Ann Thorac Surg 2005;80:708-710
© 2005 The Society of Thoracic Surgeons
Case report
Virtual Vascular Endoscopy for Acute Aortic Dissection
Fernando Hornero, MD, PhD
a
,
*
,
Vicente Cervera, MD
b
,
Jorge Estornell, MD
b
,
Ignacio Rodriguez, MD
a
,
Jose A. Buendía, MD
a
,
Jose M. Esteban, MD
b
,
Jose A. Montero, MD, PhD
a
a Department of Cardiac Surgery, Hospital General Universitario de Valencia, Valencia, Spain
b Department of Radiology-CT Scan Unit (ERESA), Hospital General Universitario de Valencia, Valencia, Spain
Accepted for publication January 22, 2004.
* Address reprint requests to Dr Hornero, Servicio de Cirugía Cardíaca, Hospital General, Universitario de Valencia, Av. Tres Cruces s/n, 46014 Valencia, Spain (Email: hornero_fer{at}gva.es).
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Abstract
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Virtual endoscopy of the aorta is a new three-dimensional reconstruction method from multislice computed tomography or magnetic resonance that offers a virtual navigation through the aorta, and the possibility of having a new preoperative endoluminal vision. We present a case of subacute aortic dissection with a preoperative virtual endoscopy of the aorta.
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Introduction
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Computed tomography (CT) is presently a promising new imaging technique that has improved the diagnosis of cardiovascular diseases. Virtual endoscopy of the aorta, or virtual aortoscopy (VA), is generated with the use of volume rendering techniques and uses two-dimensional (2D) and three-dimensional (3D) data sets, to create an endoluminal view of blood vessels and allows the viewer to explore the inner surfaces from a unique perspective [1–4]. We present a case of subacute aortic dissection illustrated with images from CT with preoperative virtual aortoscopy using 3D reconstruction and comment on the aspects of this new technology.
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Technique
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A 69-year-old male was referred to the hospital with a history of four days of interscapular pain, and a chest roentgenogram with mediastinal widening. Transthoracic echocardiography (TTE) detected a dissecting membrane and dilation (54 mm) of the ascending aorta, without aortic regurgitation and minimal pericardial effusion. Spiral CT scan (Hispeed CT/I, GE Medical Systems, Milwaukee, WI) was performed after the injection of a bolus of iopromida (Clarograft 300, Sandoz). The acquisition of the images was performed with the patient holding his breath for 15 seconds. More than 325 image slices of the aorta could be obtained during a total time of 10 seconds. Slice thickness was 1.25 mm. All images were generated with the Advantage Navigator software (GE Medical Systems), on an Advantage Windows 4.1 workstation (GE Medical Systems).
Navigation through the aorta was performed in a fly-through mode and moving the cursor on axial, sagittal, and coronal reformatted images. Spiral CT with bidimensional reconstruction (Fig 1) diagnosed aortic dissection type A, with a well-defined intimal flap in the lumen of the ascending aorta and a dissection (false lumen) extended into the arch as far as the left subclavian artery reaching the infrarenal aorta. The entry site of the dissection was in the ascending aorta, 2 cm over the sinotubular junction. Transverse diameters of the true and false lumens were measured at all levels of the ascending and descending thoracic aorta, and at the abdominal aorta. The extension of the thrombosis in the false lumen and the perfusion of the branch vessels were evaluated. The 3D reconstruction (Figs 2 and 3)
showed the aspect of the aortic dissection and the morphology of the flap; it was also possible to generate endoscopic images. In the operation, an identical tear was documented in the midposition of the ascending aorta. No other tears were appreciated in the arch and proximal portion of the descending aorta. The dissection extended proximally into the noncoronary sinus and distally beyond the left subclavian artery. The false lumen did not extend into arch vessels. The aortic valve was normal. The proximal aorta was transected circumferentially and the concave portion of the arch was excised. A 28-mm woven Dacron graft was sutured in supracoronary position, incorporating arch vessels after 46 minutes of circulatory arrest. The patient presented a normal course and was discharged on the seventeenth postoperative day.
