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Cone Beam CT, Image Fusion, and Needle Guidance Planning

Tuesday, August 23, 2016

Background: With the advent of fixed imaging systems (cone beam CT scanning), which permit rotational image acquisition, vascular surgeons now find themselves with a very important new tool: a CT scan in the operating room. This  permits vascular surgeons and other surgical subspecialtists to perform procedures that were previously only in the realm of radiologists. In this video, the authors demonstrate how to perform cone beam CT scanning, how to use this to fuse a previously acquired CTA, and how to plan needle access to an otherwise non-accessible vascular target.

Methods: When planning to perform a cone beam CT, it is very important to communicate to both the nursing and anesthesia staff that the patient and the bed need to be wrapped in a sterile drape circumferentially. Both the radiation sources and flat panel are draped. Anesthesia will typically wrap of all the ventilation tubing and monitoring systems with a towel. This allows the anesthesia team to manage all of the lines during rotation of the C arm and to prevent inadvertent extubation. The rotational acquisition is then performed according to the manufacturer’s protocols. No dye is required if a high quality CT has been performed previously. 

The previous CTA is imported into the inspace workstation and fused with the recently acquired cone bean CT. Most imaging manufacturers perform a bone to bone fusion. The authors have been developing a vascular calcification image fusion algorithm, which will permit an even more accurate vascular fusion. This fusion process is used to align the current patient position with the prior CTA. The image can be flipped if the patient is in the prone position.

Using the proprietary guide on the workstation, the target is delineated and the access point also defined. A needle path is then demonstrated, which will appear on the screen as a needle guide. The C arm is then moved to the "bullseye" position, which looks down the barrel of the path and demonstrates the needle entry point. By looking in two views the needle can be advanced to the target along the needle guide.

Summary: This method is a highly accurate way of accessing a target. The authors have used this methodology without complication in 25 translumbar embolizations, 4 lung nodules, and in accessing a venous malformation deep within the thigh. This technique could be used in a variety of surgical subspecialties where CT-guided needle localization is beneficial and provides one-stop care for the patient.

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