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Using detector-based spectral CT to augment contrast enhancement in conventional CT venograms for the improved evaluation of venous anatomy and pathology
JVIR
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Scientific e-Posters
S195
Results: Of 194 GI bleeding scans performed in the study period, 71 were positive for active lower GI bleed. 37 of these had conventional angiograms, and 9 had positive angiography (24%). All positive angiograms did correlate with the area of bleeding on scintigraphy. Using ROI percent change quartiles, we observed a statistically significant association between increasing ROI and the probability of having a positive angiogram (Cochran-Armitage trend test, p-value ¼ 0.01), such that there are no positive angiogram cases when ROI change was o20% and a majority of the cases (6/9) in the highest quartile. Thus, a percent increase of less than 20% on a positive GI bleed study in this series yielded no positive angiograms. This can impact the overall number of angiograms performed in IR for lower GI bleed, while also increasing the percentage of procedures where active bleeding is found and intervention can be performed. Conclusions: This novel quantitative tool for evaluating GI bleeding scans has the potential to improve patient selection for IR angiography and intervention.
Abstract No. 454 Using detector-based spectral CT to augment contrast enhancement in conventional CT venograms for the improved evaluation of venous anatomy and pathology A. Patel1, M. Toliyat2, X. Yin1, P. Sutphin3, S. Kalva2; 1 University of Texas Southwestern, Dallas, TX; 2 University of Texas Southwestern Medical Center, Dallas, TX; 3N/A, Dallas, TX
Abstract No. 455 Comparing CT angiography with Doppler ultrasound evaluation in the diagnosis of median arcuate ligament syndrome L. Dalag1, M. Patel1, L. Kang1, J. Lorenz1; 1University of Chicago Medicine, Chicago, IL Purpose: Compression of the celiac artery (CA) by the median arcuate ligament can severely reduce blood flow leading to abdominal pain referred to as median arcuate ligament syndrome (MALS). Traditionally, conventional angiography has been the gold standard for MALS diagnosis. Herein we evaluate the diagnostic role of noninvasive methods through screening Doppler ultrasonography (DUS) and computed tomographic angiography (CTA). Materials: A retrospective analysis was performed on all patients with non-acute abdominal pain who underwent work-up for mesenteric ischemia with DUS and CTA from 2009 to 2014. Correlation between maximum inspiratory and expiratory CA velocities per DUS and minimum CA diameter per CTA was evaluated with linear regression. Correlation between maximum velocities per DUS and Radiologist’s subjective presence of MALS morphology was evaluated with Student’s t-test. Results: 60 patients were evaluated with both DUS and CTA. Mean peak velocity on DUS was 328 cm/s (sdev ¼ 106) on expiratory and 203 cm/s (sdev ¼ 55) on inspiratory phases. Mean minimum CA diameter on CTA was 3.3mm (sdev ¼ 1.6) on expiratory and 5.3mm (sdev ¼ 1.6) on inspiratory phases. MALS morphology was subjectively identified on 35 (58%) cases. Linear regression analysis demonstrated that both inspiratory and expiratory phase DUS measurements of CA velocities were inversely correlated to minimum CA diameter measured on CTA (p ¼ 0.013 and p ¼ 0.004, respectively). Subjective presence of CA compression on CTA is significantly associated with increased expiratory Doppler velocities (p ¼ 0.022) but not inspiratory Doppler velocities (p ¼ 0.861). Conclusions: CTA can confirm the diagnosis of MALS by demonstrating focal narrowing of the celiac artery in patients positively screened with DUS. The degree of CA narrowing is significantly correlated with DUS velocities. Moreover, subjective identification of MALS morphology on CTA is significantly correlated with increased DUS velocities on expiration, an expected finding in the pathophysiology of CA compression by the median arcuate ligament during expiration. CTA is a noninvasive alternative to conventional angiography and correlates well with DUS findings in MALS diagnosis.
