHIFU) Virtual Treatment Planning for Abdominal Neuroblastoma Utilizing Retrospective Diagnostic 3D CT Images

Magnetic resonance–guided high-intensity focused ultrasound (MRgHIFU) is a novel treatment for neuroblastoma using ultrasound-induced thermal ablation with real-time MR thermometry. It is unclear which patients would be amenable to MRgHIFU given the retroperitoneal location of many neuroblastomas within the smaller pediatric abdomen. In addition, planning relies on MR scans, which are not routine in the standard pediatric neuroblastoma workup. This study sought to demonstrate that neuroblastomas are targetable with MRgHIFU and available computed tomographic imaging could be utilized for MRgHIFU virtual treatment. Cross-sectional images of 88 pediatric abdominal neuroblastoma patients were retrospectively processed with custom software to be made compatible with the Sonalleve MRgHIFU platform. Targetability measured percent treatment to lesion volume, within adequate safety margins from critical structures. All images were successfully converted into treatment planning files. Median lesion size was 191±195 cm³ and depth was 29±17 mm. Up to 78 (85%) patients had targetable lesions with a median targetable volume of 15% and ranging up to 79%. Targetability was highest in superficial, right upper quadrant lesions >200 cm³, but limited by proximity to bowel and ribs. This study demonstrates the capacity for MRgHIFU to potentially treat the majority of abdominal neuroblastomas and the feasibility of using computed tomographic images for MRgHIFU virtual treatment planning.