4-Dimensional Computed Tomography Angiography for capturing cardiac cycle-induced volume change of intracranial aneurysms.

Background: Several studies suggest 4-Dimensional Computed Tomography Angiography (4D CTA) to assess wall motion of intracranial aneurysms as an indicator of stability. However, capturing cardiac cycle-related motion may exceed limits of imaging techniques. The goal is to evaluate consistency of aneurysm volume change across three consecutive cardiac cycles.

Methods: Eighteen adult patients with unruptured and untreated intracranial aneurysms were recruited at Radboud University Medical Center. Three cardiac cycles were captured on a wide detector CT system, using electrocardiogram-gated 4D CTA. To reduce the impact of movements, a rigid-body registration was employed. Aneurysms were manually segmented and a deformable registration algorithm was used to determine volume change. The amplitude of absolute volume change, relative volume change, derived mean diameter were determined. The Pearson correlation was calculated as a measure of volume change pattern similarity across cardiac cycles.

Results: Three of eighteen subjects were excluded because of technical difficulties, resulting in fifteen subjects with seventeen aneurysms. Among the remaining aneurysms, the mean absolute maximum volume change was 13.7 ± 26.5 mm3, the mean relative maximum volume change was 3.49 ± 1.45 %, and the mean averaged maximum diameter change per cardiac cycle was 0.068 ± 0.025 mm. In two aneurysms, the volume change pattern was consistent across cardiac cycles, and a fall-and-rise pattern was observed.

Conclusion: This study indicates low consistency in intracranial aneurysm volume change patterns across cardiac cycles, questioning the feasibility of current CT scanners in capturing volume changes. Future research should focus on higher-resolution imaging on alternative metrics like shape changes, to improve assessment of aneurysm wall motion.