The Intrinsic Signal-to-Noise Ratio in Human Cardiac Imaging at 1.5, 3, and 4 T

✍ Scribed by H. Wen; T.J. Denison; R.W. Singerman; R.S. Balaban

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 910 KB
• Volume: 125
• Category: Article
• ISSN: 1090-7807
• DOI: 10.1006/jmre.1996.1072

✦ Synopsis

Cardiac imaging is inherently demanding on the signal-to-noise strengths, the RF wavelength and the RF penetration depth performance of the MR scanner and may benefit from high field approach the dimension of the body, resulting in a significant strengths. However, the complex behavior of the radiofrequency contribution of the induced conductive and dielectric curfield in the human body at high frequencies makes model-based rents and phase variation of the RF field across the body. analyses difficult. This study aims to obtain reliable comparisons Under these conditions, the quasi-static approximation needs of the signal-to-noise profile in the human chest in vivo at 1.5, 3, to be replaced with the full Maxwell equations. This point and 4 T. By using an RF-field-mapping method, it is shown that was illustrated by phase-sensitive electric field measurethe intrinsic signal-to-noise increases with the field strength up to ments up to 110 MHz in elliptical phantoms in the context 4 T with a less than linear relation. The RF field profile is markedly of hyperthermia (6, 7), and by measurements of the power distorted at 4 T, and the onset of this distortion is dependent on the body size. The high power deposition and the consequences of deposition (8) and loading effect of the body on whole-body the RF field distortion are discussed. ᭧ 1997 Academic Press

RF coils at frequencies up to 85 MHz (9), as well as loading effects of surface coils up to 100 MHz (10). Head images collected at 4 T also showed substantial dielectric resonant