Pixel-by-Pixel Arterial Spin Labeling Blood Flow Pattern Variation Analysis for Discrimination of Rheumatoid Synovitis: A Pilot Study

Abstract

We examined the capability of a gray-scale arterial spin labeling blood flow pattern variation (BFPV) map with two different post labeling delay (PLD) times to discriminate pannus in patients with rheumatoid arthritis (RA) at 3T. There was a statistically significant difference in the BFPV values between artery, pannus, and surrounding tissue. Furthermore, the color-coded BFPV map was able to accurately distinguish pannus from other tissues. These results suggest this approach may be capable of identifying pannus noninvasively.

Fig 1.

The labeling site utilized in this study.

Fig 2.

ROIs for measurement of the BFPV and perfusion values. (a) The location of the peripheral artery (arrow), pannus (arrow head), and surrounding tissue were determined on post-gadolinium-DTPA images. (b) ROIs of the peripheral artery (blue box) and pannus (red box) and surrounding tissue (yellow box) were set and measured on the gray-scale BFPV maps and the pCASL perfusion maps. ROIs, region of interests; ASL, arterial spin labeling; BFPV, blood flow pattern variation; DTPA, diethylene triamine pentaacetic acid; pCASL, pseudo-continuous arterial spin labeling.

Fig 3.

Axial MR images of a RA wrist. pCASL perfusion maps with PLD times of (a) 1025, (b) 1525, (c) 2025 ms are calculated by subtracting an image without blood preparation from that with blood preparation. (d) The BFPV map is presented as a color-coded image according to the BFPV values. The BFPV values of the radial artery (arrow) shows negative and smaller than those of pannus (arrow head). RA, rheumatoid arthritis; pCASL, pseudo-continuous arterial spin labeling, PLD, post-labeling delay, BFPV, blood-flow pattern variation.

Fig 4.

Comparison of ASL perfusion and BFPV values for artery, pannus, and surrounding tissue. Data (average ± standardized deviation) derived from pCASL perfusion maps with PLD times of 1025 (a), 1525 (b), 2025 (c) ms, and the color-coded BFPV map (d) are demonstrated. ASL, arterial spin labeling; BFPV, blood flow pattern variation; pCASL, pseudo-continuous arterial spin labeling; PLD, post labeling delay; **, P < 10⁻⁸; ns, not significant.

Fig 5.

(a), (c) shows dynamic images for a low (Low-activity group) and a high (high-activity group) degree of synovial proliferation. While, (b), (d) shows color-coded BFPV maps of (a) and (b), respectively. The color-coded BFPV maps are calculated by setting threshold values on the gray-scale BFPV map to distinguish pannus from surrounding tissues. Peripheral artery (blue color wash) and pannus (yellow and red color wash) are visualized on each image. BFPV, blood flow pattern variation.