Review of CT Angiography of Aorta

Multiple Adversarial Learning based Angiography Reconstruction for Ultra-low-dose Contrast Medium CT

Iodinated contrast medium (ICM) dose reduction is beneficial for decreasing potential health risk to renal-insufficiency patients in CT scanning. Due to the lowintensity vessel in ultra-low-dose-ICM CT angiography, it cannot provide clinical diagnosis of vascular diseases. Angiography reconstruction for ultra-low-dose-ICM CT can enhance vascular intensity for directly vascular diseases diagnosis. However, the angiography reconstruction is challenging since patient individual differences and vascular disease diversity. In this paper, we propose a Multiple Adversarial Learning based Angiography Reconstruction (i.e., MALAR) framework to enhance vascular intensity. Specifically, a bilateral learning mechanism is developed for mapping a relationship between source and target domains rather than the image-to-image mapping. Then, a dual correlation constraint is introduced to characterize both distribution uniformity from across-domain features and sample inconsistency with domain simultaneously. Finally, an adaptive fusion module by combining multiscale information and long-range interactive dependency is explored to alleviate the interference of high-noise metal. Experiments are performed on CT sequences with different ICM doses. Quantitative results based on multiple metrics demonstrate the effectiveness of our MALAR on angiography reconstruction. Qualitative assessments by radiographers confirm the potential of our MALAR for the clinical diagnosis of vascular diseases. The code and model are available at https://github.com/HIC-SYSU/MALAR.

Ductus diverticulum associated with Takayasu disease and incidental finding of Wolff Parkinson White syndrome

Ductus diverticulum is either a remnant of the ductus arteriosus or the right dorsal aortic root. The most common diagnosis is the differentiation of an aortic isthmus pseudoaneurysm from a type III ductal diverticulum. Both aortic entities occur at roughly the same anatomical location often leading to diagnostic confusion. Aortic dissection should be considered if it is Takayasu's disease. We are reporting the case of a 31-year-old woman with chest pain and muscle weakness, functional impotence of the left upper limb with intermittent palpitations. Thoraco-abdominal CT angiography was in favor of inflammatory arteritis of the thoraco-abdominal aorta, common carotids and the left subclavian artery. Sub-occlusive stenosis of the left axillary artery was noted, in favor of Takayasu disease. There was an aspect of aortic ductus diverticulum type III, 24mm from the emergence of the subclavian artery simulating aortic dissection or ulceration of the aortic isthmus. An electrocardiogram revealed Wolff Parkinson White syndrome with left lateral Kent. There was good clinical outcome after immunosuppressive drugs and antiarrhythmic therapy.

Accessing 3D Printed Vascular Phantoms for Procedural Simulation

Introduction: 3D printed patient-specific vascular phantoms provide superior anatomical insights for simulating complex endovascular procedures. Currently, lack of exposure to the technology poses a barrier for adoption. We offer an accessible, low-cost guide to producing vascular anatomical models using routine CT angiography, open source software packages and a variety of 3D printing technologies.

Methods: Although applicable to all vascular territories, we illustrate our methodology using Abdominal Aortic Aneurysms (AAAs) due to the strong interest in this area. CT aortograms acquired as part of routine care were converted to representative patient-specific 3D models, and then printed using a variety of 3D printing technologies to assess their material suitability as aortic phantoms. Depending on the technology, phantoms cost $20–$1,000 and were produced in 12–48 h. This technique was used to generate hollow 3D printed thoracoabdominal aortas visible under fluoroscopy.

Results: 3D printed AAA phantoms were a valuable addition to standard CT angiogram reconstructions in the simulation of complex cases, such as short or very angulated necks, or for positioning fenestrations in juxtarenal aneurysms. Hollow flexible models were particularly useful for device selection and in planning of fenestrated EVAR. In addition, these models have demonstrated utility other settings, such as patient education and engagement, and trainee and anatomical education. Further study is required to establish a material with optimal cost, haptic and fluoroscopic fidelity.

