Funding period: Feb 2018 to Apr 2022

Researcher: Fatima Saad

Wrap-up

Keywords: Digital Tomosynthesis, Image Reconstruction, Image Registration, Interventional Bronchoscopy, Prior Information

Background:
X-ray radiography is one of the mostly used modalities for guiding interventions. Whereas it poses low radiation dose, its weakness is in the superposition of the different image structures in a 2D image which challenges the depiction of the intervention targets (e.g. lesions). While CBCT might provide exact 3D information, it is at the cost of a higher dose, longer imaging time and more space requirements. 

Objective:
The goal was to develop acquisition and reconstruction protocols using very few angularly limited projections to obtain high-quality intraoperative images. 

Methods:
Introducing some depth information with relatively low dose and requiring less space, we proposed the use of digital tomosynthesis DTS for guiding interventions. To mitigate the limited depth resolution of linear DTS and address the space demands of circular DTS, we proposed a novel C-arm-based spherical ellipse DTS trajectory. Moreover, given that high-quality prior CT scans are often performed prior to the intervention and that such images share a fair amount of information with the intraoperative DTS images, we proposed a new prior-based iterative DTS image reconstruction framework for improving the image quality. In this context, we proposed a novel CT-to-Tomosynthesis registration technique and combined it with the proposed reconstruction algorithm. 

Results:
Compared to the standard methods, our experiments on interventional bronchoscopy data showed a good compromise between image quality and workspace requirements with the spherical ellipse trajectory, and the reconstruction algorithm proved a considerable improvement in the DTS image quality.

Conclusions:
An efficient and robust C-arm-based acquisition and reconstruction protocol using very few arbitrary and angularly limited projections for guiding interventional bronchoscopy procedures was developed. 

Originality:
To the best of my knowledge, the spherical ellipse DTS scan trajectory, the CT-to-DTS registration framework and the prior-based reconstruction algorithm are all original.