Uei Pua

CFD Modelling of Abdominal Aortic Aneurysm on Hemodynamic Loads Using a Realistic Geometry with CT

The objective of this study is to find a correlation between the abdominal aortic aneurysm (AAA) geometric parameters, wall stress shear (WSS), abdominal flow patterns, intraluminal thrombus (ILT), and AAA arterial wall rupture using computational fluid dynamics (CFD). Real AAA 3D models were created by three-dimensional (3D) reconstruction of in vivo acquired computed tomography (CT) images from 5 patients. Based on 3D AAA models, high quality volume meshes were created using an optimal tetrahedral aspect ratio for the whole domain. In order to quantify the WSS and the recirculation inside the AAA, a 3D CFD using finite elements analysis was used. The CFD computation was performed assuming that the arterial wall is rigid and the blood is considered a homogeneous Newtonian fluid with a density of 1050 kg/m3 and a kinematic viscosity of 4 × 10−3 Pa·s. Parallelization procedures were used in order to increase the performance of the CFD calculations. A relation between AAA geometric parameters (asymmetry index (β), saccular index (γ), deformation diameter ratio (χ), and tortuosity index (ε)) and hemodynamic loads was observed, and it could be used as a potential predictor of AAA arterial wall rupture and potential ILT formation.

Iliac branch graft in the treatment of complex aortoiliac aneurysms: early results from a North American institution.

PURPOSE To describe early experience with the use of iliac branch grafts (IBGs) in aortoiliac aneurysm repair. MATERIALS AND METHODS From July 2007 to August 2009 (25 months), 14 patients (13 men, one woman) with a mean age of 70.1 years (range, 59.3-80.0 y) were treated with IBGs. Indications were abdominal aneurysm with common iliac artery (CIA) involvement (n = 11), juxtarenal aortic aneurysm with CIA involvement (n = 1), and bilateral CIA and internal iliac artery (IIA) aneurysms (n = 1). Postoperative endoleaks and patency rate were determined with computed tomography within 1 month of implantation and 1 year thereafter, with concurrent clinical evaluation for pelvic ischemia. Mean follow-up period was 18.7 months (range, 6-35 mo). RESULTS Technical success rate, as defined by successful implantation of IBG with no intraprocedural type I or type III endoleak, was 86% (12 of 14). A total of 14 IBGs were successfully deployed in 12 patients. Two cases of technical failure were related to excessive iliac tortuosity. The mean hospitalization duration was 6.5 days (range, 3-14 d), with zero mortality at 30 days. There were two cases of type II endoleak treated conservatively and a single case of IBG-related type III endoleak that required repeat intervention. The rest of the stent-implanted aortic and iliac aneurysms remained stable in size, with no aneurysm rupture or death recorded. All stent-implanted iliac branches remained patent on follow-up. None of the patients who received IBGs had new symptoms of pelvic ischemia. CONCLUSIONS Iliac branch graft placement is a feasible technique with excellent short-term results in the treatment of aortoiliac aneurysms.

CT appearance of complications related to thoracic endovascular aortic repair (TEVAR): a pictorial essay

Thoracic endovascular aortic repair (TEVAR) is a recognized treatment for various diseases involving the thoracic aorta. Patients treated with TEVAR require lifelong surveillance for potential complications, with CT being highly utilized in most centres. Endoleak is the most common complication and can be detected using CT. However, other complications such as stent strut perforations and end organ ischemia can also be detected on CT. The purpose of this pictorial essay is to illustrate the CT appearance of post-TEVAR complications encountered in our institution and to highlight their significance.

Imaging of carcinoma of the external auditory canal: a pictorial essay.

Abstract Carcinoma of the external auditory canal presents a challenge in management, largely due to limited experience in treating this rare disease and the lack of a universally accepted staging system. Prognosis is most dependent on the extent of local disease at presentation, while resection margin status is also a strong determinant of survival in post-operative patients. The intent of this pictorial essay is to review the pattern of tumour spread and highlight the value of imaging, particularly magnetic resonance imaging in pre-operative tumour mapping.

Emergency computed tomography for acute pelvic trauma: Where is the bleeder?

Contrast medium extravasation at computed tomography (CT) is an accurate indicator of active haemorrhage in pelvic trauma. When this is present, potentially lifesaving surgical or endovascular treatment should be considered. Identification of the site or territory of haemorrhage is helpful for the interventional radiologist as it allows for focused angiographic evaluation and expedites haemostatic angio-embolisation. Even with thin-section arterial phase CT, tracing the bleeding vessel is not always possible and is often time consuming. We introduce a technique for predicting the bleeding vessel based on knowledge of the cross-sectional anatomical territory of the vessel as an alternative to tracing the vessels course. Several case examples with digital subtraction angiography (DSA) correlation will be provided.

Revisiting renovascular imaging for renal sympathetic denervation: current techniques and applications

AbstractRenal sympathetic denervation (RDN) is an emerging technique in the treatment of resistant hypertension, most commonly performed using an endovascular approach. Clinical and anatomical criteria for RDN are well established and imaging plays an integral role in selecting patients with suitable anatomy, procedural planning and device selection. Nevertheless, the current body of literature surrounding imaging related to RDN remains limited. The purpose of this article is to illustrate the expectations and limitations of various imaging techniques, including Doppler ultrasound, CT angiography, MR angiography and newer techniques such as non-contrast MR angiography, in the context of RDN.Key Points• To understand the role of imaging in renal denervation • To understand strengths and weaknesses of current imaging techniques • To understand the relevant imaging findings in the context of renal denervation

Catheter-induced aorto-coronary artery dissection: utility and appearance on CT coronary angiogram.

Aorto-coronary artery dissection (CCAD) is rare but potentially fatal complication of catheter coronary angiography. Management is dependent on the state of distal arterial flow and the extension of retrograde aortic dissection. This manuscript describes the use and appearance of CCAD on ECG-gated multi-detector CT coronary angiogram in the acute setting.

Spontaneous cholecystocolic fistula and locoregional liver tumour ablation: a cautionary tale

A liver abscess is a feared and potentially fatal complication following transarterial chemoembolisation (TACE) and radiofrequency ablation (RFA) of liver tumours. Iatrogenic bilio-enteric communications, such as bilio-enteric anastomosis, sphincterotomy and biliary stents, are considered major risk factors and are due to bacterial colonisation of the biliary tree with enteric flora. Naturally occurring spontaneous cholecysto-enteric fistula poses a similar risk as its iatrogenic counterparts but is rarely described in the literature. We present a case where abscess formation complicated a combined TACE and RFA in an unrecognised cholecystocolic fistula.

Percutaneous liver biopsy: a cause of hepatic portal venous gas

A 72-year-old man who was a known carrier of hepatitis B underwent computed tomographic (CT)–guided biopsy of a mass in the liver, which had been detected during routine surveillance. Needle biopsy was performed using a coaxial technique with an 18-gauge Quick-Core biopsy needle set (Cook Medical

Multidetector row CT diagnosis of an infected right atrial thrombus following repeated dialysis catheter placement

Right atrial thrombus formation is a known complication of dialysis catheter placements. We describe the case of a 61-year-old woman with end-stage renal failure who presented with gram-negative septicaemia. A gas-containing filling defect was noted incidentally in the right atrium during a CT scan of the abdomen and pelvis, indicative of a thrombus infected by a gas-forming organism. The finding correlated with a positive blood culture of Klebsiella pneumoniae and the two-dimensional echocardiography finding of an echogenic atrial thrombus.