Good agreements were obtained between the replicated measurements (interclass correlation coefficient > 0.99)
When compared to normal, benign lesions showed higher BF and BV but were not statistically significant(p >0.05). MTT and TTP values in benign lesions were comparable to that of normal.
On the perfusion maps, malignant nodes showed remarkable hypoperfusion compared to non-malignant ones.
Except for MTT and TTP, which were statistically (p <0.05) lower in malignant lesions, all CTP parameter values were significantly (P <0 .05) higher in malignant nodes when compared with the benign and the normal nodes.
The mean value of BF in malignant nodes was 12.6 (± 2.9), BV was 2.1 (± 0.34) and MTT was 6.8 (± 1.7).
Comparing to non-malignant nodes, the malignant ones showed significantly low BF values (P< 0.05) and low BV values.
The accuracy of detecting malignant nodes was 91%, sensitivity 92%, specificity 84%, positive predictive value 92.5% and negative predictive value 78.7%.
The smallest detected node on CTP was 6 mm.
Higher median perfusion index in malignant nodes than for those with benign nodes and the normal nodes can be explained on the basis of intrinsic high neoangiogenic activity of tumor or a secondary response to tissue hypoxia The arteriovenous shunts have very low resistance to flow, which results in markedly increased blood flow and shorter MTT. Benign nodes constitutes inflammed nodes and does not show much distortion in the vascular architecture and thus shows similar perfusion indices as that of the normal nodes.
We observed that in our series many malignant nodes show clear perfusion changes that may be helpful for differentiation from benign nodes. Although our experience is limited, we believe that perfusion CT can reveal blood flow in cases with malignancy and therefore may aid in the differentiation of the benign Vs malignant Vs normal Nodes.
We did not study tumor permeability, which might have served as an independent predictor of tumor grade or response. The observational period was relative short, and the clinical outcomes based on the perfusion parameters obtained using dynamic CT could not be analyzed.