Cerebral microembolisation during radiofrequency ablation of lung tumours: detection by carotid duplex ultrasound

The aim of this study was to investigate the appearance of microbubbles during radiofrequency ablation (RFA) of lung tumours. Eight consecutive patients (mean age, 73.1 years; 3 men and 5 women; 10 malignant lesions; mean lesion size, 24.8 mm) who underwent RFA of lung tumours using internally cooled single electrodes were enrolled. During the RFA procedure, the right internal carotid artery was continuously monitored by duplex ultrasound. High-intensity transient signals (HITS) that occurred in the Doppler blood flow waveform were taken to indicate microbubbles. 21 RFA applications were performed for the 10 lesions. HITS were observed in 19 of 21 RFA applications; the mean frequency in a single application was 10+/-13.3. A statistical correlation was seen between the duration of energy deposition and the number of HITS, and between tumour size and the number of HITS. Microbubbles were detected in all patients in the late phase of the first session of RFA.