Semi-automated evaluation of right ventricular volumes using gradient cine magnetic resonance data sets: an in vitro validation study

Purpose: The current cardiac magnetic resonance (CMR) based approach to assessment of right ventricular (RV) volumes is time-consuming and not optimized for routine clinical use. This study tested a new CMR based 3-Dimensional (3D) method of RV volume estimation that employed automated tracking to reduce analysis time. Methods: Twenty RV-shaped latex models of different sizes (25-225 ml) were studied. Each RV model was driven by a pulsatile pump at 3-5 different stroke volumes (SV, 20-80 ml), and scanned for gradient cine stacks of multiple adjacent short axes, along with sagittal and coronal planes on a 3T MR scanner (Siemens). Individual scans were combined in an offline RV analysis program (RVMR) embedded in Research Arena VA® (TomTec) to compose a dynamic 3D polyhedron RV image loop. Each cine loop was analyzed using automated border tracking to compute RV volume. Reference volumes were obtained by immersing these models in water filled graduated cylinders and measuring displaced volume. Results: The 3D RVMR derived volumes showed strong correlation with displacement derived reference volumes (Spearman coefficient = 0.992 for ESV, 0.999 for EDV; all p < 0.0001). Good interand intra-observer variability was observed. The intra-class correlation coefficients for ESV were 0.993 and 0.998 respectively, and for EDV 0.989 and 0.995 respectively. Bland-Altman analysis showed >95% of data points within limits of agreement. Conclusions: Technical feasibility and accuracy of the 3D RVMR program was validated in this study. The speed of analysis is a distinct advantage. Studying normal and diseased human RVs would be the next step. List of Abbreviations: RV: right ventricle, CMR: cardiac magnetic resonance, CHD: congenital heart disease, 2D: two-dimensional, 3D: three-dimensional, EF: ejection fraction, ESV: end-systolic volume, EDV: end-diastolic volume, SV: stroke volume, TOF: tetralogy of fallot, RVOT: right ventricular outflow tract, SSFP: steady state free precession, True FISP: true fast imaging with steady state precession, DICOM: digital imaging and communications in medicine