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Radiology Research and Practice
Volume 2019, Article ID 7630671, 6 pages
https://doi.org/10.1155/2019/7630671
Research Article

Quantitative Evaluation of Display Contrast of Gd-EOB-DTPA-Enhanced Magnetic Resonance Images: Effects of the Flip Angle and Grayscale Gamma Value

1Department of Diagnostic Radiology, Kitasato University School of Medicine, Sagamihara, Kanagawa, Japan
2Department of Radiology, Kitasato University Hospital, Sagamihara, Kanagawa, Japan
3Department of Diagnostic Radiology, Kitasato University Hospital, Sagamihara, Kanagawa, Japan

Correspondence should be addressed to Yusuke Inoue; moc.liamg@43syeuoni

Received 3 July 2018; Accepted 9 January 2019; Published 16 January 2019

Academic Editor: Paul Sijens

Copyright © 2019 Yusuke Inoue et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Introduction. Display contrast can be changed nonlinearly by manipulating the gamma value of the grayscale. We investigated the contrast of the hepatobiliary-phase images acquired with different flip angles (FAs) and displayed with different gamma values in Gd-EOB-DTPA-enhanced magnetic resonance imaging. Material and Methods. Twenty patients with liver tumors were studied. Hepatobiliary-phase images were acquired at low (12°) and high (30°) FAs. Low-FA images were converted to simulate images displayed with different gamma values, using ImageJ software. To assess image contrast, the liver-to-muscle signal ratio (LMR), liver-to-spleen signal ratio (LSR), contrast ratio (CR), liver signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were calculated. Results. The LMR, LSR, and CR were higher in the high-FA images than in the low-FA original images. Although the SNR was lower in the high-FA images, indicating an increase in noise, the CNR was higher. Raising the gamma value increased the LMR, LSR, and CR, notably decreased the SNR, and slightly decreased the CNR. Conclusion. Increasing the FA enhanced image contrast, supporting its usefulness for improving the delineation of focal liver lesions. Although the associated increase in noise may be problematic, raising the grayscale gamma value enhances the display contrast of low-FA images.