Rationale and objectives: To test utility and specific properties of a commercially available MRI compatible power drill for MR guided transcortical bone biopsy.
Methods: In 17 patients MR-guided bone biopsy was performed in an open low-field scanner (0.2 T), using a piezoelectrically powered drilling machine. Target lesions were osteoblastic in four and nonsclerosed intramedullary in 13 cases. Titanium drills sized 3 to 4 mm and an outer cannula were coaxially used for power assisted cortical trephination. For intramedullary lesion sampling, spring loaded biopsy guns and sharpened cannulas were additionally applied in seven and fluid aspiration in two patients, respectively.
Results: The piezoelectric device proved to be fully MR compatible. Trephination and subsequent biopsy was successful in all patients without major complications. The drilling procedure could entirely be performed inside the magnet in case of a lateral approach (n = 11). The net drilling time averaged 7.8 minutes for trephination of nonimpaired diaphyseal bone, but was up to 50 minutes in case of thickened femoral bone. Procedures were complicated by frequent drill loosening, drill obstruction by cortical bone (n = 4) and impaired periosteal grip (n = 5) with damage to the outer cannula (n = 3).
Conclusions: The piezoelectric power drill can be applied safely in a low-field MRI environment and is a valuable tool to facilitate transcortical bone biopsy.