Intracranial aneurysm growth quantification in CTA

Next to aneurysm size, aneurysm growth over time is an important indicator for aneurysm rupture risk. Manual assessment of aneurysm growth is a cumbersome procedure, prone to inter-observer and intra-observer variability. In clinical practice, mainly qualitative assessment and/or diameter measurement are routinely performed. In this paper a semi-automated method for quantifying aneurysm volume growth over time in CTA data is presented. The method treats a series of longitudinal images as a 4D dataset. Using a 4D groupwise non-rigid registration method, deformations with respect to the baseline scan are determined. Combined with 3D aneurysm segmentation in the baseline scan, volume change is assessed using the deformation field at the aneurysm wall. For ten patients, the results of the method are compared with reports from expert clinicians, showing that the quantitative results of the method are in line with the assessment in the radiology reports. The method is also compared to an alternative method in which the volume is segmented in each 3D scan individually, showing that the 4D groupwise registration method agrees better with manual assessment.