Quantification of the Hemodynamic Changes of Cirrhosis with Free-Breathing Self-Navigated MRI

Abstract

Background: Non-invasive assessment of the hemodynamic changes of cirrhosis might help guide management of patients with liver disease but are currently limited.

Purpose: To determine whether free-breathing 4D flow MRI can be used to quantify the hemodynamic effects of cirrhosis and introduce hydraulic circuit indexes of severity.

Study type: Retrospective.

Population: Forty-seven patients including 26 with cirrhosis.

Field strength/sequence: 3 T/free-breathing 4D flow MRI with soft gating and golden-angle view ordering.

Assessment: Measurements of the supra-celiac abdominal aorta, supra-renal abdominal aorta (SRA), celiac trunk (CeT), superior mesenteric artery (SMA), splenic artery (SpA), common hepatic artery (CHA), portal vein (PV), and supra-renal inferior vena cava (IVC) were made by two radiologists. Measures of hepatic vascular resistance (hepatic arterial relative resistance [HARR]; portal resistive index [PRI]) were proposed and calculated.

Statistical analysis: Bland-Altman, Pearson's correlation, Tukey's multiple comparison, and Cohen's kappa. P < 0.05 was considered significant.

Results: Forty-four of 47 studies yielded adequate image quality for flow quantification (94%). Arterial structures showed high inter-reader concordance (range; ρ = 0.948-0.987) and the IVC (ρ = 0.972), with moderate concordance in the PV (ρ = 0.866). Conservation of mass analysis showed concordance between large vessels (SRA vs. IVC; ρ = 0.806), small vessels (celiac vs. CHA + SpA; ρ = 0.939), and across capillary beds (CeT + SMA vs. PV; ρ = 0.862). Splanchnic flow was increased in patients with portosystemic shunting (PSS) relative to control patients and patients with cirrhosis without PSS (P < 0.05, difference range 0.11-0.68 liter/m). HARR was elevated and PRI was decreased in patients with PSS (3.55 and 1.49, respectively) compared to both the control (2.11/3.18) and non-PSS (2.11/2.35) cohorts.

Data conclusion: 4D flow MRI with self-navigation was technically feasible, showing promise in quantifying the hemodynamic effects of cirrhosis. Proposed quantitative metrics of hepatic vascular resistance correlated with PSS.

Level of evidence: 3 TECHNICAL EFFICACY STAGE: 2.

Keywords: 4D flow; TIPS; cirrhosis; liver; portal vein; splanchnic.

Figure 1:. 4D flow with self-navigation and example measurements.

Color coded images at peak systolic flow from a patient with cirrhosis. Blue means slower blood flow while red reflects peak systolic blood flow velocity in the abdominal aorta. (A) Oblique view of 4D flow-SN images showing the course of the celiac trunk and common hepatic artery (CHA) from the aorta into the hepatic hilum (B) Conventional coronal view of 4D flow-SN images showing the bifurcation of the celiac trunk into the splenic artery and CHA, as well at the superior mesenteric vein draining into the portal vein (PV). In both panels A and B, the yellow circles indicate typical location of measurements. (C) Axial T1 weighted imaging showing the course of the proper hepatic and right hepatic arteries. The gray star indicates the location of prominent loop in the proper hepatic artery.

Figure 1:. 4D flow with self-navigation and example measurements.

Color coded images at peak systolic flow from a patient with cirrhosis. Blue means slower blood flow while red reflects peak systolic blood flow velocity in the abdominal aorta. (A) Oblique view of 4D flow-SN images showing the course of the celiac trunk and common hepatic artery (CHA) from the aorta into the hepatic hilum (B) Conventional coronal view of 4D flow-SN images showing the bifurcation of the celiac trunk into the splenic artery and CHA, as well at the superior mesenteric vein draining into the portal vein (PV). In both panels A and B, the yellow circles indicate typical location of measurements. (C) Axial T1 weighted imaging showing the course of the proper hepatic and right hepatic arteries. The gray star indicates the location of prominent loop in the proper hepatic artery.

Figure 1:. 4D flow with self-navigation and example measurements.

Color coded images at peak systolic flow from a patient with cirrhosis. Blue means slower blood flow while red reflects peak systolic blood flow velocity in the abdominal aorta. (A) Oblique view of 4D flow-SN images showing the course of the celiac trunk and common hepatic artery (CHA) from the aorta into the hepatic hilum (B) Conventional coronal view of 4D flow-SN images showing the bifurcation of the celiac trunk into the splenic artery and CHA, as well at the superior mesenteric vein draining into the portal vein (PV). In both panels A and B, the yellow circles indicate typical location of measurements. (C) Axial T1 weighted imaging showing the course of the proper hepatic and right hepatic arteries. The gray star indicates the location of prominent loop in the proper hepatic artery.

