REGULAR CONTENT
Final ID
454
Type
Original Scientific Research-Poster Only
Authors
A Patel1, M Toliyat2, X Yin1, P Sutphin3, S Kalva2
Institutions
1University of Texas Southwestern, Dallas, TX, 2University of Texas Southwestern Medical Center, Dallas, TX, 3N/A, Dallas, TX
Purpose
Spectral CT allows for the use of virtual monoenergetic energies (VME) to retrospectively augment vascular enhancement from conventional polyenergetic images to further interrogate regions of interest. The purpose of this study is to identify the optimal VME images that provide 100% more venous enhancement than the polychromatic CT venogram in order to increase the signal-to-noise ratio (SNR) and improve the evaluation of venous structures.
Materials & Methods
True venous phase CT obtained from a detector-based spectral CT (IQon, Philips Healthcare) was compared to VME data reconstructed from venous phase images in 16 patients at various anatomic locations (multilevel IVC and renal, portal, hepatic, common iliac, and femoral veins). VME images were reconstructed at energy levels ranging from 40-66 keV in 2 keV increments. ROIs were drawn and average attenuation (HU) and standard deviations were obtained. A linear mixed model was used to compare the SNR between true venous and VME images. The SNR was defined as the ratio of mean HU density to standard deviation on ROIs.
Results
The monochromatic energies that doubled the native venous enhancement SNR were as follows: Portal vein (52-54 keV), hepatic vein (50-52 keV), suprarenal IVC (50-52 keV), juxtarenal IVC (50-52 keV), renal veins (48-50 keV), infrarenal IVC (48-50 keV), right iliac vein (46-48 keV), left iliac vein (50-52 keV), right femoral vein (44-46 keV), left femoral vein (46-48 keV). The highest SNR achievable occurred at the lowest VME level of 40 keV. The noise from the virtual venous images was consistently measured as lower in all locations, with statistical significance (p < 0.05) in all but the lowest keV levels.
Conclusions
Central venous vessels required VMEs around 50-54 keV to double their SNR while more peripheral vessels required lower energies around 44-50 keV for the same effect, likely due to contrast dilution. Although noise increased slightly by about 3-4 HU with lower keV, the highest SNR occurred with the lowest energies, allowing use for diagnostic purposes. The overall noise was lower in the VME images across all measured locations. Subjectively, the virtual venous images displayed greater delineation of venous anatomy.
Final ID
454
Type
Original Scientific Research-Poster Only
Authors
A Patel1, M Toliyat2, X Yin1, P Sutphin3, S Kalva2
Institutions
1University of Texas Southwestern, Dallas, TX, 2University of Texas Southwestern Medical Center, Dallas, TX, 3N/A, Dallas, TX
Purpose
Spectral CT allows for the use of virtual monoenergetic energies (VME) to retrospectively augment vascular enhancement from conventional polyenergetic images to further interrogate regions of interest. The purpose of this study is to identify the optimal VME images that provide 100% more venous enhancement than the polychromatic CT venogram in order to increase the signal-to-noise ratio (SNR) and improve the evaluation of venous structures.
Materials & Methods
True venous phase CT obtained from a detector-based spectral CT (IQon, Philips Healthcare) was compared to VME data reconstructed from venous phase images in 16 patients at various anatomic locations (multilevel IVC and renal, portal, hepatic, common iliac, and femoral veins). VME images were reconstructed at energy levels ranging from 40-66 keV in 2 keV increments. ROIs were drawn and average attenuation (HU) and standard deviations were obtained. A linear mixed model was used to compare the SNR between true venous and VME images. The SNR was defined as the ratio of mean HU density to standard deviation on ROIs.
Results
The monochromatic energies that doubled the native venous enhancement SNR were as follows: Portal vein (52-54 keV), hepatic vein (50-52 keV), suprarenal IVC (50-52 keV), juxtarenal IVC (50-52 keV), renal veins (48-50 keV), infrarenal IVC (48-50 keV), right iliac vein (46-48 keV), left iliac vein (50-52 keV), right femoral vein (44-46 keV), left femoral vein (46-48 keV). The highest SNR achievable occurred at the lowest VME level of 40 keV. The noise from the virtual venous images was consistently measured as lower in all locations, with statistical significance (p < 0.05) in all but the lowest keV levels.
Conclusions
Central venous vessels required VMEs around 50-54 keV to double their SNR while more peripheral vessels required lower energies around 44-50 keV for the same effect, likely due to contrast dilution. Although noise increased slightly by about 3-4 HU with lower keV, the highest SNR occurred with the lowest energies, allowing use for diagnostic purposes. The overall noise was lower in the VME images across all measured locations. Subjectively, the virtual venous images displayed greater delineation of venous anatomy.