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Application of MR Magnetization Transfer Imaging in patients with liver fibrosis
Yanli Jiang1, Shaoyu wang2, and Jing Zhang1
1magnetic resonance imaging department, Lanzhou university second hospital, Lanzhou, China, 2DI MR RCT, Siemens Healthineers, Shanghai, China

Synopsis

Keywords: Liver, Magnetization transfer

Motivation: Liver fibrosis is likely to progress into cirrhosis, which affect the patient’s quality of life. Magnetization transfer (MT) imaging can indirectly reflect the content of structural macromolecular substances.

Goal(s): To evaluate the diagnostic accuracy of MTR imaging in staging of liver fibrosis and probe the sarcopenia in liver fibrosis stage.

Approach: 74 chronic liver diseases patients and 24 health control underwent MR examinations, MTR and
all the patients’ MTR value, APRI and FIB-4 value were recorded.

Results: MTR -Muscle was higher than MTR-Liver in any fibrosis stages except S1. And as the liver fibrosis stages increased, the MTR-Musle decreased accordingly.

Impact: MTR appeared may not serve as a specific marker for detecting the different liver fibrosis stages.

Introduction

Liver fibrosis is a common process associated with many liver diseases. If left untreated, liver fibrosis can progress to cirrhosis, leading to complications such as ascites and portal hypertension. In recent years, there has been growing awareness of sarcopenia, a condition that has been shown to be linked to a higher incidence of cirrhosis-related complications and a negative impact on the patient's quality of life [1]. Several studies [2, 3] have utilized CT or MRI to assess skeletal muscle mass and diagnose sarcopenia. However, whether sarcopenia is present in the early stages of liver fibrosis remains unclear. Magnetization transfer (MT) imaging is an MRI technique that uses off-resonance radiofrequency (RF) pulses to selectively saturate macromolecule-bound protons [4]. This approach indirectly provides insights into the content of structural macromolecular substances in biological tissues by quantitatively measuring the magnetization transfer ratio (MTR) value. The aim of this study was to utilize MTR to assess the condition of the liver and erector spinae muscles in patients at different stages of liver fibrosis.

Methods

74 patients with chronic liver diseases and 24 healthy controls underwent MR examinations on a 1.5T MR scanner (MAGNETOM Aera, Siemens Healthcare, Erlangen, Germany) utilizing a combination of 18-channel body and 12-channel spine matrix coil elements. MT imaging was acquired using a two-dimensional fast low-angle shot sequence, involving two scans with (MT on) and without (MT off) the application of an off-resonant prepulse. The parameters for MT imaging were as follows: TR 280ms, TE 4.6ms, FOV 309×380, thickness 6mm, effective flip angle 70°, bandwidth 140 Hz, amplitude 375 Hz, length 9.984 msec, and a frequency offset of 1200 Hz. To calculate the MTR map, the following equation was used: MTR = (MT off – MT on) × 100 / MT off. MTR values were measured on the MTR map of each subject using the region of interest method, denoted as MTR-L (MTR of the liver) and MTR-M (MTR of muscle). The histopathologic diagnosis of liver fibrosis (S) and necroinflammatory activity (G) was confirmed through liver biopsy. Laboratory indicators related to the patients were collected to calculate the APRI and FIB-4 scores.

Results

Table 1 presents the mean values and standard deviations (SD) of MTR for the liver and muscle at different stages of liver fibrosis and necroinflammatory activity. Neither MTR-L nor MTR-M showed significant differences among different liver fibrosis stages and necroinflammatory activity (P > 0.05). The correlation between MTR of the liver and muscle with liver fibrosis stages is depicted in Figure 2. Notably, MTR-M was higher than MTR-L at every stage of liver fibrosis, and this difference was statistically significant (0.001 < P < 0.024), except for stage 1 (P = 0.088). MTR-L increased with the liver fibrosis stage, while MTR-M decreased. However, there was no significant correlation between the two (Table 2).

