Study on the clinical value of computed tomography angiography in the diagnosis of aortic aneurysm

Abstract

Background

The aim of this study is to explore the clinical value of computed tomography angiography (CTA) in the diagnosis of aortic aneurysm.

Methods

The imaging data of 60 patients suspected of having aortic aneurysms who were examined in the Radiology Department of the First Affiliated Hospital of Nanjing Medical University from April 2017 to April 2020 were analyzed retrospectively. CTA and digital subtraction angiography (DSA) were used to examine the patients, and CTA image findings were collected and compared with DSA findings.

Results

There was no significant difference in the accuracy of diagnosing aortic aneurysms (P > 0.05) between DSA [98.33% (59/60)] and CTA [95.00% (57/60)]. There was no significant difference in the diagnosis of image features (e.g., typing, site, form) of aortic aneurysms (P > 0.05).

Conclusion

CTA can be used to successfully confirm if patients suffer from an aortic aneurysm; it produces quality images with high specificity, sensitivity, and accuracy and can be promoted in clinical practice.

Background

Aortic aneurysm is a cardiovascular disease that poses a major risk to the life of patients. It is clinically defined as an aortic dilation greater than 50% of the normal diameter [1], and is divided into thoracic aortic aneurysms (TAA) and abdominal aortic aneurysms (AAA) according to the anatomical locations. Previous clinical data suggest that patients with aortic aneurysms generally have no visible clinical signs, however, aortic aneurysms dilate progressively until they rupture, endangering the life of patients. According to relevant clinical reports, the mortality rate was around 80% in case of aortic aneurysm rupture [2]. It is like a clinical bomb in the body, with high disability and fatality rates that has a serious impact on the life of patients. Clinically, operations such as endovascular aortic repair (EVAR) and aortic valve replacement (AVR) are commonly used to treat patients [3]. Therefore, early detection and repair of aortic aneurysms in patients aids in controlling the disease and improving the life quality of patients and improving the mortality rate. In this study, we explored the accuracy and clinical value of computed tomography angiography (CTA) in the diagnosis of aortic aneurysms to provide reference methodologies for the clinical diagnosis of aortic aneurysms. The details are reported as follows.

Data and methods

General data

The imaging data of 60 patients suspected of having aortic aneurysms who were examined in the Radiology Department of the First Affiliated Hospital of Nanjing Medical University from April 2017 to April 2020 were analyzed retrospectively. Inclusion criteria: patients suspected of having an aortic aneurysm; no severe organic diseases; absence of coagulation disorders; no medical history or previous history of mental disorders; absence of any medical history or past history of malignancy. Exclusion criteria: lactating or pregnant women. Patients were aged between 39 and 75 years, with a male to female ratio of 36:24 and a mean age of 63 years.

Methods

Instruments used in the digital subtraction angiography (DSA) examination: Philips Allure Xper FD 20; the thoracic and abdominal aortic contrast agent was generally 35 mL of Visipaque—iodixanol injected at a rate of 20 mL/s, and multi-position projection was used to ensure that each vascular tube could be effectively developed.

Instruments used in the CTA examination: Definition AS 64-slice spiral CT scanning system [Siemens Ltd. China], thoracic and abdominal CTA; the layer thickness and interlayer spacing were both 5 mm; auto tube current; Ultravist 370 (80 mL) was injected by a high pressure injector via forearm veins at a rate of 4 mL/s; delay time was 15 s, and the contrast agent automatic tracking technique (Bolus Tracking) was used to trigger automatic tracking. After scout image scanning, the cross-section of the thoracic aorta vessel was selected as the target vessel of interest on the thoracic and abdominal CTA, and the selected target vessel was the contrast agent concentration tracking area, where the threshold was set to 100 HU, and the range to be scanned was from cervical 7 (C7) to pubis; finally, the high pressure injector was used for bolus injection of the contrast agent; when the contrast agent concentration in the target vessel of interest reached the threshold of 100 HU, the computer automatically triggered scanning; at the end of scanning, the raw data were postprocessed in the workstation using methods such as maximum intensity projection (MIP), volume rendering (VR), multiplanar reformation (MPR) and shaded surface display (SSD) to reconstruct the image.

Observational indexes

The accuracy of CTA and image features was analyzed using the golden standard of DSA examination.

The accuracy of detecting the site, form, and type of aortic aneurysm was compared using the image features. The DeBakey classification was used to classify the disease.

Statistical methods

The statistical software SPSS22.0 was used to analyze the data, and measurement data—mean ± standard deviation ($\bar x \pm s$) and enumeration data (%) were compared using the t-test and the chi-squared test, respectively. P < 0.05 indicated statistical differences.

Results

Diagnostic efficiency

There was no difference in the accuracy of diagnosing aortic aneurysm (P > 0.05 between DSA [98.33% (59/60)] and CTA [95.00% (57/60)]).

Comparison of image features

As shown in Table 1, there was no difference between the two examination methods in the diagnosis of image features (e.g., type, site, and form) of an aortic aneurysm (P > 0.05).

Table 1 Comparison of image features

CTA image and DSA image of an aortic aneurysm

After thoracic and abdominal CTA examination, raw data were postprocessed in the workstation to obtain the MIP image of AAA, as shown in Fig. 1; following thoracic and abdominal CTA examination, raw data were postprocessed in the workstation to obtain the VR image of AAA, as shown in Fig. 2; and bulging AAA was detected at the abdominal aorta by thoracic and abdominal DSA examination, as shown in Fig. 3.

