CN111568459A - Method for determining CT pulmonary artery imaging scanning delay time - Google Patents

Abstract

The invention discloses a method for determining CT pulmonary artery imaging scanning delay time, when a contrast agent test method is adopted in scanning, a test stage is to simultaneously set similar circular ROI with corresponding size in a pulmonary artery trunk and a pulmonary vein at the same layer to obtain a pulmonary artery-vein intensified time density hyperbola, and the time of a hyperbola cross point is taken as T_CROSSWith scan duration as T_SDThrough T_CROSS‑T_SDCalculating the scan delay time T from the difference_DELAY. The scanning delay time calculated by the method of the invention is adopted, and the exposure scanning can obtain a high-quality pulmonary artery strengthening image.

Description

A method for determining the delay time of CT pulmonary angiography

technical field

The invention belongs to the technical field of CT angiography, in particular to a method for determining the scanning delay time of CT pulmonary artery imaging.

Background technique

Pulmonary embolism (PE) is a general term for a group of diseases or clinical syndromes in which various emboli obstruct the pulmonary artery or its branches as the cause, including pulmonary thromboembolism (PTE), fat embolism syndrome, amniotic fluid embolism, air embolism, etc. . PTE is the most common type of PE, accounting for the vast majority of PE, while the vast majority of PTE is acute pulmonary embolism (APE). The main clinical and pathophysiological features are pulmonary circulation and respiratory dysfunction, and it is the most common cause of clinical acute cor pulmonale. APE is a life-threatening disease and the third most common acute cardiovascular disease after myocardial infarction and stroke. PTE has a high mortality and disability rate. A recent international registration study showed that the 7-day all-cause mortality rate was 1.9%-2.9%, and the 30-day all-cause mortality rate was 4.9%-6.6%. PTE has always been regarded as a rare disease in China. In the past 10 years, relevant clinical epidemiological investigations have found that the number of diagnosed cases of PTE in my country has increased rapidly. The number of PE cases diagnosed in most hospitals has increased by 10-30 times compared with 10 years ago. . Statistics from 60 large domestic hospitals show that the proportion of PTE in inpatients increased from 0.26‰ in 1997 to 1.45‰ in 2008.

CT angiography refers to the rapid injection of iodine contrast agent from the subject's vein, through the human blood circulation, when the concentration of the contrast agent in the target organ reaches the highest peak, the spiral CT volume scan is performed, and the three-dimensional image of the blood vessel is reconstructed after the workstation. Stereoscopic image. CT pulmonary angiography (CTPA) can visually display the thrombus shape, location and degree of vascular occlusion in the pulmonary artery. It has high sensitivity and specificity for the diagnosis of PTE, and is non-invasive and convenient. The direct sign is a filling defect in the pulmonary artery, partially or completely surrounded by opaque blood flow (orbit sign), or a complete filling defect with no visualization of distal vessels; indirect signs include lung field wedge-shaped, band-like density Heightened shadow or discoid atelectasis, central pulmonary artery dilatation and distal vascular branch reduction or disappearance. CTPA can simultaneously display other chest diseases in the lung and outside the lung, and has important diagnostic and differential diagnosis value.

Scanning timing is a decisive variable in achieving good uniform enhancement on CT angiography. Determining the optimal scan delay time to generate sufficient vascular enhancement is a challenging task, and modern CT scans are getting faster and faster, and low kV scans require only a small amount due to the k-edge of iodine and patient-specific parameters. Contrast agents are therefore more widely used. Consequently, there is an increasing risk of missing peak arterial enhancement on CT angiography. Contrast tracking (BT) and contrast testing (TB) are the two most widely used CT angiography techniques in clinical practice. The main advantages of BT technology with a fixed trigger delay time compared to TB technology are the need for less contrast agent, less radiation dose, and time efficiency. Although BT technology has been used for decades, it still has drawbacks. A major disadvantage of it is that the fixed trigger delay time after reaching the threshold does not take into account patient-specific cardiovascular parameters such as cardiac output or blood circulation time. For example, in patients with high cardiac output, a fixed and pre-set trigger delay time may result in missed arterial enhancement peaks because the scan may start too late. In contrast, in patients with low cardiac output, scans may start too early, terminating image acquisition before peak arterial enhancement is reached.

