Estimation of Optimum Flip Angle using 3D VANE XD Technique: Focused on Pre-Contrast and Hepatobiliary Phase

Abstract

To investigate the optimum flip angle that can enhance image quality, SNR (signal to noise ratio), and CNR (contrast to noise ratio), comparing the images obtained, applying flip angles, 11°, 14°, 17°, 20°, and 23° in get-ting Liver Hepatobiliary Phase image using 3D VANE XD(3D Multivane mDixon, Philips Healthcare) technique. Experiments were conducted on a total of 30 outpatients and inpatients to our hospital (HCC:10, Metastasis:10, Abscess:10). As for the equipment used in the experiments, Philips Ingenia 3.0T CX was used, and all parameters other than the flip angle were set the same to conduct the tests. As for the image analysis method, using the Image-J program (National Institutes of Health and LOCI), the SNR of the liver, kidney, and pancreas obtained from the images by flip angle before the contrast medium injection and the CNR between the lesion and the normal tissue after the contrast medium injection were measured to conduct comparative analysis. As a result of a comparison of images before and after the contrast medium injection by disease, when the flip angle of 17° was applied, SNR and CNR were measured higher than in the images of other flip angles (p<0.05). In the comparisons of the images taken before and after the injection of contrast medium by disease, when a flip angle of 17° was applied, the SNR before contrast medium injection was 28-29 % higher, and the SNR after the injection of contrast medium was 11 % up to 49 % higher than that at other flip angles. There was a difference in CNR before contrast medium injection of 30-43 % and CNR after contrast medium injection of 58-68 %. The measured value increased up to 17° and then decreased after that. Additionally, in the qualitative evaluation, Lesion Conspicuity (p=0.003), Image Artifact (p=0.0001), Lesion Delineation (p=0.0002), and Vascular Anatomy (p=0.0002) received the most excellent evaluations at 17°. In conclusion, in this study, the flip angle of 17° provided the highest SNR and CNR values when the tests were conducted using the free breath hold technique, 3D VANE XD Sequence. Thus, in liver MRI protocol tests, the overall diagnostic information was provided, including hypervascular tumor.