High Acceleration Three-Dimensional T1-Weighted Dual Echo Dixon Hepatobiliary Phase Imaging Using Compressed Sensing-Sensitivity Encoding: Comparison of Image Quality and Solid Lesion Detectability with the Standard T1-Weighted Sequence

OBJECTIVE: To compare a high acceleration three-dimensional (3D) T1-weighted gradient-recalled-echo (GRE) sequence using the combined compressed sensing (CS)-sensitivity encoding (SENSE) method with a conventional 3D GRE sequence using SENSE, with respect to image quality and detectability of solid focal liver lesions (FLLs) in the hepatobiliary phase (HBP) of gadoxetic acid-enhanced liver MRI. MATERIALS AND METHODS: A total of 217 patients with gadoxetic acid-enhanced liver MRI at 3T (54 in the preliminary study and 163 in the main study) were retrospectively included. In the main study, HBP imaging was done twice using the standard mDixon-3D-GRE technique with SENSE (acceleration factor [AF]: 2.8, standard mDixon-GRE) and the high acceleration mDixon-3D GRE technique using the combined CS-SENSE technique (CS-SENSE mDixon-GRE). Two abdominal radiologists assessed the two MRI data sets for image quality in consensus. Three other abdominal radiologists independently assessed the diagnostic performance of each data set and its ability to detect solid FLLs in 117 patients with 193 solid nodules and compared them using jackknife alternative free-response receiver operating characteristics (JAFROC). RESULTS: There was no significant difference in the overall image quality. CS-SENSE mDixon-GRE showed higher image noise, but lesser motion artifact levels compared with the standard mDixon-GRE (all p < 0.05). In terms of lesion detection, reader-averaged figures-of-merit estimated with JAFROC was 0.918 for standard mDixon-GRE, and 0.953 for CS-SENSE mDixon-GRE (p = 0.142). The non-inferiority of CS-SENSE mDixon-GRE over standard mDixon-GRE was confirmed (difference: 0.064 [−0.012, 0.081]). CONCLUSION: The CS-SENSE mDixon-GRE HBP sequence provided comparable overall image quality and non-inferior solid FFL detectability compared with the standard mDixon-GRE sequence, with reduced acquisition time.

Correlation of the Speed of Enhancement of Hepatic Hemangiomas with Intravoxel Incoherent Motion MR Imaging

PURPOSE: To evaluate the relationship between the speed of enhancement of hepatic hemangiomas on gadolinium-enhanced MRI and ADC values by using various parameters, including the D, f, D* and ADC(fit) on intravoxel incoherent motion (IVIM) MR Imaging. MATERIALS AND METHODS: The institutional review board approved this retrospective study. A total of 47 hepatic hemangiomas from 39 patients were included (20 men and 19 women). The hemangiomas were classified into three types according to the enhancement speed of the hepatic hemangiomas on gadolinium-enhanced dynamic T1-weighted images: rapid (Type A), intermediate (Type B), and slow (Type C) enhancement. The D, f, D* and ADC(fit) values were calculated using IVIM MR imaging. The diffusion/perfusion parameters and ADC values were compared among the three types of hemangiomas. RESULTS: Both the ADC(fit) and D values of type C were significantly lower than those of type A (P = 0.0022, P = 0.0085). However, for the f and D*, there were no significant differences among the three types. On DWI with all b values (50, 200, 500 and 800 sec/mm2), the ADC values of type C were significantly lower than those of the type A (P < 0.012). For b values with 800 sec/mm2, the ADC800 values of the type C hemangiomas were significantly lower than those of type B (P = 0.0021). We found a negative correlation between hepatic hemangioma enhancement type and ADC50 (rho= -0.357, P = 0.014), ADC200 (rho= -0.537, P = 0.0001), ADC500 (rho= -0.614, P = 0.0001), and ADC800(rho= -0.607, P = 0.0001). Therefore, four ADC values of ADC50, ADC200, ADC500, and ADC800 were decreased with decreasing enhancement speed. CONCLUSION: Hepatic hemangiomas had variable ADCs according to the type of enhancement, and the reduced ADCs in slowly enhancing hemangiomas may be related to the reduced pure molecular diffusion (D).