Fig. 1

CTA radiography MIP image; the arrow points to an abdominal aortic aneurysm

Fig. 2

CTA radiography VR image; the arrow points to an abdominal aortic aneurysm

Fig. 3

DSA image; the arrow points to an abdominal aortic aneurysm

Discussion

TAA and AAA are potentially fatal cardiovascular diseases caused by genetic predisposition and multiple factors. Under excessive pressure, the aortic tube wall thickens as the pressure increases, and eventually leads to an aortic aneurysm. Aortic aneurysms are highly risky in adults over the age of 60, and frequently result in death [4]. In clinical practice, the cause of aortic aneurysms is currently thought to be the most closely associated with atherosclerosis. Blood lipid levels in the elderly increase, leading to the degeneration of elastic fibers and rupture and calcification of the aortic wall, while an aortic aneurysm is caused by the formation of atherosclerotic plaques in the arterial wall [5]. Aortic aneurysm, which is common in the middle-aged and elderly, has become a serious threat to human health; with a rapid onset, it may result in 80% of deaths within 6 weeks if not detected and treated early. Patients in the early stage have no obvious clinical symptoms, but aortic aneurysms gradually increase as patients get older until the aorta cannot withstand it and ruptures, seriously endangering the life of patients. Thus, early detection, intervention, and treatment can help control the disease and prolong the lives of patients [6]. In addition, point of care ultrasound (POCUS) can rapidly and accurately diagnose and guide the treatment of critical illness, and has been widely used in emergency medicine, critical care and other fields [7, 8]. DSA has been the “golden standard” for the diagnosis of vascular disease, and it is clinically used to clearly and accurately check the size, site, quantity, form, and other features of aortic aneurysms [9]. However, the traumatic nature of the procedure as well as the high risk and cost dissuade many patients, creating a market for the non-invasive and inexpensive CTA. Patients with TAA and AAA generally have no visible clinical symptoms. Those under the age of 50 are more likely to have a pulsatile mass around the umbilicus or in the middle and superior abdomen, with some developing abdominal pulsation when lying on the back and some even developing abdominal distension. Patients with TAA and AAA may feel pain, and persistent pain often indicates sudden, persistent, and sharp dilation and rupture of the aortic aneurysm, mostly on the back and in the lower abdomen [10]. In this case, patients frequently suffer from sudden pain in the back, accompanied by acute abdominal pain and tenderness, and the majority develop a pulsatile mass and hypotension [11]. TAA and AAA are serious complications that endanger health; nevertheless, only one third of patients exhibit clinical manifestations, with the remainder being misdiagnosed with other diseases with similar symptoms, such as appendicitis [12].

Multi-slice spiral CT, especially 64-slice spiral CT, scans at a sub-second rate and over a wide range, producing thinner layers and images with high time and space resolution, allowing it to be used in any direction. It has strong post-processing functions, such as MPR, MIP, and VR techniques. CTA has developed rapidly and there is increasingly application of the technology [13]. It is the most common examination method for aortic aneurysms, and can be used for observation and analysis based on the lesion site in the image, thereby improving the reliability of diagnosis. In this study, the CTA had an accuracy of 95.00% (57/60) in the diagnosis of aortic aneurysm. The winding blood vessels in numerous CTA reconstruction methods can be analyzed by intelligent analysis technology and observed from multiple directions and angles. In comparison with DSA, CTA processes the images with different colors and transparency based on internal and external data using software, to more clearly present the entire TAA and AAA, as well as the relationship between TAA and AAA and surrounding tissues such as the renal artery, retroperitoneum, and spinal cord. It can measure and type the TAA and AAA from multiple angles, including aortic bifurcations and retroperitoneal hematomas to clearly display the local site of an aortic aneurysm and its relationship with surrounding tissue and vascular anatomy [14]. It can be used to better observe the entire aortic blood vessels and bifurcations thanks to its strong postprocessing and multidimensional rotation features combined with axial scanning of images. Furthermore, it plays an important role in developing clinical treatment schemes and surgical approaches, evaluating surgical risks, and observing postoperative efficacy [15]. CTA is sensitive to calcification, so CTA images are based on different material densities. A surgical diagnosis is made based on the vascular wall thickening and thrombus. CTA scans at a rapid rate and produces images with thinner layers and high space and density resolution; it is non-invasive and painless, and can simultaneously be used to observe surrounding organs, allowing for accurate diagnosis and typing of the disease within a short period of time. Furthermore, it is cost-effective and simple to administer, and causes minimal trauma to patients, and is thus more acceptable to patients and their families. It is capable of rapid imaging, with image quality grading, detection accuracy, and sensitivity comparable to those of DSA.

In addition, there are still deficiencies in this study. First of all, the sample size we included is small. In the later stage, we will continue to expand the sample size, conduct continuous research, and increase the reliability of the data; Secondly, our study is relatively simple and does not explore the diagnostic efficacy of CTA in depth. It is only simple to compare with DSA, which is less innovative.

Conclusion

Finally, CTA can be used to effectively confirm if patients suffer from an aortic aneurysm; it produces quality images with high accuracy and sensitivity and can be promoted in clinical practice.