CT perfusion imaging can detect residual lung tumor early after radiofrequency ablation: a preliminary animal study on both tumoral and peri-tumoral region assessment

Background: Radiofrequency ablation (RFA) is a minimally invasive procedure to treat lung cancer. Timely evaluation on residual lung tumor after RFA is crucial to the prognosis, hence, our objective is to assess CT perfusion (CTP) on detection of residual lung tumor early after RFA. Methods: CTP imaging was performed in 24 lung VX2 tumor models 1 day before and within 1 hour after RFA. CTP maps with dual-input (n=24) and single-input [n=13, with predominant ground glass opacity (GGO) after RFA] models were generated using the maximal slope method. Regions of interest were independently placed on the maximal cross-sectional tumor before and after RFA and on GGO after RFA by two thoracic radiologists. The bronchial flow (BF), pulmonary flow (PF) and perfusion index (PI) were compared between pre-RFA and post-RFA images. The parameters (BF, PF and PI of tumor; PF of GGO) of the complete and incomplete RFA groups were compared based on NADH and TUNEL staining and were correlated with the microvascular density (MVD). Results: The BF and PF decreased after RFA (all P values <0.03). The decrease in BF and PF (Delta BF and Delta PF) in the complete RFA group was higher (P=0.01; 0.02). The areas under the curve (AUC) of Delta BF and Delta PF at 14.85 and 17.25 mL/min/100 mL in determination of tumor with complete ablation were 0.80 and 0.78, respectively. Delta BF was positively correlated with MVD (P=0.046, r=0.468). PF of GGO with incomplete RFA was higher (P=0.001). The AUC of PF <= 29.4 mL/min/100 mL in determination of tumor with complete ablation was 0.99. Conclusions: CTP could detect residual lung tumor early after RFA in a rabbit model, which might provide a clinical solution to early treatment assessment after RFA.