Intracranial aneurysm is a permanent dilatation formed by a part of the canal wall protruding outward due to lesions mainly caused by congenital defects of the canal wall, atherosclerosis and hypertension, and has a high rate of death and disability after the rupture and bleeding of the aneurysm, therefore, early and correct diagnosis of intracranial aneurysm is of great clinical significance. With the continuous improvement of multilayer spiral CT angiography and post-processing technology, multilayer spiral CT angiography (CTA) as a new technology in the diagnosis of intracranial aneurysm has shown certain advantages and values. At present, CT angiography (CTA) has become the preferred imaging means in the diagnosis of vascular diseases. The author analyzed the clinical data of 30 cases of intracranial aneurysm patients in our hospital from September 2007 to February 2010, and discussed the application value of 16-layer spiral CT arteriography in the diagnosis of intracranial aneurysm.
1. Data and methods
1.1 General information
Normal group (randomized patients without any symptoms) 10 cases, 5 males and 5 females, aged 35-50 years old. There were 30 cases in the case group, 19 males and 17 females, aged 39-85 years old. Among the 38 cases of cerebral aneurysm in this group, 20 were male and 18 were female; the minimum age was 22 years old and the maximum age was 80 years old, with a mean age of 56.5 years. There were 36 cases of single and 2 cases of multiple aneurysms, totaling 41 aneurysms. Among them, there were 33 cases of subarachnoid hemorrhage.
1.2 Equipment and methods
1.2.1 Equipment: Siemens Somatom Sensation 16-layer spiral CT machine was used for scanning.
1.2.2 Scanning conditions: voltage 120 KV, current 180-200 mA, layer thickness 5 mm, pitch 0.875:1, pitch array 512×512, FOV 25 cm×25 cm. all cases were scanned plus enhanced examination. : The reconstruction was chosen to start from the line between the foramen magnum and the anterior skull base with a layer thickness of 0.5-1 mm. A high-pressure syringe was used to inject the non-ionic contrast agent iohexol through the elbow vein doughnut with a dosage of 80-lOO ml, a concentration of 300 mgI/ml, an injection rate of 3 mL/s, and a delay of 10-20 s before starting the scan.
1.2.3 Image post-processing: The resulting images were transferred to the post-processing workstation for image post-processing using the Syngo CT 2006G software package, using the original data line maximum density projection (MIP), multiplanar reconstruction (MPR), surface masking display (SSD), volume reproduction (VR), fully displaying the relationship between the simple cerebral artery volume image and the skull base bone structure, appropriately adjusting the The image post-processing is required to clearly show the general anatomy of the aneurysm, such as the neck of the aneurysm, the aneurysm-carrying artery and its adjacent bone structure, and all images can be rotated in three dimensions at the workstation.
1.2.4 Image analysis: Two experienced radiologists analyzed and evaluated the CTA images.
2. Results
Normal group of 10 cases. The internal carotid artery and its branches were clearly shown. 41 aneurysms were detected in 38 cases of CTA, 35 single cases, 3 multiple cases, 2 lesions were small, and the cT report was negative; the distribution of morbidity sites were 27 basilar artery rings in order, including 19 anterior communicating arteries and 8 posterior communicating arteries; 5 internal carotid arteries in segment c1; 3 middle cerebral arteries in segment M1 and 2 in segment M2; 1 anterior cerebral artery in segment A1 2 of the A2 segment; 1 of the cerebral segment of the vertebrobasilar artery and 1 of the superior cerebellar artery. The largest tumor was 13 mm, which was located in the anterior communicating artery and was seen for rupture and bleeding; the smallest was 3 mm, which had no individual symptoms and was found incidentally; most of the tumors were 4 mm to 8 mm. 2 cases had intra-tumor thrombosis and calcification.