Figure 2:. Circuit diagram of HARR and PRI

Panel A: Assuming conventional anatomy and assuming left gastric artery and gastroduodenal artery flow is negligible, blood flow into the celiac trunk splits into the common hepatic artery (Q_H) and the splenic artery (Q_S). Increased resistance in the hepatic artery (R_H) or decreased resistance in the splenic artery (R_s) leads to increased flow in the splenic artery, and vice-versa. Applying Poisuille’s relationship yields the hepatic artery relative resistance $\left(\text{HARR}\right)=\left({\text{R}}_{\text{H}}/{\text{R}}_{\text{S}}\right)=\left({\text{Q}}_{\text{S}}/{\text{Q}}_{\text{H}}\right),$, with Q_S and Q_H being measurable terms using 4D flow. Panel B: By similar logic to Panel A, we can derive a marker for the resistance of the portal venous system relative to the systemic circulation. Increased resistance in the portal veins will reduce flow in the splenic artery (Q_S) and SMA (Q_SMA) while increasing flow in the hepatic artery (Q_H) and aortic outflow (Q_OUT) via the suprarenal aorta. Applying Poisuille’s relationship yields the portal resistive index $\left(\text{PRI}\right)=\left({\text{R}}_{\text{SMA}}+{\text{R}}_{\text{S}}\right)/\left({\text{R}}_{\text{OUT}}+{\text{R}}_{\text{H}}\right)=\left({\text{Q}}_{\text{OUT}}+{\text{Q}}_{\text{H}}\right)/\left({\text{Q}}_{\text{SMA}}+{\text{Q}}_{\text{S}}\right)$. SMA = superior mesenteric artery

Figure 2:. Circuit diagram of HARR and PRI

Panel A: Assuming conventional anatomy and assuming left gastric artery and gastroduodenal artery flow is negligible, blood flow into the celiac trunk splits into the common hepatic artery (Q_H) and the splenic artery (Q_S). Increased resistance in the hepatic artery (R_H) or decreased resistance in the splenic artery (R_s) leads to increased flow in the splenic artery, and vice-versa. Applying Poisuille’s relationship yields the hepatic artery relative resistance $\left(\text{HARR}\right)=\left({\text{R}}_{\text{H}}/{\text{R}}_{\text{S}}\right)=\left({\text{Q}}_{\text{S}}/{\text{Q}}_{\text{H}}\right),$, with Q_S and Q_H being measurable terms using 4D flow. Panel B: By similar logic to Panel A, we can derive a marker for the resistance of the portal venous system relative to the systemic circulation. Increased resistance in the portal veins will reduce flow in the splenic artery (Q_S) and SMA (Q_SMA) while increasing flow in the hepatic artery (Q_H) and aortic outflow (Q_OUT) via the suprarenal aorta. Applying Poisuille’s relationship yields the portal resistive index $\left(\text{PRI}\right)=\left({\text{R}}_{\text{SMA}}+{\text{R}}_{\text{S}}\right)/\left({\text{R}}_{\text{OUT}}+{\text{R}}_{\text{H}}\right)=\left({\text{Q}}_{\text{OUT}}+{\text{Q}}_{\text{H}}\right)/\left({\text{Q}}_{\text{SMA}}+{\text{Q}}_{\text{S}}\right)$. SMA = superior mesenteric artery

Figure 3:. Cohort selection.

Patient flow charts demonstrating selection of patient cohorts.

Figure 3:. Cohort selection.

Patient flow charts demonstrating selection of patient cohorts.

Figure 4:. Bland-Altman analysis of inter-reader agreement.

Bland Altman analysis comparing averaged measurements from reader 1 and reader 2 across all vessels.

Figure 5:. Comparison of blood flow across cohorts.

Quantification of blood flow in the different cohorts across all vessels assessed in the study. Details of p values are provided in Table 4. **** p < 0.0001 ** p < 0.005 #### p < 0.0001 †††† p < 0.0001 † p < 0.05

Figure 6:. HARR and PRI.

Comparison of hepatic arterial relative resistance (HARR) and portal resistive index (PRI) between the three cohorts of patients: the control cohort, the cirrhosis without portosystemic shunting (non-PSS) cohort, and the cirrhosis with portosystemic shunting (PSS) cohort. HARR was significantly higher in the PSS cohort, as compared to both the control and non-PSS cohort. PRI was significantly reduced in the non-PSS cohort as compared to the control cohort, and the PRI was significantly reduced in the PSS cohort as compared to both other cohorts. ††† p < 0.05 # p < 0.05 * p < 0.0005