Analysis of respiration-related movement of upper abdominal arteries: preliminary measurement for the development of a respiratory motion compensation technique of roadmap navigation

Real-time 3D reconstruction of guidewires and stents using two update X-ray projections in a rotating imaging setup

BACKGROUND

Vascular diseases are often treated minimally invasively. The interventional material (stents, guidewires, etc.) used during such percutaneous interventions are visualized by some form of image guidance. Today, this image guidance is usually provided by 2D X-ray fluoroscopy, that is, a live 2D image. 3D X-ray fluoroscopy, that is, a live 3D image, could accelerate existing and enable new interventions. However, existing algorithms for the 3D reconstruction of interventional material require either too many X-ray projections and therefore dose, or are only capable of reconstructing single, curvilinear structures.

PURPOSE

Using only two new X-ray projections per 3D reconstruction, we aim to reconstruct more complex arrangements of interventional material than was previously possible.

METHODS

This is achieved by improving a previously presented deep learning-based reconstruction pipeline, which assumes that the X-ray images are acquired by a continuously rotating biplane system, in two ways: (a) separation of the reconstruction of different object types, (b) motion compensation using spatial transformer networks.

RESULTS

Our pipeline achieves submillimeter accuracy on measured data of a stent and two guidewires inside an anthropomorphic phantom with respiratory motion. In an ablation study, we find that the aforementioned algorithmic changes improve our two figures of merit by 75 % (1.76 mm → 0.44 mm) and 59 % (1.15 mm → 0.47 mm) respectively. A comparison of our measured dose area product (DAP) rate to DAP rates of 2D fluoroscopy indicates a roughly similar dose burden.

CONCLUSIONS

This dose efficiency combined with the ability to reconstruct complex arrangements of interventional material makes the presented algorithm a promising candidate to enable 3D fluoroscopy.

[Usefulness of Respiratory Suppression for Abdominal Using EPI Sequences]

The upper abdomen was imaged with diffusion weighted images for free breathing and respiratory suppression using single shot-echo planar imaging (SS-EPI) and readout segmented-EPI (RS-EPI). We examined the usefulness of respiratory suppression imaging for the subject of healthy volunteers. Motion artifacts, apparent diffusion coefficient (ADC) values, and organs movement distances were evaluated. As a result, motion artifacts and organs movement distances were reduced in respiratory suppression than free breathing. The ADC values did not change. Respiratory suppression was simple and useful. In addition, it was found that RS-EPI imaging could be used for imaging the upper abdomen in the same way as SS-EPI by respiratory suppression.

Initial Experience With Viabahn VBX as the Bridging Stent Graft for Branched and Fenestrated Endovascular Aneurysm Repair

PURPOSE

To evaluate the feasibility and safety of a novel balloon-expandable, heparin-bonded endoprosthesis (Viabahn VBX, W. L. Gore and Associates) when used as a bridging stent graft (BSG) with fenestrated and branched endovascular aneurysm repair (FB-EVAR). FB-EVAR and BSGs increase repair complexity with the potential for endoleak formation, stenosis, thrombosis, and graft migration. The mechanical construction of the Viabahn VBX and its antithrombogenic properties may provide an advantage for FB-EVAR over existing BSGs. The efficacy, safety, and clinical outcomes were assessed.

MATERIALS AND METHODS

Research ethics board approved, prospective, single arm cohort, pilot study of patients undergoing FB-EVAR between February 2017 and January 2018. Fenestrated and branched endovascular aneurysm repair was performed per the standard institutional protocol by a team composed of vascular surgeons and interventional radiologists. Viabahn VBX endografts were used for all intended visceral branches as long as appropriately sized devices were available (Under Investigational Testing Authorization from Health Canada). Patient characteristics, procedural details, and technical and clinical outcomes were reviewed and summarized.

RESULTS

FB-EVAR was performed in 13 patients (9 male and 4 female) mean age of 74 (range: 61-83) with a total of 41 Viabahn VBXs stents implanted. Mean maximum aneurysm size was 6.7 cm (range: 5.5-9.0 cm) and included 5 juxtarenal abdominal aortic aneurysms and 8 thoracoabdominal; 3 type V, 3 type IV, and 2 type III (Crawford Classification). The Viabahn VBX was successfully deployed in 40 (98%) of 41 of cases. At median follow-up of 223 days (range: 2-462), there was a (40/40) 100% Viabahn VBX patency rate. Seven endoleaks were identified intra- or post procedurally in 6 (46%) of 13 cases, including 1 type IB, 3 type II, 2 type III, and 1 unclassified. Nine complications occurred in 6 patients.

CONCLUSION

The Viabahn VBX stent is a safe and effective BSG for FB-EVAR with no early stent thrombosis. Further evaluation is required to determine longer term stent efficacy.

Quantitative analysis of respiration-related movement for abdominal artery in multiphase hepatic CT

Objectives

Respiration-induced motion in the liver causes potential errors on the measurement of contrast medium in abdominal artery from multiphase hepatic CT scans. In this study, we investigated the use of hepatic CT images to quantitatively estimate the abdominal artery motion due to respiration by optical flow method.

Materials and Methods

A total of 132 consecutive patients were included in our patient cohort. We apply the optical flow method to compute the motion of the abdominal artery due to respiration.

Results

The minimum and maximum displacements of the abdominal artery motion were 0.02 and 30.87 mm by manual delineation, 0.03 and 40.75 mm calculated by optical flow method, respectively. Both high consistency and correlation between the present method and the physicians’ manual delineations were acquired with the regression equation of movement, y = 0.81x+0.25, r = 0.95, p<0.001.

Conclusion

We estimated the motion of abdominal artery due to respiration using the optical flow method in multiphase hepatic CT scans and the motion estimations were validated with the visualization of physicians. The quantitative analysis of respiration-related movement of abdominal artery could be used for motion correction in the measurement of contrast medium passing though abdominal artery in multiphase CT liver scans.