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. 2021 Aug;11(8):3726-3734.
doi: 10.21037/qims-20-992.

Quantitative analysis of renal blood flow during thoracic endovascular aortic repair in type B aortic dissection using syngo iFlow

Kun Fang  1 , Jiawei Zhao  1 , Mingyao Luo  1 , Yunfei Xue  1 , Hui Wang  2 , Luming Ye  3 , Xuelan Zhang  4 , Liancun Zheng  4 , Chang Shu  1   2
Affiliations

Quantitative analysis of renal blood flow during thoracic endovascular aortic repair in type B aortic dissection using syngo iFlow

Kun Fang et al. Quant Imaging Med Surg. 2021 Aug.

Abstract

Background: Currently, the thoracic endovascular aortic repair is the recommended clinical treatment for type B aortic dissections. Unfortunately, malperfusion or ischemia of the kidneys is a major complication of type B aortic dissections. Despite this, few studies have focused on the effects of thoracic endovascular aortic repair on blood flow in renal arteries and parenchyma. This current investigation used novel real-time imaging software to quantitatively analyze the hemodynamic changes in renal artery blood flow and perfusion before and after stent graft placement.

Methods: A total of 51 patients with type B aortic dissection undergoing thoracic endovascular aortic repair between April 2017 and September 2019 were retrospectively recruited. The pre-and post-procedural digital subtraction angiography images were converted into color-coded maps using syngo iFlow for quantitative comparison. Time-intensity curves and related parameters, including the average peak ratio (avg.Pr), average delayed time to peak (avg.dTTP), and average area under the curve ratio (avg.AUCr) of the renal arteries and renal cortex were obtained and analyzed. Wilcoxon signed-rank test was used to compare iFlow parameters before and after endovascular repair. Spearman correlation analyses were performed to study iFlow parameters and renal function parameters and the estimated glomerular filtration rate (eGFR) and blood urea nitrogen (BUN).

Results: A total of 102 images including 51 pre-operative and 51 post-operative image datasets were successfully post-processed. Following endovascular repair, syngo iFlow showed a significant 33.0% increase in avg.Pr (P<0.001) and a significant 35.1% increase in avg.AUCr (P<0.001) in the renal artery. Additionally, there was a significant 12.2% decrease in the avg.dTTP (P=0.001), a significant 24.5% increase in avg.Pr (P=0.004), and a significant 38.3% increase in avg.AUCr (P=0.009) in the renal cortex. Spearman correlation analysis showed that after endovascular repair there was a significant correlation between the avg.Pr of the renal artery and eGFR (r=0.30; P=0.0349), the avg.Pr of the renal cortex and eGFR (r=0.30; P=0.0300), and the avg. AUCr of the renal cortex and BUN (r=0.31; P=0.0289).

Conclusions: syngo iFlow provided a novel quantitative method for evaluating renal hemodynamic changes in patients with type B aortic dissection undergoing endovascular treatment. Time-intensity curve parameters may facilitate the intraprocedural evaluation of renal blood flow and perfusion to complement the color-coded map.

Keywords: Thoracic endovascular aortic repair (TEVAR); renal blood flow; renal parenchymal perfusion; syngo iFlow; type B aortic dissection (TBAD).

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Conflict of interest statement

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/qims-20-992). The authors have no conflicts of interest to declare.

Figures

Figure 1
Figure 1
Selection criteria for the cases included in this study. TBAD, type B aortic dissection; TEVAR, thoracic endovascular aortic repair.
Figure 2
Figure 2
Illustration of the time-intensity curve (TIC) and related parameters, including peak as the maximum intensity value, the time to peak (TTP) contrast intensity, and the area under the curve (AUC).
Figure 3
Figure 3
Display of the specific regions of interest (ROIs) in the syngo iFlow color-coded map. Nine ROIs were selected, including the reference (Ref) ROI located in the true lumen of the abdominal aorta near T12, ROI [1] and ROI [5] located in the upper pole of the bilateral renal cortex, ROI [2] and ROI [6] located in the mid-pole of the bilateral renal cortex, ROI [3] and ROI [7] located in the lower pole of the bilateral renal cortex, and ROI [4] and ROI [8] located in the bilateral renal arteries.
Figure 4
Figure 4
Wilcoxon signed rank test of pre- and post-operative measurements using syngo iFlow. (A) The difference between the pre- and post-operative avg.dTTP of the renal artery (1.02±1.56 versus 0.72±1.05 s, P=0.080); (B) the difference between the pre- and post-operative avg.Pr of the renal artery (0.56±0.28 versus 0.75±0.32, P<0.001); (C) the difference between the pre- and post-operative avg.AUCr of the renal artery (0.66±0.26 versus 0.90±0.38, P<0.001); (D) the difference between the pre- and post-operative avg.dTTP of the renal cortex (6.52±2.09 versus 5.73±2.04 s, P=0.001); (E) the difference between the pre- and post-operative avg.Pr of the renal cortex (0.30±0.13 versus 0.37±0.14, P=0.004); (F) the difference between the pre- and post-operative avg.AUCr of the renal cortex (0.72±0.32 versus 0.99±0.80, P=0.009). *, P<0.05. avg.dTTP, average delayed time to peak; avg.Pr, average peak ratio; avg.AUCr, average area under the curve ratio.
Figure 5
Figure 5
Imaging analysis of a typical patient undergoing endovascular treatment for TBAD. A comparison of the pre- and post-operative original DSA images (A,B) and the syngo iFlow color-coded maps (C,D). A comparison of the pre- and post-operative time-intensity curves of the renal arteries (E,F), the right renal cortex (G,H), and the left renal cortex (I,J). In these curves, the x-axis refers to time (second) and y-axis represents the ratio of intensity within the ROI. ROI 1 and ROI 2 (E,F) were located in the renal arteries; ROI 1, ROI 2, and ROI 3 (G,H,I,J) were located in the renal cortex. TBAD, type B aortic dissection; DSA, digital subtraction angiography; ROI, region of interest.
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