Determination of wall tension in cerebral artery aneurysms by numerical simulation.

BACKGROUND AND PURPOSE: Cerebral artery aneurysms rupture when wall tension exceeds the strength of the wall tissue. At present, risk-assessment of unruptured aneurysms does not include evaluation of the lesions shape, yet clinical experience suggests that this is of importance. We aimed to develop a computational model for simulation of fluid-structure interaction in cerebral aneurysms based on patient specific lesion geometry, with special emphasis on wall tension. METHODS: An advanced isogeometric fluid-structure analysis model incorporating flexible aneurysm wall based on patient specific computed tomography angiogram images was developed. Variables used in the simulation model were retrieved from a literature review. RESULTS: The simulation results exposed areas of high wall tension and wall displacement located where aneurysms usually rupture. CONCLUSIONS: We suggest that analyzing wall tension and wall displacement in cerebral aneurysms by numeric simulation could be developed into a novel method for individualized prediction of rupture risk.

Integrating segmentation methods from the Insight Toolkit into a visualization application.

The Insight Toolkit (ITK) initiative from the National Library of Medicine has provided a suite of state-of-the-art segmentation and registration algorithms ideally suited to volume visualization and analysis. A volume visualization application that effectively utilizes these algorithms provides many benefits: it allows access to ITK functionality for non-programmers, it creates a vehicle for sharing and comparing segmentation techniques, and it serves as a visual debugger for algorithm developers. This paper describes the integration of image processing functionalities provided by the ITK into VolView, a visualization application for high performance volume rendering. A free version of this visualization application is publicly available and is available in the online version of this paper. The process for developing ITK plugins for VolView according to the publicly available API is described in detail, and an application of ITK VolView plugins to the segmentation of Abdominal Aortic Aneurysms (AAAs) is presented. The source code of the ITK plugins is also publicly available and it is included in the online version.

[Teleradiologic follow up of patients treated with aortic stent grafting]. / Teleradiologisk oppfølging av pasienter behandlet med stentgraft i aorta.

BACKGROUND: A study has confirmed the possibility of follow up in the local hospital of patients who have undergone endovascular repair. We present a cost analysis of such a regimen compared to follow up at a university hospital. MATERIAL AND METHODS: By using discharge data from the Norwegian Patient Register we identified a group of patients which could have been followed up at their local hospital for their stent-grafted abdominal aortic aneurysm and estimated the cost effects of performing follow ups locally. RESULTS: The cost analysis showed a potential for cost savings from local follow ups, especially from moving from inpatient care at the university hospital to outpatient care locally. The result of this cost analysis differs from other Norwegian studies of teleradiology by identifying a possibility for more cost-effective treatment. INTERPRETATION: Using teleradiology to follow up these patients will free up capacity in the university hospital. Most probably, other groups of patients can also be followed up by teleradiology. The university hospitals can use this freed-up capacity for new patients. Teleradiology could lead to more efficient use of health care facilities, which should be in the interest of the health authorities.

Three-dimensional teleradiology for surveillance following endovascular aortic aneurysm repair: a feasibility study.

PURPOSE: To study the feasibility of 3-dimensional (3D) teleradiology in surveillance of patients treated with stent-grafts for abdominal aortic aneurysm (AAA). METHODS: Between April 2002 and November 2003, 8 AAA patients (7 men; median age 73 years, range 62-84) with stent-grafts had follow-up computed tomograms (CT) performed at their local hospital and transmitted without loss across a broadband connection to the university hospital. On both monitors, the radiologists were presented with the complete CT axial dataset, sagittal and coronal reformatted slices, and a 3D volume-rendered reconstruction. The two radiologists were then able to simultaneously perform measurements and real-time manipulations of the axial and 3D pictures, which were discussed over the telephone or using a videoconferencing unit. Patient satisfaction, the radiologists' evaluation of the method, and the potential cost savings were explored. RESULTS: Twelve follow-up CT scans were performed on the 8 patients. The time for transmission over the teleradiological network averaged 5 minutes, and the evaluation required 15 minutes at the university hospital. The overall technical quality of the images was rated as good by the university radiologist. In 11 studies, the stent-grafts were satisfactory, but a type III endoleak was detected in one 5.5-year-old stent-graft. Neither radiologist had a problem identifying the endoleak. Patients had confidence that the examination at the local hospital was of good quality; they all felt that they received good care and were pleased with avoiding travel to the university hospital. From the economic analysis, an annual savings of 40,000 Euros (USD 52,304) was projected, mostly due to avoiding hospital stays and outpatient consultations at the university hospital. CONCLUSIONS: The experiences from this study are encouraging, but a larger series will be necessary for a thorough evaluation of 3D teleradiology as a surveillance method for aortic stent-graft patients.

[3-D navigation in laparoscopic surgery]. / Tredimensjonal navigasjon i laparoskopisk kirurgi.

BACKGROUND: The main drawback with the laparoscopic approach is that the surgeon lacks the possibility to palpate vessels, tumours and organs during surgery. Furthermore, the laparoscope only provides a surface view of organs. There is a need for more advanced visualization that enhances the view to include information below the surface of the organs when the procedure is planned and for control and guidance during treatment. MATERIAL AND METHODS: We propose 3-D navigation technology based on preoperatively acquired MR or CT data used in combination with a laparoscopic navigation pointer. The pointer has an attached position tracker which enables the surgeon to interactively control the display of images prior to and during surgery. RESULTS: We have used this technology during treatment of four patients with adrenal tumours. Preoperative registration of images of the patients was performed within two minutes with an average accuracy of 7.1 mm. 2-D and 3-D visualizations interactively controlled by the pointer were used both for planning and for guidance of the surgical procedures. INTERPRETATION: The pointer was a useful tool in image guidance of laparoscopic surgery in the reported cases both for planning the approach in detail and for guidance. We believe abdominal 3-D image guidance using a laparoscopic navigation pointer has a large potential for improving laparoscopic surgery, especially in cases where vessels and anatomical relations might be difficult to identify using only a laparoscope. Accordingly, this new technology will increase safety and facilitate successful laparoscopic surgery.