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Q：
The role of contrast medium injection system in CT enhanced scan
A:
The contrast injection method has two methods: the nurse manually pushes the contrast agent and the machine pushes the contrast agent, and the machine method can be divided into a simple electric injector and a contrast medium injection system (high-pressure syringe or CT-enhanced syringe). .
The contrast medium injection system is completely different from a simple electric injector, such as the Zenith-620 contrast medium injection system (also known as a high-pressure syringe or CT-enhanced syringe) designed to meet current CT enhancement techniques, with its main features and functions. There are: 1) selectable contrast agent speed (0.1ml / s ~ 8.0ml / s); 2) dedicated disposable syringe capacity (200ml); 3) can be set up to 4 stages of the push procedure; 4) Interval time can be set between each stage; 5) Configure an extension tube with a length of 1m to meet the requirements of scanning at any part of the scan; 6) Input and output interfaces are convenient for synchronization with CT equipment.
When using the contrast medium injection system in CT-enhanced scanning, the doctor only needs to control the system to start injection after setting (rate, dose, phase, delay time, etc.) . The system will accurately complete the injection process according to the set requirements.
Due to the limitation of the scanning speed of the CT device itself, it is impossible to realize the dual-phase or three-phase scanning of the whole part, but a small number of layers such as the lesion layer can be selected for the enhanced scanning, so that a small number of layers can be scanned in a shorter time. To achieve a two- or three-phase scan enhancement of these few slices, provided that the delay time to start scanning after the contrast injection is accurately controlled, and the manual injection of the contrast agent cannot do this, only the automatic injection of the contrast agent is used. The system can be implemented because the contrast medium injection system can push the contrast agent at the required speed, and can scan while pushing the contrast agent, that is, the scan can be started at any time after the start of the injection.
Methods for improving the clearness of scanned images
When using the contrast medium injection system for CT enhanced scanning, the CT scanner can be controlled to start scanning when the contrast agent reaches the scanning site and the contrast agent intensity is maximum, and of course the quality of the enhanced scanned image is greatly improved.
If the speed of the CT scanner is too slow, the contrast agent intensity may have been attenuated very low during the last scan of several slices. You can design a two-stage solution: the first stage (high speed: 2 ~3.5ml/s), the second phase of instillation (low speed: about 0.2ml / s), so that in most of the scanning process, a continuous flow of contrast agent into the blood.
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Q：
Application of vascular synchronization planning technique in spiral CT angiography
A:
SCTA is a vascular imaging technique in which the volumetric acquisition of continuous raw data is performed at the peak of the filling of the target angiography agent after spiral CT examination, and then the workstation is used to reconstruct the stereoscopic image of the target vessel. The vascular anatomy, the image of realistic stereoscopic blood vessels, the key is to obtain the source image of the angiographic agent filling peak period.
SVIP technology is to detect the optimal scanning time of different individuals by injecting a small amount of contrast agent and monitoring the change of target angiographic contrast agent concentration in the blood vessel before the actual scanning [1], so as to obtain the source image of high quality SCTA.
Premature scanning will low the concentration of contrast medium. Too late will lead to the intravascular contrast not in the peak in the late scan, which makes all or part of the blood vessels show poor [2]. The choice of delay time is related to the cycle time. If it is fixed at the same time for delayed scanning, it is impossible to completely ensure that the source image is obtained in the optimal time. The previous solution is to increase the amount of contrast agent to enhance the effect, and the SVIP technology can provide the operator with a direct delay from the injection of the contrast agent to the start of the scan. The enhanced scan is performed without wasting the contrast agent, and the injection delay time is determined by observing the scan time and the CT value change curve to compare the increase of the target blood vessel CT value with the post-injection time [3]. The highest peak CT value and the best scan time (Tab1). SVIP scan is performed according to this value, using three-dimensional revascularization technique. [4-7], effectively improve the degree of visualization of blood vessels, so that the density of target vessels and adjacent tissues and organs is significantly contrasted, avoiding the interference of unrelated structures, thus reconstructing the target vessel structure and its branches.
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