Cone beam CT use enabled researchers to predict percutaneous access location more accurately.


WASHINGTON, D.C.—An imaging modality called cone beam CT may improve intraprocedural management decisions during percutaneous nephrolithotripsy (PCNL), researchers say.

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Cone beam CT enables reconstruction of cross-sectional or 3D images from rotational fluoroscopy, thus adding significantly improved spatial resolution over routine planar imaging alone. This technology is superior to routine intraprocedural fluoroscopic or digital planar imaging in assessing post-procedural stone burden.


“This approach gives you more information,” said James Stone, MD, PhD, a resident in the Interventional Radiology Clinical Pathway track at the University of Virginia in Charlottesville.


“In this study, we found that cone beam CT allowed us to more accurately determine the location of our percutaneous access. It also allowed for more accurate assessment of residual stone burden within the renal collecting system. By adding the cross-sectional component of cone beam CT, we are able to more effectively evaluate for access and for stone clearance when compared to conventional two-dimensional planar imaging alone.”


The investigators conducted a retrospective review of 30 patients (mean age, 50 years). The group consisted of 12 men and 18 women. All 30 patients underwent cone beam CT before and following percutaneous access; the last 21 patients also underwent a post-procedural cone beam CT scan. The researchers evaluated the technology for accuracy of percutaneous access, stone location, and residual stone burden compared with intraprocedural digital planar images.


When researchers compared cone beam CT to routine intraprocedural fluoroscopy, they found cone beam CT identified six cases in which access was different than expected based on standard fluoroscopy and digital planar images. Among these six cases, one required placement of a new access. Sixteen of the 21 post-procedural cone beam CT cases showed residual stones greater than 3 mm and these stones were seen by planar imaging in only 10 of these 16 cases (63%). 


When the researchers compared intraprocedural cone beam CT with routine, post-procedural CT, they found that 9 of 16 cases were equivalent. In the 7 of 16 cases where routine CT was superior, patient motion and residual contrast on the cone beam CT series were the primary limiting factors. Of note, in the cases where residual stone burden was significant enough to warrant a secondary intervention, both cone beam CT and routine CT detected sufficient stone burden to recommend pursuing an additional procedure.


The study was conducted through a collaborative effort between the department of urology and division of interventional radiology at the University of Virginia. Senior investigators included Noah Schenkman, MD, associate professor of urology, and division chief John Angle, MD, associate professor of radiology.


The investigators, who presented their findings here at the Society of Interventional Radiology’s 33rd Annual Scientific Meeting, believe the significance of their findings lies in the intraprocedural availability of improved imaging that may allow for re-intervention in a timelier and less invasive fashion.


“This could improve management,” Dr. Stone said. “The key point is the ability to make intraprocedural management decisions with more effective imaging. The availability of cross-sectional imaging used to be confined to the post-procedural period, after the patient has left the interventional suite. We now have the ability to acquire cross-sectional imaging while the patient is on the table. We still have access in place and can reintervene within a given procedure. This may help eliminate a second trip back to the interventional suite.”