High-quality CTPA imaging should achieve obvious enhancement of the pulmonary artery but not obvious enhancement of the pulmonary vein, and no enhancement in the aorta. And use as little iodine contrast agent as possible, ideally with as little iodine contrast agent remaining in the superior vena cava (this may lead to radiosclerosis beam artifacts, affecting the observation of pulmonary artery branches). At the same time, radiation dose should be minimized while maintaining acceptable image noise levels, and scan acquisition times should be kept as short as possible to mitigate motion artifacts.

SUMMARY OF THE INVENTION

Aiming at the uneven image quality level and venous pollution in the current CT pulmonary artery angiography, the invention aims to obtain the optimal scanning delay time through TB technology, reduce the pollution of iodine contrast agent in the pulmonary vein, and avoid the iodine contrast agent in the superior vena cava. Concentration, thereby improving image quality and reducing the amount of iodine contrast agent used by patients.

In order to achieve the above object, the technical scheme adopted by the present invention is as follows:

A method for determining the delay time of CT pulmonary artery imaging scan. When the contrast agent test method is used for scanning, the monitoring stage is in the main pulmonary artery and the same layer of pulmonary veins, and a circular ROI of corresponding size is set at the same time, so as to obtain the pulmonary artery-vein enhancement time density double Curve, the hyperbolic intersection time is taken as T _CROSS , the scan duration is taken as T _SD , and the optimal scan delay time T _DELAY is calculated by the difference between T _CROSS - T _SD .

Specifically, the method for determining the delay time of CT pulmonary artery imaging scan includes the following steps:

(1) The positioning image after scanning is completed: the patient is lying on the scanning bed, the upper limbs are placed on both sides of the head, the patient is trained to breathe, and the breath is easily held under calm breathing, and the scanning range includes the apex of the lung to the costophrenic angle;

(2) Obtain pulmonary arterial-venous enhancement time density hyperbola: According to the localization image obtained in step (1), place the monitoring plane at 1 cm below the tracheal bifurcation, hold your breath easily under calm breathing, inject iodine contrast agent, and perform synchronously Monitor the scan, stop the scan after the ascending aorta is enhanced, and obtain a group of circulating enhanced images of iodine contrast agent;

Select a picture with obvious pulmonary vein enhancement in the circulatory enhancement image, and set a circular ROI of corresponding size in the main pulmonary artery and the same layer of pulmonary veins to obtain the pulmonary artery-vein enhancement time density hyperbola;

(3) calculate the pulmonary artery angiography scan delay time: obtain the hyperbolic intersection time T _CROSS according to the step (2) pulmonary artery-vein enhancement time density hyperbola; meanwhile, according to the positioning image obtained in the step (1), determine the pulmonary artery After imaging the scanning direction and range, the scanning duration T _SD is obtained; finally, the optimal scanning delay time T _DELAY is calculated by the difference of T _CROSS - T _SD .

Preferably, in step (1), the scanning conditions are the tube voltage of 80-120kVp, the tube current of 20mA, and the window width/window level is set to 500/50HU.

In step (2), a double-barreled high-pressure syringe is used to inject iodine contrast agent, one side of the tube is iodine contrast agent, and the other side is physiological saline, the iodine contrast agent is injected first, followed by physiological saline at the same flow rate. The dosage of iodine contrast agent is 5-10ml, the normal saline is 40-45ml, and the injection flow rate is 4.0-5.0ml/s.

In step (2), the monitoring scan mode is axial scan, the frame rotation speed is 1.0s/r, the tube voltage is 80-120kVp, the tube current is 40mA, the layer thickness is 5mm, the reconstruction type is the standard mode, the window width/window level It is set to 350/50HU, and the reconstruction algorithm is iterative reconstruction.

In step (2), the test scan is set to 15-30 times, and the scan is performed once every 1-2 seconds.

Specifically, in step (2), the pulmonary artery-vein enhancement time density hyperbola is obtained by placing the ROI in the pulmonary artery and the pulmonary vein at the monitoring level at the same time.

In step (3), the pulmonary artery imaging scanning direction and range are 2 cm below the top of the diaphragm to 2 cm above the aortic arch.

