The Potential Utility of CT Perfusion in Differentiating Benign from Malignant Solitary Pulmonary Nodules (SPN)

Introduction: Contrast-enhanced computed tomography (CT) remains the primary imaging modality for characterizing and assessing focal parenchymal pulmonary nodules (SPN), utilizing morphological features and enhancement patterns for diagnostic purposes. Despite its utility, there is considerable overlap in imaging characteristics between malignant and benign lesions, which often necessitates invasive procedures for definitive tissue diagnosis through percutaneous or endoscopic sampling. Consequently, there is a growing need for non-invasive methods to distinguish between malignant and benign lung lesions. In this context, CT perfusion represents a novel technological advancement that offers a functional evaluation of tissue vascularity and perfusion through various parameters, potentially aiding in differentiating benign from malignant focal lung lesions. Objectives: This study aimed to evaluate the effectiveness of the CT perfusion technique in distinguishing between malignant and benign focal parenchymal pulmonary nodules. Materials and Methods: This prospective observational study involved performing CT perfusion on 60 patients with focal parenchymal lung lesions between January 2023 and June 2024. The imaging protocol included a four-dimensional scan designed to encompass the full craniocaudal length of each lesion, followed by a volume perfusion CT examination. The CT perfusion parameters, including blood flow (BF), blood volume (BV), and the transfer constant (k-trans) of the lesions, were quantified using the mathematical algorithms integrated into the Syngo.via CT perfusion software (Siemens Healthcare). Results: The study revealed that the median blood volume (BV) in benign lesions was 5.66 mL/100 g, with an interquartile range (IQR) of 1.42 (5.35 to 6.77). In contrast, the median BV in malignant lesions was 12.5 mL/100 g, with an IQR of 1.99(12.1 to 14.0). The median blood flow (BF) for benign lesions was 44.8 mL/100 g/min, with an IQR of 8.66(43.0 to 51.6). For malignant lesions, the median BF was 59.4 mL/100 g/min, with an IQR of 4.07(56.6 to 60.7). Regarding the transfer constant (k-trans), the median value for benign lesions was 5.25 mL/100 g/min, with an IQR of 1.73 (4.0 to 5.73). In malignant lesions, the median k-trans was 13.1 mL/100 g/min, with an IQR of 7.58 (5.73 to 14.0). Conclusion: The findings reveal that CT perfusion parameters, including blood volume (BV), blood flow (BF), and transfer constant (k-trans), are effective in distinguishing benign from malignant lung lesions, with blood flow and k-trans demonstrating very high specificity.