Scientific e-Posters
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: True venous phase CT obtained from a detectorbased 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 o 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.
’
Scientific e-Posters
S195
Results: Of 194 GI bleeding scans performed in the study period, 71 were positive for active lower GI bleed. 37 of these had conventional angiograms, and 9 had positive angiography (24%). All positive angiograms did correlate with the area of bleeding on scintigraphy. Using ROI percent change quartiles, we observed a statistically significant association between increasing ROI and the probability of having a positive angiogram (Cochran-Armitage trend test, p-value ¼ 0.01), such that there are no positive angiogram cases when ROI change was o20% and a majority of the cases (6/9) in the highest quartile. Thus, a percent increase of less than 20% on a positive GI bleed study in this series yielded no positive angiograms. This can impact the overall number of angiograms performed in IR for lower GI bleed, while also increasing the percentage of procedures where active bleeding is found and intervention can be performed. Conclusions: This novel quantitative tool for evaluating GI bleeding scans has the potential to improve patient selection for IR angiography and intervention.
Abstract No. 454 Using detector-based spectral CT to augment contrast enhancement in conventional CT venograms for the improved evaluation of venous anatomy and pathology A. Patel1, M. Toliyat2, X. Yin1, P. Sutphin3, S. Kalva2; 1 University of Texas Southwestern, Dallas, TX; 2 University of Texas Southwestern Medical Center, Dallas, TX; 3N/A, Dallas, TX
Abstract No. 455 Comparing CT angiography with Doppler ultrasound evaluation in the diagnosis of median arcuate ligament syndrome L. Dalag1, M. Patel1, L. Kang1, J. Lorenz1; 1University of Chicago Medicine, Chicago, IL Purpose: Compression of the celiac artery (CA) by the median arcuate ligament can severely reduce blood flow leading to abdominal pain referred to as median arcuate ligament syndrome (MALS). Traditionally, conventional angiography has been the gold standard for MALS diagnosis. Herein we evaluate the diagnostic role of noninvasive methods through screening Doppler ultrasonography (DUS) and computed tomographic angiography (CTA). Materials: A retrospective analysis was performed on all patients with non-acute abdominal pain who underwent work-up for mesenteric ischemia with DUS and CTA from 2009 to 2014. Correlation between maximum inspiratory and expiratory CA velocities per DUS and minimum CA diameter per CTA was evaluated with linear regression. Correlation between maximum velocities per DUS and Radiologist’s subjective presence of MALS morphology was evaluated with Student’s t-test. Results: 60 patients were evaluated with both DUS and CTA. Mean peak velocity on DUS was 328 cm/s (sdev ¼ 106) on expiratory and 203 cm/s (sdev ¼ 55) on inspiratory phases. Mean minimum CA diameter on CTA was 3.3mm (sdev ¼ 1.6) on expiratory and 5.3mm (sdev ¼ 1.6) on inspiratory phases. MALS morphology was subjectively identified on 35 (58%) cases. Linear regression analysis demonstrated that both inspiratory and expiratory phase DUS measurements of CA velocities were inversely correlated to minimum CA diameter measured on CTA (p ¼ 0.013 and p ¼ 0.004, respectively). Subjective presence of CA compression on CTA is significantly associated with increased expiratory Doppler velocities (p ¼ 0.022) but not inspiratory Doppler velocities (p ¼ 0.861). Conclusions: CTA can confirm the diagnosis of MALS by demonstrating focal narrowing of the celiac artery in patients positively screened with DUS. The degree of CA narrowing is significantly correlated with DUS velocities. Moreover, subjective identification of MALS morphology on CTA is significantly correlated with increased DUS velocities on expiration, an expected finding in the pathophysiology of CA compression by the median arcuate ligament during expiration. CTA is a noninvasive alternative to conventional angiography and correlates well with DUS findings in MALS diagnosis.
Scientific e-Posters
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: True venous phase CT obtained from a detectorbased 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 o 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.