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Assessment of Hepatic Perfusion Before and After a Meal Challenge Using Pseudo-Continuous Arterial Spin Labeling in MRI: Comparison with Intravoxel Incoherent Motion and Phase Contrast
Saori Watanabe1, Takashi Hamaguchi1, Naoki Ohno2, Yudai Shogan1, Yu Ueda3, Tadanori Takata1, Satoshi Kobayashi1,2,4, Tosiaki Miyati2, and Toshifumi Gabata4

1Department of Radiology, Kanazawa University Hospital, Kanazawa, Japan, 2Faclty of Health Sciences, Institute of Medical, Pharmaceutial and Health Sciences, Kanazawa University, Kanazawa, Japan, 3Philips Japan, Tokyo, Japan, 4Department of Radiology, Kanazawa University Graduate School of Medical Sciences, Kanazawa, Japan

Synopsis

To assess hepatic blood flow (HBF) with a noninvasive method, we acquired HBF flow before and after meal ingestion using the pCASL method. In addition, we investigated the relationship of HBF, perfusion-related diffusion coefficient (D*) with intravoxel incoherent motion and portal vein blood flow (PVBF) with phase contrast. For each value of HBF, D*, and PVBF following meal ingestion increased significantly compared with the values prior to ingestion. However, there were no correlations between hepatic blood flow, perfusion-related diffusion coefficient, or portal flow with either pre- or post-ingestion.

INTRODUCTION:

The quantification of hepatic perfusion parameters is a crucial step in the evaluation of liver function, making a diagnosis of hepatocellular carcinoma, or deciding on courses of treatment for liver disease. Pseudo-continuous arterial spin labeling (pCASL) in MRI has been previously used as a noninvasive method to assess blood flow.1 However, there have been few reports of hepatic perfusion being investigated using the pCASL technique. Hence, the aim of the present study was to assess hepatic blood flow before and after meal ingestion using the pCASL method.

METHODS:

Ten healthy volunteers (7 men and 3 women; mean age, 33.6 years; range, from 23 to 52 years) were enrolled in this study. All volunteers underwent liver MRI using a 3.0-T unit（Ingenia CX 3.0T，Philips Medical Systems, Best, Netherlands), following more than six hours of fasting and prior to ingestion of a commercially prepared meal (80 g, 400 kcal). Participants ingested the meal and were then rescanned during the next 30 to 60 minutes, using three imaging pulse sequences as follows: 1) Hepatic blood flow with pCASL. We set a label plane at the main portal vein and a scan plane immediately above the label plane(Fig. 1). A single post labeling delay (1800 ms) was used, with a label duration of 1800 ms. We calculated the hepatic blood flow map from the pCASL data (control, label, and proton density weighted images) using theoretical formulae (Fig. 2).2 2) Perfusion-related diffusion coefficient (D*) with intravoxel incoherent motion (IVIM). We placed an imaging plane in the same locations as for pCASL. Diffusion weighted images for IVIM analysis were used with 9 b-values of 0, 10, 30, 50, 100, 200, 400, 800, and 1000 s/mm2.3 3) Portal vein blood flow with phase contrast (PC). We acquired 2-dimensional PC gradient echo MR images perpendicular to the main trunk of the portal vein to measure portal flow over the cardiac cycle using Q-flow software (Philips Medical Systems, Best, Netherlands). Statistical tests to investigate differences before and after the meal challenge were conducted using a paired Wilcoxon test for all three imaging sequences.

RESULTS:

Before meal ingestion, hepatic blood flow, D*, and portal vein flow were 58.0 mL/100 g/min, 104.5×10−3 mm2/s, and 5.42 mL/s, respectively. Following meal ingestion, hepatic blood flow, D*, and portal vein flow were 80.4 mL/100 g/min, 209.1×10−3 mm2/s, and 9.82 mL/s, respectively (Fig. 3). For each volunteer group, the analytical values of pCASL, IVIM, and PC following meal ingestion increased significantly compared with the values prior to ingestion (P = 0.032, 0.019, 0.0049, respectively) (Fig. 4). However, there were no correlations between hepatic blood flow, D*, or portal flow with either pre- or post-ingestion (Fig. 5).

DISCUSSION:

This study provides evidence to show that it is possible to use the pCASL technique to measure dynamic changes in hepatic blood flow following meal stress. The perfusion-related diffusion coefficient, as determined by IVIM and the main portal flow, as determined by PC, also showed significant increases following ingestion, which is in agreement with results from previous studies.4,5 However, the label plane of the pCASL in this study included artery branches or intrahepatic vessels other than the main portal vein. Further studies are required to investigate regional blood flow using separately labeled portal veins and hepatic arteries.

CONCLUSION:

Significant increases in hepatic blood flow derived from a meal challenge can be detected using the pCASL-MRI technique. This noninvasive procedure may be a useful approach for the evaluation of liver function.

Acknowledgements

No acknowledgement found.

References

  1. Alsop DC, Detre JA, Golay X, et al. Recommended implementation of arterial spin-labeled perfusion MRI for clinical applications: A consensus of the ISMRM perfusion study group and the European consortium for ASL in dementia. Magn Reson Med. 2015; 73(1); 102-116.
  2. Buxton RB, Frank LR, Wong EC, et al. A general kinetic model for quantitative perfusion imaging with arterial spin labeling. Magn Reson Med. 1998;40(3);383-396.
  3. Le Bihan D, Breton E, Lallemand D, et al. Separation of diffusion and perfusion in intravoxel incoherent motion MR imaging. Radiology. 1988;168(2);497-505.
  4. Cox EF, Palaniyappan N, Aithal GP, et al. Using MRI to study the alterations in liver blood flow, perfusion, and oxygenation in response to physiological stress challenges: Meal, hyperoxia, and hypercapnia. J Magn Reson Imaging. 2018; in press.
  5. Regini F, Colagrande S, Mazzoni LN, et al. Assessment of Liver Perfusion by IntraVoxel Incoherent Motion (IVIM) Magnetic Resonance-Diffusion-Weighted Imaging: Correlation With Phase-Contrast Portal Venous Flow Measurements. J Comput Assiss Tomogr. 2015;39(3);365-372.

Figures

Fig. 1: Example placements of a label and scan plane.

Fig. 2: Hepatic blood flow map (a) before and (b) after meal ingestion from pCASL. Following meal injection hepatic blood flow increased.

Fig. 3: The analytical values of pCASL, IVIM, and PC before and after meal ingestion. For each value of after meal ingestion increased compared with the values prior to ingestion.

Fig. 4: Hepatic blood flow before and following meal ingestion. Hepatic blood flow after meal ingestion increased significantly compared with the values prior to ingestion (P = 0.032).

Fig. 5: The relationship of (a) hepatic blood flow and D* and (b) hepatic blood flow and portal vein flow. There were no correlations between hepatic blood flow, D*, or portal flow with either pre- or post-ingestion.

Proc. Intl. Soc. Mag. Reson. Med. 27 (2019)
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