SU-D-18A-03: Markerless Motion Tracking of Lung Tumors Using Dual-Energy Fluoroscopy

Authors


Abstract

Purpose:

To evaluate the efficacy of dual energy (DE) vs. single energy (SE) fluoroscopic imaging in lung tumors using a markerless template-based tracking algorithm.

Methods:

Ten representative patient breathing patterns were programmed into a Quasar™ motion phantom. The phantom was modified by affixing pork ribs to the surface, and a cedar insert with a small spherical volume was used to simulate lung and tumor, respectively. Gated 60kVp(6mA) and 120kVp(1.5mA) fluoroscopic sequences were acquired using the Varian TrueBeam Integrated Imaging Solution. These high and low energy frames were subsequently aligned by phase and amplitude. Frame-by-frame weighted logarithmic subtraction was performed resulting in a DE fluoroscopic image sequence that highlighted soft tissue structures. A template-based algorithm was then used to track tumor motion throughout the sequence for DE and SE images (120kVp). Tracking coordinates were evaluated against ground truth tumor locations as identified by a physician. A displacement of greater than 3 mm was considered a non-successful track. The same process was also repeated for images obtained from 3 SBRT lung patients, none of which had implanted fiducials.

Results:

For phantom imaging, a total of 1925 frames were analyzed. The algorithm successfully tracked the target on 91.6%(1763/1925) of DE frames vs. 74.9%(1441/1923) SE images (p<0.001). The displacement between tracking coordinates and ground truth for the phantom was 1.1mm+/−0.7mm for DE and 1.5mm+/− 0.6mm for SE (p<0.001). Images from 3 patients were analyzed with the tumor tracked on 84.9%(478/563) of frames for DE vs. 53.5%(301/563) for SE (p<0.001). The average difference to ground truth for successfully tracked DE frames was 0.6mm+/−0.6mm vs. 1.7mm+/−0.7mm SE (p<0.001).

Conclusion:

This work indicates the potential for markerless tumor tracking utilizing DE fluoroscopy. With DE imaging, the algorithm showed improved detectability vs. SE fluoroscopy and was able to accurately track the tumor in a majority of cases.

This work was supported by Varian Medical Systems

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