Aortic balloon occlusion can be used by emergency physicians to rescue patients with massive bleeding.The purpose of this study is to study the anatomical characteristics of aortic balloon occlusion based on aortic CT angiography, so as to provide evidence for improving the success rate of aortic balloon occlusion guided by body surface markers.

Study Design:

This study is a retrospective descriptive study. The study will be conducted by Radiology Department, Second Affiliated Hospital, Zhejiang University.

Selection of patients:

The investigators included 57 patients who underwent enhanced contrast full-length aortic CTA scanning in the Radiology Department of Grade 3A General Hospital affiliated to a university from April to December 2019. Data of all participants following no apparent vascular tortuosity in CT diagnosis aged 18-70 years with contrast-enhanced computed tomography (CT) images of chest, abdomen, and pelvis from April to December in 2019 were analyzed. Participants whose images accompanied by vascular malformation, poor contrast enhancement, and history of aortic surgery were precluded.

Method General data of patients were collected through the hospital's electronic medical record system, including age, sex, height, weight, average body mass index ((Body Mass Index,BMI), history of surgery, etc.

The CTA examination of the participants' full aorta was performed with a 128-slice dual-energy CT scanner (Siemens, Germany), and the images were saved in the database. After screening the suitable participants, the images were transmitted to the CT workstation (Syngo VB10B Image processing system, Siemens, Germany). Multiplanar reconstruction, curvature plane reconstruction, and volume rendering were used for three-dimensional reconstruction. The diameters and lengths of blood vessels and the distances on the body surface were measured. The diameters of blood vessels included the diameter of the aorta at the edge of left subclavian artery, celiac trunk, lowest renal artery, and aortic bifurcation. The intravascular length included the lengths of zone I, zone II, zone III and the descending aorta. The length from the bilateral femoral artery puncture site to the midpoint of zone I and III, left subclavian artery, celiac trunk, lowest renal artery and aortic bifurcation, and the distances on the body surface included the distance from the bilateral femoral artery puncture site to the suprasternal notch, xiphoid process and umbilicus.

The results were described as mean ±standard deviation. SPSS20.0 software (IBM, USA) was used for analysis. Paired sample t-test was used to compare the differences between the left and right sides of the data. The difference was statistically significant when the P value was less than 0.05.

Data Management and Confidentiality Data Management: Using paper version for data management and storage. The person responsible for collecting paper version will input data in Excel database, summary paper and electronic versions for further statistical analysis and preservation.

Security measures: All records related to the identity of participants are to be confidential and not open to the public outside the scope of relevant laws or regulations.

Informed consent: This study is a retrospective study. Retrospective measurement of participants' previous aortic CTA imaging data does not infringe upon the interests of participants, so informed consent can be exempted.

Possible risks of participating in this study: disclosure of personal information.

Precautions against possible risks:

1. All the experimental data of the paper version and the electronic version shall be kept by the person in charge of the test data.
2. Close the measurement software in time after the end of the study, and confirm that the personal information has been cleared.

Intervention measures for possible risks:

If there is a disclosure of personal information, it is necessary to record the research report form and inform the person in charge of the research to intervene in time, and notify the Ethics Committee immediately.

Inclusion Criteria:

• Complete full-length CTA scan of aorta
• Aged 18-70 years old
• No obvious tortuosity diagnosed by CT

Exclusion Criteria:

• Aortic dissection
• Aortic aneurysm
• Severe aortic malformation
• Severe aortic plaque
• History of aortic operation.

We conduct an observational retrospective study.The patients underwent aortic CT angiography examination in the radiology department of the hospital from April to December in 2019.