Technical Note: 4D cone-beam CT reconstruction from sparse-view CBCT data for daily motion assessment in pencil beam scanned proton therapy (PBS-PT)

Otter, den, L., Chen, K., Janssens, G., Meijers, A., Both, S., Langendijk, J. A., Rosen, L. R., Wu, H. T. & Knopf, A., 25-Oct-2020, In : Medical Physics. 12, p. 6381-6387 7 p.

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Purpose: The number of pencil beam scanned proton therapy (PBS-PT) facilities equipped with
cone-beam computed tomography (CBCT) imaging treating thoracic indications is constantly rising.
To enable daily internal motion monitoring during PBS-PT treatments of thoracic tumors, we assess
the performance of Motion-Aware RecOnstructiOn method using Spatial and Temporal Regularization
(MA-ROOSTER) four-dimensional CBCT (4DCBCT) reconstruction for sparse-view CBCT
data and a realistic data set of patients treated with proton therapy.
Methods: Daily CBCT projection data for nine non-small cell lung cancer (NSCLC) patients and
one SCLC patient were acquired at a proton gantry system (IBA Proteus® One). Four-dimensional
CBCT images were reconstructed applying the MA-ROOSTER and the conventional phase-correlated
Feldkamp-Davis-Kress (PC-FDK) method. Image quality was assessed by visual inspection,
contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), and the structural similarity index measure
(SSIM). Furthermore, gross tumor volume (GTV) centroid motion amplitudes were evaluated.
Results: Image quality for the 4DCBCT reconstructions using MA-ROOSTER was superior to the
PC-FDK reconstructions and close to FDK images (median CNR: 1.23 [PC-FDK], 1.98 [MA-ROOSTER],
and 1.98 [FDK]; median SNR: 2.56 [PC-FDK], 4.76 [MA-ROOSTER], and 5.02 [FDK]; median
SSIM: 0.18 [PC-FDK vs FDK], 0.31 [MA-ROOSTER vs FDK]). The improved image quality of
MA-ROOSTER facilitated GTV contour warping and realistic motion monitoring for most of the
Conclusion: MA-ROOSTER based 4DCBCTs performed well in terms of image quality and appear
to be promising for daily internal motion monitoring in PBS-PT treatments of (N)SCLC patients.
Original languageEnglish
Pages (from-to)6381-6387
Number of pages7
JournalMedical Physics
Issue number12
Early online date25-Oct-2020
Publication statusE-pub ahead of print - 25-Oct-2020


  • 4D-CBCT, image reconstruction, Lung cancer, inter-fractional motion, pencil beam scanning, proton therapy

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