3-D Cone Beam CT Makes Interventions Easier

Fluoroscopy technology has advanced to produce CT scan-like images taken by the new models of C-arms called “C-arm cone beam CT.” This is performed on floor- or ceiling-mounted C-arms that have a flat panel detector instead of a conventional image intensifier.

Commercially, the systems are called DynaCT (Siemans), XperCT (Phillips), or Innova CT (GE).

The images produced are not the caliber or quality of today’s multi-detector CT machines, but the contrast has been greatly improved by using intravascular contrast during acquisition.

C-arm cone beam CT may improve angiography by decreasing radiation dose, decreasing complications and improving safety.

The Study
The authors reviewed the papers published about this new technology, and listed the ways that C-arm cone-beam CT is being used by angiographers in both vascular and non-vascular procedures.

Discussion
Depending on whether the vessels or the parenchyma need to be visualized, many things must be tweaked, such as the concentration of the dye injected, the delay of image acquisition, and the speed of the injection.

The limitations of this procedure include set up time and image processing time.

The vascular applications include pre-procedure anatomic diagnosis, treatment planning, intra-procedure device or implant placement, and post-procedure end point check.

C-arm cone-beam CT helps the interventionalist correctly identify the sites to perform embolization while avoiding the complications caused by non-target embolization.

During transjugular intrahepatic portosystemic shunt placement, the position of the portal vein with reference to the hepatic vein can be accurately determined, thus decreasing the time spent, number of punctures, and the incidence of severe complications.

During arterial and venous stent placement, correct spatial evaluation of the areas of stenosis can be performed, as well as post-deployment results.

During triple A angiogram placement, difficult anatomy can easily be evaluated and treated.

Even subtle endoleaks can be detected and treated while the patient is still on the table.

Vascular anomalies can be quickly and completely visualized before, during, and after sclerotherapy.

For non-vascular uses, during spinal interventions, the location of the cement administered in relation to the spinal cord can be quickly determined.

During gastrostomy placement, the location of the bowel and liver can be identified and avoided.

For biliary interventions, cone-beam CT is being used during cholangiography to determine the volume of liver drained or to identify isolated ducts.

In general, the dose of radiation was higher per each acquisition than fluoroscopy or digital substraction angiography (DSA); however, the CT-like images decreased the number and angles of DSA runs needed, thus decreasing total patient and doctor dose.

Reviewer’s Comments
C-arm cone beam CT is a new technology that produces CT scan like images from flat panel C-arm systems, and may improve angiography by decreasing radiation dose, decreasing complications and improving safety for patients and medical staff alike.

This new imaging technology will be the basis of innovations involving 3-D roadmapping and navigational tools.

This technology should improve safety, decrease radiation exposure, decrease complications, and decrease the dose of contrast needed. This technology should also make some of the more difficult procedures easier to perform.

Author: Sharon Gonzales, MD

Reference:
Wallace MJ, Kuo MD, et al. Three-Dimensional C-Arm Cone-Beam CT: Applications in the Interventional Suite. J Vasc Interv Radiol; 2008; 19 (June): 799-813