Gadolinium-Enhanced Phase-Contrast Magnetic Resonance Portography

Non-contrast MR portography using time-spatial labeling inversion pulse for diagnosis of portal vein pathology

Background

To study the ability of non-contrast MR portography using time-spatial labeling inversion pulse (T-SLIP) as a non-invasive contrast-free imaging modality to delineate different portal vein pathological conditions.

The study included 25 patients with known history of portal vein disease and another 25 age-matched patients with normal portal vein. Both groups were examined by respiratory-triggered non-contrast MR portography using time-spatial labeling inversion pulse technique. Image quality was assessed first, and findings of diagnostic scans were compared to color duplex ultrasonography and selectively in those with diseased portal vein to portal-phase images of dynamic contrast-enhanced MRI.

Results

Significant relation was found between breathing regularity and image quality in T-SLIP sequence, with diagnostic scans sensitivity and specificity of 89.29% and 86.21%, respectively, for diagnosis of different portal vein pathological conditions.

Conclusions

Non-contrast MR portography is a useful technique for diagnosis of portal vein pathology in carefully selected patients.

MR-based measurements of portal vein flow and liver stiffness for predicting gastroesophageal varices

OBJECTIVES

We evaluated flow parameters measured by phase-contrast magnetic resonance (MR) imaging (PC-MRI) of the portal venous system and liver stiffness measured by MR elastography (MRE) to determine the usefulness of these methods in predicting gastroesophageal varices (GEV) in patients with chronic liver disease (CLD).

METHODS

In patients with CLD and controls, we performed PC-MRI on the portal (PV) and superior mesenteric veins; calculated mean velocity (V, cm/s), cross-sectional area (S, mm²), and flow volume (Q, mL/min); and determined markers of liver fibrosis (liver stiffness [kPa]) and aspartate aminotransferase (AST) platelet ratio index [APRI]). We visually assessed GEV and development of collateral pathways of the PV on routine contrast-enhanced dynamic MR imaging and compared patient characteristics, flow parameters, liver stiffness markers, and visual analysis among 3GEV groups, those with mild, severe, or no GEV with reference to endoscopic findings.

RESULTS

Child-Pugh grade, VPV, SPV, liver stiffness, APRI, and visually identified GEV (visible GEV) differed significantly among the 3 groups (P<0.05). We investigated VPV, SPV, liver stiffness, and visible GEV as independent markers to distinguish patients with and without GEV and examined VPV and visible GEV to predict severe GEV. Visible GEV showed low sensitivity (14 to 30%) and high specificity (98%) for predicting GEV in patients with CLD. A subgroup analysis that excluded cases with collateral pathway demonstrated slightly improved diagnostic performance of VPV and liver stiffness.

CONCLUSIONS

Portal vein flow parameters and liver stiffness can be useful markers for predicting GEV in patients with CLD.

MR evaluation of portal hypertensive collateral shunting vessels for predicting outcome after transjugular intrahepatic portosystemic shunt

PURPOSE

We assessed whether magnetic resonance (MR) imaging evaluation of portosystemic collateral shunts can aid prediction of therapeutic effectiveness and complications after creation of a transjugular portosystemic shunt (TIPS), and technical difficulty during the TIPS procedure.

MATERIALS AND METHODS

We retrospectively reviewed 32 patients (27 men, 5 women; mean age, 56.4 years) who underwent TIPS creation following gadolinium-enhanced MR examination. We measured the diameters of pre-existing portosystemic collateral shunting vessels, added the measurements together to generate a shunting collateral score for each patient, and divided patients into 2 groups by score of 4 or greater or less than 4. We then compared therapeutic effectiveness, technical difficulty and complications of the TIPS procedure, and portal venous (PV) pressure, PV-inferior vena cava (IVC) pressure gradient, and PV diameter between the groups.

RESULTS

The patients with a pre-existing large portosystemic shunt showed insignificant trends toward higher technical difficulty of the shunt procedure and rate of shunt dysfunction. The 2 groups showed no significant difference in early mortality rate, onset or worsening rate of hepatic encephalopathy after TIPS creation, PV pressure, PV-IVC pressure gradient, or PV diameter.

CONCLUSION

Gadolinium-enhanced MR imaging may help in predicting technical difficulty and complications of TIPS.

Optimization of the contrast dose and injection rates in whole-body MR angiography at 3.0T

PURPOSE

To optimize the contrast agent dose and delivery rate used in a novel whole-body magnetic resonance angiography (MRA) protocol using a 3.0T MR scanner.

MATERIALS AND METHODS

Six groups of 20 consenting volunteers underwent whole-body MRA, with each group receiving a different contrast dose and contrast delivery rate. The arterial tree was divided into 16 segments and the image quality at each of the anatomical locations, covering the whole body, was assessed. Qualitative analysis was carried out using a scoring assessment of image quality, and quantitative assessments were performed by measuring contrast-to-noise (CNR) and a signal-to-noise (SNR) index.

RESULTS

Reducing the contrast dose from 40 mL to 25 mL was found to significantly increase the CNR in several vessels of interest in the arterial tree. There was also a significant increase in the qualitative image quality score (P < 0.001).

CONCLUSION

This study demonstrates that reducing the contrast dose at 3.0T can result in an increase in the CNR in the vessels of interest without significantly affecting the SNR.

Preoperative imaging of left portal vein at the Rex recess for Rex shunt formation using wedged hepatic vein carbon dioxide portography

BACKGROUND

In children with extrahepatic portal vein obstruction (EHPVO), formation of a mesentericoportal bypass (Rex shunt) restores hepatopetal flow, relieves portal hypertension, and reduces variceal bleeding and hypersplenism. The Rex shunt is created by inserting a vein graft between the superior mesenteric vein and the umbilical segment (Rex) of the left portal vein within the Rex recess of the liver. The preoperative evaluation of a patient with EHPVO includes an accurate assessment of the venous inflow and outflow. The inflow portal vein is readily assessed by ultrasound and magnetic resonance imaging. The outflow intrahepatic portal vein is harder to assess. We report our experience of patients evaluated with wedged hepatic vein carbon dioxide portography (WHVCP).

METHOD

All children referred for venography from October 2001 to October 2007 were prospectively identified, and clinical and radiologic data were reviewed retrospectively. The imaging findings were correlated to findings at surgery.

RESULTS

Eleven children (range, 3-14 years, median, 6 years) were referred for preoperative wedged hepatic venography. The left portal vein at the Rex recess was clearly identified in 9 patients (82%). In the other 2 patients (18%), the Rex segment was not identified despite opacification of left and right intrahepatic portal veins; this was taken to indicate an occluded segment. Wedged venography was performed with carbon dioxide in 10 patients (91%). Carbon dioxide was contraindicated in the final patient because of the presence of a ventricular septal defect.

CONCLUSION

Our series demonstrates the use of WHVCP as a diagnostic tool in preoperative assessment of the Rex segment of left portal vein in children with extrahepatic portal vein obstruction.

Portal venous system: evaluation with unenhanced MR angiography with a single-breath-hold ECG-synchronized 3D half-Fourier fast spin-echo sequence

OBJECTIVE

Eighteen healthy persons underwent unenhanced MR angiography with a breath-hold ECG-synchronized 3D half-Fourier fast spin-echo technique to evaluate the visibility of the portal vein and its branches.

CONCLUSION

Our results indicated that unenhanced MR angiography with a singlebreath-hold ECG-synchronized 3D half-Fourier fast spin-echo sequence facilitates precise visualization of the anatomic features of the portal vein and its branches without the use of contrast agents.