Dual energy scanning for lung perfusion

The following question has been sent by Dr. Zhouyisheng, China:

Could you tell me how to scan and postprocess: Could you tell me the scan protocol on dual-energy (lung perfusion) and how to postprocess if you use MINinum -960 ,MAX -600 (siemens default). You can get one result then you use MINinum -960, MAX -500, then you can get another result, and so on then how we can juge these results?
Thanks.

Thorsten R.C. Johnson M.D., University Hospitals Grosshadern, Munich:  

By increasing the maximum threshold to a higher value, you make the algorithm include denser parts of the lung in the evaluation. In a healthy patient this should not make a significant difference. However, if for example a patient has a pulmonary edema due to congestion or has pnemonic consolidation, this can result in areas which are not color-coded because they are not recognized as lung by the algorithm. If you then increase the maximum value, you get the perfusion information for these areas. The intensity of the color coding is not affected, because these values do not affect the estimation of iodine content by detecting beam hardening substances but the threshold only makes the algorithm include or exclude the respective voxels in the evaluation.