Optimization of the Flip Angle and Scan Timing in Hepatobiliary Phase Imaging Using T1-Weighted, CAIPIRINHA GRE Imaging

PURPOSE: This study was designed to optimize the flip angle (FA) and scan timing of the hepatobiliary phase (HBP) using the 3D T1-weighted, gradient-echo (GRE) imaging with controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA) technique on gadoxetic acid-enhanced 3T liver MR imaging. MATERIALS AND METHODS: Sixty-two patients who underwent gadoxetic acid-enhanced 3T liver MR imaging were included in this study. Four 3D T1-weighted GRE imaging studies using the CAIPIRINHA technique and FAs of 9° and 13° were acquired during HBP at 15 and 20 min after intravenous injection of gadoxetic acid. Two abdominal radiologists, who were blinded to the FA and the timing of image acquisition, assessed the sharpness of liver edge, hepatic vessel clarity, lesion conspicuity, artifact severity, and overall image quality using a five-point scale. Quantitative analysis was performed by another radiologist to estimate the relative liver enhancement (RLE) and the signal-to-noise ratio (SNR). Statistical analyses were performed using the Wilcoxon signed rank test and one-way analysis of variance. RESULTS: The scores of the HBP with an FA of 13° during the same delayed time were significantly higher than those of the HBP with an FA of 9° in all the assessment items (P < 0.01). In terms of the delay time, images at the same FA obtained with a 20-min-HBP showed better quality than those obtained with a 15-min-HBP. There was no significant difference in qualitative scores between the 20-min-HBP and the 15-min-HBP images in the non-liver cirrhosis (LC) group except for the hepatic vessel clarity score with 9° FA. In the quantitative analysis, a statistically significant difference was found in the degree of RLE in the four HBP images (P = 0.012). However, in the subgroup analysis, no significant difference in RLE was found in the four HBP images in either the LC or the non-LC groups. The SNR did not differ significantly in the four HBP images. In the subgroup analysis, 20-min-HBP imaging with a 13° FA showed the highest SNR value in the LC-group, whereas 15-min-HBP imaging with a 13° FA showed the best value of SNR in the non-LC group. CONCLUSION: The use of a moderately high FA improves the image quality and lesion conspicuity on 3D, T1-weighted GRE imaging using the CAIPIRINHA technique on gadoxetic acid, 3T liver MR imaging. In patients with normal liver function, the 15-min-HBP with a 13° FA represents a feasible option without a significant decrease in image quality.

Polyethylene Liner Wear in Harris-Galante Acetabular Cup: Two Dimensional versus Three Dimensional Method / 대한정형외과학회잡지

PURPOSE: The purpose of this study was to compare the two-dimensional with three-dimensional radiographic measurements of polyethylene liner wear in the Harris-Galante II acetabular cup. MATERIALS AND METHODS: We measured the polyethylene liner wear amount and the wear rate of 64 hips with Harris-Galante II acetabular cup by two methods: Livermore's method and modified Devane's method. We evaluated the relationships between the two methods. RESULTS: The average total amount of wear and the average wear rate are 0.86+/-1.01 mm and 0.18+/-0.20 mm/year using the two-dimensional method and 0.99+/-1.01 mm and 0.21+/-0.2 mm/year using three-dimensional method respectively. The amount of wear and the wear rate by the three-dimensional method was larger than those by the two dimensional method. CONCLUSION: The amount of polyethylene liner wear can be measured by the two-dimensional method because it is highly correlated with the amount that is measured by the three-dimensional method, since there was no differences between the two methods.