Air bubbles are released by thoracic endograft deployment: An in vitro experimental study

Purpose: Embolic stroke is a dreaded complication of thoracic endovascular aortic repair. The prevailing theory about its cause is that particulate debris from atherosclerotic lesions in the aortic wall are dislodged by endovascular instruments and embolize to the brain. An alternative source of embolism might be air trapped in the endograft delivery system. The aim of this experimental study was to determine whether air is released during deployment of a thoracic endograft. Methods: In an experimental benchtop study, eight thoracic endografts (five Medtronic Valiant Thoracic and three Gore TAG) were deployed in a water-filled transparent container drained from air. Endografts were prepared and deployed according to their instructions for use. Deployment was filmed and the volume of air released was collected and measured in a calibrated syringe. Results: Air was released from all the endografts examined. Air volumes ranged from 0.1 to 0.3 mL for Medtronic Valiant Thoracic and from <0.025 to 0.04 mL for Gore TAG. The largest bubbles had a diameter of approximately 3 mm and came from the proximal end of the Medtronic Valiant device. Conclusion: Air bubbles are released from thoracic endografts during deployment. Air embolism may be an alternative cause of stroke during thoracic endovascular aortic repair

Three-dimensional guidance for Endovascular Aortic Repair

Image fusion (IF) of preoperative computed tomography (CT) with intraoperative cone-beam CT (CBCT) is a potentially powerful tool for guidance during endovascular aortic repair (EVAR). It may improve intraoperative anatomic visualization and reduce doses of radiation and contrast medium. The technique is still new, however, and has not yet been standardized for routine use in all centers that have the facilities to perform it. The main aims of this thesis were: 1. to describe the use of orthogonal rings for 3D guidance during EVAR and to investigate sources of registration and overlay error; 2. to investigate the feasibility of combining 3D fusion with carbon dioxide (CO2 ) digital subtraction angi-ography (DSA) during EVAR, in order to reduce the dosage of iodinated contrast; 3. to determine whether 3D image fusion can be used to localize intercostal arteries during thoracic EVAR; 4. to evaluate the performance of a feature-based algorithm for 3D3D image registration; and 5. to assess iliac artery deformation due to stiff endovascular devices during EVAR. In a prospective single-center study (I) involving 19 patients undergoing EVAR, we found that automatic intensity-based registration only was insufficient for guidance. Manual vertebrae-based registration was sufficient in only 37% of the patients. After aorta-based registration, the median overlay alignment error for the lowest renal artery at pre-deployment DSA was 2 mm (range 0‒5 mm) sideways and 2 mm (range 0‒9 mm) longitudinally. Study II was a feasibility study showing that EVAR can be performed with 3D image fusion guidance combined with CO2 DSA, instead of iodinated contrast medium DSA, which was only used for the completion angiography. Study III was also a feasibility study showing that image fusion can facilitate thoracic EVAR (TEVAR) by visualization of intercostal arteries adjacent to the distal landing zones. In study IV, a feature-based and an intensity-based registration algorithm were compared using datasets from 14 patients who underwent complex EVAR. The feature-based algorithm was more robust and accurate. The median 3D error for the feature-based algorithm was 2.3 mm (range 0.4‒7.9 mm) as compared to 31.6 mm (range 0.5‒112.2 mm) for the intensity-based algorithm (p < 0.001). In study V, preoperative, postoperative, and intraoperative 3D image datasets were reviewed in order to assess iliac artery deformation by stiff endovascular devices during EVAR. The common iliac artery was shorter in both the intraoperative images (p < 0.001) and the postoperative images (p = 0.015) relative to the preoperative CTA. Furthermore, there was a dislocation of the aortic bifurcation in the cranial direction (93%) and a dislocation of the iliac bifurcation in the ventral direction (89%). The intraoperative C-arm angulation for optimal projection of the iliac bifurcation increased with 21 ± 43 degrees in the contralateral oblique direction relative to the angle predicted from the preoperative CTA. In conclusion, 3D image fusion for EVAR guidance is a promising technique allowing improved intraoperative visualization of critical anatomical structures. However, limitations in registration accuracy and anatomy distortion compensation mandate further research

