Functional residual capacity breath hold for subtraction image of dynamic liver MRI

Purpose: In dynamic liver magnetic resonance imaging (MRI) studies, there are problems with misregistration when subtraction images are processed. For reduction of the misregistration, a functional residual capacity (FRC) phase breath-hold (FRC B-H) method was used. Material and methods: Sixty patients (32 males and 28 females, aged 33-85 years, median age 69 years) were examined. The subjects were chronologically categorized into two groups: a voluntary expiratory (VE) B-H group and a FRC B-H group. The blood-flow phase images were classified as plain, arterial, portal and parenchymal phases. To evaluate the reproducibility of liver positions between VE B-H and FRC B-H in each phase (between Plain and Arterial, Arterial and Portal, Plain and Parenchymal), the misregistration areas were compared on the top of the liver. Results: The misregistration area between Plain-Arterial, Arterial-Portal and Plain-Parenchymal in VE B-H was 731.0 ± 1153.6, 1134.9 ± 1357.2 and 628.4 ± 844.5 (cm2), respectively. The misregistration area between each phase in FRC B-H was 386.4 ± 874.9, 574.5 ± 1086.1 and 279.8 ± 551.2 (cm2), respectively. Using the Mann-Whitney U-test as quantitative analysis, the difference in misregistration areas between two groups was statistically significant (p < 0.05). Differences in the qualitative analysis were also significant according to the χ2 test (p < 0.05). Conclusion: The liver positions with FRC B-H were markedly more reproducible than those with VE B-H. To improve the registration accuracy of subtraction dynamic liver MRI, the FRC B-H should be used.