Estimation of fusiform intracranial aneurysm growth by serial magnetic resonance imaging

Purpose: Intracranial aneurysm (IA) growth is associated with increased morbidity. We sought to establish a quantitative computational method based on contrast-enhanced MR angiography (CE-MRA) for estimating aneurysmal volume changes over time. Materials and Methods: Computational volume calculations were tested against a distensible phantom. Untreated patients with IA were followed longitudinally with annual MRI. Maximal linear dimensions along the longitudinal axis and two transverse axes were determined by visual review of maximum intensity projection (MIP) data, and aneurysm volume was approximated as (length x width x height)/2. Averages of the visual approximations were compared to the lumenal volume as determined with a computational algorithm using the MRI data. Results: MRI-based measurements accurately represented volume changes in the phantom (R² = 0.97, Y = 1.06x + 271 CM³). In the clinical study there were a total of 11 intervals of one-year follow-up in six patients (mean ± SD, age = 53 ± 20 years). The raw one-year growth using the computational volume was 9% ± 17%. The corresponding value for the averaged measurement of the reviewers was 8% ± 14%. Neither the mean values nor the SDs were different (P = .51). Conclusion: MRI-based measurement of aneurysm volume appears feasible for longitudinal studies of aneurysm natural history.