Performance of simultaneous high temporal resolution quantitative perfusion imaging of bladder tumors and conventional multi-phase urography using a novel free-breathing continuously acquired radial compressed-sensing MRI sequence

Abstract

Purpose: To investigate the feasibility of high temporal resolution quantitative perfusion imaging of bladder tumors performed simultaneously with conventional multi-phase MR urography (MRU) using a novel free-breathing continuously acquired radial MRI sequence with compressed-sensing reconstruction.

Methods: 22 patients with bladder lesions underwent MRU using GRASP (Golden-angle RAdial Sparse Parallel) acquisition. Multi-phase contrast-enhanced abdominopelvic GRASP was performed during free-breathing (1.4×1.4×3.0mm(3) voxel size; 3:44min acquisition). Two dynamic datasets were retrospectively reconstructed by combining different numbers of sequentially acquired spokes into each dynamic frame: 110 spokes per frame for 25-s temporal resolution (serving as conventional MRU for clinical interpretation) and 8 spokes per frame for 1.7-s resolution. Using 1.7-s resolution images, ROIs were placed within bladder lesions and normal bladder wall, a femoral artery arterial input function was generated, and the Generalized Kinetic Model was applied.

Results: Biopsy/cystectomy demonstrated 16 bladder tumors (13 stage≥T2, 3 stage≤T1) and 6 benign lesions. All lesions were well visualized using 25-s clinical multi-phase images. Using 1.7-s resolution images, K(trans) was significantly higher in tumors (0.38±0.24) than normal bladder (0.12±0.02=8, p<0.001) or benign lesions (0.15±0.04, p=0.033). Ratio between K(trans) of lesions and normal bladder was nearly double for tumors than benign lesions (4.3±3.4 vs. 2.2±1.6), and K(trans) was nearly double in stage≥T2 than stage≤T1 tumors (0.44±0.24 vs. 0.24±0.24), although these did not approach significance (p=0.180-0.209), possibly related to small sample size.

Conclusion: GRASP allows simultaneous quantitative high temporal resolution perfusion of bladder lesions during clinical MRU examinations using only one contrast injection and without additional scan time.

Keywords: Bladder cancer; MR urography; MRI techniques; Novel techniques.

Copyright © 2016 Elsevier Inc. All rights reserved.

Figures

Fig. 1

79 year old male with high-grade urothelial carcinoma of the bladder based on histologic assessment from cystoscopy. (A) Pre-contrast and (B) post-contrast images retrospectively reconstructed at 1.7-s temporal resolution from the continuously acquired radial sequence using parallel imaging and compressed sensing (GRASP) show an enhancing mass along the right lateral bladder wall (arrow). (C) A color-coded Ktrans map was generated using the high temporal-resolution data and overlaid on the post-contrast image. (D) Time–activity curves (TACs) of the individual arterial input function generated from the common femoral artery and of a region-of-interest encompassing the bladder mass used for pharmacokinetic modeling.

Fig. 2

Same patient as in Fig. 1. (A) Corticomedullary, (B) nephrographic, and (C) early excretory phase images that were reconstructed prospectively at 25-s temporal resolution for purposes of clinical interpretation using the continuously acquired abdominopelvic GRASP acquisition.