Dual-energy MDCT: comparison of pulmonary artery enhancement on dedicated CT pulmonary angiography, routine and low contrast volume studies.

PURPOSE: The aim of this study was (a) to compare arterial enhancement in simultaneously acquired high- and low-kilovoltage images; and (b) to determine whether low tube-voltage imaging would permit PE evaluation on routine chest CT studies or CTPA studies performed with a low volume of contrast media.

MATERIALS AND METHODS: We compared 20 CTPA studies (CTPA group), 20 routine thoracic CT studies (RT group) and 10 CTPA studies performed with reduced volume of contrast media (RC group). HU values were measured in all groups at 80 kVp and 140 kVp images in multiple pulmonary arterial segments bilaterally. The diagnostic quality of the central and peripheral vascular enhancement and the image noise were evaluated at both energies using a five-point scale.

RESULTS: For all patients, the mean CT attenuation values were greater at 80 kVp than 140 kVp images (p<0.001). At 80 kVp, CTPA group attenuation values were greater than RT group (p=0.03) with a similar trend at 140 kVp (p=0.08). At both 140 kVp and 80 kVp, CTPA group attenuation values were greater than RC group (p=0.02 and p=0.03, respectively). Qualitative analysis showed that at 140 kVp CTPA studies had better global image quality scores than RT (p=0.003) and RC (p=0.001) groups. However, at 80 kVp, there was no significant difference of global image quality between CTPA and the other groups (p=0.4 and p=0.5, respectively). Although measurable image noise was greater at 80 kVp than 140 kVp (p<0.001), qualitative analysis revealed lower image noise at 80 kVp images.

CONCLUSION: DECT at 80 kVp increases arterial enhancement in both CTPA and routine studies. For routine studies this results in central and peripheral enhancement quality equivalent to that of CTPA studies. Low tube-voltage imaging allows marked contrast volume reduction for CTPA. In selected cases, satisfactory lower radiation dose CT might be achievable using lower kVp imaging alone.