Performance of a feature-based algorithm for 3D-3D registration of CT angiography to cone-beam CT for endovascular repair of complex abdominal aortic aneurysms

Background: A crucial step in image fusion for intraoperative guidance during endovascular procedures is the registration of preoperative computed tomography angiography (CTA) with intraoperative Cone Beam CT (CBCT). Automatic tools for image registration facilitate the 3D image guidance workflow. However their performance is not always satisfactory. The aim of this study is to assess the accuracy of a new fully automatic, feature-based algorithm for 3D3D registration of CTA to CBCT. Methods: The feature-based algorithm was tested on clinical image datasets from 14 patients undergoing complex endovascular aortic repair. Deviations in Euclidian distances between vascular as well as bony landmarks were measured and compared to an intensity-based, normalized mutual information algorithm. Results: The results for the feature-based algorithm showed that the median 3D registration error between the anatomical landmarks of CBCT and CT images was less than 3mm. The feature-based algorithm showed significantly better accuracy compared to the intensity-based algorithm (p<0.001). Conclusion: A feature-based algorithm for 3D image registration is presented

Air bubbles are released by thoracic endograft deployment: An in vitro experimental study

Purpose: Embolic stroke is a dreaded complication of thoracic endovascular aortic repair. The prevailing theory about its cause is that particulate debris from atherosclerotic lesions in the aortic wall are dislodged by endovascular instruments and embolize to the brain. An alternative source of embolism might be air trapped in the endograft delivery system. The aim of this experimental study was to determine whether air is released during deployment of a thoracic endograft.Methods: In an experimental benchtop study, eight thoracic endografts (five Medtronic Valiant Thoracic and three Gore TAG) were deployed in a water-filled transparent container drained from air. Endografts were prepared and deployed according to their instructions for use. Deployment was filmed and the volume of air released was collected and measured in a calibrated syringe.Results: Air was released from all the endografts examined. Air volumes ranged from 0.1 to 0.3 mL for Medtronic Valiant Thoracic and fro

Air bubbles are released by thoracic endograft deployment: An in vitro experimental study

Purpose: Embolic stroke is a dreaded complication of thoracic endovascular aortic repair. The prevailing theory about its cause is that particulate debris from atherosclerotic lesions in the aortic wall are dislodged by endovascular instruments and embolize to the brain. An alternative source of embolism might be air trapped in the endograft delivery system. The aim of this experimental study was to determine whether air is released during deployment of a thoracic endograft.Methods: In an experimental benchtop study, eight thoracic endografts (five Medtronic Valiant Thoracic and three Gore TAG) were deployed in a water-filled transparent container drained from air. Endografts were prepared and deployed according to their instructions for use. Deployment was filmed and the volume of air released was collected and measured in a calibrated syringe.Results: Air was released from all the endografts examined. Air volumes ranged from 0.1 to 0.3 mL for Medtronic Valiant Thoracic and fro

Intra-observer agreements in multidisciplinary team assessments of pancreatic cancer patients

Background and Methods  Treatment strategies for pancreatic cancer patients are made by a multidisciplinary team (MDT) board. We aimed to assess intra-observer variance at MDT boards. Participating units staged, assessed resectability, and made treatment allocations for the same patients as they did two years earlier. We disseminated clinical information and CT images of pancreatic cancer patients judged by one MDT board to have nonmetastatic pancreatic cancer to the participating units. All units were asked to re-assess the TNM stage, resectability, and treatment allocation for each patient. To assess intra-observer variance, we computed %-agreements for each participating unit, defined as low (75%) agreement.  Results  Eighteen patients were re-assessed by six MDT boards. The overall agreement was moderate for TNM-stage (ranging from 50%-70%) and resectability assessment (53%) but low for treatment allocation (46%). Agreement on resectability assessments was low to moderate. Findings were similar but more pronounced for treatment allocation. We observed a shift in treatment strategy towards increasing use of neoadjuvant chemotherapy, particularly in patients with borderline resectable and locally advanced tumors.  Conclusions  We found substantial intra-observer agreement variations across six different MDT boards of 18 pancreatic cancer patients with two years between the first and second assessment