Discussion

MT imaging is a contrast mechanism that is sensitive to the concentration of macromolecules in a physiological aqueous environment [5]. Our study yielded three main findings. Firstly, we found that MTR-L exhibited no significant differences in relation to liver fibrosis stages and necroinflammatory activity. This finding is in line with certain prior studies. This lack of distinction may be due to the liver's short T2 relaxation time, leading to direct water saturation, which can confound MT measurements.Secondly, MTR-M was higher than MTR-L in all fibrosis stages except for S1. These results align with previous studies. Rosenkrantz et al. [6 7] noted a higher mean MTR for muscle compared to the liver. Martirosian et al. [8] found that the MTR of muscle was consistently higher than that of the liver at different field strengths. This suggests that MT sequences can effectively differentiate substances with varying macromolecule concentrations.Thirdly, MTR-M decreased with the severity of liver fibrosis, although this decline was not statistically significant. This observation might be attributed to the concurrent occurrence of sarcopenia and muscle mass decline, accompanied by fat tissue infiltration, which could reduce the MTR. In our study, the decline in MTR-M was not prominent during the fibrosis stage. This could be due to the chronic nature of liver fibrosis, with mild fibrosis being the predominant stage in our study. This stage might lack the specificity for cross-relaxation processes detected using the MT sequence [7].

Conclusion

In conclusion, our results suggest that MTR may not be a specific marker for distinguishing different liver fibrosis stages.

Acknowledgements

No acknowledgement found.

References

  1. Norman K, Kirchner H, Lochs H, and Pirlich M. Malnutrition affects quality of life in gastroenterology patients. World journal of gastroenterology. 2006;12:3380-5.2.
  2. Liu J, Ma J, Yang C, et al. Sarcopenia in Patients with Cirrhosis after Transjugular Intrahepatic Portosystemic Shunt Placement. Radiology. 2022;303:711-719.3.
  3. Praktiknjo M, Book M, Luetkens J, et al. Fat-free muscle mass in magnetic resonance imaging predicts acute-on-chronic liver failure and survival in decompensated cirrhosis. Hepatology (Baltimore, Md.). 2018;67:1014-1026.
  4. Grossman R, Gomori J, Ramer K, Lexa F, and Schnall M. Magnetization transfer: theory and clinical applications in neuroradiology. Radiographics : a review publication of the Radiological Society of North America, Inc. 1994;14:279-90.
  5. Van Zijl P, Lam W, Xu J, Knutsson L, and Stanisz G. Magnetization Transfer Contrast and Chemical Exchange Saturation Transfer MRI. Features and analysis of the field-dependent saturation spectrum. NeuroImage. 2018;168:222-241.
  6. Kim H, Booth C, Pinus A, et al. Induced hepatic fibrosis in rats: hepatic steatosis, macromolecule content, perfusion parameters, and their correlations--preliminary MR imaging in rats. Radiology. 2008;247:696-705.
  7. Rosenkrantz A, Storey P, Gilet A, et al. Magnetization transfer contrast-prepared MR imaging of the liver: inability to distinguish healthy from cirrhotic liver. Radiology. 2012;262:136-43.
  8. Martirosian P, Boss A, Deimling M, et al. Systematic variation of off-resonance prepulses for clinical magnetization transfer contrast imaging at 0.2, 1.5, and 3.0 tesla. Investigative radiology. 2008;43:16-26.

Figures

Figure 1, The MTR imaging of a patient graded as G1S1, the blue circle is the ROI of liver, and the red circle is the ROI of erector spinae muscle

Figure 2, the mean MTR of liver and muscle in different liver fibrosis stage

Table 1, The mean value and standard deviation (SD) of MTR of liver and erector spinae muscles in different staging of liver fibrosis and necroinflammatory activity

Table 2 the spearman correlation between MTR and liver fibrosis stage and necroinflammatory activity

Proc. Intl. Soc. Mag. Reson. Med. 32 (2024)
4155
DOI: https://doi.org/10.58530/2024/4155