Preoperative localization of intracranial lesions with MRI using marking pills

ObjectiveTo describe a simple technique for preoperative surface localization of intracranial lesions.Methods11 pills in total, including Alfarol (alfacalcidol) capsules, were affixed to a phantom with adhesive tape and a MRI scan was performed. The visibility of the pills and any spatial errors in determining their locations were evaluated. Between June 2006 and April 2009, we employed Alfarol capsules as a skin marker in MRI in clinical surgical cases.ResultsAlfarol capsules, whose actual size is 5.6 mm in diameter, were identified as a hyperintense spot at a size of 4.2, 4.2, and 4.5 mm in diameter in T1-weighted, T2-weighted, and FLAIR (fluid attenuated inversion recovery) sequence images, respectively. The size discrepancies were within 1.4 mm. The average spatial errors were 0.7, 0.6, and 0.7 mm in T1-weighted, T2-weighted, and FLAIR sequence images, respectively. Other pills were not identified in the MRI scans.During this 35-month period, 8 patients underwent preoperative MRI-guided localization at our institution. There were 5 men and 3 women in whom 8 biopsies were performed. In all cases, the result of the biopsy was positive and useful for the treatment that followed. No perioperative complications were encountered.ConclusionAlfarol capsule can be used as an external skin marker. Our simple and inexpensive method is a useful addition to preoperative evaluation of superficial intracranial lesions.