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Optimization and evaluation of reference region variable flip angle (RR‐VFA) B 1 + and T 1 Mapping in the Prostate at 3T
Author(s) -
Rangwala Novena A.,
Dregely Isabel,
Wu Holden H.,
Sung Kyunghyun
Publication year - 2017
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.25410
Subject(s) - prostate , flip angle , nuclear medicine , scanner , relative standard deviation , prostate cancer , mathematics , standard deviation , medicine , physics , magnetic resonance imaging , statistics , radiology , optics , cancer , detection limit
Purpose To optimize and evaluate the reference region variable flip angle (RR‐VFA) technique for simultaneousB 1 +and T 1 mapping of the prostate at 3 Tesla (T). Materials and Methods The fat region surrounding the prostate was first identified using a fractional fat segmentation constant ( t F ) and a signal fat‐fraction threshold ( r F ), and the relative flip angle (FA) was characterized using an effective fat T 1 ( T 1f ) within the fat region. Optimal values of t F , r F , and T 1f were chosen by comparing relative FA maps using RR‐VFA ( A RR‐VFA ) with a reference relative FA maps ( A REF ) in the surrounding fat and evaluating interpolation errors within the prostate. The optimized RR‐VFA was evaluated in volunteers at 3T on a single scanner (n = 10) and across three scanners (n = 4). Results t F , r F and T 1f were optimized as 0.5, 90%, and 320 ms, respectively. Prostate A RR‐VFA showed differences of 30% among volunteers on one scanner, with no significant differences between A RR‐VFA and A REF ( P = 0.41). Prostate T 1 afterB 1 +correction was 1998 ± 113 ms with significantly ( P = 0.004) lower standard deviation than T 1 beforeB 1 +correction. The average coefficient of variation of prostate T 1 across multiple scanners decreased from 15% to 5% afterB 1 +correction. Conclusion The optimized RR‐VFA can simultaneously measureB 1 +and T 1 in the prostate without the need for an additional scan and improve T 1 consistency within and across MRI scanners at 3T. Level of Evidence: 3 J. Magn. Reson. Imaging 2017;45:751–760.