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Comparison of the Localization Accuracy in Conventional and Ultra-Low Dose CT Fluoroscopy - A Simulation Study

M Wagner*, F Lee , L Hinshaw , P Laeseke , T Szczykutowicz , M Speidel , C Mistretta , University of Wisconsin, Madison, WI


(Sunday, 7/29/2018) 1:00 PM - 1:55 PM

Room: Karl Dean Ballroom B1

Purpose: Percutaneous needle procedures are commonly performed using CT or CT fluoroscopy guidance. This requires repeated CT acquisitions to ensure accurate needle placement. For each acquisition a full gantry rotation is performed where on the order of 1000 projection images are gathered. Low tube currents are commonly used to limit the dose resulting in low image quality, which might be further reduced by metal artifacts around the needle. Additionally, the repeated CT acquisitions might cause high radiation exposure to patients and physicians. The goal of this work is to present a novel ultra-low dose (ULD) needle guidance technique with diagnostic image quality and no metal artifacts.

Methods: The proposed technique uses only two projection images per gantry rotation. The device is segmented in each image and backprojected into the volume space. The intersection of the projections from both images is then used to determine the location, orientation and shape of the needle. The reconstructed needle is then superimposed on a previously acquired helical or axial planning CT to provide anatomical context. A motion compensation approach is used to estimate possible deformations of the planning CT due to respiratory motion. Evaluation was performed on digital CT phantoms with realistic anatomy and image quality. Virtual needles were placed within the phantoms and the accuracy of the ULD technique was compared to automatic needle segmentation in conventional CT reconstructions.

Results: The ULD technique provided significantly higher accuracy (0.64±0.60mm vs 1.32±0.30mm, paired T-test, p=0.00) compared to conventional reconstruction while allowing a potential dose reduction of 492x. An additional study with respiratory motion achieved needle localization errors relative to the anatomy of 1.55±1.26mm.

Conclusion: Successful implementation of ultra-low dose CT fluoroscopy for clinical settings could improve the accuracy of needle placements for percutaneous needle procedures, while reducing radiation exposure for patients and physicians.

Funding Support, Disclosures, and Conflict of Interest: Drs. Wagner, Lee, Hinshaw, Szczykutowicz, and Mistretta have a financial [ownership] interest in LiteRay Medical LLC, the company holding the patent for this technology. If the company is successful they may financially benefit from this research.


Localization, Reconstruction, Registration


IM/TH- Image-guided surgery: Registration and localization

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