Computed tomography pulmonary angiography and venography with a low dose of contrast medium

A Triphasic Split-bolus Contrast Injection Protocol for Artery-vein Separation During Pulmonary Computed Tomographic Angiography

PURPOSE

Accurate artery-vein separation on pulmonary computed tomographic (CT) angiography is desirable for preoperative 3-dimensional image simulation, while using a minimal amount of contrast medium. This study aimed to verify whether a split-bolus contrast enhancement protocol with test-bolus tracking would provide contrast differentiation between the pulmonary arteries (PA) and pulmonary veins (PV) during high-pitch single-pass CT angiography.

MATERIALS AND METHODS

Fifty patients underwent pulmonary CT angiography with a triphasic split-bolus injection protocol with the main bolus of contrast medium for 6 seconds, followed by a subsequent bolus of 20% diluted contrast medium/80% saline for another 6 seconds and a 5-second saline chaser. The single-scan timing was individually tailored to the peak enhancement at the left atrium, that is, the pulmonary-venous dominant phase, by monitoring a time-enhancement curve with test bolus.

RESULTS

Time-enhancement curves of the test bolus demonstrated that the interval times between the peak enhancements at the PA and PV were ~6 seconds. For contrast enhancement image analyses with our protocol, the attenuation measurements at the main PA and left atrium were performed. The mean (SD) CT numbers were 246.4 (50.0) HU at the main PA, and 410.8 (59.0) HU at the left atrium. The mean difference in the CT numbers was 164.4 HU (95% confidence interval: 149.2-179.6, P <0.001) between the main PA and left atrium.

CONCLUSIONS

Our contrast enhancement protocol for high-pitch single-pass pulmonary CT angiography could provide the desired artery-vein separation while maintaining adequate attenuations of the pulmonary vasculature.

[Effect of Automatic Extraction Accuracy by Different Image Reconstruction Methods Using a Three-dimensional Image Analysis System for Pulmonary Segmentectomy Preoperative CT Angiography]

This study aimed to determine the optimal image reconstruction method for preoperative computed tomography (CT) angiography for pulmonary segmentectomy. This study enrolled 20 patients who underwent contrast-enhanced CT examination for pulmonary segmentectomy. The optimal image reconstruction algorithm among four different reconstruction algorithms (filtered back projection, hybrid iterative reconstruction, model- based iterative reconstruction, and deep learning reconstruction [DLR]) was investigated by assessing the CT numbers, vessel extraction ratios, and misclassification ratios. The vessel extraction ratios for main and subsegment branches reconstructed using DLR were significantly higher than those using other reconstruction algorithms (96.7% and 90.8% for pulmonary artery and vein, respectively). The misclassification ratios at the right upper lobe pulmonary vessels (V1 and V2) were especially high because they were close to the superior vena cava, and their CT numbers were similar in all four reconstructions. In conclusion, the DLR allows a high extraction rate of pulmonary blood vessels and a low misclassification rate of automatic extraction.

Efficacy of non-rigid registration technique for misregistration in 3D-CTA fusion imaging

PURPOSE

To assess whether fusion 3D-CTA images can be corrected using non-rigid registration (NRR) for gastroenterology imaging.

METHODS

This study included 55 patients before gastroenterology surgery who underwent preoperative 3D-CTA prior to gastroenterological surgery. We recorded the coordinate of measurement points on the arterial vessels (X, Y, and Z) in each portal phase, original image of the arterial phase, and arterial phase with NRR. The distance of misregistration between the two points was calculated with the coordinate of the original image with NRR and that of the portal phase as true value.

RESULTS

The distance of misregistration between the two points in the original arterial and portal phase images was significantly higher than that in the arterial phase image with NRR on all directions (p < 0.01).

CONCLUSIONS

This study showed that NRR may correct misregistration on fusion 3D-CTA imaging. Hence, it can visualize correctly the anatomy of the vessel.

[Utility of Split-bolus Single-phase Protocol for Pulmonary Artery and Vein Separation Preoperative 3D-CTA in Lung Cancer Video-assisted Thoracic Surgery]

There are many variations in branching and running of pulmonary artery (PA) and pulmonary vein (PV). It is desirable to separate as a surgical simulation of lung cancer and important to grasp before video-assisted thoracic surgery (VATS) to perform quick and safe. Therefore, the purpose of this study was to evaluate objective and subjective image quality (contrast attenuation, separation ability, and vascular visualization) of PA and PV of splitbolus single-phase protocol (SBSPP) in preoperative three-dimensional computed tomography angiography (3DCTA). CT value of PA was 410.2±71.0 Hounsfield unit (HU), PV was 245.1±24.8 HU, difference between CT value of PA and CT value of PV was 164.5±60.9 HU. Subjective image quality of PA and PV could be visualized until more than the segmental branch level. SBSPP can obtain sufficient CT value for separate visualization of PA and PV, and before VATS useful PA and PV 3D-CTA imaging.