Beneficial effects:

Using the scanning delay time calculated by the method of the invention, high-quality pulmonary artery enhanced images can be obtained by exposure scanning, which can not only accurately collect the enhanced pulmonary artery, reduce the development of the accompanying pulmonary veins, but also reduce the consumption of iodine contrast agent and reduce the number of patients. The iodine load can avoid the radiosclerotic beam artifacts caused by the concentration of iodine contrast agent in the subclavian vein and superior vena cava on the injection side.

Description of drawings

The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the above-mentioned and/or other aspects of the present invention will become clearer.

Figure 1 is the preparation before the TB technology test scan, A is the positioning image of the subject, and B is the set test level and scan range.

Figure 2 is the process of obtaining the pulmonary artery-vein enhancement time density hyperbola. A is the one with obvious pulmonary vein enhancement in the selected test group, and B is in the main pulmonary artery and the same layer of pulmonary veins, and a circular ROI of corresponding size is set at the same time. .

Figure 3 is a time-density hyperbola of pulmonary arteriovenous enhancement obtained.

FIG. 4 is the time T _CROSS of the hyperbolic intersection point obtained with reference to the coordinates.

Figure 5 is a high-quality CT pulmonary artery vascular image obtained using the resulting scan delay time exposure scan.

Detailed ways

The present invention can be better understood from the following examples.

The structures, proportions, sizes, etc. shown in the drawings in the description are only used to cooperate with the contents disclosed in the description, so as to be understood and read by those who are familiar with the technology, and are not used to limit the conditions for the implementation of the present invention. The technical substantive significance, any modification of the structure, the change of the proportional relationship or the adjustment of the size, should still fall within the technical content disclosed by the present invention without affecting the effect that the present invention can produce and the purpose that can be achieved. within the range that can be covered. Meanwhile, terms such as "upper", "lower", "front", "rear" and "middle" quoted in this specification are only for the convenience of description and clarity, and are not used to limit the scope of the present invention. , the change or adjustment of the relative relationship, without substantial change of the technical content, should also be regarded as the scope of the present invention.

The following is a specific example of determining the delay time of CT pulmonary angiography scans.

(1) The positioning image after scanning is completed: the patient is lying on the scanning bed with advanced feet, and the upper limbs are placed on both sides of the head. The next inspection procedure is introduced to the patient, and effective communication is obtained, so that the patient can avoid tension, and perform breathing training for the patient to calm down. Hold the breath easily under breathing, the scanning range includes the lung apex to the costophrenic angle (as shown in Figure 1), the scanning conditions are tube voltage 80kVp, tube current 20mA, and the window width/window level is set to 500/50HU.

(2) Obtain pulmonary artery-venous enhancement time density hyperbola: According to the positioning image obtained in step (1), place the monitoring plane at 1 cm below the tracheal bifurcation (the plane of the main pulmonary artery), hold your breath easily under calm breathing, and inject 5 ml of iodine Contrast agent + 45ml normal saline, flow rate 5.0ml/s, monitoring scan mode is axial scan, gantry rotation speed 1.0s/r, tube voltage 80kVp, tube current 40mA, slice thickness 5mm, reconstruction type is standard mode, window width / The window level was set to 350/50HU, the reconstruction algorithm was iterative reconstruction, the iodine contrast agent injection was performed synchronously with the monitoring scan, and the monitoring scan was preset for 15 times, every 2 seconds, and the scan was stopped after the ascending aorta was enhanced. Obtain a set of circulating enhanced images of iodine contrast agents. Select a picture with obvious pulmonary vein enhancement in the circulatory enhancement image, and set a circular ROI of corresponding size in the main pulmonary artery and the same layer of pulmonary veins (as shown in Figure 2) to obtain a pulmonary artery-vein enhancement time density hyperbola (such as shown in Figure 3).

(3) Calculate the pulmonary artery angiography scan delay time: According to step (2) pulmonary artery-vein enhancement time density hyperbola, the hyperbolic intersection time T _CROSS is 9 seconds; at the same time, according to the positioning image obtained in step (1) , determine the scanning direction and range of pulmonary artery imaging from 2 cm below the top of the diaphragm to 2 cm above the aortic arch, and the scanning duration T _SD is 1.9 seconds; finally, the optimal scanning delay time T _DELAY is calculated by the difference of T _CROSS - T _SD as 7.1 seconds.

(4) The scanning delay time calculated by the above method is 7.1 seconds, and high-quality pulmonary artery vascular imaging can be obtained by exposure scanning, as shown in FIG. 5 .

