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Four-Dimensional Dual Cone-Beam CT (4D-DCBCT): Preliminary Experimental Results


H Li

H Li*, I Vergalasova, W Giles, J Bowsher, F Yin, Duke University Medical Center, Durham, NC

WE-G-134-4 Wednesday 4:30PM - 6:00PM Room: 134

Purpose:
One of the major challenges for clinical implementation of 4D-CBCT is long scan time. This study aims to develop a 4D-DCBCT technique to improve the efficiency of 4D imaging (for motion management in radiation therapy).

Methods:
A bench-top DCBCT system, which consists of two orthogonal 40x30cm flat panel detectors and two conventional x-ray tubes with two individual high-voltage generators, sharing the same rotational axis, was used to develop the technique. The x-ray source to detector distance was 150 cm and x-ray source to rotational axis distance was 100 cm for both subsystems. The dual CBCT system utilized 110° of projection data from one detector and 90° from the other, as opposed to a single CBCT utilizing 200° of projection data per each detector. Motion phantom studies were conducted to validate the efficiencies by comparing 4D images generated from 4D-DCBCT and 4D-CBCT. First, a simple sinusoidal profile was used to confirm the scan time reduction. Next, both irregular sinusoidal and patient-derived profiles were used to investigate the advantage of temporally correlated orthogonal projections due to a reduced scan time. Normalized mutual information (NMI) between 4D-DCBCT and 4D-CBCT was used for quantitative evaluation.

Results:
For the simple sinusoidal profile, the average NMI for ten phases between two single 4D-CBCTs was 0.336, indicating the maximum NMI that can be achieved for this study. The average NMIs between 4D-DCBCT and each single 4D-CBCT were 0.331 and 0.320. For both irregular sinusoidal and patient-derived profiles, 4D-DCBCT generated phase images with less motion blurring when compared with single 4D-CBCT.

Conclusion:
The 4D-DCBCT provides an efficient 4D imaging technique for motion management. The scan time is approximately reduced by a factor of two. The temporally correlated orthogonal projections improved the image blur across 4D phase images.

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