Comparison of a novel Compressed SENSE accelerated 3D modified relaxation-enhanced angiography without contrast and triggering with CE-MRA in imaging of the thoracic aorta

Abstract

To compare a novel Compressed SENSE accelerated ECG- and respiratory-triggered flow-independent 3D isotropic Relaxation-Enhanced Angiography without Contrast and Triggering (modified REACT) with standard non-ECG-triggered 3D contrast-enhanced magnetic resonance angiography (CE-MRA) for imaging of the thoracic aorta in patients with connective tissue diseases (CTD) or other aortic diseases using manual and semiautomatic measurement approaches. This retrospective, single-center analysis of 30 patients (June-December 2018) was conducted by two radiologists, who independently measured aortic diameters on modified REACT and CE-MRA using manual (Multiplanar-Reconstruction) and semiautomatic (Advanced Vessel Analysis) measurement tools on seven levels (inner edge): Aortic annulus and sinus, sinotubular junction, mid- and high-ascending aorta, aortic isthmus, and descending aorta. Bland-Altman analysis was conducted to evaluate differences between the mean values of aortic width and ICCs were calculated to assess interobserver agreement. For each level, image quality was evaluated on a four-point scale in consensus with Wilcoxon matched-pair test used to evaluate for differences between both MRA techniques. Additionally, evaluation time for each measurement technique was noted, which was compared applying one-way ANOVA. When comparing both imaging and measurement methods, CE-MRA (mean difference 0.24 ± 0.27 mm) and the AVA-tool (- 0.21 ± 0.15 mm) yielded higher differences compared to modified REACT (- 0.11 ± 0.11 mm) and the MPR-tool (0.07 ± 0.21 mm) for all measurement levels combined without yielding clinical significance. There was an excellent interobserver agreement between modified REACT and CE-MRA using both tools of measurement (ICC > 0.9). Modified REACT (average acquisition time 06:34 ± 01:36 min) provided better image quality from aortic annulus to mid-ascending aorta (p < 0.05), whereas at distal measurement levels, no significant differences were noted. Regarding time requirement, no statistical significance was found between both measurement techniques (p = 0.08). As a novel non-CE-MRA technique, modified REACT allows for fast imaging of the thoracic aorta with higher image quality in the proximal aorta than CE-MRA enabling a reliable measurement of vessel dimensions without the need for contrast agent. Thus, it represents a clinically suitable alternative for patients requiring repetitive imaging. Manual and semiautomatic measurement approaches provided comparable results without significant difference in time need.

Keywords: Connective tissue diseases; Magnetic resonance angiography; Non-contrast-enhanced magnetic resonance angiography; Thoracic aorta.

Fig. 1

Coronal and sagittal planes of modified REACT (source images) with lines depicting the measurement levels in a 41-year-old female patient with Ehlers-Danlos syndrome. Proximal to distal: Aortic annulus, aortic sinus, sinotubular junction (indicated by the left coronary artery branch; thin arrow), mid- and high-ascending aorta, aortic isthmus, and descending aorta. Note: The main pulmonary artery (wide arrows) is displayed in high quality

Fig. 2

Examples for the levels of measurements in a 34-year-old male patient with Marfan syndrome (same patient as in Fig. 5) at the level of the aortic annulus (a and b), aortic sinus (c and d), and sinotubular junction (e and f) in modified REACT (a, c, and e) and CE-MRA (b, d, and f) in axial plane

Fig. 3

Workflow for inclusion and exclusion of patients

Fig. 4

Bland–Altman comparison of measured diameters of the thoracic aorta at the seven levels of measurement (A aortic annulus, B aortic sinus, ST sinotubular junction, MA mid-ascending aorta, HA high-ascending aorta, I aortic isthmus, D descending aorta) for the different methods of imaging and measurement. The middle lines represent the mean absolute difference of measurements, the outer boundaries the 95% confidence interval. Due to known recurrent measurement errors of the AVA-tool, measurements at aortic annulus and sinus were excluded

Fig. 5

Parasagittal planes (source images) of modified REACT (a) and CE-MRA (b) in a 34-year-old male patient with Marfan syndrome. While image quality is comparable at the aortic arch, modified REACT provides better delineation of the vessel wall at the aortic root than CE-MRA given pulsation artifacts of the latter. Additionally, modified REACT enables the depiction of the pulmonary arteries in high quality (thin arrows)

Fig. 6

Coronal planes (source images) of modified REACT (a) and CE-MRA (b) in a 46-year-old male patient with Marfan syndrome ten years after valve-sparing aortic root replacement (David procedure) and replacement of the proximal aortic arch. Modified REACT enables an improved delineation of the thoracic aorta, pronounced at the aortic root (wide arrows) due to light mistiming of image acquisition regarding first pass of the contrast bolus and pulsation artifacts hampering image quality in CE-MRA. Note the clearly visible aortic regurgitation in modified REACT (thin arrow), indicating aortic insufficiency

Fig. 7

Sagittal planes (source images) of modified REACT (a) and CE-MRA (b) in a 60-year-old male patient with Marfan syndrome two years after valve-sparing aortic root replacement (David procedure). Modified REACT provides an improved depiction of the thoracic aorta, pronounced at the root (arrows) with pulsation artifacts impeding image quality of CE-MRA