Abstract
ObjectiveTo establish a baseline of susceptibility-weighted imaging (SWI) phase value as a means of detecting iron abnormalities in cirrhotic liver and to analyze its relationship with R2*.Materials and MethodsSixteen MnCl2 phantoms, thirty-seven healthy individuals and 87 cirrhotic patients were performed SWI and multi-echo T2*-weighted imaging, and the signal processing in NMR (SPIN) software was used to measure the radian on SWI phase images and the R2* on T2* maps. The mean minus two times standard deviation (SD) of Siemens Phase Unit (SPU) in healthy individuals was designated as a threshold to separate the regions of interest (ROIs) into high- and low-iron areas in healthy participants and cirrhotic patients. The SWI phase values of high-iron areas were calculated. The R2* values was measured in the same ROI in both healthy participants and patients.ResultsSWI phase values correlated linearly with R2* values in cases of MnCl2 concentrations lower than 2.3 mM in vitro (r = −0.996, P<0.001). The mean value and SD of 37 healthy participants were 2003 and 15 (SPU), respectively. A threshold of 1973 SPU (−0.115 radians) was determined. The SWI phase value and R2* values had a negative correlation in the cirrhotic patients (r = −0.742, P<0.001). However, no similar relationship was found in the healthy individuals (r = 0.096, P = 0.576). Both SWI phase values and R2* values were found to have significant correlations with serum ferritin concentrations in 42 patients with blood samples (r = −0.512, P = 0.001 and r = 0.641, P<0.001, respectively).ConclusionSWI phase values had significant correlations with R2* after the establishment of a baseline on the phase image. SWI phase images may be used for non-invasive quantitative measurement of mild and moderate iron deposition in hepatic cirrhosis in vivo.
Highlights
There is a significant association between hepatic iron deposition and many chronic hepatic diseases; hepatic iron deposition could be an important synergistic risk factor for hepatic fibrosis, cirrhosis, and hepatocellular carcinoma [1,2]
Siemens Phase Unit (SPU) Measurements in Healthy Subjects The SPU measurement obtained from entire regions of interest (ROIs) of 37 healthy subjects showed a normal distribution (Z = 0.676, P = 0.751)
In the 37 healthy subjects, the mean and standard deviation (SD) of the susceptibility-weighted imaging (SWI) phase values were 2003 and 15 (SPU), respectively. Because it was a right-handed system, 1973 SPU (20.115 radians) was used as the threshold to divide the ROIs of the SWI phase images from the healthy participants and the cirrhotic patients into high- and low-iron areas (Figure 3)
Summary
There is a significant association between hepatic iron deposition and many chronic hepatic diseases; hepatic iron deposition could be an important synergistic risk factor for hepatic fibrosis, cirrhosis, and hepatocellular carcinoma [1,2]. When diagnosing, evaluating and treating hepatic iron deposition, it is important to quantitatively measure the liver iron concentration in vivo. The gold standard for measuring hepatic iron concentration (HIC) is the liver biopsy. Iron is a paramagnetic substance that can shorten the T2 and T2* relaxation time measurements. For this reason, non-invasive magnetic resonance imaging (MRI) methods for the quantitative measurement of HIC have attracted more attention in recent years. Previous MRI methods for non-invasive quantitative measurement have been divided into two categories: 1) measuring the ratio of signal intensities of the liver and paraspinal muscles [6,7,8]; and 2) measuring the T2 and T2* values directly through the application of multi-echo gradient echo T2 and T2* sequences, which are converted into reciprocal R2 and R2* values for the quantitative measurement of HIC [9,10,11]. The multi-echo T2* scan is the most sensitive of these methods and the most reproducible method for measuring HIC [7,12]
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