Conclusion: We share our experiences and methodology for developing inexpensive 3D printed vascular phantoms which despite material limitations, successfully mimic the procedural challenges encountered during live endovascular surgery. As the technology continues to improve, 3D printed vascular phantoms have the potential to disrupt how endovascular procedures are planned and taught.

Morphologic Evaluation of Ductus Diverticulum Using Multi - Detector Computed Tomography: Comparison with Traumatic Pseudoaneurysm of the Aortic Isthmus

Objectives

To evaluate morphologic variations at the aortic isthmus with particular attention to ductus diverticulum, a mimicker of traumatic pseudoaneurysm, and to describe differences using Computed Tomography (CT) images.

Patients and Methods

From December 2013 to December 2014, patients who underwent a chest CT examination after blunt trauma at our emergency department were included. Aortic isthmus morphologies were evaluated using multiplanar reconstruction (MPR) and maximum intensity projection (MIP) images as follows. Type I -concave contour, type II -convexity without a discrete bulge, or type III -a discrete focal bulge (defined as ductus diverticulum).

Results

After excluding 11 cases of traumatic pseudoaneurysm of the aortic isthmus, a total of 432 trauma patients (mean age = 47.1 ± 19.1 years, number of males = 318) were evaluated for aortic isthmus morphology, and classified as follows; type I (n = 240, 55.6%), type II (n = 157, 36.3%), and type III (n = 35, 8.1%). As compared with traumatic pseudoaneurysm (n = 11), ductus diverticulum had a smaller vertical diameter (5.5 ± 1.3 mm vs. 11.2 ± 2.7 mm, P < 0.001), a broader base (14.9 ± 4.1 mm vs. 8.8 ± 4.5 mm, P < 0.001), a smoother margin (97.1% vs. 27.3%, P < 0.001), and formed obtuse angle with the aortic wall. Furthermore, ductus diverticulum was not associated with the presence of a dissection flap or hemomediastinum.

Conclusion

Ductus diverticulum, a mimicker of traumatic pseudoaneurysm of the aortic isthmus, is a frequently observed anatomic variant during CT examinations. Familiarity with its CT imaging findings could avoid it being confused with traumatic pseudoaneurysm in blunt trauma patients.

Quality of abdominal computed tomography angiography: hand versus mechanical intravenous contrast administration in children

BACKGROUND

Abdominal CT angiography has been increasingly used for evaluation of various conditions related to abdominal vasculature in the pediatric population. However, no direct comparison has evaluated the quality of abdominal CT angiography in children using hand versus mechanical administration of intravenous (IV) contrast agent.

OBJECTIVE

To compare hand versus mechanical administration of IV contrast agent in the quality of abdominal CT angiography in the pediatric population.

MATERIALS AND METHODS

We retrospectively reviewed the electronic medical record to identify pediatric patients (≤18 years) who had abdominal CT angiography between August 2012 and August 2013. The information obtained includes: (1) type of administration of IV contrast agent (hand [group 1] versus mechanical [group 2]), (2) size (gauge) of IV catheter, (3) amount of contrast agent administered and (4) rate of contrast agent administration (ml/s). Two reviewers independently performed qualitative and quantitative evaluation of abdominal CT angiography image quality. Qualitative evaluation of abdominal CT angiography image quality was performed by visual assessment of the degree of contrast enhancement in the region of interest (ROI) based on a 4-point scale. Quantitative evaluation of each CT angiography examination was performed by measuring the Hounsfield unit (HU) using an ROI within the abdominal aorta at two levels (celiac axis and the inferior mesenteric artery) for each child. Analysis of variance (ANOVA) using the F-test was applied to compare contrast enhancement within the abdominal aorta at two levels (celiac axis and inferior mesenteric artery) between hand administration and mechanical administration of IV contrast methods with adjustment for age.

