Contrast-free postoperative pulmonary artery imaging: intraindividual comparison of REACT (Relaxation-Enhanced Angiography without Contrast and Triggering) and time-resolved contrast-enhanced MRA

Friday, February 6, 2026

3:45 PM - 3:52 PM

Location: Galapagos / Aruba / Ilhabela (2nd Lower Level)

Presenting Author(s)

Robert A. Terzis, MD

Resident
Faculty of Medicine and University Hospital Cologne, University of Cologne
Köln, Nordrhein-Westfalen, Germany

Primary Author(s)

JJ

Jan Paul Janßen, MD

Resident
University of Cologne
Cologne, Nordrhein-Westfalen, Germany

Co-Author(s)

KK

Kenan Kaya, MD

Resident
University of Cologne
Cologne, Nordrhein-Westfalen, Germany
CG

Carsten H. Gietzen, MD

Consultant
University of Cologne
Cologne, Nordrhein-Westfalen, Germany
LP

Lenhard Pennig, MD

Consultant
University of Cologne
Cologne, Nordrhein-Westfalen, Germany

Background: As a novel 3D isotropic flow-independent non-contrast-enhanced MRA (non-CE-MRA) technique, Relaxation-Enhanced Angiography without Contrast and Triggering (REACT) has shown promising results in imaging of the pulmonary vasculature, primarily in patients without prior surgery. The purpose of this study was to assess the performance of REACT in comparison to time-resolved contrast-enhanced MRA (4D CE-MRA) in patients with prior surgery of the pulmonary arteries or right ventricular outflow tract, with a focus on the impact of various implants.

Methods: This retrospective single-center study included 53 patients (median age: 29 years [18-37], 26 male) with congenital heart disease, who underwent both 4D CE-MRA (scan time: 247s [167-354]) and REACT (electrocardiogram- and respiratory-triggering, Compressed SENSE (factor 9); scan time: 363s [282-422]) at 1.5 T. Surgical history included: conduit (n=15), valve replacement (n=10), stent implantation (n=19), patch repair (n=18), and others. Three radiologists independently assessed image quality (IQ) as well as susceptibility and motion artifacts on 5-point Likert scales (5=excellent) for the main, left, and right pulmonary arteries (MPA/LPA/RPA). Diameters were measured, and presence of stenosis or dilatation was recorded.

Results: REACT showed higher overall IQ than CE-MRA (3.78 [3.11-4.22] vs. 3.11 [2.33-3.44]; p< 0.001), less motion (4.22 [3.89-4.67] vs. 3.11 [2.67-3.56]; p< 0.001) and comparable susceptibility artifacts (4.33 [3.22-4.78] vs. 4.44 [3.56-4.67]; p=0.254). Subanalysis revealed higher image quality with REACT regardless of the implant type (all p< 0.05); only stents resulted in equally poor image quality in both sequences (2.00 [1.33-3.0] vs. 2.00 [1.67-3.00]; p=0.860) with impairing susceptibility artifacts (1.67 [1.33-3.50] vs. 2.00 [1.67-3.67]; p=0.148). Individual cases showed slightly better visualization of the stent lumen in 4D CE-MRA (n=3). Diameter measurements (intraclass correlation: 0.967–0.987) tended to be larger in 4D CE-MRA, although only RPA differed significantly (17.29±5.00 mm vs. 18.08±4.96 mm; p=0.002). Stenoses (10.06%; 16 of 159 segments) and dilations (15.06%; 24 of 153 segments) were detected equally.

Conclusion: REACT provides robust, contrast-free imaging after surgery of the pulmonary arteries with superior image quality compared to 4D CE-MRA. However, susceptibility artifacts remain a relevant limitation in stented segments. While 4D CE-MRA may offer slightly improved visualization in selected cases, neither technique currently allows for reliable stent assessment. REACT is a valuable alternative to 4D CE-MRA for postoperative imaging of the pulmonary arteries, especially in patients without stents, and can help reduce contrast exposure in routine follow-up imaging.

Comparison of REACT and 4D CE-MRA in a 29-year-old male patient with a stent in the left pulmonary artery (LPA) following multiple surgical corrections of tetralogy of Fallot.