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CT IVC venogram: normalized quantitative criteria for patency and thrombosis
Marina Mityul1, David J Kim1, Amber Salter2
1Mallinckrodt Institute of Radiology, Washington University School of Medicine, Campus Box 8131, 510 S. Kingshighway Blvd, St Louis, MO, 63110, USA.
Insights
A normal vein to artery attenuation ratio on CT IVC venogram is approximately 0.91. A ratio below 0.67 strongly suggests the presence of venous thrombus, aiding in diagnosis.
Area of Science:
- Radiology
- Vascular Imaging
- Diagnostic Accuracy
Background:
- Deep vein thrombosis (DVT) diagnosis relies on imaging techniques.
- Computed Tomography Inferior Vena Cava (CT IVC) venography is used to visualize venous structures.
- Establishing normal imaging parameters is crucial for accurate interpretation.
Purpose of the Study:
- To establish normal attenuation ratios between veins and arteries in CT IVC venography.
- To determine a diagnostic vascular attenuation ratio for identifying venous thrombus.
Main Methods:
- Retrospective analysis of 56 CT IVC venograms.
- Calculation of vein-to-artery attenuation ratios in four venous stations.
- Receiver operating characteristic (ROC) analysis to determine a thrombus-specific threshold.
Main Results:
- Median normal attenuation ratios ranged from 0.89 to 0.91.
- ROC analysis yielded an area under the curve (AUC) of 0.994.
- A threshold ratio of 0.67 demonstrated high sensitivity (100%) and specificity (97.5%) for thrombus detection.
Conclusions:
- The normal vein-to-artery attenuation ratio on CT IVC venography is approximately 0.91.
- A ratio less than 0.67 is highly suggestive of venous thrombus.
- This ratio serves as a valuable diagnostic tool for thrombus identification.
Purpose:
Establish normal attenuation ratios for vein to artery on CT IVC venogram and determine a vascular attenuation ratio diagnostic of thrombus.
Methods:
This retrospective, HIPAA-compliant study included 56 CT IVC venograms. Images were reviewed for the presence of femoral vein or IVC thrombus. Attenuation ratios for each vein and its corresponding artery were calculated by two observers and averaged in four venous stations (right and left femoral veins, and IVC at the confluence of the iliac veins and at the left renal vein). The reference standard for the absence of thrombus was clinical follow-up and for the presence of thrombus it was thrombectomy or catheter venogram. Receiver operating characteristic (ROC) analysis was performed using ratios from one venous station and threshold for thrombus was determined using the Youden's index.
Results:
36 of 56 CTs demonstrated no thrombus. 20 CTs demonstrated thrombus, confirmed in eight patients. For CTs with no thrombus, median ratios among the venous stations ranged from 0.89 (IQR 0.83-0.93) to 0.91 (IQR 0.86-0.94). ROC analysis of ratios from a single representative station (left femoral vein, n = 4 confirmed clots) demonstrated an area under the curve (AUC) of 0.994 (p = 0.001) and a threshold of 0.67 for diagnosing thrombus [sensitivity 100% (95% CI 39.76-100%), specificity 97.5% (86.84-99.94%)].
Conclusion:
The normal attenuation ratio of vein to artery in the absence of venous thrombus on a 3-min delay CT IVC venogram is approximately 0.91. A ratio less than 0.67 is highly suggestive of thrombus.
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