Ex vivo pulmonary nodule detection with miniaturized ultrasound convex probes

The intraoperative localization of small and deep pulmonary nodules is often difficult during minimally invasive thoracic surgery. We compared the performance of three miniaturized ultrasound (US) convex probes, one of which is currently used for thoracic endoscopic diagnostic procedures, for the detection of lung nodules in an ex vivo lung perfusion model.

Three porcine cardiopulmonary blocks were perfused, preserved at 4°C for 6 h and reconditioned. Lungs were randomly seeded with different patterns of echogenicity target nodules (9 water balls, 10 fat, and 11 muscles; total n = 30). Three micro-convex US probes were assessed in an open setting on the pleural surface: PROBE 1, endobronchial US 5-10 MHz; PROBE 2, laparoscopic 4-13 MHz; PROBE 3, fingertip micro-convex probe 5-10 MHz. US probes were evaluated regarding the number of nodules localized/not localized, the correlation between US and open specimen measurements, and imaging quality.

For detecting target nodules, the sensitivity was 100% for PROBE 1, 86.6% for PROBE 2, and 78.1% for PROBE 3. A closer correlation between US and open specimen measurements of target diameter (r = 0.87; P = 0.0001) and intrapulmonary depth (r = 0.97; P = 0.0001) was calculated for PROBE 1 than for PROBES 2 and 3. The imaging quality was significantly higher for PROBE 1 than for PROBES 2 and 3 (P < 0.04).

US examination with micro-convex probes to detect pulmonary nodules is feasible in an ex vivo lung perfusion model. PROBE 1 achieved the best performance. Clinical research with the endobronchial US micro-convex probe during minimally invasive thoracic surgery is advisable.