CT-guided agar marking for localization of nonpalpable peripheral pulmonary lesions.

BACKGROUND Small pulmonary lesions with ground-glass opacity (GGO) are increasingly detected by CT; however, intraoperative localization of such lesions is difficult because these lesions are often invisible and nonpalpable. STUDY OBJECTIVES To localize and resect nonpalpable and invisible small pulmonary lesions, a new marking technique that we call "agar marking" was developed. METHODS AND PATIENTS Powdered agar was dissolved in distilled water at a concentration of 5% and kept at > 50 degrees C to maintain its liquid form. Agar was injected through an 18-gauge needle and placed near the target lesion with CT. After animal experiments, agar marking was applied to the nine patients who had lesions < 20 mm in diameter and lesions with GGO. The mean diameter of these lesions was 11 mm, with a mean depth of 19 mm from the pleural surface on CT. RESULTS Agar could be detected as a hard nodule by manual palpation, and the lesion was resected during thoracotomy in all cases. There were no complications associated with the agar injection, aside from one case of slight pneumothorax. CONCLUSIONS Agar marking may represent a feasible alternative technique for localizing nonpalpable occult lesions located away from the pleural surface.