Non-invasive Tissue Characterization of Lung Tumors Using Integrated Backscatter Intravascular Ultrasound: An ex vivo Comparative Study with Pathological Diagnosis.

Endobronchial ultrasonography (EBUS) facilitates lung cancer diagnosis. However, qualitative tissue characterization of lung tumors is difficult using EBUS. Integrated backscatter (IBS) is an ultrasound technique that calculates the power of ultrasound signal to characterize tissue components in coronary arteries. We hypothesized that qualitative diagnosis of lung tumors is possible using the IBS technique. The aim of the present study was to elucidate whether IBS technique can be used in lung tissues diagnosis.We prospectively enrolled 35 consecutive patients who underwent surgery for lung cancer. We measured IBS values of lung and tumor tissues that were obtained during surgery within 48 hours. We compared histological images of lung and tumor tissues with IBS values. We determined the relative interstitial area by Masson's trichrome stain using an imaging processor.The IBS values in tumor tissue were significantly lower than those in normal lung tissue (-50.9±2.6 and -47.6±2.6 dB, respectively, p<0.001). The IBS values of adenocarcinomas associated with a good 5-year survival rate were higher than those of non-adenocarcinomas (-48.1±1.6 and -52.6±1.4 dB, respectively, p <0.001). There were significant correlations between the IBS values and the relative interstitial area or micro air area in tumor (r=0.53 and r=0.67, p<0.01, respectively). After combining normal lung tissue and adenocarcinomas with good prognosis, the sensitivity and specificity for establishing the presence of lung tumors were 84% and 85%, respectively.Qualitative diagnosis of lung tumors was possible with a sensitivity of 84% and a specificity of 85% using the ultrasound IBS technique.