the goal of this clinical trail is to evaluate the clinical efficiency of intracranial aneurysm assistive software in the morphological measurement. The trail is designed as retrospective, multicenter, controlled clinical trail. Collecting probable cases images retrospectively according to inclusion criteria and exclusion criteria strictly. Controlling bias strictly, to make sure the measurement of intracranial aneurysm assistive software is evaluated reliably and precisely. In our trail, six physicions were recruited, containing three neuroradiologists, two radiologists and a residents. Software-assistant planning controls against no software-assisant planning，which aims to evaluate the improvement of morphological measurement efficiency of physicians.

Inclusion Criteria:

1. aged 18-75y, no gender limitation.
2. non-ruptured intracranial saccular aneurysm with specific intracranial CTA images.
3. Intracranial aneurysm was not treated.

Inclusion criteria of images:

1. the number of detector rows of Computed Tomography(CT) is more than 16 rows.
2. slice thickness ≤ 0.625mm, whole-brain image is considered.
3. Both plain scan sequences and enhancer sequence are required.

Exclusion Criteria:

1. combined with cerebral hemorrhage;
2. combined with cerevascular malformation or cerebral occupying lesion;
3. fusiform aneurysm or dissection aneurysm;
4. intracaverous internal carotid artery aneurysm;

Exclusion criteria of images:

1. none DICOM format;
2. quality score less than 3 scores;
3. metal artifacts existance.

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