Biomedical Imaging and Intervention Journal Follow BIIJ on Twitter Find BIIJ on Facebook

Current issue Contact us

Editorial Board
Instruction for Authors
Editorial Workflow
Recorded Presentations
Remote Education

Free subscription

Subscription will allow you to receive automatic alerts and announcements from biij

13th Asian Oceanian Congress of Radiology (AOCR), Taipei, Taiwan March 20-23, 2010

5th Congress of Asian Society of Cardiovascular Imaging, Hong Kong, 18-19 June 2011

Engineering and Physical Sciences in Medicine and the Australian Biomedical Engineering Conference, Australia, 14-18 August 2011

Home > Contents


Biomed Imaging Interv J 2010; 6(3):e22
doi: 10.2349/biij.6.3.e22
© 2010 Biomedical Imaging and Intervention Journal

PDF version Case Report

Aortic dissection: Identification of entry site with CT virtual intravascular endoscopy

Y Cao1, MM, Z Sun*,2, PhD, Y Shang1, BSc, B Jiang3, PhD, X Ma3, MB
1 Department of Medical Imaging, Shandong Medical College, Jinan, Shandong, People�s Republic of China
2 Discipline of Medical Imaging, Department of Imaging and Applied Physics, Curtin University of Technology, Perth, Western Australia, Australia
3 Department of Radiology, Qilu Hospital, Shandong University, Shandong, People�s Republic of China


Aortic dissection is a common vascular disease which has high morbidity and mortality if it presents with acute onset. Early diagnosis, characterisation of the type of dissection and identification of intimal tear (entry site) is important for patient management. CT angiography, especially with widely-used multislice CT imaging technique, is the method of choice for diagnosis of aortic dissection. This article presents the additional value of 3D visualisation, using virtual intravascular endoscopy, for assessment of aortic dissection when compared to conventional 2D views. The article focuses particularly on identifying the entry site of dissection with the aid of virtual intravascular endoscopy in three selected cases. It is expected that the intraluminal findings will assist radiologists to accurately diagnose and treat patients with suspected aortic dissection. � 2010 Biomedical Imaging and Intervention Journal. All rights reserved.

Keywords: Aortic dissection, CT, 3D visualisation, virtual intravascular endoscopy


Aortic dissection is a life-threatening condition which occurs nearly three times as frequently as the rupture of abdominal aortic aneurysm [1]. It is critical to make a prompt diagnosis of aortic dissection, as this can decrease mortality and increase the survival rate. Currently, multislice CT (MSCT) imaging is the method of choice for diagnosis of aortic dissection due to its high spatial and temporal resolution with nearly 100% sensitivity and specificity [2, 3]. CT has been reported to be more sensitive than invasive angiography for diagnosing aortic dissection [4].

Differentiation of true and false lumen, and identification of the entry site of aortic dissection is important in planning percutaneous treatment with endovascular grafts or surgical repair of aortic dissection [5, 6]. In most of the cases, axial CT imaging is able to identify the intimal flap which separates the true lumen from the false lumen. However, this may not be possible in all cases due to variable appearances corresponding to different types of aortic dissection [2, 7, 8]. Moreover, the three-dimensional (3D) aortic arch is difficult to assess on an axial 2D plane. 3D virtual intravascular endoscopy (VIE) allows for acquisition of unique intraluminal views of the blood vessel and it has been previously reported to be valuable for assessment of aortic aneurysms and endovascular stent grafts [9-11]. VIE has been shown to offer better understanding of the abnormalities of aortic arch after endovascular repair [12]; however, its application in pre-operative aortic dissection has not been studied before, to the best of the authors� knowledge. The purpose of this paper is to illustrate VIE findings in patients diagnosed with aortic dissection. This paper presents different types of aortic dissection in three sample cases with the aim of exploring the potential value of VIE for identification of the entry site of aortic dissection.