RESULTS

We identified 46 pediatric patients (24 male, 22 female; mean age 7.3 ± 5.5 years; range 5 weeks to 18 years) with abdominal CT angiography performed during the study period. Of these patients, 16 (35%; 1.7 ± 2.2 years; range 5 weeks to 5 years) had hand administration of IV contrast agent and 30 (65%; 10.2 ± 4.2 years; range 4-18 years) had mechanical administration of IV contrast agent. All 46 abdominal CT angiography studies were of diagnostic quality based on qualitative evaluation (all ≥3). All abdominal CT angiography studies from both groups showed diagnostic quality of contrast enhancement (>150 HU) at both the celiac axis and the inferior mesenteric artery (IMA) levels. The contrast enhancement of the abdominal aorta was not significantly different between the IV contrast administration methods at either the celiac axis level (360 ± 158 vs. 353 ± 116, P = 0.24) or the IMA level (340 ± 140 vs. 351 ± 90, P = 0.27), adjusting for age.

CONCLUSION

Diagnostic-quality abdominal CT angiography can be achieved using hand administration of IV contrast agent in infants and young children (≤5 years).

Adaptation of contrast injection protocol to tube potential for cardiovascular CT

OBJECTIVE

The purpose of this study was to investigate and validate adaptation of a cardiovascular CT angiography contrast injection protocol for lower tube potential.

MATERIALS AND METHODS

Eighty-three patients evaluated for thoracic aortic disease with a 256-MDCT scanner were imaged at 120 kV (group 1) or 100 kV (group 2) with the same contrast protocol (90 mL iopromide 370 mg I/mL at 3.5 mL/s). A pharmacokinetic model was validated and used to simulate aortic attenuation in group 2 patients with 20%, 33%, and 44% reduction in contrast volume. A 44% volume reduction was applied to 50 additional patients who underwent imaging at 100 kV (group 3). Patient characteristics, scanning and radiation parameters, and objective and subjective image indexes were compared among groups.

RESULTS

Group 2 patients had higher mean aortic blood attenuation (399±61 HU) than group 1 patients (281±48 HU) (p<0.001) but similar image noise. Group 3 and group 1 patients had similar mean aortic attenuation and noise. Subjective assessment of image quality indicated that group 3 and group 1 had comparable percentages of images with good or excellent diagnostic confidence scores (reader 1, 98% vs 96%; reader 2, 96% vs 96%).

CONCLUSION

Lower tube potential (100 kV) for cardiothoracic CT could be accompanied by a 44% reduction in contrast volume with satisfactory aortic blood-pool attenuation in most patients. More personalized adaptation of the contrast protocol that takes into account patient characteristics and tube potential is necessary to ensure sufficient contrast enhancement for all patients.

Multidetector CT findings of complications of surgical and endovascular treatment of aortic aneurysms

Aortic aneurysms remain a significant problem in the population, and there is a concerted effort to identify, define, image, and treat these conditions to ultimately improve outcomes. The rapid development of diagnostic modalities, operative strategies, and endovascular techniques within the realm of this aortic disease has transformed the field and broadened the spectrum of patients that can be treated with minimally invasive techniques. This investigation has a broad spectrum of normal expected findings that must be differentiated from early or late complications in which intervention is required. In this article, normal and abnormal postoperative and post-TEVAR/EVAR MDCT findings are described.

Efficacy of 'fine' focal spot imaging in CT abdominal angiography

OBJECTIVES

To assess the efficacy of fine focal spot imaging in calcification beam-hardening artefact reduction and vessel clarity on CT abdominal angiography (CTAA).

METHODS

Adult patients of any age and gender who presented for CTAA were included. Thirty-nine patients were examined with a standard focal spot size (SFSS) of 1 × 1 mm in the first 3 months while 31 consecutive patients were examined with a fine focal spot size (FFSS) of 1 × 0.5 mm in the following 3 months. Vessel clarity and calcification beam-hardening artefacts of the abdominal aorta, celiac axis, superior mesenteric artery, inferior mesenteric artery, renal arteries, and iliac arteries were assessed using a 5-point grading scale by two blinded radiologists randomly.

RESULTS

Cohen's Kappa test indicated that on average, there was substantial agreement among reviewers for vessel wall clarity and calcification artefact grading. Mann-Whitney test showed that there was a significant difference between the two groups, with FFSS performing significantly better for vessel clarity (U, 6481.50; p < 0.001; r, 0.73) and calcification artefact reduction (U, 1916; p < 0.001; r, 0.77).

