Andrew Sher MD, Abstract Co-Author: Research Grant, Koninklijke Philips NV

Abed Ghandour MD, Abstract Co-Author: Nothing to Disclose

Rong Rong MD, Abstract Co-Author: Institutional Grant support, Koninklijke Philips NV

Amar Dhanantwari, Abstract Co-Author: Employee, Koninklijke Philips NV

Prabhakar Rajiah MD, FRCR, Presenter: Institutional Research Grant, Koninklijke Philips NV

Evaluate the ability of  a novel Spectral Detector CT (SDCT)  to augment aortic attenuation of low attenuating exams and assess whether the resulting monoenergetic image set enables diagnostic evaluation of vascular structures. 

On an SDCT (Philips Healthcare) 49 patients underwent contrast-enhanced examinations of the chest and abdomen following routine or CTA protocols. A subset of 36 examinations were chosen which had mean aortic attenuation of less than 200 HU calculated as the average of 8 regions of interest within the aorta. Subjective evaluation of vascular enhancement and overall image noise was graded on a 5-point scale (1= Non-diagnostic, 5 = Excellent). Monoenergetic image sets of 40 to 180 keV at every 10 keV were created. An ideal monoenergetic energy level was chosen defined as the highest energy that provided mean aortic attenuation greater than 200 HU and maintained diagnostically acceptable subjective image noise and vascular enhancement. At this energy level attenuation, noise, and signal-to-noise ratios as well as subjective image quality and vascular enhancement were compared to the standard 120 kVp polyenergetic study. Paired t-test and Wilcoxon signed-rank test were used for analysis. 

34 studies (94%) met criteria for successful optimal monoenergetic reconstruction, with a mean optimal energy of 57 ± 6.4 keV. Optimizing energy levels significantly increased aortic attenuation compared to the 120 kVp studies by an average of 66% (238 ± 25 vs. 144 ± 25 HU; p<.001). Image noise averaged 16% higher in the monoenergetic energy studies than the 120 kVp exams (19.6 ± 3.9 vs. 16.9 ± 4.1; p<.001), while SNR was 41% higher (13.3 ± 2.9 vs. 9.4 ±2.5; p <.001). Subjective vascular enhancement was significantly higher on the monoenergetic images (4.7 vs 2.4, p < .001). While subjective image noise increased (4.2 vs. 5.0, p < .001), the resulting image set was diagnostically acceptable.    

SDCT enables retrospective creation of an optimal monoenergetic image set which achieves attenuation levels comparable with dedicated aortic angiographic exams and remains acceptable for diagnosis despite increased image noise.

SDCT enables the creation of retrospective aortic angiograms from studies that otherwise may not be diagnostic, suggesting the ability to create angiograms from routine or low contrast studies. 

Sher, A, Ghandour, A, Rong, R, Dhanantwari, A, Rajiah, P, Evaluating Optimal Monochromatic Energy Reconstruction on Aortic Angiography Obtained from Spectral Detector CT.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14019279.html