van Rijssel MJ, Pluim JPW, Chan HSM, van den Wildenberg L, Schmitz AMT, Luijten PR, Gilhuijs KGA, Klomp DWJ. Correcting time-intensity curves in dynamic contrast-enhanced breast MRI for inhomogeneous excitation fields at 7T.
Magn Reson Med 2019;
84:1000-1010. [PMID:
31880346 PMCID:
PMC7217168 DOI:
10.1002/mrm.28147]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 12/05/2019] [Accepted: 12/06/2019] [Indexed: 12/13/2022]
Abstract
Purpose
Inhomogeneous excitation at ultrahigh field strengths (7T and above) compromises the reliability of quantified dynamic contrast‐enhanced breast MRI. This can hamper the introduction of ultrahigh field MRI into the clinic. Compensation for this non‐uniformity effect can consist of both hardware improvements and post‐acquisition corrections. This paper investigated the correctable radiofrequency transmit (B1+) range post‐acquisition in both simulations and patient data for 7T MRI.
Methods
Simulations were conducted to determine the minimum B1+ level at which corrections were still beneficial because of noise amplification. Two correction strategies leading to differences in noise amplification were tested. The effect of the corrections on a 7T patient data set (N = 38) with a wide range of B1+ levels was investigated in terms of time‐intensity curve types as well as washin, washout and peak enhancement values.
Results
In simulations assuming a common amount of T1 saturation, the lowest B1+ level at which the SNR of the corrected images was at least that of the original precontrast image was 43% of the nominal angle. After correction, time‐intensity curve types changed in 24% of included patients, and the distribution of curve types corresponded better to the distribution found in literature. Additionally, the overlap between the distributions of washin, washout, and peak enhancement values for grade 1 and grade 2 tumors was slightly reduced.
Conclusion
Although the correctable range varies with the amount of T1 saturation, post‐acquisition correction for inhomogeneous excitation was feasible down to B1+ levels of 43% of the nominal angle in vivo.
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