TITLE:
Accuracy Comparison of 4D Computed Tomography (4DCT) and 4D Cone Beam Computed Tomography (4DCBCT)
AUTHORS:
Tzu-Cheng Lee, Stephen R. Bowen, Sara St. James, George A. Sandison, Paul E. Kinahan, Matthew J. Nyflot
KEYWORDS:
4DCT, 4DCBCT, Verification Imaging, Respiratory Motion Phantom
JOURNAL NAME:
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology,
Vol.6 No.3,
August
30,
2017
ABSTRACT: The
ability of respiratory-correlated fan beam CT (4DCT) and respiratory-correlated
cone beam CT (4DCBCT) to accurately estimate tumor volume is critical to
accurate dosimetry and treatment verification for lung stereotactic body
radiation therapy (SBRT) and other motion-managed therapies. However, it is
known that 4DCT and 4DCBCT differ in aspects of image acquisition and
reconstruction that may lead to discrepancies between the two modalities. To
evaluate quantitative differences between 4DCT and 4DCBCT imaging under
respiratory motion, we performed a phantom study in the ground truth setting. A
programmable respiratory motion phantom was used to simulate the 1D S-I position
of a known-size lesion. Ten sinusoidal and twenty patient-specific breathing
waveforms were applied to drive lesion motion during the 4DCT and 4DCBCT acquisitions.
The difference in lesion volume acquired between the two imaging modalities was
as high as 34.4% and 18.4% for sinusoidal and patient-specific breathing
motions, respectively. When compared to the true volume, 4DCT measurement often
underestimated the lesion size whereas 4DCBCT overestimated the lesion volume
in most of the cases. 4DCBCT gave more accurate recovery of the volume than
4DCT for most settings tested in this study. These findings may be helpful for
improving the definition of internal target and planning target volume margins,
and extracting quantitative information from on-board treatment verification
imaging.