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Fig 1. Bidimensional reconstruction of spiral CT scan in coronal (A) and axial (B) plane. False lumen (FL) with the proximal tear into the proximal and descending aorta. Images (C) and (D) are three-dimensional reconstruction with intimal flap in the aorta. (D), false lumen with late back flow beyond the left subclavian artery.
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Fig 2. Four different virtual endoluminal images of the aorta, reconstructed in three dimensions, using volume rendering techniques. (A) Vision of the ascending aorta from the arch. (B) Vision of the false lumen through the tear. (C) Aspect of the intimal tear. (D) Inner vision of the false lumen. (av = atrioventricular; nc = noncoronary).
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Comment
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Diagnosis and treatment of patients with acquired aortic disease demands a complete appreciation of the anomaly and adjacent anatomy in three dimensions. The term of VA is referred to the use of either spiral CT or magnetic resonance scanning and computers to produce high resolution 2D and 3D imaging of the aorta [1–4]. Spiral CT scan technology takes multiple potential slices for aortic reconstruction during a total scan time of 10 to 20 seconds. The images are processed by means of software packages that simultaneously display 2D axial, coronal, and sagittal images of a given point designated by the radiologist. In addition, the software will simultaneously display a 3D endoluminal view that simulates surgical imaging and allows multidirectional viewing. At this time, 3D image reconstruction may be as short as 10 minutes, and the radiologist’s interpretation less than 60 minutes.
In our case, VA was useful to evaluate the size of the intimal tear, to locate the tear, to measure the size of the false lumen, and to explore the occluded branches and coronary vessels, etc. A priori, at the point of view of the surgeon, striking images are useful to assess the aortic procedure, which could be superior to the best available techniques with images close to the surgical view. However, although VA is perceived as a quick and noninvasive examination, there is not enough experience with this novel technology and need to test its sensitivity and specificity in the clinical practice to detect and reconstruct the aortic pathology. In our case a distal tear was not detected, and this created doubts about the accuracy in detecting small intimal tears. Virtual navigation through the false lumen was difficult in some portions because there were plenty of numerous pierced surface artifacts. Endoluminal view of the true lumen of the arch showed a beaded appearance with multiple shelflike projections within the lumen that were interpreted as floating shape artifacts. Errors and artifacts were present and probably were related to images from suboptimal data sets.
The diagnostic accuracy of CT scanning ranges between 90% and 100% [4]. The major drawbacks of CT scanning are the need for contrast material that may cause allergic reactions or renal dysfunction, and it cannot be performed if the patient is unstable. Presently, we need to balance the benefits of the current spiral CT, which can scan the chest in less than 20 seconds in a typical protocol for CT aortography with a minimal collaboration of the patient, allowing detailed evaluation of the aortic dissection and of the coronary arteries. One case may not be enough to evaluate this technology and more experience is necessary to become competitive as an alternative diagnostic modality, but VA seems to be an attractive new radiologic method to explore the aorta. The technique is still new, and probably important clinical applications will be demonstrated.
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Fig 3. Virtual endoluminal images of the dissection. (A) Vision of the left coronary sinus, ostium of the left coronary artery and aortic valve. (B) Vision of the ascending aorta from the aortic valve showing the intimal proximal tear. (* = False lumen.) (C) Branch vessels of the aortic arch. (D) True lumen of the thoracic aorta compressed by the false lumen.
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References
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- Neri E, Caramella D, Falaschi F, et al. Virtual CT intravascular endoscopy of the aortapierced surface and floating shape thresholding artifacts. Radiology 1999;212:276-279.[Abstract/Free Full Text]
- Smith PA, Heath DG, Fishman EK. Virtual angioscopy using spiral CT and real-time interactive volume-rendering techniques J Comput Assist Tomogr 1998;22:212-214.[Medline]
- Rubin GD, Beaulieu CF, Argiro V. Perspective volume rendering of CT and MR imagesapplications for endoscopic imaging. Radiology 1996;199:321-330.[Abstract/Free Full Text]
- Nienaber CA, vonKodolitsch Y, Nicolas V. The diagnosis of thoracic aortic disection by noninvasive imaging procedures N Engl J Med 1993:1-9.
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Abstract
Introduction
