A Study on the Flip Angle for an Optimal T1-weighted Image based on the 3D-THRIVE MRI Technique: Focusing on the Detection of a Hepatocellular Carcinoma (HCC)

摘要

This study examined the optimal flip angle (FA) for a T1-weighted image in the detection of a hepatocellular carcinoma (HCC). A 3D-T1-weighted high-resolution isotropic volume examination (THRIVE) technique was used to determine the dependence of the signal to noise ratio (SNR) and the contrast-to-noise ratio (CNR) on the change in FA. This study targeted 40 liver cancer patients (25 men and 15 women aged 50 to 70 years with a mean age of 60.32 ± 6.2 years) who visited this hospital to undergo an abdominal MRI examination from January to June 2013. A 3.0 Tesla MRI machine (Philips, Medical System, Achieva) and a MRI receiver coil for data reception with a 16-channel multicoil were used in this study. The THRIVE (repetition time (TR): 8.1 ms, echo time (TE): 3.7 ms, matrix: 172 × 172, slice thickness: 4 mm, gap: 2 mm, field of view (FOV): 350 mm, and band width (BW): 380.1 Hz) technique was applied as a pulse sequence. The time required for the examination was 19 seconds, and the breath-hold technique was used. Axial images were obtained at five FAs: 5, 10, 15, 20 and 25?. The signal intensities of the liver, the lesion and the background noise were measured based on the acquired images before the SNR and the CNR were calculated. To evaluate the image at the FA, we used SPSS for Windows ver. 17.0 to conduct a one-way ANOVA test. A Bonferroni test was conducted as a post-hoc test. The SNRs of the hemorrhagic HCC in the 3D-THRIVE technique were 35.50 ± 4.12, 97.00 ± 10.24, 66.09 ± 7.29, 53.84 ± 5.43, and 42.92 ± 5.11 for FAs of 5, 10, 15, 20, and 25?, respectively (p = 0.0430), whereas the corresponding CNRs were 30.50 ± 3.84, 43.00 ± 5.42, 36.54 ± 4.09, 32.30 ± 2.79, and 31.69 ± 3.21 (p = 0.0003). At a small FA of 10, the SNR and the CNR showed the highest values. As the FA was increased, the SNR and the CNR values showed a decreasing tendency. In conclusion, the optimal T1-weighted image FA should be set to 10? to detect a HCC by using the 3D-THRIVE abdominal MRI technique.