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Placement of marker coils at biopsy: usefulness in the localization of poorly visualized renal neoplasms for subsequent CT-guided radiofrequency ablation.

PURPOSE
To determine whether placement of marking coils at biopsy of small renal neoplasms to facilitate localization at subsequent radiofrequency (RF) ablation is safe and can reduce fluoroscopy time during the ablative procedure.


MATERIALS AND METHODS
This retrospective study was approved by the hospital institutional review board and was compliant with HIPAA. The requirement to obtain informed consent was waived. A search of the renal RF ablation database (235 patients) identified 23 consecutive patients who had a marking coil placed at biopsy of a renal neoplasm (coil group) and 23 patients who did not have a marking coil placed at biopsy (control group). The patients were matched for tumor characteristics, including size, parenchymal position, location in the kidney, and laterality. All patients underwent subsequent RF ablation. The authors compared computed tomographic (CT) fluoroscopy times and technical success rates between the two groups. Statistical analyses were performed by using a single-tailed paired t test for comparison of CT fluoroscopy times, a two-tailed paired t test for comparison of age and tumor size, and a single-tailed McNemar test for comparison of the technical success rate of ablation.


RESULTS
The mean CT fluoroscopy time for the RF ablation procedure was 28 seconds ± 11.7 (standard deviation) for the coil group and 66 seconds ± 85.8 for the control group (P = .025). There was no significant difference in the technical success rates of renal RF ablation.


CONCLUSION
For small renal neoplasms that are poorly visualized at unenhanced CT, placement of a metallic marking coil at biopsy facilitates tumor localization, thus reducing CT fluoroscopy time and radiation dose for subsequent RF ablation procedures.