Multislice CT scanning protocols

The spiral CT angiography (CTA) was performed for all three patients using a dual-source CT scanner (Siemens, Definition, Forchheim, Germany), and scanning protocol was as follows: beam collimation 64x 0.6 mm with slice thickness between 0.5-1.0 mm, and pitch 1.0 with reconstruction interval of 50% overlap. 100 ml non-ionic contrast medium (Visipaque) was injected intravenously at a flow rate of 4-6 ml/s via antecubital vein with a high-pressure injector, followed by 40-60 ml of normal saline chasing. To account for individual cardiac output, bolus triggering technique was used with the region of interest placed at the proximal descending thoracic aorta and triggering threshold was set at 120HU to initiate the scan. CT angiography was completed with a single breath-hold technique and the length of scan required for acquisition of data was determined by the total scan length in each patient.

Generation of virtual intravascular endoscopy images

Multislice CT volume data were converted from original DICOM (Digital Imaging and Communication in Medicine) images using Analyze 7.0 ( Similar to previous studies, a CT number thresholding technique was used to produce virtual intravascular endoscopic (VIE) views of the aorta and its branches, as well as abnormal changes [9, 10]. This was determined by selecting an appropriate threshold value through measuring the CT attenuation at the aorta (either ascending or descending aorta). An upper threshold of 200-300 HU was applied to remove the contrast-enhanced blood from the aorta while keeping the artery wall intact without luminal disruption. Orthogonal views were used to assist VIE identification of the true, false lumen as well as intimal flap and entry site of aortic dissection (Figure 1).

Case report and VIE findings

Case 1

A 64-year-old patient with a history of chest pain for 2 days involving his back, chest and abdomen underwent CTA for exclusion of cardiovascular disease. Stanford type B aortic dissection was diagnosed based on 2D axial images as the entry site was located in the convexity of the aortic arch distal to the left subclavian artery (Figure 2A). VIE clearly demonstrated a circular entry site of the dissection inside the medical wall of the ascending aorta (Figure 2B). The true and false lumens were separated by an intimal flap, which is clearly shown on both axial and VIE images (Figures 2B and C). Extending from the aortic arch to the descending aorta, another small re-entry point was identified by VIE in the aorta (Figure 2D).

In contrast to 2D CT views, VIE accurately identified the entry site and clearly demonstrated the relationship of aortic dissection to the surrounding anatomic structures.

Case 2

A CTA scan was performed on a 39-year-old patient with 1 day of chest pain involving her interscapular region and anterior chest. Stanford type A dissection was diagnosed on 2D views as aortic dissection arises from the ascending aorta extending to the descending and abdominal aortic branches (Figures 3A and B). The ultrasound examination detected an abdominal aortic aneurysm. VIE showed the entry site of dissection which is located in the ascending aorta, adjacent to the left ventricle (Figure 3 C). In addition, the intimal flap which separates the true from false lumens is clearly visualised on VIE image, as shown in Figure 3D.

This case demonstrates the superiority of intraluminal appearance provided by VIE as it is able to precisely recognise the location of the aortic dissection entry site which is close to the left ventricle. It is difficult to directly locate the entry site or intimal tear of aortic dissection based on conventional 2D images, especially for type A dissection.

Case 3

A 65-year-old man presenting with a history of hypertension and two days of interscapular, chest and abdomen pain underwent a CTA scan. Chest radiograph showed mediastinal widening, and this suggested aortic artery disease. Stanford type A dissection was diagnosed since the entry site was located in the middle section of the ascending aorta based on CT images (Figure 4A), and this was confirmed by VIE showing a very narrowed true lumen and a long entry site (Figures 4B and C). The false lumen was apparently larger than the true lumen which was compressed to a greater extent, leading to a protrusion sign inside the true lumen, which was clearly visualised on VIE views. The curved intimal flap formed a ridge towards true lumen and the intimal tear was located posterior to the intimal flap (Figure 4C).

The communication between true and false lumen was demonstrated on 2D axial CT images; however, the accurate location of intimal tear could not be adequately assessed on 2D views. In contrast, VIE possesses the advantage of being able to confirm the entry site and intimal tear, in terms of both location and extent, as shown in Figures 4 B and C.


Aortic dissection can be characterised as the splitting of the aortic wall by high-pressure arterial blood entering the media through an intimomedial entrance tear. CT imaging has been the method of choice for diagnosis and characterisation of aortic dissection, due to the high diagnostic accuracy achieved [2, 3]. However, in some cases, conventional CT views fail to detect the entry site of aortic dissection due to variable appearances presented by aortic dissection or the fact that the location of intimal tear makes it difficult for 2D views to follow [7, 13]. The ability of VIE to provide intraluminal views offers an advantage over conventional views, and this was confirmed in a recent report by Louis et al. [12]. This case report corroborates their findings about the diagnostic value of VIE through identification of the intimal tear, thus it is believed that VIE could be used as a complementary tool to 2D CT imaging for accurate evaluation of aortic dissection.

