The potential of cardiac magnetic resonance (CMR) imaging to provide precise and reproducible measurements might not be realized currently. Methods: We acquired CMR images on 30 healthy adults and compared readings of 2 experienced physicians to determine sources of measurement variability. Results: Simultaneous review of tracings revealed 3 major sources of interobserver variability: 1) choice of enddiastolic/end-systolic frames; 2) choice of the most basal left and right ventricular

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... slices; and, 3) approach to endocardial edge selection. Conclusions: CMR-derived volumes and mass are measurement-methodology specific. Formal measurement rules and improved computerized edge detection algorithms are needed. Study Plan. These objectives were to be achieved through a prospective study in an adequate number of healthy subjects. Qualifying subjects were to undergo a standardized functional CMR evaluation. Predefined cardiovascular measurements were made using workstation-specific methods. Key volume and mass measurements were to be performed independently by 2 observers to improve accuracy, to determine reproducibility, and to develop consensus methods. Results were to be used for clinical and research applications. Study Population. Thirty study subjects were drawn from among healthy volunteers who responded to advertisements within the hospital community to participate in a study to determine normal CMR measurements using methodology-specific algorithms. Qualifying subjects were uncompensated adults of ages between 40-60 years of either sex (equal proportions women and men) who gave written informed consent for study participation, which included a standard functional CMR, and who had no clinically apparent cardiovascular diseases, including hypertension (history of hypertension, blood pressure 140 systolic or 90 mm Hg diastolic, or on antihypertensive medication) or diabetes on screening history, or had abnormal physical findings (abnormal heart sounds or murmurs, other abnormal cardiovascular findings) on screening examination. Subjects also were excluded who had significant other-organ diseases (e.g., chronic obstructive pulmonary disease, renal or liver failure, cancer) or obesity (body mass index >30 kg/m 2 ) or rhythm other than sinus. The LDS Hospital Institutional Review Board approved the study. Cardiac MRI Study. Following axial and sagittal localizer sequences (fast GRE/SPGR), standard cardiac 2, 3, Normal CMR Measurements The Open