Feasibility of a Curvature-based Enhanced Display System for Detecting Cerebral Aneurysms in MR Angiography

Abstract

Purpose: To assess the feasibility of a curvature-based enhanced display system for detecting cerebral aneurysms in MR angiography.Methods: MR angiography studies of 18 patients (eight male and 10 female, average age 65.7, age range 50 to 75 years old) with 23 known aneurysms were evaluated with a curvature-based display system. The two curvature features-the volumetric shape index and curvedness values-were calculated at each voxel. These were displayed independently on a workstation, overlaid on volume-rendered images. Two neuroradiologists evaluated the images for visibility and diagnosis of the cerebral aneurysms. The diagnostic results were compared with the original reports.Results: The calculation time for each curvature index was 30 to 40 s for 120 to 140 slices of original MR angiography data. Shape index images emphasized smooth and round aneurysms more than aneurysms with irregular surfaces. Curvedness images revealed aneurysms well when the aneurysms had diameters that diŠered from those of the surrounding vessels. The computer-assisted-detection method detected 24 aneurysms, three of which were not pointed out in the initial report.Conclusion: Our results show that the curvature-based display system we have developed is feasible and that it may help to detect small aneurysms that are prone to be overlooked in routine readings.

Computer-Assisted Detection of Cerebral Aneurysms in MR Angiography in a Routine Image-Reading Environment: Effects on Diagnosis by Radiologists

“…Stand-alone performance figures of various CAD algorithms for cerebral aneurysms have been studied mainly by using datasets of known aneurysms, and high sensitivities have been reported. [10][11][12][13] Previous observer performance studies showed that CAD for cerebral aneurysms raises the sensitivity of radiologists 14,15 or reduces reading time while maintaining the sensitivity. 16 However, those studies were performed under experimental conditions with a relatively small number of aneurysms.…”

Computer-Aided Diagnosis Systems for Brain Diseases in Magnetic Resonance Images

“…However, it is difficult and time consuming for radiologists to detect small aneurysms, because of their overlap with adjacent vessels or unusual locations in maximum intensity projection (MIP) images of MRA. Therefore, a number of CAD systems have been developed for assisting radiologists in detection of intracranial aneurysms [25,26,41,65,66]. Table 1 shows a comparison of methods and results of CAD systems for detection of intracranial aneurysms using MRA.…”

“…For example, small intracranial aneurysms, which are imaged by MR scanners, could be enhanced by using an enhancement filter for a 3D Gaussian shape, because the shapes of the aneurysms are similar to 3D Gaussian function. Therefore, several enhancement filters for specific lesions have been developed in the CAD field [36][37][38][39][40][41][42]. Giger et al developed a difference image technique for the detection of lung nodules in radiographs, based on the subtraction of the objectsuppressed image using a ring filter from the object-enhanced image using an object-matched filter [36,43].…”

“…Figure 4 shows the effect of a dotenhancement filter for an MRA image with an unruptured intracranial aneurysm．The balloon-like aneurysms are well enhanced by the dot-enhancement filter. Hayashi et al proposed a curvature-based enhanced display system for detecting cerebral aneurysms in MR angiography [41]. Yamamoto and Arimura et al proposed a simple method for enhancing MS lesions in 2D fluid-attenuated-inversionrecovery (FLAIR) images by subtracting the background image approximated by the first order polynomial in a brain parenchymal region [30,31].…”

“…These relationships back up the assumption derived from our observation in Figure 6. Many image features have been designed for characterizing specific lesions or diseases in the neuroradiological CAD system [25][26][27][28][29][30][31]41].…”