Detection of the entry site in aortic dissection is important for several physiologic and therapeutic reasons [6, 14]. It is imperative to determine whether major aortic arteries originate from true or false lumens before placement of endovascular grafts or stents because any branch arteries being supplied by the false lumen may be occluded with an intervention unless surgically bypassed [13]. VIE not only allows for generation of static intraluminal views of the aorta and its branches, but also provides virtual fly-through and navigation of the entire aorta lumen, despite the presence of a very-narrowed true lumen (video clips, online viewing only). Therefore, accurate assessment of the involvement of the artery branches by dissection, in addition to the identification of entry site, can be achieved with VIE visualisation. Moreover, the extent of the entry site can be further explored by VIE as shown in case 3.

Although VIE is a visualisation tool that enables demonstration of intimal flap and entry site of aortic dissection, the image quality is determined by the original CT data, which depends on the scanning protocols selected for CTA. With the current CT scanners such as 64-slice or dual-source CT, high spatial and temporal resolution allow for acquisition of isotropic volume data which ensures VIE image quality. Generation of VIE images is affected by the selection of appropriate CT threshold, since artifacts arising from an inappropriate threshold could interfere with visualisation of the aortic dissection with regard to intimal flap or intimal tear. Detecting full-directional information about the dissection should be assisted by cross-sectional and multiplanar reformatted CT images. Correlation with orthogonal views is necessary to confirm the exact position of anatomic details on VIE visualisation.

In conclusion, VIE provides unique intraluminal information to demonstrate the location and extent of entry site of aortic dissection. VIE could be used as a complementary tool to conventional 2D CT views for accurate evaluation of aortic dissection.

Figure 1 Virtual intravascular endoscopy (VIE) demonstration of the intimal flap (arrows) in a dissection aneurysm. Corresponding orthogonal views (axial, coronal and sagittal) confirm the location of VIE position inside the ascending aorta. Three main artery branches arising from the aortic arch can be clearly seen on VIE image which are shown in the top left VIE image.

Figure 2 Stanford type B dissection in case 1 with the dissection arising from the descending aorta distal to the left subclavian artery (arrow in A). Intimal tear was identified on VIE image (B) when viewed from the false lumen. The false lumen is much larger than the true lumen (C). F indicates false lumen and T refers to true lumen.

Figure 3 Stanford type A dissection in case 2 with the dissection originating at the ascending aorta. The intimal flap is clearly displayed on 2D axial and coronal reformatted images (long arrows in 3A and B) with left coronary artery arising from the true lumen (arrowhead). VIE shows the intimal tear which is located at the ascending aorta (arrow in C) proximal to the left ventricle. VIE clearly identifies the intimal flap which separates the true lumen from the false lumen (D). IF indicates intimal flap. T and F refer to true lumen and false lumen, respectively. Short arrows in A indicate the cobweb sign in the false lumen.

Figure 4 Stanford type A dissection in case 3 with communication between the true lumen and false lumen (arrow in A). The true lumen was obviously narrowed due to compression by the false lumen (B), and a protrusion sign was observed on VIE images (C). The intimal tear was identified posterior to the protrusion from the false lumen (D). Thrombus is formed in the false lumen (F).

Movie 1 Virtual fly-through of the thoracic aorta looking at the intimal flap, which separates the true lumen from the false lumen. The three artery branches arising from the aortic arch are located in the true lumen.

Movie 2 Virtual fly-through inside the narrow true lumen. A protruding sign arising from the false lumen is noticed from the anterior artery wall.


