Feasibility of 5-minute delayed transition phase imaging with 30° flip angle in gadoxetic acid-enhanced 3D gradient-echo MRI of liver, compared with 20-minute delayed hepatocyte phase MRI with standard 10° flip angle.

Objective: The purpose of this study was to compare 5-minute delayed transitional phase imaging using a 30° flip angle (hereafter, 5 min-FA30) and 20-minute hepatocyte phase imaging using a 10° flip angle (hereafter, 20 min-FA10) in gadoxetic acid-enhanced MRI for focal hepatic lesion detection and lesion-to-liver contrast-to-noise ratio (CNR), and to determine whether 5 min-FA30 could replace 20 min-FA10 with a 15-minute time saving.
Materials and Methods: One hundred sixteen patients with 282 focal hepatic lesions (size range, 0.2-12.5 cm; malignant, n = 146; benign, n = 136) underwent gadoxetic acid-enhanced MRI with 5 min-FA30 and 20 min-FA10 with a 3D T1-weighted gradient-echo sequence. Three radiologists independently assessed the presence of focal hepatic lesions using a 4-point scale, and detection sensitivity of focal hepatic lesions was calculated. Lesion-to-liver CNRs were calculated and compared in two image groups.
Results: There was no significant difference in detection sensitivity of focal hepatic lesions for all three readers between 5 min-FA30 (mean, 95.4%) and 20 min-FA10 (mean, 95.6%), irrespective of lesion size or malignancy. The mean CNR on 5 min-FA30 (167.9 ± 84.1) was significantly higher than that on 20 min-FA10 (160.2 ± 79.5). However, the mean CNR difference between the two image groups was relatively small (7.8 ± 41.9).
Conclusion: Compared with 20 min-FA10, 5 min-FA30 provided higher CNR and similar sensitivity. These findings indicate that 5 min-FA30 could replace 20-min delayed hepatocyte phase imaging using a 10° flip angle with similar diagnostic performance and 15 minutes of time saving.