The amount of iodine contrast agent used in conventional pulmonary arterial imaging technology is more than 25ml. The method of the present invention can complete the examination with only 15ml when the patient's BMI is less than 28kg/m ² and the body weight is less than 80kg. In the monitoring phase, 5ml of iodine contrast agent + 45ml of normal saline was used, and 10ml of iodine contrast agent + 40ml of normal saline was used in the final CTPA scan.

The present invention provides an idea and method for determining the delay time of CT pulmonary artery imaging scans. There are many specific methods and approaches for realizing the technical solution. The above are only the preferred embodiments of the present invention. For those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can also be made, and these improvements and modifications should also be regarded as the protection scope of the present invention. All components not specified in this embodiment can be implemented by existing technologies.

Claims (8)

1. a determination method of CT pulmonary artery imaging scan delay time, it is characterized in that, when scanning adopts contrast agent test method, test phase is in pulmonary artery trunk and the same layer pulmonary vein, set the quasi-circular ROI of corresponding size simultaneously, obtain pulmonary artery. - The venous enhancement time density hyperbola, the time at the intersection of the hyperbolas is taken as T _CROSS , the scan duration is taken as T _SD , and the scan delay time T _DELAY is calculated from the difference between T _CROSS - T _SD . 2. The determination method of CT pulmonary artery imaging scan delay time according to claim 1, is characterized in that, comprises the steps: (1) The positioning image after scanning is completed: the patient is lying on the scanning bed, the upper limbs are placed on both sides of the head, the patient is trained to breathe, and the breath is easily held under calm breathing, and the scanning range includes the apex of the lung to the costophrenic angle; (2) Obtain pulmonary arteriovenous enhancement time density hyperbola: According to the localization image obtained in step (1), place the monitoring plane at 1 cm below the tracheal bifurcation, hold breath easily under calm breathing, inject iodine contrast agent, and monitor synchronously Scanning, stop scanning after the ascending aorta is enhanced, and obtain a group of circulating enhanced images of iodine contrast agent; Select a picture with obvious pulmonary vein enhancement in the circulatory enhancement image, and set a circular ROI of corresponding size in the main pulmonary artery and the same layer of pulmonary veins to obtain the pulmonary artery-vein enhancement time density hyperbola; (3) calculate the pulmonary artery angiography scan delay time: obtain the hyperbolic intersection time T _CROSS according to the step (2) pulmonary artery-vein enhancement time density hyperbola; meanwhile, according to the positioning image obtained in the step (1), determine the pulmonary artery After imaging the scanning direction and range, the scanning duration T _SD is obtained; finally, the optimal scanning delay time T _DELAY is calculated by the difference of T _CROSS - T _SD . 3. the determination method of CT pulmonary artery imaging scan delay time according to claim 2, is characterized in that, in step (1), scanning condition is tube voltage 80-120kVp, tube current 20mA, and window width/window level is set as 500/50HU. 4. the determination method of CT pulmonary artery imaging scan delay time according to claim 2, is characterized in that, in step (2), use double-barreled high-pressure syringe to inject iodine contrast agent, the iodine contrast agent consumption is 5-10ml, and physiological saline is 40-45ml, and the injection flow rate is 4.0-5.0ml/s. 5. The method for determining the delay time of CT pulmonary artery imaging scan according to claim 2, wherein in step (2), the monitoring scan mode is axial scan, the gantry rotation speed is 1.0s/r, the tube voltage 80-120kVp, tube current 40mA, slice thickness 5mm, reconstruction type is standard mode, window width/window level is set to 350/50HU, reconstruction algorithm is iterative reconstruction. 6 . The method for determining the delay time of CT pulmonary artery imaging scan according to claim 2 , wherein in step (2), the monitoring scan is set to 15-30 times, and the scan is performed once every 1-2 seconds. 7 . 7. The method for determining the delay time of CT pulmonary artery imaging scan according to claim 2, wherein in step (2), the pulmonary artery-vein enhancement time density hyperbola is in the monitoring level pulmonary artery and pulmonary vein, and simultaneously. Place the ROI to get. 8 . The method for determining the delay time of CT pulmonary artery imaging scan according to claim 2 , wherein, in step (3), the pulmonary artery imaging scan direction and range are 2 cm below the top of the diaphragm to 2 cm above the aortic arch. 9 .

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