  1. Coady MA, Rizzo JA, Goldstein LJ, et al. Natural history, pathogenesis, and etiology of thoracic aortic aneurysms and dissections. Cardiol Clin. 1999;17(4):615-35; vii.   [Medline]
  2. Castaner E, Andreu M, Gallardo X, et al. CT in nontraumatic acute thoracic aortic disease: typical and atypical features and complications. Radiographics. 2003;23 Spec No:S93-110.   [Medline] [CrossRef]
  3. Sebastia C, Pallisa E, Quiroga S, et al. Aortic dissection: diagnosis and follow-up with helical CT. Radiographics. 1999;19(1):45-60; quiz 149-50.   [Medline]
  4. Cigarroa JE, Isselbacher EM, DeSanctis RW, et al. Diagnostic imaging in the evaluation of suspected aortic dissection. Old standards and new directions. N Engl J Med. 1993;328(1):35-43.   [Medline]
  5. LePage MA, Quint LE, Sonnad SS, et al. Aortic dissection: CT features that distinguish true lumen from false lumen. AJR Am J Roentgenol. 2001;177(1):207-11.   [Medline]
  6. Williams DM, Lee DY, Hamilton BH, et al. The dissected aorta: percutaneous treatment of ischemic complications--principles and results. J Vasc Interv Radiol. 1997;8(4):605-25.   [Medline]
  7. Scaglione M, Salvolini L, Casciani E, et al. The many faces of aortic dissections: Beware of unusual presentations. Eur J Radiol. 2008;65(3):359-64.   [Medline] [CrossRef]
  8. Berger FH, van Lienden KP, Smithuis R, et al. Acute aortic syndrome and blunt traumatic aortic injury: pictorial review of MDCT imaging. Eur J Radiol. 2010;74(1):24-39.   [Medline] [CrossRef]
  9. Sun Z, Winder RJ, Kelly BE, et al. Diagnostic value of CT virtual intravascular endoscopy in aortic stent-grafting. J Endovasc Ther. 2004;11(1):13-25.   [Medline]
  10. Sun Z. 3D multislice CT angiography in post-aortic stent grafting: a pictorial essay. Korean J Radiol. 2006;7(3):205-11.   [Medline]
  11. Sun Z, Mwipatayi BP, Allen YB, et al. Multislice CT angiography of fenestrated endovascular stent grafting for treating abdominal aortic aneurysms: a pictorial review of the 2D/3D visualizations. Korean J Radiol. 2009;10(3):285-93.   [Medline] [CrossRef]
  12. Louis N, Desgranges P, Kobeiter H, et al. Virtual angioscopy and 3-dimensional navigation findings of the aortic arch after vascular surgery. Circulation. 2009;119(7):1052-5.   [Medline] [CrossRef]
  13. Kapoor V, Ferris JV, Fuhrman CR. Intimomedial rupture: a new CT finding to distinguish true from false lumen in aortic dissection. AJR Am J Roentgenol. 2004;183(1):109-12.   [Medline]
  14. Williams DM, Lee DY, Hamilton BH, et al. The dissected aorta: part III. Anatomy and radiologic diagnosis of branch-vessel compromise. Radiology. 1997;203(1):37-44.   [Medline]

Received 31 December 2009; received in revised form 24 February 2010, accepted 6 March 2010

Correspondence: Discipline of Medical Imaging, Department of Imaging and Applied Physics, Curtin University of Technology, GPO Box, U1987, Perth, Western Australia 6845, Australia. Tel.: +61-8-9266 7509; Fax: +61-8-9266 2377; E-mail: (Zhonghua Sun).

Please cite as: Cao Y, Sun Z, Shang Y, Jiang B, Ma X, Aortic dissection: Identification of entry site with CT virtual intravascular endoscopy, Biomed Imaging Interv J 2010; 6(3):e22

University of Malaya, Kuala Lumpur, Malaysia


Bayer Healthcare
Elekta Fujifilm Barco Transmedic

Official publication of

ASEAN Association of Radiologists
ASEAN Society of Interventional Radiology
Asia-Oceania Federation of Organizations for Medical Physics
Asian Oceania Society of Radiology
College of Radiology, Academy of Medicine Malaysia
Southeast Asian Federation of Organisations of Medical Physics
South East Asian Association of Academic Radiologists

Published by

Department of Biomedical Imaging, Faculty of Medicine, University of Malaya, Malaysia


Biomedical Imaging and Intervention Journal. ISSN 1823-5530 RSS | Facebook | Twitter

Creative Commons License
Except where otherwise noted, articles published in the Biomedical Imaging and Intervention Journal
are distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
cited, including full bibliographic details and the URL, and this statement is included.