CONCLUSION

Fine focus CT angiography produces images with better vessel wall clarity and less vessel calcification beam-hardening artefact.

KEY POINTS

Focal spot size affects the spatial resolution of a CT system. Fine focus CTAA produces images with improved vessel wall clarity. Fine focus CTAA is associated with fewer calcification beam-hardening artefacts. Fine focus CTAA may improve accuracy in assessment of luminal stenosis.

Multidetector computed tomography angiography findings of chronic-contained thoracoabdominal aortic aneurysm rupture with severe thoracal vertebral body erosion

Chronic-contained aortic aneurysm rupture with vertebral erosion is a rare entity with fatal complications. Multidetector computed tomography (CT) angiography is an important diagnostic method for the evaluation of the aortic aneurysms, their complications, and also the relationship between aneurysm and branching vessels and adjacent structures. We present the multidetector CT angiography findings of a 62-year-old patient with chronic-contained thoracoabdominal aortic aneurysm rupture causing severe vertebral body erosion.

Cardiothoracic CT angiography: current contrast medium delivery strategies

OBJECTIVE

Over the last decade, rapid technologic evolution in CT has resulted in improved spatial and temporal resolution and acquisition speed, enabling cardiothoracic CT angiography to become a viable and effective noninvasive alternative in the diagnostic algorithm. These new technologic advances have imposed new challenges for the optimization of contrast medium delivery and image acquisition strategies.

CONCLUSION

Thorough understanding of contrast medium dynamics is essential for the design of effective acquisition and injection protocols. This article provides an overview of the fundamentals affecting contrast enhancement, emphasizing the modifications to contrast material delivery protocols required to optimize cardiothoracic CT angiography.

CT and MRI in diseases of the aorta

OBJECTIVE

This review focuses on the role of CT and MRI in the diagnosis, follow-up, and surgical planning of aortic aneurysms and acute aortic syndromes, including aortic dissection, intramural hematoma, and penetrating aortic ulcer. It also provides a systematic approach to the definition, causes, natural history, and imaging principles of these diseases.

CONCLUSION

An understanding of the pathophysiology, natural history, and imaging features is the key to successful diagnosis and appropriate management of patients with these aortic diseases.

64-Slice CT angiography of the abdominal aorta and abdominal arteries: comparison of the diagnostic efficacy of iobitridol 350 mgI/ml versus iomeprol 400 mgI/ml in a prospective, randomised, double-blind multi-centre trial

Purpose

The purpose of this study was to assess the influence of iodine concentration on diagnostic efficacy in multi-detector-row computed tomography (MDCT) angiography of the abdominal aorta and abdominal arteries.

Methods

IRB approval and informed consent were obtained. In this double-blind trial, patients were randomised to undergo MDCT angiography of the abdominal arteries during administration of iobitridol (350 mgI/ml) or iomeprol (400 mgI/ml). Each centre applied its own technique for delivery of contrast medium, regardless of iodine concentration. Diagnostic efficacy, image quality, visualisation of the arterial wall and arterial enhancement were evaluated. A total of 153 patients received iobitridol and 154 received iomeprol.

Results

The ability to reach a diagnosis was “satisfactory” to “totally satisfactory” in 152 (99.3%) and 153 (99.4%) patients respectively. Image quality was rated as being “good” to “excellent” in 94.7 and 94.8% segments respectively. Similar results were observed for image quality of arterial walls (84.3 vs. 83.2%). The mean relative changes in arterial enhancement between baseline and arterial phase images showed no statistically significant differences.

Conclusion

This study demonstrated the non-inferiority of the 350 versus 400 mgI/ml iodine concentration, in terms of diagnostic efficacy, in abdominal MDCT angiography. It also confirmed the high robustness and reliability of this technique across multi-national practices.

General surgical manifestations of Marfan's syndrome

Marfan's syndrome can manifest as various general surgical pathologies (herniae, diverticulosis, bowel obstruction and abdominal vasculature aneurysms). These pathologies often have abnormal presentations, and in some cases can be life-threatening.