An In Vitro and In Vivo Analysis of the Correlation between Susceptibility-Weighted Imaging Phase Values and R2* in Cirrhotic Livers

Objective To 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 Methods Sixteen MnCl 2 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. Results SWI phase values correlated linearly with R2* values in cases of MnCl 2 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). Conclusion SWI 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.