Thirty consecutive patients older than 75 years with previous EVAR were enrolled and underwent a quadruple phase dual-energy CT examination using a split bolus injection protocol,
in order to obtain a dual-energy combined Arterial-Delayed-Enhanced-Phase as well as a triple-phase (Real-Unenhanced-Phase plus Arterial-Enhanced-Phase plus Delayed-Enhanced-Phase).
After Real-Unenhanced-Phase acquisition,
a test-bolus technique with 20mL CM was performed to determine the aortic bolus-arrival-time.
Two separate boli of CM (40mL@4mL/s) were injected.
Arterial-Enhanced-Phase was acquired one bolus-arrival-time after injection of the first bolus,
whereas Arterial-Delayed-Enhanced-Phase was acquired one bolus-arrival-time after injection of the second bolus,
with a 80sec interval delay from the first bolus.
Finally,
Delayed-Enhanced-Phase was acquired 80sec after the second bolus.
A Virtual-Unenhanced-Phase was generated from the dual-energy Arterial-Delayed-Enhanced-Phase acquisition.
Three blinded radiologists qualitatively assessed the presence of endoleak in different reading sessions,
evaluating the diagnostic value of Virtual-Unenhanced-Phase plus Arterial-Delayed-Enhanced-Phase versus the triphasic gold-standard; a quantitative evaluation was performed in terms of enhancement and signal-to-noise ratio; the two acquisition protocols were compared in terms of radiation dose (Effective dose - mSv).
All CT examinations were technically adequate.
The Arterial-Delayed-Enhanced-Phase images combined the information from the arterial and delayed phases.
Virtual-Unehnanced-Phase images well replaced the Real-Unenhanced-Phase ones.
No significant differences were noted in terms of image quality,
noise and diagnostic performance,
even though both the Arterial-Delayed-Enhanced-Phase acquisition and the Virtual-Unenhanced one obtained a lower score in terms of imge quality due to the increase in the noise index,
without affecting the diagnostic performance; in particular,
this set of images granted an adequate diagnostic accuracy,
detecting 21/22 endoleaks.
Radiation dose saving was up to 78% compared with the reference triphasic study.