Influence of observers, threshold values, and measurement methods on volumetric analysis of cerebral aneurysms with three-dimensional rotational angiography.

INTRODUCTION Exact measurements of cerebral aneurysms are important in terms of their treatment. However, there is no definitive way to estimate the exact volume of an aneurysm. Our aim was to compare aneurysm volume measured under different conditions: threshold values, observers, and measurement methods. METHODS 40 aneurysms and 7 phantom models were included in the study. Three-dimensional rotational angiography was used, and volumes were compared based on the following factors: two methods (two-dimensional formula calculation and three-dimensional software measurement); three observers; and three threshold values for imaging. In addition, in the phantom models, measured volumes were compared with real volumes. The consistency of the volume measurements under different conditions was assessed using the intraclass correlation coefficient (ICC). RESULTS The consistency of the measured volumes was excellent in both the patient aneurysms (ICC >0.98) and phantom models (ICC >0.95), irrespective of the influencing factors. Median volume differences were small for observers, threshold values, and methods. When the measured and real volumes of the phantom models were compared, the software measurement achieved the highest reproducibility for real volumes compared with the formula calculation (ICC=0.86-0.93 vs 0.71-0.80). CONCLUSIONS Measurement of aneurysm volume showed high agreement within each influencing factor, such as methods, observers, and threshold values.