Purpose: Benign and malignant pulmonary lesions are not easy to distinguish in a clinical setting. We investigated the feasibility of using parametric imaging of the rate constant Ki to diagnose the nature of pulmonary lesions.
Methods: Dynamic multi-bed scanning followed by a routine examination was performed on 21 patients with pulmonary lesions who were divided into two groups with malignant or benign lesions based on biopsy and follow-up. The number of patients in the malignant and benign groups were 10 with 15 lesions and 11 with 14 lesions, respectively. The left ventricular blood pool was used for an image-derived input function. The influx rate constant Ki of the pulmonary lesions and parametric images was generated with the Patlak plot method, and the inter-group differences for Ki, maximum standardized uptake value (SUVmax), and the time-activity curves (TAC) of fluorine-18-fludeoxyglucose ((18)F-FDG) were analyzed. At the same time, we investigated the correlation of Ki to SUVmax.
Results: The maximum diameters of the pulmonary lesions were not significantly different between the malignant and benign groups (p>0.05). Ki and SUVmax were significantly higher in malignant lesions compared to benign lesions (p<0.05). Ki was highly correlated with SUVmax in pulmonary lesions (r=0.815, p<0.01). The malignant lesions showed gradually increasing TAC, and benign lesions exhibited gradually decreasing curves. The parametric images of Ki were useful to distinguish malignant lesions from normal tissue.
Conclusion: Our results indicate that Ki parametric imaging in (18)F-FDG PET/computed tomography (CT) dynamic multi-bed scanning may be useful in the differential diagnosis of pulmonary lesions.