3D guidance improves interventional capabilities

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Precise localization is critical for the optimal performance of interventional radiology procedures. A new technology, in which fluoroscopy and 3D imaging from a cone-beam CT flat-panel detector C-arm unit are combined with an integrated tracking and navigation system, may offer clinicians increased interventional radiologic capabilities, according to a recent study published in the American Journal of Roentgenology.

“The primary benefit of CT is the 3D spatial understanding of bones and soft tissues together,” the authors wrote. “The drawbacks are lack of patient access and lack of real-time visualization of the procedure, including monitoring needle advancement.”

Researchers from the department of radiology, division of pediatric interventional radiology, at Cincinnati Children’s Hospital Medical Center in Cincinnati, investigated the use of the new technology, the XperCT and XperGuide FD20 interventional-angiography system from Philips Medical Systems.

The modality allows for 3D isotropic soft-tissue volume reconstruction from rotational acquisition. Live fluoroscopy can then be co-registered with the 3D data set and superimposed on it. According to the authors, the co-registration is integrated with the movement of C-arm so that the 3D data set changes as the C-arm moves through various oblique angles. This allows for the 3D data to be viewed and manipulated both on a control room workstation and at tableside in the procedure room.

“The relation between the 2D and 3D data sets is maintained during C-arm movements (angulations and rotations), changes in source–image distance, and modifications of image size,” the authors wrote. “Because all of these data sets (CT-like data, 2D fluoroscopy, and 3D reconstructions) are acquired inside the same calibrated space, it is possible to register and display them as one imaging entity.”

Images from a study conducted on a 14-year-old boy with chronic back pain and bilateral pars interarticularis defects. XperCT (FD20 angiography–interventional system, Philips Medical Systems) image with graphics shows planned needle path ( green) into left-sided pars defect. Purple line is actually purple circle indicating skin entry site, which on 90° tangent (progression view) appears as a line. The planned needle path ( purple line) is shown on a 3D volume image. Image and caption by permission of the American Roentgen Ray Society.

The technology, according to the researchers, allows for x-ray-based, real-time 3D image-guided interventions to be performed in the interventional suite. In their utilization of the CT/fluoroscopy fusion modality, they reported that it provided the capability to interactively define the skin entry point and anatomic target point via virtual graphics, which displayed the ideal needle trajectory for the procedure. In addition, they were able to monitor the needle’s progress in real time.

The clinicians noted that a limitation of the system was that a patient was required to remain still during the procedure.

“XperCT requires the patient to stay still for 21 seconds,” they wrote. “XperGuide needle trajectory requires that the patient continue to be still so that the virtual-CT data set remains co-registered with the true anatomy (same limitation as with CT guidance, although the 3D update takes more than 1 minute, compared with seconds for the CT update).”

Although the patient immobilization constraint of the CT/fluoroscopy fusion system was seen as a limitation of the technology, the interventional radiologists were favorably impressed with its utilization in a variety of clinical procedures performed at their institution.

“These new techniques expand the procedural capabilities of interventional radiologists and should thus improve patient care and outcomes,” they wrote.