3, Discussion
3.1 Intracranial aneurysms are most commonly seen in middle-aged people, with the internal carotid artery being the most common, followed by the anterior communicating artery, middle cerebral artery, anterior cerebral artery and vertebrobasilar artery. Intracranial aneurysms are generally classified into three types: saccular, spindle and intermural aneurysms. Saccular aneurysms account for 90% of all intracranial aneurysms and are the most common type, and can be classified into four categories according to their diameters. Small aneurysms and general aneurysms are most common. Intracranial aneurysms have different clinical manifestations depending on their location, size and whether they rupture or not. Aneurysms that develop in the branches of the basilar artery ring at the base of the skull, especially at the bifurcation of the artery, have extremely thin walls and are prone to rupture. About half of the patients show symptoms of local headache, facial and eye pain, reduced visual acuity, visual field loss and extraocular muscle paralysis before the rupture of the aneurysm, mostly due to acute enlargement and compression of the aneurysm; some patients also show symptoms of total headache, nausea, neck stiffness, low back pain, photophobia and tiredness and salivation due to a small amount of blood leakage from the aneurysm. There are also symptoms of ischemia caused by arterial spasm or vascular occlusion, manifested as motor and sensory disorders, balance disorders, hallucinations, vertigo, etc. In this group of cases
3.2 Image post-processing techniques of 16-layer spiral CT
The post-processing methods of 16-layer spiral CT in the osteoarticular system include multi-planar reconstruction (MPR), surface masking display (SSD)
Masked display (SSD), maximum density projection (MIP), volume reproduction (VR), etc. MPR is superior to intra-aneurysmal tethering and wall plaque and stenosis, while MIP and SSD images can provide an important basis for surgical planning and postoperative evaluation by showing intracranial aneurysms with a strong sense of spatial stereo [25 However, some of the original data will be lost in the reconstruction process. VR utilizes all the scanned information and is a higher form of reconstruction, and can be cut and rotated in any orientation by arbitrary manual selection of levels, maintaining the spatial relationship of the original data, with multiple anatomical levels and a realistic 3D stereoscopic sense, allowing observation of the aneurysm from different angles. At present, it is agreed that post-processing imaging techniques of multilayer CF should be used jointly.
3.3 For the diagnosis of intracranial aneurysm, cerebral angiography (DSA) using intra-arterial cannulation technique is the gold standard for the diagnosis of intracranial aneurysm. Cerebral angiography can clearly show the size, morphology, location and number of aneurysms, as well as the presence or absence of arterial spasm and its location, and the anatomical relationship between the aneurysm-carrying artery and other vessels. Most importantly, when an intracranial aneurysm is detected by cerebral angiography, endovascular embolization can be performed immediately. However, cerebral angiography is an invasive test that may lead to complications such as vasospasm or aneurysm rupture, vascular entrapment, and transient or permanent neurological deficits, and requires a high level of operator skill.
In recent years, with the update of spiral CT machines, 64-row and 128-row spiral CT have been put into clinical use, and the post-processing technology has been gradually improved. CTA can observe the location, size, morphology, apex pointing and spatial relationship with surrounding vessels from different angles, especially unique in judging the neck of aneurysm and its width, and can identify calcified lesions, and the three-dimensional image can be rotated arbitrarily to observe aneurysm from multiple angles, which can let clinicians understand various parameters of aneurysm more directly and intuitively and guide the formulation of surgical plan. CTA can not only diagnose aneurysm accurately, but also help to evaluate the difficulty of surgery and the surgical method before operation.
3.4 However, CTA has shortcomings in diagnosing intracranial aneurysms, such as false positives and false negatives, which are related to cerebral vasospasm, small aneurysm, aneurysm location and operation techniques.
1. Inaccurate delay time and contrast injection rate before scanning will affect the quality of arterial development, so it is necessary to correctly estimate and judge the patient’s age, cardiac function and other factors, and adjust the delay time contrast injection rate according to the patient’s specific situation.
2, three-dimensional images in the reconstruction process, more or less pixel loss, so in the diagnostic process, we should pay attention to the combination of the original image, but also pay attention to the integrated application of a variety of three-dimensional imaging means.
3, For patients with subarachnoid hemorrhage bleeding with normal CTA display and high clinical suspicion of aneurysm, further DSA examination or secondary CTA examination can be performed.
In conclusion, the analysis of this group of cases shows the clinical value of CTA and its post-processing image reconstruction in the diagnosis of intracranial aneurysms. With the continuous improvement and development of computer hardware and processing software, cerebrovascular CTA, as a relatively non-invasive, safe and reliable, and accurate vascular examination, will play a greater role in clinical diagnosis and treatment.