Preliminary Study Of Spectral CT Imaging In Differential Diagnosis Of Benign And Malignant Pulmonary Lesions

Objective: To investigate the value of spectral CT imaging in differential diagnosis of benignand malignant pulmonary lesions.Methods:93patients with pulmonary focal lesions were underwent plain and enhanced CTscanning in the chest using the dual energy spectral CT imaging mode from August2011toFebruary2013. The spectrum analysis was used to create spectral curves, the iodineconcentration images and the calcium concentration images used the same size region ofinterest (ROI) on the three slices. CT spectral imaging parameters for the lesions wereobtained: calcium concentration and effective-Z in plain CT, normalized iodine concentration(NIC) and spectral HU curve in enhanced CT. Slope k of the spectral HU curve wascalculated as k=[HU(40keV)-HU(90keV)]/50. All results were analyzed with ANOVA and ttest. Receiver operating characteristic curves were generated to determine parameters foroptimizing sensitivity, specificity and accuracy in this study.Results: Differential diagnosis of benign and malignant pulmonary lesions: In plain CT,calcium concentration of lung cancer was different from that of benign pulmonary lesions(P<0.05). And the effective-Z between the two groups had no statistically significantdifference (P=0.086). In enhanced CT, Slope k and NIC of lung cancer were all differentfrom those of benign lesions (t=-4.85,-2.76, all P<0.05). The difference of above fourparameters was not significant in classifying pulmonary lesions as benign or malignant.Differential diagnosis of different pathological types of pulmonary lesions:①In plain CT,calcium concentration and effective-Z of inflammatory lesions were different from those oftuberculosis, while there was no statistically significant difference in effective-Z between the two groups (P=0.678). In enhanced CT, NIC of inflammatory lesions was different from thatof tuberculosis (P<0.05). And the slope k between the two groups had no statisticallysignificant difference (P=0.144). The NIC in enhanced CT provided high sensitivity andspecificity in differentiating inflammatory lesions from tuberculosis(100%and100%,respectively).②There were statistically differences in calcium concentration and effective-Zamong squamous cell carcinoma (SCC), adenocarcinoma (AC) and small cell lung carcinoma(SCLC) in plain CT (F=9.94,9.73, all P<0.05). In enhanced CT, the slope k and NIC amongdifferent pathological type lesions had statistically significant difference (F=25.18,59.78, allP<0.05). The slope k in the enhanced CT provided high sensitivity and specificity indifferentiating SCC from AC (90%and85%, respectively), SCC from SCLC (95%and100%, respectively) and AC from SCLC (96%and83%, respectively), and the area undercurve were0.94、0.99、0.91respectively.Conclusion: Spectral CT provided additional parameters than conventional CT for benignand malignant pulmonary lesions and their different pathological types that were different,and may become an effective diagnostic method to improve the sensitivity and specificity todifferentiate them.