In present PET/CT scanners, PET attenuation correction is performed by relying on the information given by CT scan. In the CT-based attenuation correction methods, dual-energy technique (DECT) is the most accurate approach, which has been limited due to the increasing patient dose. In this feasibility study, we have introduced a new method that can implement dual-energy technique with only a single energy CT scan. The implementation was done by CT scans of RANDO phantom at tube voltages of 80 kV_P and 140 kV_P. The acquired data was used to obtain conversion curves (which scale CT numbers at different kV_P to each other), in three regions including lung tissue (HU<-100), soft tissue (-100<HU<200) and bone tissue (HU>200) for the combination of 80 kV_P /140 kV_P. Therefore, with having the CT image in one energy, we generate the CT image at the second energy (from now we call it virtual dual-energy technique) using these kV_P conversion curves. The attenuation map at 511 keV was generated using bilinear (the most commonly used method in commercially available PET/CT scanners), real dual-energy and virtual dual-energy technique in a polyethylene phantom. In the phantom study, the created attenuation map using mentioned methods are compared to the theoretical values calculated using XCOM cross section library. The results in the phantom data show 10.1 %, 4.2 % and 4.3 % errors for bilinear, dual-energy and virtual dual-energy techniques respectively. Further evaluation using a larger patient data is underway to evaluate the potential of the technique in a clinical setting.