UCSF

Determination of changes in the volume of a cerebral aneurysm over time is important as increased growth rates are indicators of elevated rupture risk. Two major magnetic resonance (MR) angiographic options are available for defining the contours of cerebral aneurysms: time-of-flight (TOF) MRA and Contrast-Enhanced (CE) MRA. Past work aimed to assess the reliability of contrast-enhanced MRA in monitoring serial volumetric changes of unruptured intracranial aneurysms but less has been reported for TOF methods. The relative performance of these two methods is poorly established. In the past, comparisons between the two techniques have used single time point patient data. In this project, we used patient data from multiple time points to compare and evaluate the degree of reproducibility between TOF-MRA and CE-MRA using co-registration techniques to see which method has better consistency. Using a standardized protocol for non-invasive MRI, specifically TOF and CE, a preliminary sample size of 9 aneurysms was analyzed through the co-registration and segmentation pipeline. Results showed that 61.5% of the TOF-MRA imaging data and 23.1% of the CE-MRA imaging scans were invalid to meaningfully analyze the aneurysm volume changes. Additionally, it was consistently shown that TOF-MRA had magnetization saturation effects that were more pronounced with increasing aneurysm size and volumes at the first timepoint were consistently reported lower than their CE-MRA counterparts. Thus, while TOF-MRA seems to work reliably in aneurysms that are less than 6 mm in size, it fails to reliably work on aneurysms larger than 6 mm. Future directions will focus on increasing the sample size with the aim of obtaining the TOF-MRA coefficient of variance; the potential of adding smoothing for the TOF-MRA image processing should also be assessed. In short, based on preliminary data analysis, TOF-MRA has many image quality problems affecting the reliability and validity of its aneurysm volumetric analysis.