Influence of the short-axis cine acquisition protocol on the cardiac function evaluation: A reproducibility study

Abstract

Purpose: To define the optimal cardiac short-axis cine acquisition protocol for the assessment of the left and rightventricular functions.

Materials and methods: 20 volunteers were recruited and breath-hold CINE images were acquired on a Siemens Prisma 3T MRI. Four short-axis acquisition planes were defined from the 4-chamber view. AV Junctions: short-axis slices parallel to the plane that cuts through the external right and left atrioventricular junctions. Left AV Junctions: short-axis slices parallel to the plane that cuts through both left atrioventricular junctions. Septum: short-axis slices perpendicular to the septum with one cutting through the septum junction. LongAxis: short-axis slices perpendicular to the long axis with one cutting through the septum junction. Intra and inter reproducibility was assessed using Bland-Altman coefficient of variation (CV) and Lin's concordance correlation coefficient (CCC). The influence of the protocol on the ejection fraction (EF) and stroke volume (SV) was quantified statistically using pair-wise CV and Pearson's correlation coefficient R (2).

Results: All protocols led to high reproducibility for the LV EF (mean intra CV = 3.83%, mean inter CV = 4.81%, lowest CV = 4.20% (AV junctions) and highest CV = 5.24% (Left AV Junctions)). Reproducibility of the RV measurements was lower (mean intra CV = 7.84%, mean inter CV = 9.17%). Septum protocol led to significantly lower variability compared to the other 3 protocols for RV EF (CV = 7.62% (Septum), CV = 8.42% (Long Axis), CV = 9.54% (Left AV Junctions) and CV = 11.08% (AV Junctions) with Lin's CCC varying from 0.4 (AV Junctions) to 0.69 (Septum) for inter-observer reproducibility). No differences in group average for clinical parameters was found for both LV and RV clinical measurements. However, patient-specific RV EF evaluation is dependent on the chosen protocol (CV = 9.95%, R (2) = 0.52).

Conclusion: Based on the results of the study cine mode short-axis acquisitions should be planned perpendicular to the septum in order to guarantee optimal RV and LV measurements.

Keywords: Cine MRI; Left ventricle; Reproducibility study; Right ventricle; Short-axis acquisition.

Fig. 1

Definition of the 4 protocols. (A) AV Junctions: short-axis slices parallel to the plane that cuts through the right and the left atrioventricular junctions. (B) Left AV Junctions: short-axis slices parallel to the plane that cuts through the left atrioventricular junction. (C) Septum: short-axis slices perpendicular to the septum with one cutting through the septum junction. (D) Long Axis: short-axis slices perpendicular to the long axis with one cutting through the septum junction.

Fig. 2

Basal short-axis slice selection for the left ventricle. Illustration of the basal plane selection following the SCMR guidelines . “The left atrium can be identified when less than 50% of the blood volume is surrounded by myocardium and the blood volume cavity is seen to be expanding during systole”. The basal slice is the slice with more than 50% of myocardium muscle around the blood. In this example, slice 1 is in the left atria while slice 2 is the ventricle and can therefore be considered as the basal slice.

Fig. 3

Basal descent selection for the left ventricle. Example of the basal descent estimation following the SCMR guidelines . Using cross-referencing from long axis locations and the definition of the basal plane, we estimate the basal plane at end-systole to be between slice 2 and slice 3 when the basal plane at end-diastole was slice 1. We therefore estimate the basal descent to be 1.5× resolution in z, in our case (8 mm thickness and 25% gap) this gives 15 mm.

Fig. 4

Basal short-axis slice selection for the right ventricle. Illustration of the basal plane selection following SCMR guidelines : RV basal slice was defined as the first RV slice not superior to the level of the tricuspid valve. In this example, slice 1 is superior to the level of tricuspid valve while slice 2 is the first slice not superior to the level of the tricuspid valve and thus it is considered as the basal slice.

Fig. 5

Example of basal slice selection for the four acquisition planes. (Left) Example of selected basal slice at end-diastole for the four protocols. (Right) Slice positions on the 4-chamber view. In this example, the 4 definitions led to 4 distinct basal slices. This impacts the segmentation for both the right and left ventricles.

Fig. 6

Bland-Altman plots: inter-observer reproducibility of the Septum and AV Junctions protocols. Comparison of two protocols in terms of reproducibility for the left and right ejection fraction.